Tower Mounted Amplifier Testing

8/20/2019 Tower Mounted Amplifier Testing

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IntroductionThe use of Tower Mounted Amplifiers (TMAs) in cellular, PCS, G SM and 3G B ase Station s has offered signifi-

cant improvements to carriers to minimize call drops, loss of commun ication, an d pro vide a m ore reliable serv-

ice to customers in both outdo or an d ind oor co verage. Their use with an y new installation is another way to

provide better coverage an d increase the numb er of subscribers witho ut deploying n ew Base Stations in th e

same geographic area.

This application n ote will focus on testing of TMAs before an d after in stallation and provide diagn ostic tests

like Ca ble Loss and DTF-Load Sweep to help d etermine th e perfo rman ce of transmission lines and to wer

mounted amplifiers.

Site Master S251C simplifies per form -

ance verification of TMAs prior to

installation, th us reducing tr ouble

shooting time and future diagnostics

checks. Its easy calibration, high

dyna mic range, user-friendly men u,

and o ptiona l bias tee provides a simple

method of measuring gain of towermounted amplifiers in the field.

APPLICATION NOTE

Tower Mounted Amplifiers,Diagnostics and Isolation MeasurementsSite Master™ S251C

Improve System Performance andCoverage with Site Master S251C


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2

Application NoteSiteMaster

An example of how TMA usage increases coverage at

the PCS Base Station is shown in Figures 1 and 2. The

low no ise am plifier pro vides better coverage to the

subscriber by minimizing fad ing in th e commun ica-tion system. This reduces call drop outs and extends

battery life to the cell phon e subscriber as the tran smit

power req uired is decreased because the B ase Station

becomes more sensitive to weaker signals.

Applications of Tower Mounted AmplifiersManufacturers of Tower Moun ted Amplifiers have accom mod ated the

Base Station equipment providers with different types of TMAs to meet

system requirements. Three types commonly used are shown below.

Tower Mounted Amplifier-Single (TMA-S)

The TMA-S is a Rx-receive

only tower mounted ampli-

fier that con nects between

the Rx-receive an tenn a a nd

the rad io. Its purposeis to boost weak signals

from the subscriber. This

configura tion is specific to

systems that use separate

anten na s for Tx-transmit

and Rx-receive.

The TMA-D is a duplex tower

mounted amplifier that is

used fo r the Base Station witha single antenn a port conn ec-

tion for Tx-tran smit and

Rx-receive. These systems are

commonly called transceivers.

The TMA-DD is a dual

duplex tower mounted

amplifier that combinesTx-transmit and Rx-receive

ports from the Base Station

with a single transmission

line. This configuration

is specific to systems tha t

can utilize a single anten na

configuration.

Tower Mounted Ampli fier-Dual Duplex (TMA-DD)

Rx

Tx/Rx

Tx

Base Station

TMA-DD

Tower Mounted Ampli fier-Duplex (TMA-D)

Rx

Tx/Rx

Tx

Base Station

TMA-D

PCS SYSTEM

Tx/Rx

TowerMountedAmplifier

RxTMABenefit

IncreasedCoveragein Base Station

IncreasedPerformanceto Base Station

Figure 1. Tower Mounted Amplifier

Figure 2. Larger Coverage Area

TMA-S

Rx

Rx

Tx

Tx

Base Station


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3


TMA-S

ANT RX

TMA-DD

ANT RX

S251C

RF OUT

S251C

RF IN

S251C

RF OUT

S251C

RF IN

(Bias Tee)(Bias Tee)

TX

Two-Port Tower Mounted Ampl ifier

Two-Port RX Only/LNA with Bypass Switch Two-Port Dual-Duplex/LNAwith Bypass Switch

Three-Port Duplex/LNAwith Bypass Switch

Four-Port with Two Dual-Duplex/LNA with-out Bypass Switch

ANTTX RX

TMA-D

S251CRF OUT

S251CRF IN

(Bias Tee)

