STAY CONNECTEDThe Radio Frequency Systems Bulletin

2nd QUARTER 2008

T h e C l e a r C h o i c e ®

West coast USA: A kaleidoscope of contrast

Aluminum: The light alternativeThe journey ahead for Brazil DTV

The focus is overlays RF Technology 101

West coast USA: A kaleidoscope of contrastThe contrasts of the U.S.’s West Coast present a unique challenge to wireless communicationsproviders. In a region known for fast take-up ofnew technology, there is demand for enhancedservices and low environmental-impact solutions.

IMPR

INT

Radio Frequency SystemsWorldWideWeb: http://www.rfsworld.com

Publisher: Jörg SpringerExecutive Editor: Peter WaltersEditor EMAI: Regine SulingEditor Americas North: Paula Mennone-PreisnerEditor Americas South: Pilar LopesManaging Editor: Ben LazzaroProduction Editor: Christian Michatsch

Art Director: Sabine Wieloch, Heidi Jünemann

Authors: Allan Alderson, Paul Fry, Dr. Ellen Gregory,Ben Lazzaro, Patrick WongPhotos: RFS archives, Tony Koopmans, Pilar Lopes,Vladimir Piletic (Piletic), Regine Suling, RubensVandresen (Rede Paranaense de Comnunicação), Dr. Wolfgang Liese, Shelton Muller, Sabine Wieloch,inform ArchivesCover art: Sabine WielochPrint: Print Design, Minden

Layout and Graphics:inform Advertising, Hannover

Editorial Services:Relate Technical Communications, MelbourneTrademarks: CELLFLEX®, ClearFill®, BDA®,FLEXWELL®, MicroTennaTM, OMNI FITTM, Optimizer®,Radio Frequency Systems®, RAPID FITTM, RFS®, RFSCompactLine®, SlimLine®, RGFLEX®, HELIFLEX®,RADIAFLEX® and The Clear Choice® are trademarks,service marks or registered trademarks of RadioFrequency Systems. All other trademarks are the property of their respective owners.

8

The journey ahead for Brazil DTVAs Brazil’s transition to DTV forges ahead, localbroadcasters and technology providers are meetingthe country’s unique DTV deployment challengeshead-on. Here, RFS is playing a crucial role.

03 EditorialWorking out the ‘white spaces’

4 What’s NewOptimizer BSA—now in 32-degree

New PCP panel: Dual-feed flexibility

RFS adds tilt to global WiMAX solution

MicroFlex—the coax 'all-rounder'

New 'Optimizer Universal' ACU: Tested and proven

Second-generation broadcast RF monitor

ClearFill expands to FCC bands

8 Cover StoryWest coast USA: A kaleidoscope of contrast

10 BroadcastThe journey ahead for Brazil DTV

13 Transmission LineAluminum: The light alternative

14 Infrastructure SolutionsThe focus is overlays

16 RF Technology 101RF filter fundamentals

18 In TouchVipnet upgrades to Optimizer Rooftop

RFS myCatalog makes the jump to digital

Mobilink chooses CELLFLEX Lite

FCC allows two-foot dish

2 C O N T E N T S

13

Aluminum: The light alternativeThe soaring price of copper has led to a re-evaluation of materialselection in RF cables.Aluminum is emerging as a strong contender.

10

RF Technology 101A new column inSTAY CONNECTEDthat provides insightinto the science of RF technology. Thisissue: RF filter fundamentals.

16

The focus is overlaysOverlaying new wireless services in today’s spectrally congested wireless landscape requiresintimate knowledge of a range of wireless technologies, coupled with advanced planningand deployment strategies.

14Publisher's note: In the 10 years following its creation in 1998, STAY CONNECTED hasevolved into one of the wireless industry’s most highly-regarded customer publications. In fact, it has pushed the boundaries of suchpublications, offering readers unmatched quality and variety of news and technical RFinformation. During this time, I have relished my role as publisher, and enjoyed bringing the latest wireless communications and RFdevelopments to a global audience. This issue of STAY CONNECTED will be my last, and I take great pleasure in introducing the new publisher of STAY CONNECTED, RFS Asia Pacific South Marketing Director, PeterWalters. Thank you for your support over these past 10 years, and I hope you continue to enjoy reading STAY CONNECTED.Jörg Springer—Publisher

The biggest news in U.S. spectrum scene at the

time of writing is the Federal Communications

Commission’s (FCC) Auction 73—the so-called

‘700MHz spectrum’ auction. To-date, Auction

73 has attracted total bids well beyond the

projected high of U.S.$15 billion. This is a clear

indication of the increasing scarcity, and

inherent value, of such prime spectrum.

Yet debate over another potential FCC

spectrum allocation in a nearby band, and with

a bandwidth total around four times that of the

700MHz-spectrum auction, seems to be largely

passing unnoticed. This is the U.S. ‘white

spaces’ spectrum proposal—an important

proposal with implications that extend well

beyond North America.

The ‘white spaces’ are non-allocated spectral

‘gaps’ that will appear in the 54 to 698 MHz

band once the U.S. digital television (DTV)

switchover is completed in February 2009.

These gaps will vary in center frequency and

bandwidth across the country. A 2006 U.S.

senate ruling instructed the FCC to determine

mechanisms to allow unlicensed access to the

white spaces spectrum, in the quest to “facilitate

the development of wireless broadband

Internet services.” Like the 700MHz spectrum,

this spectrum enjoys very large propagation and

coverage characteristics, and high penetration of

buildings and other structures.

One industry group—representing both

incumbent and potential new-entrants to the

wireless market—is advocating an entirely

new model for the U.S. white space deploy-

ment. The model is founded on the use of

self-organizing mesh networks. The nodes of

the proposed mesh networks are new

handsets called White Space Devices (WSDs).

Currently under development, the WSDs will

be founded on ‘listen-before-talk’ (LBT) tech-

nology—a system that detects the vacant

spectral gaps in real time, and then transmits

in the gaps accordingly. As a result, the

proposed self-organizing mesh networks are

claimed to be almost infrastructure-free and

‘organic’ in nature. Jörg Springer

Engineers (IEEE). It is developing a standard for

white spaces ‘wireless regional area networks’

(WRANs) founded on fixed point-to-multipoint

RF network models. Its number one criterion is

to ensure that incumbent wireless services

within the band suffer no interference. The IEEE

has elected to use fixed point-to-multipoint RF

network infrastructure. It claims to have chosen

this approach for strong technical reasons:

the model is proven; it provides tangible

controllable RF performance; and it presents

an RF environment where interference can be

carefully monitored and controlled, and

network performance/QoS optimized.

This points toward an essential truth: fixed RF

infrastructure provides the tools and asset

foundation for effective wireless business

models. These are: premium QoS, network

growth and expansion, and predictable

evolution paths for next-generation services.

The ‘white spaces’ spectral situation is not

unique to North America. Such non-contiguous

spectral ‘gaps’ are rich assets that exist in many

wireless markets around the world, and are

potentially ready to be tapped. Any practical

solution that taps into this resource and helps

support the progress of our wireless world is

important, and will have global ramifications.

Radio Frequency Systems completely applauds

initiatives—such as the WSD/mesh network and

WRAN proposals for white space exploitation

—that might lead to improved use of RF

spectrum. But it is vital that we adhere to the

most important rule of good spectrum manage-

ment: that any introduced change causes no

harm. RFS is, indeed, excited about the future of

spectral efficiency—a bright future where we

believe advanced fixed RF technology will play

an increasingly essential role.

Targeting broadband wireless connectivity of

50 to 100Mbps, the WSD advocates believe that

this mesh network model could potentially solve

remote and rural area connectivity problems and

fast-track broadband roll-out across the country.

Most importantly, the ‘self-organizing mesh

network’ model is being promoted as a highly

inexpensive wireless broadband solution that

can be quickly rolled out.

But others in the wireless industry have

concerns about the WSD proposal, most

particularly regarding the risks of interference

between the WSDs and existing DTV receivers.

They claim that the ‘there/not there’ nature of

the WSDs gap detection criteria is simplistic;

that the risk of misdetection carries with it

serious risks of interference with existing

free-to-air TV and emergency services. This

could be a shortfall of the proposed WSD/mesh

network model—the absence of conventional

fixed RF infrastructure may increase the system’s

susceptibility to a range of unpredictable

interference problems.

Some have suggested that there are strong

parallels between mesh networks and the

Internet, in that both have an essentially ‘organic’

nature. In reality, the Internet actually comprises a

tiered structure of highly managed and controlled

infrastructure: ISPs, telephone companies, cable

companies, satellite service providers and so on.

