Understanding Cable and Antenna Analysis[1]

8/6/2019 Understanding Cable and Antenna Analysis[1]

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Understanding Cable & Antenna Analysis

AGENDA

Introduction Common Problems FDR vs TDR Propagation Velocity Return Loss/VSWR Cable Loss

Distance to Fault (DTF) Test Examples Interpretation Sitemaster Family Summary


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Introduction

Cable and Antenna system plays a crucialrole of the overall performance of a BaseStation system.

Degradations and failures in the antennasystem may causepoor voice quality or dropped calls.

result in loss of revenue. Problematic base stations can be replaced Cable and antenna systems not so easy to

replace.

Field technicians troubleshoot the cableand antenna system and ensure theoverall health of the system

Field technicians today rely on portablecable and antenna analyzers to analyze,troubleshoot, characterize, and maintainthe system.


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Common RF & Microwave Problems

Installation problemsPoor grounding

Excessive bendsCrimping, Crushing and

Deforming

Routine MaintenanceDamaged/Dented Ground Shield

Kinks in the cableBroken center conductor

WeatherExcessive Moisture like snow,

rainSea waterCorrosion

Mis-installationPoor center pin contactLow quality connectors

Poor weather proofingLoose connectors

WeatherWater ingress

Corroded connectorsExtreme temperatures plane

landing/cruising

Mis-installationShipping damage

Out of Specification

Routine MaintenanceStorm damage

Extreme temperatures

Cables Connectors Antennas


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Reflection

ImpedanceMismatch

Insertion Loss

System performance problems are typically seen in

one of two ways:Excessive Reflections More common

Numerous causes

Excessive Insertion Loss

Less common

Typically due to water in cable

Common RF & Microwave Problems


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Return Loss/Reflection Coefficient

Return Loss = - 20Log (reflection coefficient)

Signal PowerFrom Source = Pi

Impedance

Not Matched,Not 50 Ohms

Reflected Poweris Proportional to

Impedance Mismatch

Reflection Coefficient = = Pr / Pi

Pi

Pr

Expressed in Voltage Terms, = Er / Ei


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Standing Waves, SWR

Signal Voltage

From Source = Ei

DUT Input

ImpedanceNot Matched,Not 50 Ohms

LowFrequency

ReflectedSignal Voltage = Er

MiddleFrequency

High

Frequency

The ratio of maximum to minimum isVSWR.


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Mismatch Equations

V max V minVSWR = V max / V min = (1 + ) / (1 - )

Reflection Coefficient = = Er / Ei =VSWR -1

VSWR +1

Return Loss = RL = - 20Log ()

Return Loss = -20LogVSWR -1

VSWR +1


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Return Loss Display

Displays ratio of Reflected Power to Reference power in dB. Easier to compare small and large signals on a Logarithmic scale.

Scale is usually 0 to 60 dB

0 represents short

60 represents close to perfect match


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VSWR Display

VSWR displays the match of the system linearly. Measures the ratio of voltage peaks and valleys.

The greater this number is, the worse the match is.

A perfect or ideal match in VSWR terms would be 1:1


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VSWR Vs Return Loss Plot

The two graphs illustrate the relationship between VSWR and Return Loss.26 dB RL 1.1 VSWR

1.0

1.5

2.0

2.5

3.0

1700 1750 1800 1850 1900 1950 2000 2050 2100 2150 2200

Limit : 1.42

M1 M2M3

VSWRAntennaVSWR

Model: MT8212E Serial #: 01007099Date: 09/03/2010 Time: 03:01:16Std: --- Channel: N/AResolution: 259 FlexCAL:ON(COAX) CW: OFF

VS

WR

Frequency (1700.0 - 2200.0 MHz)

M1: 1.439 @ 1844.161 MHz M2: 1.419 @ 2081.387 MHz M3: 1.104 @ 1913.504 MHz

-60

-50

-40

-30

-20

-10

0

1700 1750 1800 1850 1900 1950 2000 2050 2100 2150 2200

Limit : -15.0

M1 M2M3

Return LossAntenna1


dB

Frequency (1700.0 - 2200.0 MHz)

M1: -15.01 dB @ 1844.161 MHz M2: -15.27 dB @ 2081.387 MHz M3: -25.98 dB @ 1913.504 MHz


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Cable Loss

Measures the energy absorbed, or lost, by the transmission line in dB/meter

or dB/ft. Different transmission lines have different losses, and the loss is frequency

and distance specific.

The higher the frequency or longer the distance, the greater the loss.


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Distance-To-Fault

Reveals the precise fault location of components in the transmission line

system. Helps to identify specific problems in the system

connector transitionsJumperskinks in the cable or moisture intrusion.