Three-Port Tower M ounted Amplifi er

ANTANT TX/RX TX/RX

Dual-TMA-DD

S251CRF OUT

S251CRF IN

S251CRF OUT

S251CRF IN

(Bias Tee) (Bias Tee)

Four-Port Tower M ounted AmplifierDual-Duplex with NON Bypass

Types of Tower Mounted Amplifiers

Internal Components and Frequency Response of TMAs

Band Pass

Filter

LNA

ANT

RX (Receive)

Gain/Insertion LossTMA-S CELLULAR

M1:13.57 dB @ 836.82 MHz

Frequency (750.0 - 925.0 MHz)

T r a n s m i s s i o n ( d B )

20

-20

-30

-40

-50

-60

-70

10

-10

0

750 775 800 825 850 875 900 925

M1

Gain/Insertion LossTMA-DD PCS

M1:12.17 dB @ 1882.36 MHz

Frequency (18250.0 - 2025.0 MHz)

1825 1 850 1 87 5 1900 1925 1950 1975 2000 2025

d B

10

-10

-20

-30

-40

-50

-60

-70

0

M1

Gain/Insertion LossTMA-DD

M1:12.17 dB @ 1882.36 MHz

Frequency (18250.0 - 2025.0 MHz)

1825 1850 1875 1900 1925 1950 1975 2000 2025

d B

10

-10

-20

-30

-40

-50

-60

-70

0

M1

d B

Gain/Insertion LossTMA-D PCS

M1:7.11 dB @ 1892.44 MHz

Frequency (18250.0 - 2025.0 MHz)

10

-10

-20

-30

-40

-50

-60

0

1825 1850 1875 1900 1925 1950 1975 2000 2025

M1

Duplex Filter

LNA

Duplex Filter

ANT

TX/RX

(Transmit / Receive)

Duplex Filter

LNA

ANT

TX(Transmit)

RX(Receive)

Duplex Filter

LNA

Duplex Filter

ANT

TX/RX


Duplex Filter

LNA

Duplex Filter

ANT

TX/RX



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Press MODE button . Move the cursor to select Insertion G ain Mod e (–30 dBm output) and Press ENTER.

Step 1. Prior to any tests, select the appropriate frequency range of the TMA system under test.

For example, when mea suring the TMA-DD in the PC S Band, set the freq uency range fr om 1850 MHz to

1990 MHz; F1 = 1850.0 MHz and F2 = 1990.0 MHz.

Step 2. Press the FREQ/DIST button and the frequency limits. F1 and F2 are the start and stop frequencies.

Performing a Full two port calibration in the Site Master S251CA full two-port ca libration is required when making either insertion loss or insertion gain measurements in the

frequency range of the system (Cellular, PCS, G SM and 3G).

Conn ect Test Po rt Extension

cables to Site Master RF In and

RF Out an d press START CAL

button to perfo rm a two-port

calibration on the Site Master

S251C.

Follow the Site Master instruc-

tions displayed on the screen.

After a full two-port calibra tion

has been completed, a 0 dB

reference level is established as

sho wn in figure 3 by the hea vy

blue line.

Site Master S251C User Setups

Measuring Tower Mounted Amplifiers prior to installation

Setting the Site Master S251C to Insertion Gain ModeSet the Site Master S251C to insertion gain mod e when testing th e tower-moun ted a mplifier prior to installa-

tion. The Power Level of insertion loss mode (+6 dBm) may cause LNA saturation and can damage the front

end of the Site Master receiver. The insertion gain mode (–30 dBm) output level keeps the LNA in the linear

range and provides an accurate gain reading without saturating the output. For 3G applications when measur-ing D ual-TMA-DD , use insertion loss (+ 6 dBm ) mod e.