All represent real businesses, each with tangible

assets, and effective business models. By

contrast, the ‘self organizing mesh network’ is

bereft of such an infrastructure foundation. There

is negligible fixed RF network infrastructure,

which may present challenges in the areas of

network business model, quality and service.

Another model being considered for the white

spaces spectrum arena is one being developed

by the Institute of Electrical and Electronic

3Jörg Springer

Vice President Global Marketing andPublisher of STAY CONNECTED

Working out the ‘white spaces’

E D I T O R I A L

4 W H A T ’ S N E W

Radio Frequency Systems has developed the

world’s first dual-feed circularly polarized UHF

panel antenna series—the new RFS PCP panel

antenna suite. The new antenna has been

specially designed to support global circularly

polarized broadcast applications. It also meets

the exacting requirements of ‘multiple input,

multiple output’ (MIMO) applications technolo-

gy for wireless communications. RFS’s new PCP

panel antenna series offers unmatched RF

performance and efficiency, and simplifies

MIMO network rollout.

The PCP panel antenna comprises four horizon-

tally polarized and four vertically polarized

dipoles, and features dual-input (two 2.5kW

inputs) functionality—all in a compact slimline

package. “The PCP’s dual input allows a range

of variously polarized signals to be broadcast

from a single antenna,” said RFS Principal

Engineer Antenna Development, Charlie

Williams. “It can produce circularly polarized

signals, ‘mixed’ or elliptical signals, or

independent vertically and horizontally

polarized signals. This provides broadcasters

with never-before-seen levels of flexibility, and

the ability to broadcast more content from a

single antenna system.”

According to Williams, RFS’s new PCP panel

antenna is also ideal for data-intensive

MIMO-based broadcasting applications.

“MIMO based applications require multiple

antennas at both the source broadcast system

and the destination receiver,” he said. “The PCP

panel offers this multi-antenna functionality at

the source end, making it MIMO-ready for

digital television and mobile TV applications.”

The Optimizer series of broadband base

station antennas (BSAs) from Radio Frequency

Systems now includes a 32-degree horizontal

beamwidth variant. This narrow-beam BSA has

been specifically designed to provide tailored

‘in-fill’ coverage, and meet increasing capacity

needs within third-generation (3G) wireless

networks.

Delivering excellent performance across the

entire 1710-2170MHz band, the Optimizer

32-degree beamwidth BSA supports all major

‘high-band’ wireless services, including GSM

1800MHz, PCS 1900MHz, UMTS 2100MHz,

and AWS 1710/2100MHz services.

According to RFS North America Area Product

Manager for Base Station Antennas, Andrew

Stronski, the new 32-degree beamwidth Opti-

mizer antenna has been developed to provide

optimized coverage within geographically

constrained areas, and to avoid RF

interference at cell boundaries. “The new

32-degree beamwidth antenna delivers typically

greater than 18dB suppression of all upper

sidelobes across the antenna’s entire downtilt

range.” he said. “This unmatched suppression

prevents interference with other cell sites or

sectors, and minimizes RF energy losses, which can

result in dropped calls. The narrow-beamwidth

BSAs also feature a ‘front-to-back’ ratio typically

greater than 30dB to ensure the RF coverage is

focused only where it is needed. Furthermore, the

32-degree beamwidth is a good alternative for

high-capacity applications prevalent in densely

populated urban centers, which often require

narrow coverage areas with increased gain.”

The 32-degree Optimizer BSA is initially available

in two lengths (1.6m/5.2ft and 1.3m/4.4ft), in a

dual-polarized array configuration. In addition,

it features variable electrical downtilt (0 to 10

degrees), and a stable vertical beamwidth

across the band. Each of the 32-degree BSA

variants is available with a pre-fitted antenna

control units (ACU) for remote antenna tilt

control functionality. With remote antenna tilt

functionality an important factor in 3G network

optimization, pre-fitting the ACUs streamlines

installation and reduces the possibility of on-site

error. Furthermore, the RFS ACUs are fully

compatible with the antenna interface

standards group (AISG) version 2.0 communica-

tions protocol.

Optimizer BSA—now in 32-degree

The PCP’s dual input allows

a range of variously polarized

signals to be broadcast from

a single antenna.

New PCP panel: Dual-feed flexibility

Continuing its proud tradition of

transmission line innovation, Radio

Frequency Systems has developed a

new micro-sized foam dielectric

coaxial cable. While the 4.2mm

(1/6-inch) outer diameter cable,

known as MicroFlex, is similar to

braided and ‘conformable’ cable

dimensionally, its performance

represents a new milestone in the

evolution of RF cables.

"The conventional approach taken

with coaxial cables of such small

dimensions is to use a braided outer

with a solid dielectric," said Gerhard

Wunder, RFS Director of International

Business Development, Transmission

Lines. "CELLFLEX MicroFlex provides

an entirely new approach—it brings

all the benefits of the CELLFLEX

family to the micro-coaxial cable

sector. CELLFLEX MicroFlex features a

corrugated outer, coupled with a

foam dielectric. The inherently

low-loss foam dielectric ensures a

significant reduction in attenuation,

leading to improved gain and noise

performance throughout the entire

system; while the corrugated outer

provides added shielding and

structural advantages."

Courtesy of a perfluoroalkoxy (PFA)

foam dielectric—unique to RFS—MicroFlex is

available in a high-power as well as a standard

version. The enhanced power rating makes the

cable ideal for internal connections to power

splitters and dipoles within base station

antennas. The standard version of MicroFlex, is

ideal for use as a jumper cable for connections

between equipment backplanes, subcompo-

nents and as interconnect jumpers.

Due to its corrugated outer conductor,

MicroFlex has both excellent crush resistance,

and flexibility, making it ideal for use in tight

and crowded spaces. It is easy to terminate, and

with both standard and high-power versions

available, has applications throughout the

wireless industry.

5

RFS adds tilt to globalWiMAX solution

MicroFlex—the coax ‘all-rounder’

The all-in-one nature of the PCP panel antenna

delivers a multitude of operational and

installation advantages over competing

antenna configurations, and represents a

significant RF design achievement. “The PCP

saves tower space, minimizes tower loading

and helps overcome environmental and zoning

constraints,” said Williams. “RFS’s engineers

have overcome the RF challenges that arise

from co-locating two separate panel arrays

under the one radome. We have developed an

integrated antenna solution that boasts

optimized input isolation and pattern polariza-

tion discrimination, as well as first-class VSWR

[voltage standing wave ratio] performance.”

RFS’s new PCP panel antenna also features a high

power-handling capability (up to 2500 watts),

making it ideal for both built-up urban environ-

ments, and remote areas requiring extensive

coverage. Initially offered in 470 to 558MHz

bandwidth, the PCP panel presents a truly

versatile broadcast solution.

Radio Frequency Systems has launched the

latest addition to its series of ‘WiMAX-ready’

tower-top solutions—a truly global electrical-tilt

WiMAX antenna series. Unveiled at the Mobile

World Congress 2008 exhibition in Barcelona,

RFS’s new Optimizer APXVx56516 antenna

series is part of the company’s broad and

growing IEEE 802.16 WiMAX-compliant

solution set—a set that includes antennas,

fiber-to-the-tower top technologies, RF

conditioning, and in-building solutions.

Comprising both variable and remote electrical-

tilt versions, the new dual-polarized WiMAX

antenna series is available in two wideband

variants—2.3 to 2.7GHz (APXV256516-x) and

3.3 to 3.8GHz (APXV356516-x). As a result, the

new antenna series supports the widest range of

sub-bands currently allocated for WiMAX

applications across Europe, the Americas and the

Asia-Pacific region.

“The Optimizer APXV electrical-tilt WiMAX

antenna series is uniquely global, and an ideal

complement to RFS’s wideband W4A adaptive

antenna series for WiMAX beam-pattern

shaping applications,” said Arnaud Baron, RFS

Wireless Infrastructure Solutions Area Product

Manager.

“The new WiMAX electrical-tilt antennas

provide the premium RF performance for which

the RFS Optimizer family is renowned—infinite

beam tilt adjustment from zero to ten degrees,

upper side-lobe suppression of better than

18dB across the entire tilt range, and null fill of

the first lower null. Global reach is achieved

with just two models, dramatically cutting

inventory requirements and costs, and

improving deployment efficiencies.”

