KavoshCom Asia R&DApril 9, 2007 1 WiMax RF chip Design Ali
Fotowat, PhD. Managing Director KavoshCom Asia R&D
[email protected] April 9, 2007 Slide 2 KavoshCom Asia R&D
April 9, 2007 What is WiMax Is 3G dead? No way. Basic WiMax RF
Specs RF System level analysis Multiband front-end, filter, Tx
design Quadrature errors Quadrature calibration Remaining
Subcarrier Errors Conclusions Outline Slide 3 KavoshCom Asia
R&D April 9, 2007 Issues Slide 4 KavoshCom Asia R&D April
9, 2007 Issues Slide 5 KavoshCom Asia R&D April 9, 2007 Issues
Slide 6 KavoshCom Asia R&D April 9, 2007 Wireless Technologies
(source: Worldwide Interoperability for Microwave Access Forum)
Slide 7 KavoshCom Asia R&D April 9, 2007 Wireless Standards
Mobility vs. User/Link Bit rate Mbps Slide 8 KavoshCom Asia R&D
April 9, 2007 WIMAX stands for Worldwide Interoperability for
Microwave Access WiMAX refers to broadband wireless networks that
are based on the IEEE 802.16 standard, which ensures compatibility
and interoperability between broadband wireless access equipment
WiMAX, which will have a range of up to 31 miles, is primarily
aimed at making broadband network access widely available without
the expense of stringing wires (as in cable-access broadband) or
the distance limitations of Digital Subscriber Line. What is WiMax?
Slide 9 KavoshCom Asia R&D April 9, 2007 802.16a Uses the
licensed frequencies from 2 to 11 GHz Supports Mesh network 802.16b
Increase spectrum to 5 and 6 GHz Provides QoS( for real time voice
and video service) 802.16c Represents a 10 to 66GHz 802.16d
Improvement and fixes for 802.16a 802.16e Addresses Mobile needs
Enable high-speed signal handoffs necessary for communications with
users moving at vehicular speeds IEEE 802.16 Specifications Slide
10 KavoshCom Asia R&D April 9, 2007 Issues Slide 11 KavoshCom
Asia R&D April 9, 2007 Issues Slide 12 KavoshCom Asia R&D
April 9, 2007 Point to Point BACKHAUL INTERNET BACKBONE Telco Core
Network or Private (Fiber) Network Non Line of Sight Point to
Multi- point FRACTIONAL E1/T1 for SMALL BUSINESS 802.11 E1/T1+
LEVEL SERVICE ENTERPRISE 802.16 Backhaul for Business Slide 13
KavoshCom Asia R&D April 9, 2007 INTERNET BACKBONE Telco Core
Network or Private (Fiber) Network Non Line of Sight Point to
Multi- point OUTDOOR CPE INDOOR CPE 802.11 Point to Point BACKHAUL
802.11 & 802.16 802.16 Consumer Last Mile Slide 14 KavoshCom
Asia R&D April 9, 2007 INTERNETBACKBONE Telco Core Network or
Private (Fiber) Network Non Line of Sight Point to Multi-point
802.16e 802.16e SEEKS BEST CONNECTION Laptop Connected Through
802.16e 2 to 3 Kilometers Away Line of Sight BACKHAUL 802.16 PC
Card 802.16e Nomadic / Portable Slide 15 KavoshCom Asia R&D
April 9, 2007 Slide 16 Issues Slide 17 KavoshCom Asia R&D April
9, 2007 Slide 18 Slide 19 Adaptive Modulation Slide 20 KavoshCom
Asia R&D April 9, 2007 Slide 21 Slide 22 Issues Slide 23
KavoshCom Asia R&D April 9, 2007 Slide 24 Slide 25 Slide 26
Slide 27 Tolerance to Multipath and Self- Interference Scalable
Channel Bandwidth Orthogonal Uplink Multiple Access Support for
Spectrally-Efficient TDD Frequency Selective Scheduling Fractional
Frequency Reuse Fine Quality of Service (QoS) Advanced Antenna
Technology Key Advantages of Mobile WiMax to 3G Slide 28 KavoshCom
Asia R&D April 9, 2007 What is WiMax Is 3G dead? No way! Basic
WiMax RF Specs RF System level analysis Multiband front-end,
filter, Tx design Quadrature errors Quadrature calibration
Remaining Subcarrier Errors Conclusions Outline Slide 29 KavoshCom
Asia R&D April 9, 2007 Issues Slide 30 KavoshCom Asia R&D
April 9, 2007 Issues Slide 31 KavoshCom Asia R&D April 9, 2007
Issues Slide 32 KavoshCom Asia R&D April 9, 2007 Issues Slide
