basic site master & antenna system theory_v5.0

BASIC SITE MASTER & ANTENNA SYSTEM THEORY

The information contained herein is the property of True Move and is provided on condition that it will not be reproduced, copied, lent or disclosed, directly or indirectly, nor used for any purpose other than that for which it was specifically furnished.

AUTHOR Komsun Bunchasak

DOCUMENT OWNER Kittisak Lohumnuaykul

DIVISION Regional Network Operation

DEPARTMENT Regional Network Operation Support

CONFIDENTIALITY STATUS Project Confidential

DOCUMENT REFERENCE

DOCUMENT REVISION 5.0

REVIEW PERIOD

Project Confidential

Document Release History

Version No.

Release Date Purpose

1.0 - Initial Release

1.1 29/09/2003 Amendments for self build project and correction of errors

2.0 09/10/2003 Updated Version

3.0 14/10/2003 Updated & Coordinate for approval

3.1 08/01/2004 Updated Isolation Test Section

3.2 08/01/2004 Updated Isolation Loss Section to mimic Phase 4



Document Review Team:

Name Division/Department

Kittisak Lohumnuaykul Regional Network Operation

Chayanon Chinapak Regional Network Operation

Komsun Bunchasak Regional Network Operation

ApprovalsApproved By Signature Date

AUTHOR: Komsun Bunchasak ELECTRONIC COPY NO PERSONAL SIGNATURE

13/02/2008

QA REPRESENTATIVE:

DOCUMENT OWNER: Kittisak Lohumnuaykul ELECTRONIC COPY NO PERSONAL SIGNATURE

13/02/2008

GENERAL MANAGER:

Page 1 of 16 9/4/2023


TABLE OF CONTENTS

Version No.___________________________________________________________________________________2Release Date__________________________________________________________________________________2Purpose______________________________________________________________________________________21.0___________________________________________________________________________________________21.1___________________________________________________________________________________________229/09/2003____________________________________________________________________________________2Amendments for self build project and correction of errors______________________________________________22.0___________________________________________________________________________________________209/10/2003____________________________________________________________________________________2Updated Version_______________________________________________________________________________23.0___________________________________________________________________________________________214/10/2003____________________________________________________________________________________2Updated & Coordinate for approval_________________________________________________________________23.1___________________________________________________________________________________________208/01/2004____________________________________________________________________________________2Updated Isolation Test Section____________________________________________________________________23.2___________________________________________________________________________________________208/01/2004____________________________________________________________________________________2Updated Isolation Loss Section to mimic Phase 4______________________________________________________24.0___________________________________________________________________________________________202/02/2004____________________________________________________________________________________2Updated Version_______________________________________________________________________________25.0___________________________________________________________________________________________213/02/2008____________________________________________________________________________________2Updated Version_______________________________________________________________________________2

1. INTRODUCTION______________________________________________________________4

2. SCOPE_____________________________________________________________________4

2.1 ANTENNA SYSTEMS________________________________________________________________4

3. ANTENNA TESTING THEORY___________________________________________________4

3.1 INSERTION LOSS___________________________________________________________________43.2 RETURN LOSS____________________________________________________________________53.3 ISOLATION LOSS__________________________________________________________________5

4. HOW DO WE TEST ANTENNA SYSTEMS?________________________________________5

4.1 DTF (TDR) MEASUREMENT_________________________________________________________74.2 INSERTION LOSS___________________________________________________________________74.3 RETURN LOSS____________________________________________________________________84.4 ISOLATION LOSS__________________________________________________________________8

5. TIPS AND TRICKS WITH THE SITE MASTER_____________________________________10

5.1 POWER OUTPUT__________________________________________________________________105.2 CALIBRATION____________________________________________________________________10

6. INTERPRETATION OF RESULTS_______________________________________________10

6.1 DTF (TDR) MEASUREMENT________________________________________________________106.2 INSERTION LOSS__________________________________________________________________116.3 RETURN LOSS___________________________________________________________________126.4 ISOLATION LOSS_________________________________________________________________13

7. USE OF SOFTWARE TOOLS__________________________________________________15

8. Appendices_________________________________________________________________16

Page 2 of 16 9/4/2023


1. INTRODUCTION

This document is designed to be a guide for True Move Engineers, to enable them to understand and verify Antenna test results, using the Site Master 251B. It is not a complete step-by-step guide to the Site Master. Detailed information can be found in the Site Master user guide. Alternatively, the Anritsu website has a series of application notes which can be downloaded in PDF format.