The RFS WiMAX remote-tilt antenna solution

(APXVx56516-RET) features a unique antenna

control unit (ACU) that is discretely built within

the antenna radome. The onboard ACU allows

precision WiMAX antenna beam tilt control

either locally (from the tower base), or remotely

from the network’s operations and

maintenance centre (OMC). Connectivity to the

antenna beam tilt-control system is achieved via

an AISG v2.0-compliant interface at the base of

the antenna.

while its small footprint and sleek design

minimizes environmental impact. Performance-

wise, it provides a continuous torque of

0.15NM and boasts an angular resolution of

better than 0.2 degrees. The new ACU also

features non-volatile on-board memory,

ensuring that all programming data is retained

in the event of power disconnections.

protocol conversions to be completed, quickly

and simply, from the base of the tower. Most

importantly, it provides network managers with

new freedom in determining exactly how and

when such protocol conversions occur.”

The ‘Optimizer Universal’ ACU is complemented

by a growing suite of RFS software tools that

facilitate a wide range of OEM protocol-to-AISG

conversions. AISG v1.1 to 2.0 conversions are

supported by RFS’s innovative Network Element

Manager (NEM) software—considered one of

the most intuitive and user-friendly software

interfaces for an antenna control and

monitoring solution set.

The ‘Optimizer Universal’ ACU’s light-

weight construction (less than half

a kilogram/only 16 ounces)

helps reduce tower loading,

The new ‘Optimizer Universal’ antenna control

unit (ACU) from Radio Frequency Systems is the

market’s only software-configurable ACU.

Launched at the Mobile World Congress exhibi-

tion in February 2008, the ‘Optimizer Universal’

permits communications across a range of open

and proprietary communications protocols.

These include the two latest revisions of the

3GPP-ratified Antenna Interface Standards

Group open communications standard

(AISG v2.0 and AISG v1.1), plus a growing

selection of OEM-proprietary protocols.

Field tests conducted by RFS in the closing

days of 2007 conclusively proved the power

and effectiveness of RFS’s site-configurable

‘Optimizer Universal’ ACU. The tests were

witnessed by representatives from a US Tier 1

carrier and a global wireless sector OEM. Both

applauded the RFS innovation and declared it

a major improvement in antenna control

technology, with significant opex saving

implications over the life of the network.

The ‘Optimizer Universal’ ACU is part of the

RFS Optimizer RT remote tower-top control

system—an end-to-end solution-set that allows

precise remote control and monitoring of

tower-top RF components either locally (from the

tower base), or remotely from the network’s

operations and maintenance center (OMC).

“The RFS ‘Optimizer Universal’ ACU represents

an enormous leap forward in tower-top

component future-proofing,” said David

Kiesling, RFS Global Product Manager Wireless

Infrastructure Solutions. “To-date, carriers have

been faced with only one option when

changing over antenna control and monitoring

protocol—to replace the actual tower-top ACU

hardware. Factored over an entire network, this

is labor-intensive, costly and demanding from a

network operations perspective.

“By contrast, the new ‘Optimizer Universal’

ACU is a pure software solution. It allows

New ‘Optimizer Universal’ ACU:Tested and proven

A true end-to-end solution, RFS Optimizer RT

remote tower-top control system comprises all

key antenna line elements—the ‘Optimizer

Universal’ ACU, the control network interface

(CNI), a selection of tower-mount amplifiers

(TMA), and a modem bias-tee. The solution set

also includes RFS’s innovative Network Element

Manager (NEM) software—considered to be

one of the most intuitive and user-friendly

software interfaces.

The suite frees the end-user from the inherent re-

strictions associated with proprietary control and

monitoring systems. This ensures the fastest and

most cost-efficient installations—both green-

field deployments and mature network retrofits.

W H A T ’ S N E W6

The RFS 19-inch rack format CNI-P incorporates

a power distribution unit (PDU), which

supports up to six TMAs and 12 ACUs

across three sectors. Individual ACU and

TMA units are linked in a ‘daisy-chain’ con-

figuration, with the CNI’s networks capable

of supporting up to a total of 18 antenna

line devices over a maximum cabling length

of 100 meters (330 feet). The CNI itself

provides three separate RS485 field output

ports (one per antenna sector). CNI

backhaul connectivity is achieved via either

point-of-protocol (PPP), SNMP or DHCP

protocols, with either fixed or dynamic IP

address management.

Optimizer RT for tower-top control

7W H A T ’ S N E W

Second-generation broadcast RF monitor

Radio Frequency Systems has developed a new

RF monitoring system—the MS Series 2.

Typically used for monitoring the RF status of

broadcast antenna and combiner systems, the

MS Series 2 supports simple network manage-

ment protocol (SNMP) communications, which

enables integration with a high-level network

management system (NMS).

At the heart of the revamped monitoring

system is a completely new operating platform.

According to RFS Broadcast Projects and

Systems Sales Engineer, Matt Betts, this makes

the MS Series 2 remarkably easy to configure.

“Using the eight-inch color touchscreen,

operators can easily program alarm thresholds

and calibrate full-scale deflection when the

transmitter is operating at full power. This sim-

plifies monitoring of forward and reflected

transmitter power,” Betts said. “An active,

real-time MIMIC display shows the U-Link—or

motorized—switch and multi-channel

combiner configurations. It can also be used to

indicate whether full- or half-power is being

delivered to the antenna.”

At the local level, alarms can be reset directly

from the touchscreen display. SNMP ‘traps’ can

be configured to alert the network operations

center (NOC) that an alarm condition is present.

If a major equipment fault is detected, action by

the NOC is triggered, protecting the sensitive

broadcast electronics from possible damage.

The status of the monitor system can also be

viewed remotely using a web browser. Alarms

can be reset via the web interface, and configu-

ration of important parameters such as VSWR

alarms is possible. A built-in security system

prevents unauthorized configuration changes.

Betts said that high-accuracy detectors measure

the RF power of multiple transmitters—up to 14

in the monitor’s standard configuration. “The

MS Series 2 handles up to 200 Modbus/RS485

devices, including the RF detectors and an array

of input/output devices. Other user-specified

Modbus modules can also be added as

required,” he said.

The RF monitoring system is typically integrated

within the RFS U-Link switch-frame, with the

display on the front panel of the frame.

Alternatively, it can be housed in a standard

19-inch rack.

ClearFill expands to FCC bandsRadio Frequency Systems has expanded its

breakthrough ClearFill suite of Wireless INdoor

Solutions (WINS) to encompass all major

frequency bands specified by the U.S. spectrum

regulator, the Federal Communications

Commission (FCC). All the band-specific active

elements of the ClearFill Air, ClearFill Space1

and ClearFill Space2 solution-sets—incorporat-

ing off-air repeaters, base transmitter station

(BTS) interface modules, plus RF-to-optical and

optical-to-RF conversion equipment—are now

market-ready for deployment across the U.S.

and the rest of the Americas.

The FCC-specified frequency bands now

supported include both the ‘Cellular’ and inte-

grated digital enhanced network (iDEN)/special-

ized mobile radio (SMR) 800MHz bands, the

personal communications services (PCS)

1900MHz band, and the advanced wireless

services (AWS) 1700MHz/2100MHz band.

The ClearFill suite comprises a modular mix of

passive and active technologies for harnessing

and distributing RF signals inside buildings and

tunnels. Offering unrivalled flexibility and cost-

effectiveness, ClearFill delivers tailored coverage

solutions for just about any environment—from

simple buildings to the most sophisticated

structure, such as airports, shopping centers

and metro stations.

The various elements of the modular suite form

three main system configurations:

· ClearFill Air—Basic indoor coverage for

small buildings or very short tunnels using

an off-air repeater and antenna assembly.

· ClearFill Line—A purely passive distribution

solution founded on an RF broadband radiating

cable or distributed antenna network, ideal

for small buildings and short tunnels.

· ClearFill Space—A truly hybrid solution for

midsize to large indoor complexes, or the

longest tunnels, comprising a ‘master unit’

and fiber-fed ‘remote units’ with RF

converters to drive the signal through the

otherwise passive RF distribution network.

The ClearFill components now available in

the FCC-specified bands include: the

OR-series off-air repeaters for harnessing the

signal from neighboring cell-sites; the L-MU

and L-RU series of Space1 master units and

fiber-fed remote units respectively; the

MU-POI series BTS interface modules; and the

FR-series of Space2 fiber-fed remote units.

he says. “Laying cable across mountain

ranges and by-passing lakes is quite tough.

Because of the geography of the region, some

operators deploy microwave exclusively

for long distance links, whereas, in other

parts of the U.S., fiber is sometimes

preferred.”