M1 M2

-75

-50

-25

0

25

50

-100

75

100

1850 1875 1900 1925 1950 1975

Gain/Insertion Loss


Freguency (MHz)

M1: -.05 dB @ 1850.00 MHz M2: -.02 dB @ 1909.70 MHz

Site Master S251C

M OD E F RE Q/ DI ST A MP LI TU DE S WE EP

1

5 6

ENTER

8

MARKER

7

LIMIT

3

START

CAL

4

AUTO

SCALE

SAVE

SETUP

RECALL

SETUP

9

SAVE

DISPLAY

ESCAPE

CLEAR

0

RECALL

DISPLAY

SYS

PRINT

.ON

OFF

RUN

HOLD

+/-

2

Reference

Level

Typical TMA-DDGain Performance

Rx

Site Master S251C

Test PortCable

Test PortCable

Figure 3. Site M aster S251C after Calibration

Operation M ode System

Insertion Gain (–30 dBm) Cellular

Insertion Gain (–30 dBm) PCS

Insertion Gain (–30 dBm) GSM


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Step 4. Measure the ga in of th e tower moun ted am plifier between the RF Out an d RF In ports of the Site

Master S251C. Typical values for gain are between 10-20 dB. Consult your TMA manufacturers specifi-

cation for exact values.

Step 5. Adjust the scale either m anua lly or using th e AU TO SCALE butto n to center ga in level in the midd le

of the display.

Step 6. Set up the markers M1 = 1880 MHz and M2 = 1910 MHz to identify the receive portion of the PCS Band.

The TMA-DD measurement is swept across the ent ire f req uency ran ge, which includ es Tx-transmit (1960-1990

MHz) and Rx-receive (1850-1910 MH z) bands. Markers M1 and M2 high light the signa l level in Rx-receive band

of the tower-moun ted

amplifier where g ain is

measured. For all TMA

types the gain is measuredby connecting the RF Out

of the S251C to the anten-

na port an d RF In of the

S251C to the Rx-receive

port of the tower mounted

amplifier (TMA-S, TMA-

DD , TMA-D, an d Dua l-

TMA-DD ). G ain measure-

ments are typically between

10 dB to 20 dB abo ve the

0 dB reference level estab-

lished during full 2-port

calibration.

5


Measuring gain in a two-port TMA-DD (Tx/Rx) using the Site Master S251C.Step 1. Con nect th e RF Out po rt of the Site Master S251C to th e ANT (an tenn a) port o f the TMA-DD and

connect the RF In port o f the Site Master S251C to th e Tx/Rx (transmit/receive) po rt o f the TMA-DD .

Step 2. The g ain m easuremen t is made when th e Bias Tee Option (240 mA max.) in the Site Master S251C is

turned “On ”.

The o ptiona l bias tee gets its power through the AC/DC co nverter or ba ttery.Step 3. To a ctivate the Bias Tee option men u on the Site Master S251C, p ress the SYS, OPTIONS, BIAS TEE but-

ton s. The B ias Tee men u ha s ON/O FF, Low/H igh Voltage (15V or 12V) and Low/H igh C urren t (1A

surge/650 mA steady state or 460 mA surge/244 mA steady state.) Press the soft keys to toggle

between the appropriate parameters.

M1 M2 M3 M4

-70

-60

-50

-40

-30

-20

-10

0

10

1850 1900 1950 2000 2050 2100

Gain/Insertion Loss1825.00 - 2100.00 MHz (cal on, Bias-Tee On, -30.0dBm)

d B

MHz

M1: 12.05 dB @ 1880.40 MHz M2: 11.52 dB @ 1910.30 MHz

M3: -1.11 dB @ 1959.30 MHz M4: -1.16 dB @ 1989.10 MHz

Site Master S251C

MODE FREQ/DIST AMPLITUDE SWEEP

1

5 6

ENTER

8

MARKER

7

LIMIT

3

START

CAL

4

AUTO

SCALE

SAVE

SETUP

RECALL

SETUP

9

SAVE

DISPLAY

ESCAPE

CLEAR

0

RECALL

DISPLAY

SYS

PRINT

.

ON

OFF

RUN

HOLD

+/-

2

ReferenceLevel

Tx-BandRx-Band

Tx/Rx

TMA-DD

Ant.