33 KavoshCom Asia R&D April 9, 2007 Slide 34 The shared channel
concept Slide 35 KavoshCom Asia R&D April 9, 2007 Key ideas in
HSDPA The HSDPA concept is based on the following features: Shared
channel transmission Higher-order modulation Short transmission
time interval (TTI) Fast link adaptation Fast scheduling Fast
hybrid automatic-repeat-request (ARQ). Slide 36 KavoshCom Asia
R&D April 9, 2007 Reduced latency Short TTI (Transmission time
interval) Channel codes from the shared code resource are
dynamically allocated every 2 ms or 500 times per second. A short
TTI reduces roundtrip time and improves the tracking of channel
variationsa feature that is exploited by link adaptation and
channel- dependent scheduling. Slide 37 KavoshCom Asia R&D
April 9, 2007 Code sharing for shared channel Shared channel
transmission HS-DSCH is based on shared-channel transmission, which
means that some channel codes and the transmission power in a cell
are seen as a common resource that is dynamically shared between
users in the time and code domains. The shared code resource onto
which the HS-DSCH is mapped consists of up to 15 codes. The
spreading factor (SF) is fixed at 16. Slide 38 KavoshCom Asia
R&D April 9, 2007 Issues Slide 39 KavoshCom Asia R&D April
9, 2007 Increase average speed by serving channels that can be best
served!! Slide 40 KavoshCom Asia R&D April 9, 2007 Issues Slide
41 KavoshCom Asia R&D April 9, 2007 Issues QPSK, 16QAM Slide 42
KavoshCom Asia R&D April 9, 2007 Issues Slide 43 KavoshCom Asia
R&D April 9, 2007 Hybrid Automatic Repeat Request Slide 44
KavoshCom Asia R&D April 9, 2007 Issues Slide 45 KavoshCom Asia
R&D April 9, 2007 HSDPA Mutli-User Diversity Efficient
scheduler High data rate Low data rate Slide 46 KavoshCom Asia
R&D April 9, 2007 Issues Slide 47 KavoshCom Asia R&D April
9, 2007 What is WiMax Is 3G dead? No way! Basic WiMax RF Specs RF
System level analysis Multiband front-end, filter, Tx design
Quadrature errors Quadrature calibration Remaining Subcarrier
Errors Conclusions Outline Slide 48 KavoshCom Asia R&D April 9,
2007 Transmitter test set-up Slide 49 KavoshCom Asia R&D April
9, 2007 Transmitter requirements (IEEE 802.16-2004 8.3.10, 8.5.2)
8.3.10.1 Transmit power level control 8.3.10.1.1 Transmit spectral
flatness 8.3.10.1.2 Transmit constellation error 8.5.2 Transmit
spectral mask ACPR, maximum output power, spurious and harmonics
are also important Slide 50 KavoshCom Asia R&D April 9, 2007
Transmitter Spectral Flatness Spectral linesSpectral flatness
Spectral lines from -50 to -1 and +1 to +50 +/--2 dB from the
measured energy averaged over all active tones Spectral lines from
-100 to -1 and +1 to +100 +2dB/--4dB from the measured energy
averaged over all active tones Adjacent subcarriers+/--0.1dB Slide
51 KavoshCom Asia R&D April 9, 2007 Burst typeRelative
constellation error (dB) BPSK-1/2-13.0 QPSK-1/2-16.0 QPSK-3/4-18.5
16QAM-1/2-21.5 16QAM-3/4-25.0 64QAM-2/3-28.5 64QAM-3/4-31.0
Transmitter Constellation Error Slide 52 KavoshCom Asia R&D
April 9, 2007 Receiver test set-up Slide 53 KavoshCom Asia R&D
April 9, 2007 Receiver requirements are defined in IEEE 802.16-2004
section 8.3.11 8.3.11.1 Receiver sensitivity 8.3.11.2 Receiver
adjacent and alternate channel rejection 8.3.11.3 Receiver maximum
input signal 8.3.11.4Receiver maximum tolerable signal
8.3.11.5Receiver image rejection Slide 54 KavoshCom Asia R&D
April 9, 2007 Modulation type and coding rateBandwidth
64QAM16QAMQPSKBPSK 3/42/33/41/23/41/2 -75.7 -72.7 -69.8 -68.1 -65.0
24.4 -77.4 -74.4 -71.3 -69.8 -66.7 22.7 -81.9 -78.9 -78.8 -74.3
-71.2 18.2 -83.7 -80.7 -77.6 -76.1 -73.0 16.4 -88.9 -85.9 -82.8
-81.3 -78.2 11.2 -90.7 -87.7 -84.6 -83.1 -80.3 9.4 -93.7 -90.7