Microwave is also widely used for

access to West Coast mobile base

stations. For a mobile operator,

owning a microwave link is a cost-

effective alternative to renting

T1, (1.544Mbit/s) lines, which

have restrictive capacity in the

modern era of bandwidth-

hungry data services. Microwave-

link ownership provides a simple path for

capacity expansion and upgrades, and according

to Mackinney, is the first choice for many operators.

The landform and demand for improved

services from a technically advanced community

lend themselves to the widespread use of

wireless communications of all kinds. However,

while West Coast cities are reported to be

leading the country in the use of wireless

services, carriers on the West Coast of the U.S.

face major obstacles in their endeavors to roll out

wireless solutions. Complex planning and

zoning permits are prime examples.

Zoning approvalsPieter Stappers, RFS District Sales Manager, says

that the ‘not in my backyard’ mentality is alive

and well on the West Coast. It is particularly

strong in California, where well-informed and

well-resourced individuals and pressure groups

frequently use their influence to block proposed

installations.

“Visual impact is the primary

concern. ‘Zoning’ is critical

for the whole wireless

industry, especially in

California, which is

one of the most

regulated states in

the U.S.,” he says.

“Each installation requires

multiple approvals. The process is

further complicated by the number of regu-

latory bodies. The final decision can rest with any

one of a number of organizations—zoning

commissions, counties, coastal authorities and

the military all have the power to halt projects

or insist on changes.”

According to Stappers, the zoning authorities

face a difficult task if their membership does not

include an RF expert. “The RF solution providers

are sometimes called upon to ‘bend’ the laws of

physics,” he says, “and the authorities need the

patient support of the RF industry to find

workable solutions.”

While Californian agencies lead the charge on

zoning, the entire West Coast faces similar

constraints. From the forests in the north to the

streets of Las Vegas, environmental impact is a

major concern. “The lobby groups are vocal

and powerful,” he says. “Yet many of the

same people who are resisting the installation

of wireless infrastructure insist on

improved mobile coverage and

access to the latest services.”

For RFS, this conflicting set

of requirements adds

incentive to an existing

culture of innovation. Each

new design—of antenna

systems, or other form of

infrastructure—takes into

The West Coast of the U.S. exudes contrast and

diversity throughout—in its geography, climate,

and importantly, its population centers. From

Washington State in the north, to California in

the south; from the Pacific coast to the Rocky

Mountains, the region boasts forests, rugged

coastlines, deserts, and mountain ranges. The

climate varies widely through the region’s 15

degrees of latitude, displaying great extremes in

rainfall and temperature. Many West Coast

inhabitants live in the shadow of multiple

localized events—wildfires, floods, hurricane force

winds and earthquakes are always a possibility,

but can be managed, rather than feared.

Since the gold rush and boom times of the

mid-nineteenth century, a growing population

has spread throughout the entire West Coast

area. This has resulted in a mix of fast-moving

urban centers, mid-sized towns and remote

communities. Cities such as Los Angeles, San

Francisco, Seattle, San Diego and Las Vegas, all

bursting with their own unique character, add to

the sense of contrast throughout the region.

In the world of wireless communications, the

combination of natural and man-made

landscape presents challenge and opportunity of

the highest order. Each aspect of the natural

environment and demography impacts on

planning decisions and technology choices.

Speed of microwaveAccording to Radio Frequency Systems District

Sales Manager, David Mackinney, much of the

terrain found on the West Coast is difficult to

access, which makes the installation of

optical fiber arduous. Carriers find

microwave quicker and easier to install.

“Microwave radio is an ideal

backhaul solution in this setting,”

8

The geographic and demographic contrasts of the U.S.’s West Coast present a unique challenge to wireless communications providers. In a region known for fast take-up of new technology, demand for enhanced services is exceeded only by calls for low environmental-impact solutions.

West Coast USA:A kaleidoscope of contrast

C O V E R S T O R Y

agencies during times

of crisis. The Western

States Contracting Alliance

(WSCA), a cross-government

procurement cooperative,

coordinated the purchase

of improved communications

systems, ensuring compatible

technology throughout the region.

RFS has contributed to the newly estab-

lished shared communications system,

providing a range of microwave solutions to the

emergency service agencies and participating

OEMs. More use of microwave was one of a

number of measures aimed at improving the

reliability of communications systems during

wildfires. It was found that the combination of

minimizing combustible material at the

microwave sites, and reducing reliance on the

more exposed long-distance cables

decreased the risk of signal losses.

Interoperability across the agencies has also

improved markedly, to the point where

frequencies are commonly shared between

the groups. The upgraded communications

systems proved invaluable during the 2007

‘wildfire season’, assisting the emergency

services to better coordinate their operations.

Reports indicate that as well as aiding the

actual fire-fighting efforts, the improved com-

munications systems allowed for smoother

evacuations than in the disastrous fires of

2003.

Such challenges of nature, and

the diversity of climate,

landform and population

centers across the U.S.’s

West Coast region,

present the wireless com-

munications industry

with a unique working environment. The

competing requirements of reliability for

essential services, low visual impact and

demand for innovative services by a well-

informed population test carriers and

suppliers alike. In this vast land of contrasts,

RFS continues its key role in extending

wireless coverage and services to a communi-

cations-hungry population.

an enormous task. Southern California has a

reputation as one of the most fire-prone

regions of the world, and in 2007,

wildfires in San Diego caused much

destruction. According to Mackinney,

base station sites burned to the ground

and up to two percent of fiber and copper

cables in the affected region simply melted in the

heat. All major carriers in the region worked

quickly over the ensuing two weeks to repair and

replace damaged facilities.

RFS has contingencies in place to fast-track the

process of reconstruction. “The

attitude is ‘whatever it takes’ when it

comes to restoring wireless commu-

nications in an emergency,” he says.

“Key RF components such as trans-

mission line, antennas and filters

are reserved for such occasions,

and once the call goes out, all

available stock is dispatched

immediately.”

This approach is not confined to

activity after wildfires--communica-

tions facilities are at risk from a variety of

sudden natural events, which sometimes

occur in quick succession. Due to the infamous

San Andreas fault-line, much of the area is

prone to small tremors and earthquakes. While

communications components and

facilities are designed for robustness, in larger

incidents, cables can be completely destroyed

and wireless facilities can suffer damage or mis-

alignment. “Regardless of the circumstances,

RFS acts with speed and gives top priority to

restoring communications as quickly as

possible,” says Mackinney.

Experience during such events has led to a

concerted effort to improve communications

between the various emergency services

account the wishes of the community, and

balances minimal impact with high performance.

Unobtrusive performanceA case-in-point is RFS’s range of antenna system

cluster configurations. According to Stappers, it

incorporates antennas in various lengths from

0.7 to 2.0 meters (2.3 to 6.5 feet); optional

tower-mount amplifiers (TMA) with associated

jumpers and connectors all hidden from view;

and optional antenna control units (ACU) for the

remote antenna tilt system. “The resulting slim

antenna system satisfies visual impact criteria,

while achieving the premium functionality

and performance often required,” he says.

“Low-profile cluster antenna configurations

have the advantage of being quick to

install, plus the benefit of having

been assembled in clean,

factory environments.”

Complementing the

integrated cluster is

the RFS mechani-

cal mounting system for

rooftop sites—the Optimizer

Rooftop. This is an all-in-one solution

comprising base, mast, tri-sector antenna

cluster and RF cabling. The base has been

computer-designed to ensure premium stability,

even in winds of up to 250 kilometers per hour

(155 miles per hour). The Optimizer Rooftop’s

slender lines ensure that it blends easily with the

building architecture and

the surrounding environ-

ment—whether viewed

from the street or the

rooftop itself.

Aside from such mounting

structures, the visual impact

of wireless deployments is

further diminished by the use

of ‘masking’. Antennas are

disguised as trees, or matched

with existing structures to blend in

with the skyline. These develop-

ments have proven ideal in West Coast urban

environments where coverage needs to be

improved—but not at the expense of visual

amenity.

Emergency responseWhile the West Coast of the U.S. is subject to

tough climatic conditions, restoring communi-

cations in the aftermath of disturbances can be

9C O V E R S T O R Y

10

The journey ahead for Brazil DTV As Brazil’s transition to DTV forges ahead, local broadcastersand technology providers are meeting the country’s uniqueDTV deployment challenges head-on. Here, RFS is playing a crucial role.