Visit: http://www.us.anritsu.com/downloads/

Central Support can provide Onsite training.

2. SCOPE

This document will cover the following:

Antenna systems Measurements required Use of Site Master How to interpret the results Use of software tools

2.1 Antenna Systems

Within the project we have several suppliers of antennas. Antennas are designed with different characteristics for varying applications. RF Planners use different types of antennas to achieve specific coverage requirements.

3. ANTENNA TESTING THEORY

To verify antenna system performance we should test for the following:

Length of feeder cable Insertion Loss Return Loss Isolation Loss

3.1 Insertion Loss

The attenuation of signals due to the impedance when passing the signals through a system. Specified as a decibel value (dB) over a frequency. – From National Instruments Library.

This is the equivalent of DC voltage drop through a system.

Page 3 of 16 9/4/2023

http://www.us.anritsu.com/downloads/


3.2 Return Loss

A measure of undesirable signal reflections from a non-ideal termination of the transmission line. Expressed in dB. – From National Instruments Library

Using AC terminology, maximum power transfer occurs when the input and output impedances are equal. However, at RF frequencies mismatches do occur due to the complexities of RF signals and Antennas. When there is an impedance mismatch, part of the signal will be reflected back to the source. What we measure is the reflected power against the transmitted power and express it logarithmically in Decibels (dB).

Return loss is the same as VSWR, except that VSWR is expressed as a direct ratio of forward versus reflected voltages.

Mathematically, Return loss is expressed as:

Return Loss Voltage StandingWave Ratio

Reflection Coefficient

RL = -20*log[r]dBVSWR =

=

3.3 Isolation Loss

A measure of electrical seperation between Tx and Rx Antennas, expressed in dB.

An important aspect in antenna engineering is EMC (electromagnetic compatibility), which covers aspects of spurious emission, switching and modulation spectrum, intermodulation, receiver sensitivity and blocking. The BTS hardware needs to fulfil these requirements according to the GSM specification 11.21 and 05.05. These requirements are based on the assumption, that there is a minimum decoupling of 30 dB between the transmitter and the receiver. In case of too small antenna spacing the decoupling becomes insufficient and a degradation of the receiver performance due to intermodulation and receiver blocking can occur. – From RF DSD

More importantly this test can determine if individual feeders have been crossed between sectors.

4. HOW DO WE TEST ANTENNA SYSTEMS?

Before we can verify the Performance of the Antenna system we must know the characteristics of the Antenna System we are going to test.

When testing Antenna system we must sweep the entire operating band of the Antenna.

Page 4 of 16 9/4/2023


Before testing Antenna systems always ensure that an outage has been approved by NMC and the BTS is ‘off the air’.

The following two tables illustrate the feeder and Antenna characteristics for Celwave feeder, RFS and Kathrein Antennas, however for full specification please refer to manufacturer specification sheets.

Table 1: Feeder Characteristics

FeederMax.

Feeder lengthTotal attenuation Velocity factor

Attenuation@ 2000MHz

1/2” 20 m 2.14 dB 0.88 0.107 dB/m

7/8” 30 m 1.83 dB 0.88 0.061 dB/m

1 1/4” 45 m 1.94 dB 0.88 0.043 dB/m

1 5/8” 55 m 2.04 dB 0.88 0.037 dB/m

Note: Above lengths exclude jumpers.

Table 2: Antenna Characteristics

Antenna Types Supplier Usage H-BW Tilt Freq Range Pol.