RF In RF Out110/220 AC TMA-DD Gain

Figure 4. TMA-DD Gain with Site Master S251C

Note: When the Option 10B Bias Tee is switched ON and the user presses the START CAL button, the following warn-

ing message will appear on the display: “Bi as Tee has been tu rned OFF for Cal ibration. Don’t Turn Bias Tee ON before

removing cali brat ion components.” After the calibrat ion the user must switch the Bias Tee Option on in order to perform

TMA gain measurement.


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6


Tx

TowerMountedAmplifier

Tx

TM AIsolation

Measurement

Receive Source

Antenna 1

Antenna 2

Site Master S251C


1

5 6

ENTER

8

MARKER

7

LIMIT

3

STARTCAL

4

AUTOSCALE

SAVE

SETUP

RECALL

SETUP

9

SAVE

DISPLAY

ESCAPE

CLEAR

0

RECALLDISPLAY

SYS

PRINT

.

ONOFF

RUNHOLD

+/-

2

Tx/Rx ANT

RF Out

Rx-Antenna

Tx-Antenna

Site Master S251C

TM A

(BiasTee)

RF In

110/220 AC

TMA Isolation Measurement–Relative GainAn alternative method of testing the TMA gain after installation is to perform a TMA Isolation test. A signal is

sent from an available Tx-transmit an tenna to the Rx-receive an tenn a o f to wer moun ted amplifier. Accessing a n

unused Tx-transmit anten na may be difficult during no rmal business ho urs and must be conducted d uring th e

maintenance window.

This test is very similar to a n a ntenn a-to-an tenna isolat ion measurement (see page 11). The RF outpu t signal ofthe S251C is conn ected to the Tx-transmit an tenn a an d th e RF input is connected to the Rx po rt of th e TMA

(TMA-S, TMA-DD, TMA-D, an d Dua l-TMA-DD).

This test measures relative gain levels of the tower-mo unted am plifier for verification an d operat ion , but does

no t provide a bsolute levels in ten ths of d B. The gain is measured by compar ing th e relative signa l chan ges

between the no n-active/bypass and a ctive gain when the B ias Tee is turn ed O FF an d O N. The signa l level meas-

ured helps to identify problems in the tower mounted amplifier and how it affects Base Station performance.

Figure 5. Tower M ounted Amplifier Figure 6. TM A Isolation M easurement

Test ProcedureStep 1. Set the Site Master S251C to In sertion Loss Mode ( + 6 dBm)

Insertion Lo ss Mode is req uired when using th e TMA Isolation Test Method a nd when testing 3G

Dual-TMA-DD applications. The Insertion G ain Mod e (-30 dBm) output level is too low to send a signal

from an tenna-to-an tenn a.

Press the MODE button . Move the cursor to select INSERTION LOSS (+ 6 dBm level) MODE and

Press ENTER.

Step 2. Select the freq uency range on the Site Master based on the TMA freq uency range.

Performing a Full two port calibration in the Site Master S251C.Step 3. Con nect th e Test Po rt Extension C ables to the Site Master RF In and RF Out ports an d pr ess the

START CAL button to per form a two-port calibration and follow the d isplay instructions.

Step 4. Press SAVE SETUP to save the calibration set up.


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Performing a TMA Isolation TestStep 1. Disconnect the Tx-transmit antenna coa x from the an tenn a. Con nect the RF Out port of the Site

Master S251C to the transmit coax and co nn ect the Rx-receive coa x from TMA-DD to th e RF In po rt

of the Site Master S251C.

Step 2. Measure the signa l level between the RF Out an d RF In ports of th e Site Master S251C with th e

Bias Tee “O FF”.

Step 3. Save the display to th e Site Master’s S251C m emo ry.

Press the SAVE DISPLAY key to a ctivate th e alpha -numeric m enu b utton to store the signa l level plot

with a descriptive nam e. Use the soft keys to name th e trace.