B R O A D C A S T

TV Globo’s DTV/analog antenna sits atop the broadcaster’s

corporate headquarters in Alameda Santos, São Paulo.

broadcast specialist, Radio Frequency

Systems is playing a crucial role.

ISDB-T initiativeBrazil is the first country outside of Japan

to employ the ISDB-T-based system.

Brazil’s SBTD-T standard features an

MPEG-4 compression transport layer and an

H.264 coding scheme to achieve SDTV, HDTV

and mobile TV broadcasting functionality—all

under a single transmission standard.

According to RFS Brazil Broadcast Manager,

José Roberto Elias, the Japanese ISDB-T

standard was adapted to accommodate

Brazil’s specific broadcast requirements. “The

SBTD-T standard allows transmission of both

HDTV and SDTV to fixed receivers, while at the

same time, allowing the delivery of content

to handheld devices,” he says. “The MPEG-4

compression standard employed by SBTD-T

allows more data to be broadcast when

compared with the MPEG-2 standard. This

means only 6MHz of bandwidth is required to

transmit SDTV plus HDTV. This level of spectrum

efficiency is more easily achieved with MPEG-4

compression.”

The segmentation of the data packets within the

bands makes the SBTD-T standard ideal for

Brazil’s unique DTV broadcast objectives. SBTD-T’s

unique ‘packetization’ makes it easy for the

receivers to differentiate signal components—

fixed and handheld—(SDTV, HDTV and mobile

TV). This is a necessity for such ‘all-in-one’ trans-

mission standards.

The ability to deliver content to mobile devices

via incumbent broadcasters’ established

infrastructure was especially attractive to

existing broadcasters. “The portability of the

ISDB-T standard made it the clear choice, as the

foundation for SBTD-T,” says Elias. “The imple-

mentation of a single transmission standard for

terrestrial TV and mobile TV means that broad-

casters do not have to rely on third-parties to

deliver content to hand-held devices.”

Early stagesBrazil’s first free-to-air digital transmissions

went to air in São Paulo on 2 December, 2007.

Urban centers, Rio de Janeiro and Brasilia, as well

as regional Brazil are scheduled to come on line

before 2015.

Leading Brazilian broadcasters, such as TV

Globo, SBT (Sistema Brasileiro de Televisão or

Brazilian Television System), and Rede

home to a vast selection of locally-produced TV

content, much of which is exported to North

America and Europe.

The Brazilian broadcast sector has recently

embarked on yet another significant period of

transition—the switch from analog television to

digital television (DTV) broadcasting.

The digital decisionBrazil’s DTV journey commenced back in late-

2003 when the Brazilian government founded

the Sistema Brasileiro de Televisão Digital

(Brazilian Digital Television System (SBTVD))

committee. Comprising members from the

government, universities and communication

companies, the SBTVD committee was charged

with developing a government-compliant DTV

standard recommendation.

The Brazilian government stipulated that the

new DTV system was to satisfy several key per-

formance criteria. The DTV standard had to

accommodate the transmission of both high-

definition TV (HDTV) and standard-definition TV

(SDTV), as well as supporting interactive

functionality. Furthermore, the same DTV

standard was required to support broadcast

transmissions to handheld wireless devices and

motor vehicles.

The SBTVD committee conducted several compar-

ative tests of various DTV standards, including

Advanced Television Systems Committee (ATSC),

Digital Video Broadcasting (DVB) and Japan’s

Integrated Services Digital Broadcasting (ISDB-T).

In late-2005 the SBTVD committee recommended

deployment of an ISDB-based standard for the

transmission of HDTV, SDTV and mobile TV.

In June, 2006, Brazil’s President, Luis

Inácio Lula da Silva, announced that the

Japanese ISDB-T standard would be used as

the foundation for the national DTV trans-

mission standard—Sistema Brasileiro de

Televisão Digital-Terrestrial (SBTD-T).

Brazil's telecommunications regulator,

Anatel, was charged with developing a

frequency plan and defining technical and

economical solutions to fast-track the DTV

switchover.

With a transmission standard selected,

Brazilian broadcasters and technology

providers commenced a program to

establish world-class DTV broadcast infra-

structure ahead of the June 2016 scheduled

analog TV switch off. This program

continues today—here, leading digital

11

Since the first analog transmissions in 1950,

Brazilian television has evolved from what

was once an elitist indulgence, to a mass

communication and entertainment staple.

Brazil’s television set penetration is one of the

highest in the world, with TVs found in 95

percent of Brazilian homes. The immense pop-

ularity of TV in Brazil is matched only by that of

the Latin American prime time serials that

saturate its screens.

Over the past 50 years, Brazilian TV has experi-

enced significant growth. Local broadcasters

now number in the hundreds, delivering

locally-produced and foreign programs to an

audience of over 160 million viewers.

Originating in the urban centre of São Paulo,

Brazil’s analog broadcast network rapidly

expanded to include vast regional areas.

Throughout the 1960s, television spread

broadly across the Brazilian population with the

provision of military-subsidized TV sets, and the

establishment of a national microwave and

satellite broadcast network.

Brazil’s TV identity really began to take shape

in the 1970s when the country’s government

encouraged broadcasters to develop increased

quantities of Brazilian TV content and reduce

their reliance on imported programs. The legacy

of this scheme is still evident today, with Brazil

Bandeirantes de Televisão, have all established

DTV services in São Paulo, and are in the prelim-

inary stages of implementing DTV services in

Brazil’s other centers. Much of Brazil’s new—and

planned—DTV broadcast infrastructure

features the latest broadcast solutions from RFS.

As a global leader in RF technology, RFS has

been at the forefront of broadcast technology

development in Brazil, and has had a continuous

operating presence in the country for over 30

years. “The switch to digital is well underway in

Brazil with numerous greenfield installations

and system overlays being deployed in the past

year,” says Elias. “RFS is leading the way in this

regard. We are providing end-to-end broadcast

solutions, as well individual broadcast system

components, such as combiners, switch-frames

and antenna systems to Brazil’s most prominent

broadcasters.”

It is expected that before the 2016 DTV

switchover, up to 4000 new antennas will be

required by Brazilian broadcasters to make the

switch from analog to digital—This equates to

the installation of more than one antenna per day

over eight years—a staggering task. “There is a

culture among Brazilian broadcasters to own

their own broadcast infrastructure,” says Elias.

“This, coupled with the fact that 1600 broadcast

licenses have been issued, means that Brazil’s

broadcast landscape is going to become very

congested. In the near future, broadcast

infrastructure sharing will be a necessity.”

Deploying digitalAnatel has stipulated that broadcasters must

transmit signals in both analog and digital

formats until the 2016 analog switch off. This is

presenting Brazil’s broadcasters with a number

of design and deployment challenges. More

particularly, keeping analog broadcasts on line

while deploying new DTV services, and keeping

new deployment costs to a minimum.

Digital switchovers require the ‘unpicking’ of

the transmission network on a site-by-site

basis, to determine the most economic and

practical way to realize the DTV service

across the network. “With much of Brazil’s

existing broadcast infrastructure over 20

years old, it can be a challenge to incorporate

new DTV equipment into existing installa-

tions,” says Elias. “Here, RFS is working with

Brazilian broadcasters, assisting them in

devising solutions for the upgrade or

replacement of existing broadcast systems.

This may comprise antenna/feeder re-use,

modification, or replacement with an entirely

new antenna/feeder assembly—or a mix of

any of these options.

“Our lightweight and compact DTV broadcast

solutions are easily incorporated into existing

installations, making system upgrades

straightforward. Alternatively, RFS is providing

complete end-to-end broadcast solutions to

those broadcasters opting to replace their

existing analog antennas with new

DTV/analog broadcast combination systems

that support infrastructure sharing.”

While not yet overly prevalent, such broadcast

infrastructure sharing is beginning to gain

popularity in some areas of Brazil, particularly

those that are limited in geographically-suitable

transmission sites. “We expect broadcast infra-

structure sharing to be more common in

regions such as Brasilia, where there is really

only a few optimum transmission sites,” says

Elias. “Instances of sharing should increase as

smaller low-power transmission sites are estab-

lished in regional areas and for coverage ‘fill in’

applications in urban areas.”

Due to the large number of broadcasters and

transmission sites, careful planning is required to

avoid interference. “Brazil’s new DTV environ-

ment dictates sophisticated broadcast systems,

boasting a balanced combination of precise

pattern-tailoring, transmission quality and

power,” says Elias. “These design and deploy-

ment challenges are intensified, as many of

Brazil’s broadcasters are privately owned

and, as a result, require more cost-efficient

broadcast solutions.”