-87.6 -86.1 -83.0 6.4 1.75MHz 3.5MHz 7.0MHz 10.0MHz 20.0MHz Rx SNR
(dB) Receiver Sensitivity (dBm) for 10e-6 BER Slide 55 KavoshCom
Asia R&D April 9, 2007 Slide 56 What is WiMax Is 3G dead? No
way! Basic WiMax RF Specs RF System level analysis Multiband
front-end, filter, Tx design Quadrature errors Quadrature
calibration Remaining Subcarrier Errors Conclusions Outline Slide
57 KavoshCom Asia R&D April 9, 2007 Almost all of the
implementations use Direct Conversion method Direct Conversion pros
and cons: Advantages: 1.High level of integration 2.Low power
consumption Disadvantages: 1.DC offset problem 2.Higher flicker
noise 3.Poor quadrature matching Examples of Implementation Trials
Slide 58 KavoshCom Asia R&D April 9, 2007 For WLAN / WiMAX [B.
Farahani-05] Direct Conv Architecture Slide 59 KavoshCom Asia
R&D April 9, 2007 Frequency Synthesizer Specifications [B.
Farahani-05] 1.The phase noise requirement for PLL : 110dBc/Hz
@1MHz offset frequency 2.The settling time should be better than:
5s Direct Conv Architecture Slide 60 KavoshCom Asia R&D April
9, 2007 Block Requirements for Direct Conversion WiMAX Receiver [B.
Farahani-05] Slide 61 KavoshCom Asia R&D April 9, 2007 Block
Requirements for Direct Conversion WiMAX Receiver [B. Farahani-05]
Slide 62 KavoshCom Asia R&D April 9, 2007 Different signal
levels in Zero-IF receiver for WiMAX system [B. Farahani-05] Slide
63 KavoshCom Asia R&D April 9, 2007 What is WiMax Is 3G dead?
No way! Basic WiMax RF Specs RF System level analysis Multiband
front-end, filter, Tx design Quadrature errors Quadrature
calibration Remaining Subcarrier Errors Conclusions Outline Slide
64 KavoshCom Asia R&D April 9, 2007 Good idea to support both
WiMax and WLAN WiMAX needs are more stringent than WLAN: 1.Tx EVM
requirement is smaller for WiMAX 2.Because of Higher number of
subcarriers in WiMAX OFDM, Phase noise of the VCO should be smaller
for WiMAX which is on the order of 1 at arbitrary channel centers
3.I/Q sideband rejection requirement is more stringent than WLAN
which is of the order of 35dB. 4.To cover different BW in WiMAX,
programmable analog channel selection filters are required Slide 65
KavoshCom Asia R&D April 9, 2007 Multi-band RF front-end for 4G
WiMAX and WLAN applications [C.Garuda-06] 1.Direct Conversion
Receiver 2.Multi band including: 2.3-2.9 GHz, 3.3-3.7 GHz, 4.9-5.9
GHz 3.Two stage & programmable LNA instead of wideband LNA
4.The gain of 30-32 dB approximately constant for all bands
5.Utilizes Gilbert cell as a mixer 6.No report about synthesizer
and filters 7.In 1.8v IBM 0.18m CMOS process. Slide 66 KavoshCom
Asia R&D April 9, 2007 Two stage wide-band programmable LNA
Slide 67 KavoshCom Asia R&D April 9, 2007 Performance summary
Slide 68 KavoshCom Asia R&D April 9, 2007 Dual-band 4.9-5.95
GHz, 2.3-2.5 GHz, 0.18m CMOS Transceiver for 802.11a/b/g and
802.16d/e(WiBro) [I.Vassiliou, et.al, Broadcom-06] 1.Direct
Conversion double band transceiver is fabricated in a 0.18m 1P6M
CMOS 2.Fractional-N synthesizer achieves 0.6(0.7) integrated phase
error at 5GHz (2.4GHz) 3.Digital calibration eliminates I/Q
mismatch and carrier leakage 4.Programmable BW filters are used
5.Achieves EVM of -35dB in both transmit and receive paths
6.Achieves sideband suppression better than 45 dB & LO leakage
lower than -30dBc Slide 69 KavoshCom Asia R&D April 9, 2007
System Architecture uses TDD Slide 70 KavoshCom Asia R&D April
9, 2007 GM-C filter and its OTA enable continuous tuning either
2-15 MHz or 10-25MHz Slide 71 KavoshCom Asia R&D April 9, 2007
Programmable RF amplifier Slide 72 KavoshCom Asia R&D April 9,
2007 Rx EVM vs. input power for different bands Slide 73 KavoshCom
Asia R&D April 9, 2007 Measured performance summary Slide 74