For example, to save the display with the name “TMA_Duplex Insertion Gain”, press the soft key

group that contains the letter “T” an d then press the “T” soft key. Repeat this sequence until the

entire name has been entered through the soft key menu. Press the ENTER key to save the display.

Step 4. Measure the signa l level between the RF Out an d RF In ports of th e Site Master S251C with th e

Bias Tee “ON”.

Step 5. Press the SYS, OPTIONS, BIAS TEE butto ns to t ogg le the Bias Tee O n. The Bia s Tee men u ha s ON/OFF,

Low/High Voltage (15V or 12V) and Low/High Current (1A surge/650 mA steady state or 460 mA

surge/244 mA steady state.) Press the soft keys to toggle between the appropriate parameters.

Step 6. TRACE OVERLAY-Co mparison of two m easuremen ts by using th e trace overlay feature o f the S251C

provides an easy verification of the operation of the TMA when the bias tee is activated. Press SWEEP,

TRACE OVERLAY, and ON/OFF butto ns. Select the trace th at was saved with the B ias Tee OFF from the

Site Master S251C’s memory. Using the UP/DOWN arrow key to highlight the appropriate trace name

and press the ENTER key to overlay the trace.

Step 7. Adjust the con trast in th e display such th at bo th th e active trace (bias tee “ON”) and th e trace from

memor y (non -bias tee trace) can be viewed o n th e screen.

Step 8. Set up the m arkers M1 = 1880 MHz and M2 = 1910 MH z to identify the Rx-receive frequency of the

PCS Band .

Step 9. The isolation level of –50 dB is indicated by the blue line and is the total loss of cables and path loss

between the two anten na s. This signal level is 50 dB below the 0 dB reference established during cali-

bration . The TMA-DD relative ga in m easurement is approximately 12 dB above the isolation signal

level. (TMA gain –38 dB–(–50 dB) = 12 dB).

M1 M2 M3 M4

-85

-80

-75

-70

-65

-60

-55

-50

-45

-40

-35

Gain/Insertion Loss1825.00 - 2100.00 MHz (cal on, Bias-Tee On, -30.0dBm)

M1: -37.42 dB @ 1880.40 MHz M2: -38.17 dB @ 1910.30 MHz

M3: -50.16 dB @ 1959. 30 MHz M4: -50.57 dB @ 1989.10 MHz

d B

1850 1900 1950 2000 2050 2100MHz

Rx Tx

Measurement: TMA Isolation Test

ANALYSIS OF TMA-DD GAIN

The relati ve gain measurement of the TMA after i nstal la-

ti on is very similar to the other gain measurements with the exception of signal level offsets due to the cable losses and

system isolation level shown by the blue line. Two plots are

compared wi th the S251C trace overl ay feature. The black

plot is non-acti ve bias tee and the blue plot gain is when the bias tee is applied to the TMA. As previ ously discussed, the

comparison of the ampli fi er plots before and after the bias

tee activat ion will not produce the accuracy to tenths of dB,but wi ll provide a good test for operati on and veri fi cati on of

the TMA-DD, TMA-D, TMA-S and Dual-TM A-DD. The

graph indicates TMA gain of about 12 dB which is very

close to the specifi ed TMA gain of 14 dB.


8/12

8


Diagnostics–Identifying Problems in a TMA SystemInsertion Loss and DTF-Load sweep are two tests that help d etermine th e integrity of th e tran smission line

in a TMA (Tower Mounted Amplifier) system that is suspected of ha ving pro blems.

Cable Loss Measurement after TMA InstallationCable Loss is one of the key measurements to verify system performance of the transmission line in Base

Stations. Cable Loss becomes especially importa nt fo r installations that incorpora te tower mo unted amplifiers.

The purpose of the tower mounted amplifier is to boo st signal an d to pro vide better coverage to ar eas tha t

conventional antenna orientations cannot service.

A transmission line mea sured with Ca ble Loss of 6 dB is approxima tely 2 dB above an a cceptable level of 3-4 dB

loss for 150 ft. cable run and ma y reduce coverage o f the B ase Station .