Fast-tracking the futureThere are exciting times ahead in the Brazilian

broadcast sector. An influx of investment into

DTV will see Brazilian TV viewers provided with

increased and optimized coverage, as well as a

range of new television services, including inter-

active options. The Brazilian Government is

attempting to fast-track the transition from

analog to digital by giving broadcasters a line of

credit to purchase DTV transmitters and other

necessary equipment.

While its regional knowledge provides

immediate benefits to Brazil, RFS’s global

broadcast experience in such digital switchovers

ensures RFS Brazil will play a significant role in

the country’s DTV rollout. “We are seeing

exciting opportunities emerging for Brazilian

broadcasters,” Elias concludes. “These

prospects will be accompanied by a whole

range of broadcast and RF deployment

challenges. We’re looking forward to continu-

ing our work with Brazil’s broadcasters to

deliver premium DTV services to the country’s

viewers.”

12

A Rede Globo analog antenna in Curitiba city,

Paraná State, awaits DTV overlay.

An SBT DTV broadcast antenna is hoisted into

position in São Paulo.

B R O A D C A S T

Copper has long been regarded as the

material of choice for use in RF communica-

tions cables—and for good reason. It is an

excellent electrical conductor and has the

strength, malleability and durability required

for both manufacturing and deployment. Yet

copper is not the only metal that is suitable

for electrical applications.

Silver is a better conductor and gold is not

far behind. In fact, gold-plating is widely

used in electronics, not only because of its

conductive properties, but also because it is

corrosion-resistant. Silver-plating is the prime

choice where conductivity is the key consid-

eration. It is also superior to gold-plating in

terms of intermodulation performance.

The fourth metal of note is aluminum. Of the

group, it is the least conductive, but does have

other advantages. In selecting an appropriate

material for RF cables and transmission line con-

ductors, the choice is clearly between these four

metals—others lack the necessary conductivity.

As materials for cables, gold and silver can be

ruled out on cost alone. While aluminum is

more than adequate, copper is electrically

better, although its higher density results in

heavier cables. Ultimately, the choice is based

on electrical and mechanical performance,

cost and availability.

Performance and valueIn periods when the cost and availability of the

two metals are comparable, it is generally the

technical parameters that dictate when and

where each material is used. More recently,

however, commercial considerations have

emerged as a major issue.

The cost of raw copper rose dramatically after

2004, with reports indicating that the price

trebled in three years. Over the same period,

stocks fell. The cost of aluminum also

increased but not as severely. In this environ-

ment, interest in the use of aluminum in RF

cables inevitably grew.

A case-in-point is the comparison of two varieties

of Radio Frequency Systems’ CELLFLEX foam dielec-

tric coaxial cable. This cable is available with either

copper (regular CELLFLEX) or aluminum (CELLFLEX

Lite) corrugated outer conductors. Since both

materials have excellent mechanical strength, the

traditional approach would have been to select

according to weight and electrical performance.

At mobile base stations, for example, lightweight

cable can be hauled up the tower more easily and

is also cheaper to transport to site. On the other

hand, in cases where the system link budget is

exceptionally demanding, premium attenuation

feeders, with a copper-based corrugated outer

would be preferred.

This situation has changed, however, as copper

has become more expensive and less readily

available. Nowadays, aluminum-based cables

have clear advantages, and are fast becoming

the preferred option.

More innovationsIn earlier times, there were concerns regarding

aluminum being used in conjunction with unsuit-

able materials. Shared by the wider population

after poor experiences with consumer goods,

these concerns largely focused on aluminum's

material flow and corrosion performance.

These early barriers to its use were overcome by

innovative design practices and improved

material selection.

In the realm of cable, RFS applied its R&D

experience to address the issues surrounding the

introduction of a new material, pioneering the

use of corrugated aluminum outer conductors.

Continuing the trend, purpose-designed acces-

sories have been developed as well. Key

amongst these, are universal connectors—such

as the OMNI FIT series—that are compatible

with both aluminum and copper.

While copper has long been regarded as the

mainstay material for use as an electrical

conductor in communications cables, other

options have always been available. Chief

among, these, due to its combination of

performance and value, is aluminum. Clearly,

this alternative material will play an

increasingly significant role in RF transmis-

sion in the years ahead.

13

Aluminum: The light alternative The soaring price of copper has led to a re-evaluation of material selection in RF cables.Aluminum is emerging as a strong contender.

T R A N S M I S S I O N L I N E

escalating vertical real-estate costs and

a shortage of new sites all add to overlay

deployment delays and costs. Equally, the

spectral landscape is now congested and

tight in the mature wireless markets. Great

care needs to be taken today to avoid interfer-

ence from spurious emissions and high-power

interfering signals. These can respectively lead

to an increase in the noise floor level of the

receiver, and ‘blocking’ interference that

degrades receiver sensitivity.

Secondly, today’s 3G and emerging 3.5G/4G

wireless technologies are far more

demanding from a network planning and RF

optimization perspective. If you consider

‘Universal Mobile Telecommunications

Service’ (UMTS) for example, its ‘breathing

cell’ nature contrasts sharply with the static

cell characteristics of its GSM predecessor. As

a result, there is now great need for dynamic

cell footprint and antenna tilt management in

UMTS. This elevated level of network

planning and optimization ‘sensitivity’ is

typical of next-generation wireless technolo-

gies. In many respects, it is the price paid for

the improved performance and spectral effi-

ciency of new-age platforms.

Thirdly the move from voice- to data-centric

platforms is creating a noticeable change in

the specific nature of the mobile traffic being

supported. Voice is statistically predictable in

terms of throughput demand. High-speed

a wireless pipe for ones and zeros—can sound

dull. Nothing could be further from the truth.

The wireless data services of the near future

are the fruits of a wireless world renaissance

that will change the way we view the mobile

phone forever. Carriers around the world are

recognizing this industry ‘sea change’, and

view wireless data as a key opportunity to

carve out long-term market differentiators.

The new overlayIn essence, an overlay of any sort comes

down to two core elements: a new service

and/or a new spectrum block. There is

nothing new or remarkable about this—it is

the way network overlays have always been.

Yet those embarking on today’s overlay face

four key challenges: physical and spectral

congestion, complexity of service planning

and management, the data nature of these

services, and the absence of standard deploy-

ment models.

When carriers embarked on the earliest

‘Advanced Mobile Phone Service’ (AMPS) to

‘Digital-AMPs’ (D-AMPS) or AMPS to ‘Global

System for Mobile Communications’ (GSM)

overlays, there were far fewer sites in place

and, on the whole, carriers tended to own

their own towers. As a result, site acquisition

and deployment was comparatively simple.

This stands in stark contrast to today, where

prohibitive zoning/planning requirements,

Network overlays are not a new phenomenon

in the global wireless sector. They have long

been the ‘pulse beat’ of the wireless sector’s

fast-paced evolution and, as such, have been

with us since the earliest transition from first-

generation (1G) analog networks to 2G

digital.

Yet the overlay scenario of 2008—and the

wireless climate in which it will occur—is

vastly different to that of years gone by. This

is most particularly the case in the more

mature wireless markets around the world. To

understand this, it is important to understand

the key drivers behind today’s overlay of next-

generation services.

The first key driver is spectral efficiency. In

most parts of the world, 3G data revenue is

‘propping up’ falling voice revenues so there

is increasing pressure to cut voice opex.

Spectral efficiency is a key element in this

opex reduction. The next generation of

wireless services exhibits a spectral efficiency

that provides voice services at a lower

marginal cost than conventional 2G.

Amortized over millions of subscribers this

margin becomes quite significant at the

bottom line. Given that many carriers are

competing on the price of a minute, such

opex savings are crucial.

Second is market differentiation. Next-gener-

ation wireless data services are central to this.

At face value, the title of 'data services’—

W I R E L E S S I N F R A S T R U C T U R E S O L U T I O N S

The focus is overlaysOverlaying new wireless services in today’s spectrally congested wireless landscape requires an intimate knowledge of a range of wireless technologies, coupled with advanced planning and deployment strategies.

14

Power and intelligence at the tower-topThe RFS overlay innovation program focuses

on all key RF elements along the RF chain.

These include RF filtering, base-station

antennas, feeder systems, duplexers and

diplexers, tower-mount amplifiers, plus

emerging ‘smart’ RF technologies such as

remote radio head (RRH), multiple

input/multiple output (MIMO) and beam-

forming antennas.