Passing DTF Plot Failing DTF Plot


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Distance-To-Fault

Maximum distance range & fault resolution is dependent upon frequency range

and number of data points.DTF Aid shows how the parameters are related.Horizontal range is increased by reducing frequency span or increasing numberof data points.

Fault resolution is inversely proportional to frequency rangeFault resolution improved by widening frequency span.


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Air Dielectric

Constant (er)

Vc

r

=

c= 3 x 108 m/sec

Propagation Velocity


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Fault Resolution and Display Resolution

Fault resolution is the system's ability to separate two closely spaced

discontinuities. If the fault resolution is 10 feet and there are two faults 5 feetapart, the instrument will not be able to show both faults unless FaultResolution is improved by widening the frequency span.

Fault Resolution (m) = 1.5 x 108 x vp /F


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Reference Plane

The reference plane defined for vector

measurements is the point at whichcalibration standards are applied.


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Low Cost, Phase Stable Cables

Phase stable Cables reach difficult locationswithout loss of accuracy.

Open/Short/Load Calibration must

be performed at the cables end.


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Precision Calibration Components

Standard N :> 35 dB

Precision N :> 42 dB

Precision 7/16:> 45 dB

Like any analyser, the quality of thecalibration components determines accuracy.

Terminations


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DC Pulse versus Frequency Sweep

Sources

SpectralDensity

f1 f2

FDR

TDR

Less than 2% of

TDR source energyis in the RF bands

FDR

FDR Versus TDR

TDR


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M1M2

Del M1-M2: .00 dB, .0 MHz

-35

-30

-25

-20

-15

-10

-5

800 810 820 830 840 850 860 870 880 890 900

Return Loss800 - 900 MHz (cal on)

dB

MHz

M1: -26.94 dB @ 857.4 MHz M2: -26.94 dB @ 857.4 MHz

M1 M2

Del M1-M2: 1.75 dB, 61.63 Feet

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

50 100

Distance To Fault0 - 150 Feet (cal on)

ReturnLoss(dB)

Feet

M1: -22.38 dB @ 46.51 Feet M2: -20.63 dB @ 108.14 Feet

-35

-30

-25

-20

-15

-10

-5

800 810 820 830 840 850 860 870 880 890 900

Return Loss800 - 900 MHz (cal on)

dB

MHz

M1 M2

Del M1-M2: 7.07 dB, 61.63 Feet

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

50 100

Distance To Fault0 - 150 Feet (cal on)

R

eturnLoss(dB)

Feet

M1: -27.33 dB @ 46.51 Feet M2: -20.26 dB @ 108.14 Feet

Frequency Domain Reflectometry

BEFORE AFTER


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Baseline The System

Record/Store DTF and Return Loss Data

M1 M2

-55

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

50 100

Distance to Fault - baseline0 - 140 feet (frequency = 800 - 1200 MHz)

ReturnLoss(dB)

Feet

M1: -36.97 dB @ 30.38 feet M2: -12.54 dB @ 112.86 feet

M1 M2

-55

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

800 850 900 950 1000 1050 1100 1150 1200

Return Loss - baseline800 - 1200 MHz (cal on)

dB

MHz

M1: -21.01 dB @ 806.2 MHz M2: -21.01 dB @ 902.3 MHz

Test Examples


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Loose Connector

Connector with pin gap problem

M1 M2

-55

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

50 100

Distance to Fault0 - 140 feet (frequency = 800 - 1200 MHz)

ReturnLoss

(dB)

Feet

M1: -26.70 dB @ 30.38 feet M2: -12.56 dB @ 112.86 feet

M1 M2

-55

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

800 850 900 950 1000 1050 1100 1150 1200

Return Loss - with pin gap800 - 1200 MHz (cal on)

dB

MHz

M1: -22.62 dB @ 806.2 MHz M2: -18.71 dB @ 902.3 MHz

baseline data

problem?

Negligible Change Here

FDR finds connector problems before water

intrusion destroys the cable.

Test Examples


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M1 M2

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

800 850 900 950 1000 1050 1100 1150 1200

Return Loss - with dent800 - 1200 MHz (cal on)

dB

MHz

M1: -17.20 dB @ 806.2 MHz M2: -17.86 dB @ 902.3 MHz

M1 M2

-55

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

50 100


ReturnLoss(dB)

Feet

M1: -24.77 dB @ 14.1 feet M2: -36.91 dB @ 30.38 feet

Cable Defect, Dent

Antenna System with dent in cable

baseline data

problem?