It is very difficult to determine which components within the system are causing system failure after the TMA is

installed. A commo n meth od o f troublesho oting th e system is to remove the tower moun ted amplifier from the

configura tion a nd perfor m an end -to-end Cable Loss measurement on the en tire transmission line which

includes jumpers, main feed er, an d a dapters.

This test identifies changes in the transmission line assembly by measuring the total Cable Loss of the system

witho ut the TMA conn ected. Ca ble Loss provides valuable info rmation about signal level coverage a nd whetherthe o utput level of the

transmitter has been com-

promised due to excessive

signal loss in either th e

jumpers or the m ain feed er.

Figure 8 shows the TMA

removed from the system con-

figuration. The Site Master

S251C perfor ms a Cable Loss

measurement of the entire

tran smission line system. Thedotted lines indicate where

the TMA and the antenn a

are removed from the con-

figuration. Cable Lo ss is

measured when a precision

short is connected to the

end of the transmission line.

Jumper M ain Feeder TM A JumperAntennaJumper

AntennaTM A

Tx/Rx

Figure 7. TMA Installation

Site Master S251C

M OD E F RE Q/ DI ST A MP LI TU DE SWEEP

1

5 6

ENTER8

MARKER

7

LIMIT

3

STARTCAL

4

AUTOSCALE

SAVESETUP

RECALLSETUP

9

SAVEDISPLAY

ESCAPE

CLEAR

0

RECALLDISPLAY

SYSPRINT

.

ONOFF

RUNHOLD

+/-

2

Test PortCable Jumper M ain Feeder

TMAJumper

AntennaJumper

CalibratedShort

AntennaRemoved

TM ARemoved

Tx/Rx

Figure 8. Insertion Loss M easurement without TMATest Procedure

Cable Loss ModeStep 1. Press the MODE key.

Step 2. Select FREQ-CABLE LOSS using the Up/Do wn arro w key and press ENTER.

Step 3. Set the start an d stop freq uencies, F1 and F2, F1 = 1850 and F2 = 1990.

Step 4. Con nect the Test Port Extension cable to the RF Out port an d press START CAL to calibrate the

Site Master.

Step 5. Follow the Site Master instruction s on the screen an d press SAVE SETUP to save the ca libration.


9/12

9


Step 6. Con nect the jumper to the Site Master phase stable Test Port Extension cable and con nect short at the

end of antenna jumper. A trace will be d isplayed on the screen as long as the Site Master is in sweep mode.

Step 7. Press the AMPLITUDE key and set the TOP and BOTTOM values of the display. In the example below,

the TOP is set to 1, and the BOTTOM is set to 6.

Step 8. Press the MARKER key.

Step 9. Set M1 to MARKER TO PEAK.Step 10. Set M2 to MARKER TO VALLEY.

Step 11. Calculate the m easured insertion loss by averaging M1 (ma rker to peak) and M2 (marker to valley)

as fo llows:

Step 12. Inserti on Loss = M1+ M2 = –3.25 –4.07 = –7.32 = –3.66 dB2 2 2

Step 13. Press SAVE DISPLAY, name the trace, and press ENTER.

Calculate Transmission Line Insertion Loss Example

Calculated Insertion Loss

=0.65+2.79+0.325+0.325+0.42=4.515 dBVerify the measured cable loss with thecalculated cable loss.

Type Attenuation Length Loss

(dB/ft) (ft) (dB)1st_J umper LDF4-50A 0.0325 X 20 =0.65

Main_Feeder LDF5-50A 0.0186 X 150 =2.79

TMA_J umper LDF4-50A 0.0325 X 10 =0.325

Antenna_J umper LDF4-50A 0.0325 X 10 =0.325

Connector Pairs Connector Loss (dB) Insertion Loss

4 X 0.14 = 0.42

Cable Loss

Frequency (1850.0 - 1990.0 MHz)

M1: -3 .25 dB @ 1911.00 MHz M2: -4.07 dB @ 1987.80 MHz

1850

-1.0

-1.5

1875 1900 1950 19751925

Cable/Waveguide Loss

-2.0

-2.5

-3.0

-3.5

-4.0

-4.5

-5.0

-5.5

-6.0

d B

M1 M2

Result of Insertion LossThe measured insertion loss

of –3.66 dB is less than the calcu-

lated –4.515 dB and the system

meets specif icati on.