In many respects, the prospective migration of

‘intelligence’ to the tower-top may address

many of the core challenges inherent in

increasingly complex overlays. Ultimately, this

migration may see the base station itself atop

the tower. This, in turn, will result in significant

power demands from the tower-top

—a domain that is largely passive today.

Consider a tower-top 80W amplifier

operating at 25 percent efficiency. This would

demand a tower-top power supply of around

1kW, but the more power assigned to the

device, the faster the ‘mean time between

failure’ (MTBF) falls.

The challenge for the future, then, will be to

technically address the relocation of powered

devices from the tightly controlled and envi-

ronmentally predictable equipment room, to

the uncertainties of a tower-top.

network architecture, or the network

equipment to be deployed. Broadcast mobile

television currently exhibits similar deploy-

ment strategy diversity and uncertainty.

Added to this complex mix is the attraction to

the wireless data world—most notably via the

WiMAX route—of a wide range of non-tradi-

tional players in the wireless sector. While an

established wireless sector player can

dampen the uncertainties and challenges of a

new-generation overlay by interleaving its

evolution path with that of its existing

networks, a greenfield entrant has no access

to such a luxury. Such new players are

therefore fully exposed to the commercial

and time-to-market impacts that stem from

the lack of standardization.

The challenge, then, is to reclaim the eco–

nomies of scale and time-to-market enjoyed

in earlier years, while still realizing the

essential RF system customization required

in new-age platforms. RFS is developing

unique overlay solutions that address this

contemporary challenge, by targeting a

unique balance: provision of highly tailored

solutions, while retaining core ‘standardiza-

tion’ and commonality attributes. Striking

this fine balance is largely centered on the

provision of advanced levels of RF solution

innovation—in short, RFS is developing

entirely new approaches to well-established

overlay challenges.

wireless data, by contrast, creates unpre-

dictable peak demands. These peaks can lead

to base transmitter (BTS) saturation, if not

adequately accommodated in the overlay.

New age—no standardLastly—and perhaps most challenging of

all—is the absence of standard deployment

models in new-age wireless overlays. This is

dramatically different to previous generation

overlays. When the ‘GSM1800-over-

GSM900’ overlay rolled out across the world,

it was largely deployed in the same spectrum

and according to the same deployment

models worldwide. This brought huge

economies of scale and time-to-market

advantages for all players.

By contrast, quizzing five contemporary

carriers as to their deployment model for

‘UMTS900-over-GSM900’ will almost certainly

elicit five different deployment ‘recipe’

responses. Each may have different channel

allocations, different network requirements,

different philosophies on feeder sharing, and

so on.

In terms of lack of global standardization,

‘Worldwide Interoperability for Microwave

Access’ (WiMAX) is perhaps the most

extreme of the new generation of wireless

platforms. Aside from the obvious global

diversity in WiMAX spectrum allocation,

there is precious little standardization in

15

reductions in the performance of another.

Consequently, each application must be

considered carefully to ensure the optimum

filter performance, depending on which of

these four parameters is most important.

Insertion loss

Insertion loss is the amount of power unavoidably

absorbed by the filter, and generally refers to the

loss incurred by the desired signal passed

through to the output after processing. In the

passband, filters are matched to the impedance

of the system (typically 50 ohms) and so loss is

relatively low; however, the more poles in the filter,

the greater the overall insertion loss. Practically,

the insertion loss should be limited to 0.5dB,

which corresponds to 10 percent of the power.

Attenuation

Attenuation measures the effectiveness of

the filter in absorbing—filtering out—the

unwanted frequencies. High attenuation of

undesired frequencies is more easily achieved

using a higher number of resonant cavities,

where 11 is a typical upper limit—although this

is generally at the expense of insertion loss. The

measure of attenuation between named ports in

a filter is known as the isolation.

Selectivity

Selectivity is a measure of how effectively the

signal is attenuated across a range of frequencies.

High-selectivity filters exhibit sharp curves and

a precise position above each resonator,

thereby subtly adjusting its resonant frequency.

Some coaxial filters incorporate cross-

couplers, which are a physical link between

two non-adjacent resonators designed to

‘trap’ specific frequencies. This significantly

increases rejection of the nominated

frequencies, which are usually just outside

the desired pass band, thereby generating a

notch in transmission (Figure 2).

The overall measure of cavity performance (related

to the ratio between energy stored in a cavity and

energy dissipated or reflected, relative to the oscil-

lation frequency) is known as the quality factor (Q).

This is improved as the filter dimensions are

increased to a limit point and/or highly conductive

materials, such as silver, are used.

Filter design considerationsThe four main performance characteristics of a

filter are insertion loss, attenuation, bandwidth

and selectivity. These are highly interdependent

and determined by factors such as the number

and dimensions of cavities/poles, cross-coupling

and filter aperture (related to the internal

dimensions of the filter, which determine the

‘width’ of the path from pole to the next). In

many cases, improvement in one is offset by

Filters are passive RF devices used to pass one or

more frequencies, while rejecting one or more

other frequencies. Their deployment is often an

essential component of RF infrastructure. Filters

are especially important where base transmitter

stations are co-located, in which case they are

used to both protect receivers from out-of-band

signals and attenuate spurious transmitter

emissions.

The most common form of RF filter is a coaxial

filter, which basically comprises an air- (or

ceramic-) filled enclosure, inside which stands a

series of resonant cavities (or poles) that sense RF

energy only at certain frequencies (Figure 1). The

‘sensed energy’ is passed from one resonator to

another, while the unwanted energy is rejected,

being dissipated or reflected. As a result, only the

desired frequencies are passed through the filter.

The resonant frequency of a cavity is dependent

on its length, which is typically less than a quarter

of the wavelength. Fine frequency tuning is

achieved using tuning rods that can be wound to

RF filter fundamentals

Figure 1: Basic filter components and terminology Figure 2: Typical filter response curve

16 R F T E C H N O L O G Y 1 0 1

17

Figure 3: Examples of filter responses Figure 4: Diplexers and Duplexers combine RF signals

Band rejectBand pass

High passLow pass

pass

reject

passpass

rejectreject

pass

reject

FrequencyFrequency

Frequency Frequency

steep ‘skirts’ on the filter response curve, and are

essential for narrow guard bands. High-order

filters (high number of poles) with narrow

apertures generally result in a high-selectivity filter.

Cross-couplings dramatically improve selectivity by

introducing notches outside the pass band. For

this reason, the number of poles can be reduced in

filters with cross couplings to yield a better combi-

nation of selectivity and filter size. The impact on

insertion loss is a trade-off between that added by

the high rejection close to the band edge, and that

gained due to a lower number of poles.

Bandwidth

Bandwidth refers to the frequency range passed

by the filter. This is determined by the filter

aperture, which is effectively the width of the

path traversed by the RF energy from one pole to

the next. The wider the aperture—where each

pole ‘sees’ more of the next, allowing increased

coupling—the wider the filter bandwidth. Higher

bandwidths also positively impact the insertion

loss. Sophisticated filters can achieve one or more

pass and/or reject bandwidths.

Types of filter include (Figure 3):

· Bandpass—The signal is passed in a band

between specified low and high frequency

cutoff points.

· Low-pass—The signal is passed at

frequencies below a certain cutoff point.

· High-pass—The signal is passed at

frequencies above a certain cutoff point.

· Band reject—The signal is rejected (or

notched out) in a band between specified

low and high frequency cutoff points.

Another factor to be considered in filter design

is physical size, which is determined by both the

number and dimension of the resonant cavities.

Diplexers and duplexersThe integration of two (or three) filters to

combine RF signals results in a diplexer (triplexer)

or duplexer (Figure 4). Fundamentally, duplexers

and diplexers are identical: a common point

couples—or decouples, depending on direction

—the signal passing through each filter. Each has

three ports, where one is shared between the two

combined signals and the other two are ‘single

band’ only.

The main factors to be considered in duplexers

and diplexers are the port-to-port frequency sep-

aration (guard band), the port-to-port isolation,

frequency bandwidths, and the insertion loss.

Duplexers are used to combine transmitter and

receiver signals into the one antenna and feeder

system. As a result, the frequency separation

between ports is generally narrow, depending on

the separation of uplink and downlink frequency

bands. Isolation between the transmitter and

receiver ports is of prime importance, and is

typically required to be 90-95dB. This is essential

to allow the system to transmit as much power as

possible, while maintaining the sensitivity of the

receive path. The closer the frequency bands, the

more complex the filter needs to be in order to

achieve the required isolation.