Negligible Change Here

Test Examples


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M1 M2

-55

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

50 100


ReturnLoss(dB)

Feet

M1: -37.83 dB @ 30.38 feet M2: -11.30 dB @ 112.86 feet

M1 M2

-55

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

800 850 900 950 1000 1050 1100 1150 1200

Return Loss - water in antenna800 - 1200 MHz (cal on)

dB

MHz

M1: -20.92 dB @ 806.2 MHz M2: -17.46 dB @ 902.3 MHz

Water in Antenna

Water can be hard to find in some antennas

Slight Changes Here

No Changes Here

Test Examples

W t i A t


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M1 M2

-55

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

50 100

Distance to Fault0 - 140 feet (frquency = 806 - 901 MHz)

ReturnLoss(dB)

Feet

M1: -25.35 dB @ 14.1 feet M2: -23.78 dB @ 115.03 feet

M1 M2

Del M1-M2: .99 dB, 95.0 MHz

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

810 820 830 840 850 860 870 880 890 900

Return Loss - water in antenna806 - 901 MHz (cal on)

dB

MHz

M1: -19.33 dB @ 806.0 MHz M2: -18.34 dB @ 901.0 MHz

Water in Antenna

Sweep only the antenna bandwidth

Slight Changes Here

problem?

baseline dataproblem?

Test Examples


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M1 M2

Del M1-M2: 2.67 dB, 99.2 MHz

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

800 850 900 950 1000 1050 1100 1150 1200

Return Loss - antenna moved800 - 1200 MHz (cal on)

dB

MHz

M1: -12.62 dB @ 803.1 MHz M2: -15.29 dB @ 902.3 MHz

M1 M2

-70

-60

-50

-40

-30

-20

-10

50 100


ReturnLoss(dB)

Feet

M1: -24.55 dB @ 14.1 feet M2: -8.09 dB @ 112.86 feet

Storm Damage

High winds can mis-position the antenna

baseline data

problem?

Changes Here Also

Test Examples


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Introduction to Trace Interpretation A Trace is the measurement that results from a Line Sweep.

A Line Sweep measures the quality of an antenna or coax cable (acable plus antenna is called a system).

Traces (Line Sweep measurements) must be interpretedto determineif they Pass or Fail.

Traces are initially stored in the Anritsu Site Master instrument at theantenna site where they are made.

Later, Traces are transferred to a computer for interpretation.

Traces may be sent via CDROM, Memory Stick or email.


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Step 1: Check the bottom

Step 2:

CheckLeftSide

Step 3: Check Limit Line & Markers

Step 4:Check

theTrace

There is a 4 step process to interpreting traces:

6-4

Trace Interpretation


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Trace Interpretation ChartTypical Measurement Ranges

Insertion Loss Open or Short

System/Antenna

Antenna

Return Loss ofCable with Load

30

40

0dB

10

15

20

60dBFreq (MHz) Meters / Feet

Connectors

Coax/Load

0dB

5

15

25

Freq RL Mode DTF Mode

Less

More

Reflections

Load after Calibration42

If your Trace has

FREQ

along the bottom,use the left side of

this chart

6-6

If your Trace hasFEET or METERS

along the bottom,use the right side of

this chart


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Freq-Return Loss Measurement with a 50 ohm Load

6-13

-60

-50

-40

-30

-20

-10

1850 1875 1900 1925 1950 1975 2000 2025 2050

Limit : -33.5


dB

Frequency (1828.0 - 2050.0 MHz)

Trace Interpretation - Basic Measurements


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Freq-Return Loss measurement with a 50 ohm Load

6-15



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Freq-Return Loss of a transmission line and antenna

6-17

-60

-50

-40

-30

-20

-10

1850 1875 1900 1925 1950 1975 2000 2025 2050

Limit : -15.0


dB

Frequency (1828.0 - 2050.0 MHz)



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Freq-Return Loss of an Antenna

6-21

-60

-50

-40

-30

-20

-10

0

1700 1750 1800 1850 1900 1950 2000 2050 2100 2150 2200

Limit : -15.0

M1 M2M3


dB

Frequency (1700.0 - 2200.0 MHz)

M1: -15.01 dB @ 1844.161 MHz M2: -15.27 dB @ 2081.387 MHz M3: -25.98 dB @ 1913.504 MHz

Operating Range of Antenna

Best Operating Frequency



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Antenna Sweep in Freq-SWR Mode

6-23

1.00

1.25

1.50

1.75

2.00

2.25

2.50

2.75

3.00

3.25

1700 1750 1800 1850 1900 1950 2000 2050 2100 2150 2200

Limit : 1.42

M1 M2M3


VSWR

Frequency (1700.0 - 2200.0 MHz)

M1: 1.439 @ 1844.161 MHz M2: 1.419 @ 2081.387 MHz M3: 1.104 @ 1913.504 MHz

Operating Range of Antenna

Best Operating Frequency



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Insertion Loss of a transmission line with a short (Freq-RL Mode)