KavoshCom Asia R&D April 9, 2007 5 GHz Dual-Mode WiMAX/WLAN
Direct Conversion Receiver [Y. Zhou, Instit. for Infocom Res-06]
1.Direct Conversion architecture 2.The dual-mode receiver is
fabricated in a 0.25m IBM BiCMOS6HP SiGe process 3.The frequency
synthesizer uses VCO running at half the RF frequency to help
reduce dc offset due to LO feedthrough 4.DC offset calibration is
performed on chip 5.The receiver employs GM-C base-band filter with
tunable cut-off frequency of either 5 or 10 MHz 6.The chip adopts a
3 wire serial bus interface to control all the functions 7.The chip
consumes 360mW from 3V power supply 8.Two mode double gain LNA is
used Slide 75 KavoshCom Asia R&D April 9, 2007 VCO with Auto
Calibration Circuit 1.Frequency fine tuning is achieved by
hyper-abrupt varactor 2.An auto calibration circuit is implemented
to select the appropriate band based on process variations Slide 76
KavoshCom Asia R&D April 9, 2007 Performance Summary Slide 77
KavoshCom Asia R&D April 9, 2007 Old article but explains the
integration problems A 2.4GHz Direct Conversion Transmitter for
Wimax Applications, C. Masse, Analog Devices Slide 78 KavoshCom
Asia R&D April 9, 2007 The I & Q analog baseband Signal
Generation Dual 14-bit DAC IQ modulator.direct up-conversion at the
RF frequency remove the alias at multiples of the sampling
frequency Low-pass Filters external fractional-N synthesizer LO (a
continuous signal with minimal Phase error) VGA with about 50dB of
gain control range. amplify or attenuate the composite RF signal
out of the modulator Precise output power control is achieved. RMS
power detector Slide 79 KavoshCom Asia R&D April 9, 2007 A
direct up-conversion architecture is attractive because: 1.Wimax
OFDM has no active sub-carrier at the origin, direct up- conversion
produces less mixing product spurs 2.Requires fewer filters which
is important when dealing with such wideband signals 3.The lower
number of parts helps minimize the current consumption. Slide 80
KavoshCom Asia R&D April 9, 2007 Performance Summary WiMax OFDM
modulation used here is a10MHz, 64QAM, 256-OFDM signal Slide 81
KavoshCom Asia R&D April 9, 2007 Slide 82 A CMOS transmitter
front-end with digital power control for WiMAX 802.16e applications
Y.H. Liu, H.C. Chen Slide 83 KavoshCom Asia R&D April 9, 2007
VGA First Stage of VGA: The gain control is realized with a current
steering structure Second Stage of VGA: The primary coil of the
on-chip transformer serves as the load inductor for a
differential-to-single-ended conversion Totally: 16 gain steps are
achieved Slide 84 KavoshCom Asia R&D April 9, 2007 What is
WiMax Is 3G dead? No way! Basic WiMax RF Specs RF System level
analysis Multiband front-end, filter, Tx design Quadrature errors
Quadrature calibration Remaining Subcarrier Errors Conclusions
Outline Slide 85 KavoshCom Asia R&D April 9, 2007 Complexities
in Quadrature signal generation for OFDM Transmitters and Receivers
What is Quadrature Modulation? First-Order Error Sources Individual
Effects of error sources Proposed New Calibration Procedure Slides
85-107 in this section based on Dr. Earl McCunes presentation Slide
86 KavoshCom Asia R&D April 9, 2007 Quadrature Modulator
Converting the quadrature modulation equation as a block diagram
gives the familiar form Slide 87 KavoshCom Asia R&D April 9,
2007 Realistic QM Model There are nine different first-order error
terms Slide 88 KavoshCom Asia R&D April 9, 2007 Realistic QM
Math Gain mismatch & Quadrature error Carrier leakages Data
leakages DC offsets Slide 89 KavoshCom Asia R&D April 9, 2007
Ideal Error Values Slide 90 KavoshCom Asia R&D April 9, 2007
Individual Error Analyses Modulation offsets Carrier Offsets
Modulation gain errors Carrier magnitude errors LO quadrature error