Diplexers are used to combine two or more

bands into a single antenna and/or feeder

system—for example GSM900 and UMTS2100.

As a result, both the bandwidth and frequency

separation between ports is often significantly

wider in a diplexer, and the isolation need not be

as stringent (typically 50–60dB). However,

diplexers can also be required to combine bands

that are very close together—such as GSM900

and UMTS900—in which case their design is

extremely complex.

Bandpass filters are typically used for

duplexers and diplexers in applications where

the frequency offsets are relatively wide. The

inherent advantage of this design is that the

rejection of unwanted signals occurs for all

frequencies outside the intended pass bands.

Where the frequency offsets are closer

(between about 0.5 and 4.5MHz), band reject

cavities can be used instead. This design offers

the benefits of high isolation and low insertion

loss, but is less effective at attenuating

frequencies other than the specified transmit

and receive frequencies (or specified

channels).

Vipnet upgrades to Optimizer Rooftop

together with RFS, conducted a mock installation

of the system. According to Paolo Morandi, RFS

Managing Director Italia Srl, this caught the

attention of Vipnet attendees. "They were very

impressed with the speed and ease of the

installation—we had a complete, integrated

antenna system set-up in a matter of hours," he

said.

Featuring a 'tilt-into-place' mounting unit, the

Optimizer Rooftop houses three RFS Optimizer

family premium-performance sector antennas,

each providing a full +/-20-degrees of azimuth

adjustment—a vital feature in modern network

management—with the option of on-board RF

conditioning modules. "Being a complete,

integrated antenna solution, the Optimizer

Rooftop solves many of the installation

problems of non-integrated rooftop systems,"

said Morandi.

Leveraging the power of today’s PC and the

Internet, the 5th Edition of the Radio Frequency

Systems Global Catalog is making the jump to

digital. DVD-based and with real-time connectiv-

ity to RFS’s live product information data base,

RFS’s new myCatalog delivers product and

solution data with speed—from the smallest

Croatia's mobile network innovation leader,

Vipnet, has installed its first Optimizer Rooftop

'all-in-one' antenna solution from Radio

Frequency Systems. The Optimizer Rooftop unit

installed on the Zagreb rooftop site features a

slim-line design offering minimal street-level

visual impact in urban areas. Vipnet also

achieved a dramatic cut in antenna system

installation time, with the Optimizer Rooftop

installed and ready-to-go in less than a day.

The RFS Optimizer Rooftop antenna-mount

system is designed with a focus on improved

visual integration with urban environments

—particularly from street-level. This combination

of low-impact aesthetics, and quick and compact

installation, offers operators new options in

their approach to siting requirements.

RFS distributor, Piletic, first raised the potential

benefits of Optimizer Rooftop with Vipnet, and

18 I N T O U C H

Viewed from street-level,

the Optimizer Rooftop from

RFS presents a visually

superior profile to a tradi-

tional tri-sector antenna

mounting. Inset: An 'at-roof'

view of the Zagreb

Optimizer Rooftop unit—

installed in less than a day.

Internet, and provides new ways to contact,

interact and provide feedback to RFS represen-

tatives.

The DVD format also introduces 'myProject'

functionality, which allows tailored groups of

products and solutions to be built. Quickly

developed via ‘drag-and-drop’ functionality,

myProject bundles can be built into tailored

application solutions to meet the user’s

immediate needs. The myProject bundles can be

saved to file, edited, and even printed as unique

stand-alone documents, bringing new levels of

flexibility and customization to the traditional

notion of a catalog search.

"The ability to easily create a customized

product solution from the full RFS infrastructure

catalog is essential for doing business as we

move forward," said Springer. "The new format

enables anyone to find the solution they require,

to assemble this information in one place, and to

work with RFS to achieve their wireless infra-

structure outcomes quickly and easily."

The push to service heavily built urban environ-

ments, coupled with the scarcity of premium

antenna sites, presents operators with a

twin-edged dilemma. The quick installation and

compact, 'all-in-one' solution offered by the

Optimizer Rooftop, offers new flexibility to

operators engaged in such urban site

negotiations and acquisition.

RFS myCatalog makes the jump to digitalconnector to entire broadcast solutions.

"Turning hundreds of pages to find information

is a thing of the past. The RFS myCatalog DVD

creates an environment worlds-apart from a

simple collection of data sheets," said Jörg

Springer, RFS Vice-President, Global

Marketing and Communications. "The

wireless sector is highly dynamic, and so

too are the solutions and products

offered by RFS. To realize the maximum

benefit from the wealth of information

available across the RFS catalog, we have

developed a digital medium that reflects

this dynamism, both in terms of search

tools and data updates."

myCatalog sorts the RFS wireless infrastructure

solution set according to nine distinct application

hierarchies. Users can navigate across these

hierarchies to specific product sets, or use

powerful search functionality to cut directly to

the product information required. The software

enables real-time product data updates via the

I N T O U C H 19

Carrying Vipnet’s GSM and UMTS/HDSPA

services, the Zagreb Optimizer Rooftop is

designed to support future upgrades to these

services, such as MIMO, and Long Term Evolution

(LTE) requirements. With further Optimizer

Rooftop installations on the way, Vipnet will

continue to benefit from this key addition to the

modern mobile network operator's toolbox.

CELLFLEX Lite is testament to the cable’s reliabil-

ity and performance. “We were extremely

impressed with the performance of the

CELLFLEX Lite transmission line,” he said.

“CELLFLEX Lite was tested over a period of six

months in Mobilink’s operating wireless

network, and easily complied with our electrical

performance criteria. In fact,

the electrical performance of

CELLFLEX Lite has proven

superior to some copper trans-

mission solutions.”

Mobilink is the first Pakistani wireless carrier to

deploy CELLFLEX Lite. “Mobilink has always

incorporated the latest technologies into its

wireless networks,” said Massoud. “With ap-

proximately 27 million subscribers, it is crucial that

we utilize the highest quality RF components to

provide our customers with the premium service

they have become accustomed to.”

FCC allows two-foot dish Rule changes in the 11GHz band by the US

Federal Communications Commission (FCC) in

late-2007 are expected to lead to an influx in

microwave backhaul services and more

efficient use of spectrum. Inspired by

ongoing improvements in microwave

antenna technology, changes to Part 101

Category B (Cat B) specifications will now

permit use of two-foot antennas in the

11GHz band, without compromising on inter-

ference protection.

“Radio Frequency Systems welcomes this FCC

initiative to permit use of smaller antennas,”

said Asad Zoberi, RFS Area Product Manager

Microwave Antenna Systems. “The economic

advantages will provide an incentive to

carriers to make greater use of the 11GHz

band for broadband data and microwave

backhaul services.”

Previously, Zoberi explained, the gain, beam

width and side lobe requirements of Cat B were

difficult to achieve with an antenna smaller than

three-feet. The revised specifications relax the re-

quirement for beam width and gain, along with

side lobe specifications close to the main beam,

while maintaining stringency of the balance of

the radiation pattern. This permits use of two-

foot antennas, leading to lower overall system

cost.

“According to the new Cat B ruling, the RFS

CompactLine two-foot antenna (SB2-107)

easily meets—and even exceeds—the specifica-

tions,” Zoberi said. “In addition, it offers advan-

tages in gain, weight, tower wind-loading and

overall depth compared with other two-foot

dishes on the market. This is now the best two-

foot solution for 11GHz microwave link

networks where Cat B is permitted.”

The RFS CompactLine SB2-107 microwave antenna is

now the best two-foot solution for 11GHz microwave

link networks where Cat B is permitted.

Radio Frequency Systems has provided

Pakistan’s leading wireless carrier, Mobilink,

with a unique transmission line solution in

support of the carrier’s ongoing nationwide

wireless network expansion. RFS’s CELLFLEX

Lite—an aluminum-based RF transmission line

solution—has been selected by Mobilink for use

at thousands of base station

sites across Pakistan’s urban

and rural regions. Before

making its selection,

Mobilink tested the RFS CELLFLEX Lite transmission

line at both urban and regional base stations

across its existing countrywide network.

Subjected to the rigors of everyday wireless

network operation, CELLFLEX Lite passed with

flying colors, displaying first-class attenuation,

return-loss and intermodulation performance.

According to Mobilink Senior Production

Manager, Omar Massoud, Mobilink’s approval of

Mobilink chooses CELLFLEX Lite

R A D I O F R E Q U E N C Y S Y S T E M S

T h e C l e a r C h o i c e ®

Please visit us at www.rfsworld.com