Distance-To-Fault (DTF) MeasurementsDTF-Load Sweep is a test to locate the faults in the transmission line tha t the Ca ble Loss measurement m ay not

identify. A DTF test verifies proper opera tion o f the tra nsmission line th at may degrad e over time and may be

man ifested a s a signal reflection.


10/12


11/12

11


Tx

TxRx

SystemIsolation

System 2 System 1

Antenna 1

Antenna 2

Figure 11. System Isolation

Site Master S251C

M OD E F RE Q/ DI ST A MP LI TU DE S WE EP

1

5 6

ENTER

8

MARKER

7

LIMIT

3

STARTCAL

4

AUTOSCALE

SAVE

SETUP

RECALL

SETUP

9

SAVE

DISPLAY

ESCAPE

CLEAR

0

RECALL

DISPLAY

SYS

PRINT

.

ON

OFF

RUN

HOLD

+/-

2

Rx

Tx

RF Output

Site Master S251C

Figure 12. Antenna Isolation wi th Site Master S251C

Setting the Site Master S251C to Insertion Loss Mode (+6 dBm)Insertion Loss Mode (+ 6 dBm) is required to drive the signal level large enough to be d etected by the

second anten na system. The Insertion G ain Mode (–30 dB m level) does not output eno ugh power to providean accurate measurement reading.

Press MODE button . Move the cursor to select INSERTIO N LOSS (+ 6 dBm level) MOD E an d P ress ENTER.

Setting the Frequency range for the antenna system.The table below indicates frequency settings for common systems.

OperationMode

SystemFrequencyStart (MHz)

FrequencyStop (MHz)

InsertionLoss

+6 dBm

CellularPCSGSM

F1 =806F1 =1850F1 =1800

F2 =960F2 =1990F2 =1900

Select the appro priate frequen cy range to mea sure the isolation of a PCS system. Set the freq uency range

from 1850 MHz to 1990 MHz, F1 = 1850.0 MHz a nd F2 = 1990.0 MHz.

Performing a Full two port calibration in the Site Master S251CA full two po rt calibration is required when m aking antenna-to-anten na isolation measurements in the a ppropriate

frequen cy range for the system

(Cellular, PCS, GSM, and 3G).

Connect test Port Extension

cables to Site Master RF In and

RF Out an d press START CAL

button to per form a two-portcalibration on the Site Master

S251C.

Follow the Site Master instruc-

tions shown on the display. After

performing a two port calibra-

tion, a 0 dB r eference level is

established shown in figure 13 by

the heavy blue line.

M1 M2

-75

-50

-25

0

25

50

-100

75

100

1850 1875 1900 1925 1950 1975

Gain/Insertion Loss


Freguency (MHz)

M1: -.05 dB @ 1850.00 MHz M2: -.02 dB @ 1909.70 MHz

Site Master S251C


1

5 6

ENTER

8

MARKER

7

LIMIT

3

START

CAL

4

AUTO

SCALE

SAVE

SETUP

RECALL

SETUP

9

SAVE

DISPLAY

ESCAPE

CLEAR

0

RECALL

DISPLAY

SYS

PRINT

.