Modulator output compression Slide 91 KavoshCom Asia R&D April
9, 2007 Standard - Use SSB Case A simple, constant- envelope signal
(LSB is shown) Slide 92 KavoshCom Asia R&D April 9, 2007
Modulation (I,Q) Offsets Cause carrier leakage AM also results
Slide 93 KavoshCom Asia R&D April 9, 2007 Carrier Offsets No
effect on RF spectrum data leakage present amplitude variations on
output signal Slide 94 KavoshCom Asia R&D April 9, 2007
Modulation Gain Errors Causes image sideband AM at double the data
frequency Slide 95 KavoshCom Asia R&D April 9, 2007 Carrier
Magnitude Errors Carrier magnitude mismatch - looks identical to IQ
gain mismatch Slide 96 KavoshCom Asia R&D April 9, 2007 LO
Quadrature Error Causes image sideband AM is phase shifted from
gain-mismatch cases Slide 97 KavoshCom Asia R&D April 9, 2007
Output Compression P1dB effect on QM output adds intermodulation
sidebands gain mismatch casedata leakage case Slide 98 KavoshCom
Asia R&D April 9, 2007 Proposed CAL Procedure Minimize
interactivity among adjustments Based on simple SSB signal Five
steps (in order!): null data leakage null carrier leakage zero
quadrature error match path gains set signal level (for signals
with AM) Slide 99 KavoshCom Asia R&D April 9, 2007
Error-Combination Case data leakageRF signal Slide 100 KavoshCom
Asia R&D April 9, 2007 1. Ideal Modulator Drive Begin with
ideal modulator SSB drive signals Slide 101 KavoshCom Asia R&D
April 9, 2007 2. Null Data Leakage Zero the carrier offset terms O
C and O S data leakageRF signal Slide 102 KavoshCom Asia R&D
April 9, 2007 3. Null Carrier Leakage Adjust data offsets tradeoff
until carrier is nulled RF signal Slide 103 KavoshCom Asia R&D
April 9, 2007 4. Minimize Image Sideband Adjust quadrature error
image sideband minimizes at e = 0 may need 0.1 dB resolution RF
signal Slide 104 KavoshCom Asia R&D April 9, 2007 5. Match Path
Gains Adjust one data-gain term (choose A I, for example) null the
image sideband compression distortion also disappears RF signal
Slide 105 KavoshCom Asia R&D April 9, 2007 6. Set Overall Gain
Apply I(t) and Q(t) for an envelope-varying signal Turn down gains
A I and A Q together to drop sidebands effects a backoff from the
P1dB of the summer Slide 106 KavoshCom Asia R&D April 9, 2007
Limited-Access Bounds Ex. : quad error limitation (no access to
quadrature error) If full access to all error terms is not
available, then the achievable performance will be limited. 1
degree2 degrees Slide 107 KavoshCom Asia R&D April 9, 2007
Conclusions Quadrature modulation is a rectangular (Cartesian)
method of implementing signals Real Quadrature-Modulators are not
as simple as the textbooks (or databooks!) claim Quadrature
modulators can be tamed if all ports are available to the design
engineer Output Noise Figure is a major problem Linear modulations
tend to require large output (and input) backoffs All error terms
are, in general, functions of temperature! Slide 108 KavoshCom Asia
R&D April 9, 2007 What is WiMax Is 3G dead? No way! Basic WiMax
RF Specs RF System level analysis Multiband front-end, filter, Tx
design Quadrature errors Quadrature calibration Remaining
Subcarrier Errors Conclusions Outline Slide 109 KavoshCom Asia
R&D April 9, 2007 How much spur rejection is needed? For 45 dB
rejection, the gain matching should be better than 0.1 dB and the
phase matching better than 0.5 degree. Some manufacturers require
better than 55 dB for individual blocks! Slide 110 KavoshCom Asia
R&D April 9, 2007 Strong and weak duo A St cos(w St t) + A We
cos (w We t) A two tone signal in time domain. Slide 111 KavoshCom
Asia R&D April 9, 2007 A quadrature transmitter overall block
diagram Slide 112 KavoshCom Asia R&D April 9, 2007 Transmitter