-9

-8

-7

-6

-5

-4

-3

-2

-1

0

1850 1875 1900 1925 1950 1975 2000

M1 M2

B-1 TX1RX1/ RTL SHORT

GSM 1900

Date: 06/28/2005 Time: 16:50:14

Resolution: 259 CAL:ON(COAX) CW: OFF

dB

Frequency (1840.0 - 2000.0 MHz)

M1: -6.15 dB @ 1862.90 MHz M2: -7.79 dB @ 1942.90 MHz

Marker to Peak-6.15dB

Marker to Valley-7.79dB

6-25



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Insertion Loss of a transmission line with a short

Marker to Peak-0.70dB

Marker to Valley-0.92dB

6-27

-4.0

-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

800 810 820 830 840 850 860 870 880 890 900

M1 M2

Cable LossCABLE1CL

Date: 09/20/2005 Time: 18:23:16 Avg.CableLoss: -.81 dBResolution: 259 FlexCAL:ON(COAX) CW: OFF

d

B

Frequency (800.0 - 900.0 MHz)

M1: -.70 dB @ 826.40 MHz M2: -.92 dB @ 842.60 MHz



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Distance to Fault - Return Loss Mode

6-29



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Distance to Fault - SWR Mode

6-31



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DTF-SWR of cable system DTF-RL of cable system

1.000

1.025

1.050

1.075

1.100

0 10 20 30 40 50 60 70

Limit : 1.07

M1M2M3 M4

Distance-to-faultSWR Mode Feet

Model: S332B Serial #: 00937026 Prop.Vel:0.880Date: 03/26/2002 Time: 08:57:55 Ins.Loss:0.013dB/ft

Resolution: 259 CAL: ON(COAX)

VSWR

Distance (0.0 - 70.0 Feet)

M1: 1.02 @ 56.43 ft M2: 1.04 @ 48.02 ft M3: 1.04 @ 8.41 ft M4: 1.11 @ 28.22 ft

-50

-40

-30

-20

-10

0

0 10 20 30 40 50 60 70

Limit : -30.0

M1M2M3 M4

Distance-to-faultRL Mode Feet

Model: S332B Serial #: 00937026 Prop.Vel:0.880Date: Mar/26/200 Time: 08:55:39 Ins.Loss:0.013dB/ft


dB


M1: -40.92 dB @ 56.43 ft M2: -33.56 dB @ 48.02 ft M3: -33.56 dB @ 8.41 ft M4: -26.02 dB @ 28.22 ft

6-33


T I i B i M


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DTF - End of transmission line terminated with an open orshort

-50

-40

-30

-20

-10

0

0 25 50 75 100 125 150 175 200

Limit : -30.0

M1 M2

Clifton Springs / 300R176ABlue 1 DTF Short


dB


M1: -30.75 dB @ 0.0 Feet M2: -1.84 dB @ 209.34 Feet

End of transmission line

Ripple pattern caused by short(Miller Effect)

Notice this peak

6-35



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T I t t ti B i M t


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DTF - End of transmission line terminated with a 50 Ohm load - FAILURE

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

0 10 20 30 40 50 60 70

Limit : -19.30

M1

Distance-to-faultDTF TERM

Resolution: 130 CAL: ON(COAX) CW On

ReturnLoss(dB)


M1: -37.077 dB @ 68.341 Feet

Last connector

Connectors at main feedand top jumper

First connector

Fault in line

Notice the Marker

6-39



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Trace Interpretation Basic Measurements


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Handheld Software Tools Trace Overlay of DTFtraces before and after setting Vp(Propagation Velocity)

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

0 10 20 30 40 50 60 70

Limit : 0.00

M1

Distance-to-faultDTF OPEN

Resolution: 130 CAL: ON(COAX) CW On

ReturnLoss(dB)


M1: -2.418 dB @ 68.341 Feet

Before Correct Cable Type EnteredEnd of cable shown at 62 feet

With Correct Cable Type EnteredEnd of cable shown at 68 feet

6-43


Master Software Tools


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Cable Analysis Products Overview


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Cable Analysis Products Overview

1-port 1-port, SPA,2-port transmission1-port,2-port transmission

S331E2 MHz to 4 GHz

S361E2 MHz to 6 GHz

S332E / Op212 MHz - 4 GHz VNA

100 kHz - 4 GHz SPA

S362E / Op212 MHz - 6 GHz VNA

100 kHz - 6 GHz SPA

S331E / Op212 MHz - 4 GHz

S361E / Op212 MHz - 6 GHz

VNA,1/2-port transmission

MS20X4A/B500 kHz 4 GHz

MS20X6A/B500 kHz - 6 GHz

1-port, SPA

2-port transmissionDemod, backhaul

MT8212E4 GHz VNA/SPADemod, Backhaul

Site Master VNA Master Cell/BTS

Master


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Documents

Understanding Cable and Antenna Analysis[1]