ON

OFF

RUN

HOLD

+/-

2

ReferenceLevel

Typical

Antenna-to-Antenna

Isolation Levels

Rx

Site Master S251C

Test Port

Cable

Test Port

Cable

Figure 13. Site M aster S251C after Calibration


12/12

SALES CENTERS:United States (800) ANRITSU Europe 44 (0) 1582-433433 Microwave Measurements Divis ionCanada (800) ANRITSU Japan 81 (46) 223-1111 490 Jarvis Drive, Morgan Hill, CA 95037-2809South America 55 (21) 2527-6922 Asia-Pacific (65) 6282-2400 http://www.us.anritsu.com

11410 00274 R A ©A it M 2004 D t i bj t t h ith t ti Di Wh t’ P ibl ®


Measuring Antenna-to-Antenna isolation using the Site Master S251CStep 1. Disconnect th e Tx (Transmit) an tenna coa x from System 1 in figure 11 and connect it to th e RF Out

port o f the Site Master S251C. D isconn ect the Rx (Receive) co ax fro m System 2 in figure 11 and con-

nect it to the RF In port of th e Site Master S251C.

Step 2. Measure the tota l isolat ion level between the RF Out ( Tx, Tran smit) an d RF In ( Rx, Receive)

ports of the Site Master S251C.

Step 3. Adjust the scale either manually or using the AUTO SCALE button to display isolation level to center

of the display.

Step 4. Set up the markers M1 = 1880 MHz and M2 = 1910 MHz to iden tify the receive portion of the PCS Ban d.

Step 5. Measurement values are between –85 dB and –92.5 dB with average antenna isolation level at –89 dB.

Set up the limit line to the estimated a verage signal level. The isolation level measurement includes

all the cable loss of both systems, antenna gains, and insertion losses.

Typical anten na-to antenna isolation measuremen ts are made in between –50 dB and –100 dB below the 0 dB ref-

erence line established by the full

2-por t calibra tion .

The measurement is swept acrossthe entire frequency range that

includes both transmit (1960-

1990 MHz) and r eceive (1850-

1910 MHz) b and s. Markers M1

and M2 high light the signal level

measured in the receive band

because this power level will affect

the performance of the receiver of

system 2 in figure 11 and identifies

the signal level from an unwan t-

ed source (an other transmitter).

When the isolation level measured is more neg ative, there is a bett er cha nce o f co-locat ion without system

degradation. An isolation level of –89 dB is very good. RF System engineers/technicians must decide what is an

accept able level for their pa rticular system. If the an tenna -to-an tenna isolatio n mea sured is closer to –60 dB ,

then re-alignmen t of the an tenn as may be necessary until the isolation becomes better. In some cases, alterna-

tive channel plans must be used to assure that all the systems at the same location can operate successfully.

Site Master S251C

MODE FREQ/DIST A M PL I TU D E S W EE P

1

5 6

ENTER

8

MARKER

7

LIMIT

3

STARTCAL

4

AUTOSCALE

SAVESETUP

RECALLSETUP

9

SAVEDISPLAY

ESCAPE

CLEAR

0

RECALLDISPLAY

SYSPRINT

.

ONOFF

RUNHOLD

+/-

2

Tx

Rx

RF Input

RF Output

AntennaIsolation

Level

Site Master S251C

-85.0

-87.5

-90.0

-92.5

-95.0

1850 1875 1900 1925 1950 1975Frequency (MHz)

Gain/Insertion Loss

M1: -88.11dB @ 1979.30 MHz M2: -92.62 dB @ 1910.80 MHz


Rx

M1 M2

Figure 14. Antenna Isolation wi th Site Master S251C

ConclusionFor a ll TMA types (TMA-S, TMA-DD , TMA-D an d Dual-TMA-D) and manufacturers, the gain is measured by con -

necting the RF Out o f S251C to the a nten na po rt and the RF In to the Rx-receive port of the TMA. When TMAs

deployed in the field do no t have bypass switches, then th e recommen ded test is to activate the b ias tee of the

S251C and measure the ga in referenced to the 0 dB level (established during calibration) . Test methods verifyingthe operation and performa nce of a TMA after installation is depend ent on the carrier specifications and test

procedures. Removal of the TMA from the system con figuration and testing th e tran smission line an d TMA

independ ently is the metho d that provides the most confidence to the field technician. H owever, the TMA Isolation

test is an alternative metho d th at measures relative gain to con firm correct operation and performance o f the TMA.

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