features 1. Allow offset adjustment blocks at the inputs 2.A
programmable low pass filter corner frequency for all WiMax needs
3.Baseband gain with G adjustment (1 dB range in 0.1 dB resolution)
4.Control on the local oscillator phase (3 degree range with 0.1
degree control) 5.A very linear transmit mixer 6.A very linear
combiner 7.A programmable attenuator (20 dB range in 1 dB steps)
8.An integrated power level detector Slide 113 KavoshCom Asia
R&D April 9, 2007 Strong and weak duo is not a duo! f Strong 3
rd Harmonic Weak 3 rd Harmonic Undesired sideband Desired sideband
LO feed- through A typical shape of spectrum out of a quadrature
transmitter Slide 114 KavoshCom Asia R&D April 9, 2007 LO feed
through minimization process Use a 4 MHz baseband tone. Reduce the
input level so that the upper side band is more than 60 dB down or
into the noise level. The detector gives a 4 MHz LO feed-through,
and a 8 MHz upper side band. Use a low frequency bandpass filter to
detect the LO feed-through Adjust offset controls till lo
feed-through is minimized (2 dimensional search) f 4 MHz LO Feed-
through Slide 115 KavoshCom Asia R&D April 9, 2007 The
Side-band minimization process f 4 MHz Minimized LO feed- through
Undesired sideband Desired sideband Change the input frequency to 2
MHz In crease the input level. The LSB and USB will both increase.
The detector detects a 4MHz USB, a 8 MHz USB 3 rd harmonic. The 4
MHz LSB 3 rd harmonic falls on the undesired signal! Adjust G and
to minimize the USB. The rejection is limited by the 3 rd harmonic
levels which is set by the transmit mixer Slide 116 KavoshCom Asia
R&D April 9, 2007 What is WiMax Is 3G dead? No way! Basic WiMax
RF Specs RF System level analysis Multiband front-end, filter, Tx
design Quadrature errors Quadrature calibration Remaining
Subcarrier Errors Conclusions Outline Slide 117 KavoshCom Asia
R&D April 9, 2007 Will this calibration work across the band?
In single carrier systems single frequency interference and even
non-flat noise spectrum can be tolerated. In OFDM systems S/N has
to be fixed across the band Optimum G and do not stay the same vs.
frequency! What are the sources of the error vs. frequency? Slide
118 KavoshCom Asia R&D April 9, 2007 Edge of the band matching
in filters In a 1 st order filter 0.5% mismatch in components
results in 1.14 degree phase error at the edge of the band. In a 5
th order filter assuming random component values the expected phase
error will be 3.6 degrees at the edge of the band. R I C C+ C R+ R
Q I out Q out Slide 119 KavoshCom Asia R&D April 9, 2007 Filter
gain response Filter phase response System gain mismatch System
phase mismatch OFDM base-band spectrum Slide 120 KavoshCom Asia
R&D April 9, 2007 Broadband gain mismatch compensated by G but
residual gain error still at the band edge! Broadband phase
mismatch compensated by control with LLL, but residual phase error
still at the band edge! Slide 121 KavoshCom Asia R&D April 9,
2007 The solution is using base-band filter loop back techniques
and saving frequency dependent calibration values in the DSP Slide
122 KavoshCom Asia R&D April 9, 2007 What is WiMax Is 3G dead?
No way! Basic WiMax RF Specs RF System level analysis Multiband
front-end, filter, Tx design Quadrature errors Quadrature
calibration Remaining Subcarrier Errors Conclusions Outline Slide
123 KavoshCom Asia R&D April 9, 2007 123 WiMax is the best the
telecom technology offers, but 3G is in hot pursuit! The testing
methodology to separate the RF and DSP designers is very critical.
Direct Conv. with new VCO/synthesizer techniques is the way to go.
The Quadrature calibrations issues are the key to success. What did
we learn?