K 739 496 Kathrein Dense Urban, Urban 65 6 1710-1990 X-Pol

APX186515-T6 RFS Dense Urban, Urban 65 6 1710-1880 X-Pol

K 739 707 Kathrein Suburban, Rural 90 2 1710-1880 X-Pol

APX189015-2T2 RFS Suburban, Rural 85 2 1710-1880 X-Pol

K 739 494 Kathrein Highways 65 0 1710-1880 X-Pol

AP186516-T2 RFS Highways 65 2 1710-1880 X-Pol

Note: Antenna data for macro sites

Before we can verify the Performance of the Antenna system we must first determine the Length of the feeder. This can be done in two ways; either measure the length physically with a tape measure, or electrically with the Site Master (DTF measurement).

Page 5 of 16 9/4/2023


4.1 DTF (TDR) Measurement

This measurement is required for commissioning and should be performed by True move so the length of the feeder can be checked.

Perform the test as follows:

Turn on the Site Master and let stabilize for 5 minutes. From the ‘MODE’ function select ‘DTF – RETURN LOSS’. Set up the sweep distance D1 & D2 parameters using table 1 (above) according to the

feeder installed. Select ‘DTF Aid’ Function’ and set the Start and stop frequencies ‘F1 & F2’, using table 2

Antenna Characteristics for the particular antennas installed. Set up the cable parameters using the ‘DTF Aid’ Function using the velocity and cable

parameters from table 1 (above). Calibrate the Site master as per the Operating manual. Connect feeder A1 and make measurement Use the ‘AUTO SCALE’ function to ensure the whole sweep is displayed on the screen Use the ‘MARKER’ function – markers 1-4 to highlight the peaks in the display Save the sweep using the ‘SAVE DISPLAY’ function. Use a file name such as

BKD059A1D Repeat measurement and save file for all feeders. (A2, B1, B2, C1, C2 etc)

4.2 Insertion Loss

This measurement must be carried out at commissioning. The measurement involves connecting a short circuit to the end of the feeder and is the only accurate method to measure Insertion Loss. Note that the isolations test should test the total loss of the feeder system including both top and bottom jumpers also including “Surge Arrestors“ if installed. Also note that TMA’s, if installed, must be physically bypassed during this test with a dongle at the top of the tower.

Warning:The “Out Of Band Method” should not be used!

The out of band method gives an indicative result only as the cable loss at the out of band frequency can be very different to the cable loss in band.


Turn on the Site Master and let stabilize for 5 minutes. Disconnect the jumper from the base of the antenna and connect a short circuit to the

end of the jumper. From the ‘MODE’ function select ‘CABLE LOSS’ or “RETURN LOSS” mode depending

on the test device you have (note: you will have to half the results if “return Loss” mode is used).

Set up the sweep frequencies ‘F1&F2’ to the operating frequency band (1710-1880 mHz) Calibrate the Site master as per the Operating manual. Connect the Site Master to the jumper on the feeder to be tested and make

measurement. Use the ‘AUTO SCALE’ function to ensure the whole sweep is displayed on the screen. Use the ‘MARKER’ function – markers 1 & 2 to highlight the peaks and valleys in the

display. Note that the worst point of the insertion loss is measured in the deepest valley. Save the sweep using the ‘SAVE DISPLAY’ function. Use a file name such as

BKD059A1G. Remove short from the jumper and reconnect to antenna. Repeat measurement and save file for all feeders. (A1,A2, B1, B2, C1, C2 etc)

Page 6 of 16 9/4/2023


4.3 Return Loss

This measurement is a key requirement from the DSD. To verify the subcontractors commissioning results we can repeat the measurements.Note that TMA’s ,if installed, must be physically bypassed during this test with a dongle at the top of the tower.


Turn on the Site Master and let stabilize for 5 minutes. From the ‘MODE’ function select ‘RETURN LOSS’. Set up the sweep frequencies ‘F1 & F2’, using table 2 Antenna Characteristics, for the

particular antennas installed. Calibrate the Site master as per the Operating manual. Connect feeder A1 and make measurement. Use the ‘AUTO SCALE’ function to ensure the whole sweep is displayed on the screen. Use the ‘MARKER’ function – markers 1 & 2 to highlight the peaks and valleys in the

display. Up to 4 markers may be used. Save the sweep using the ‘SAVE DISPLAY’ function. Use a file name such as

BKD059A1R. Repeat measurement and save file for all feeders. (A2, B1, B2, C1, C2 etc)

4.4 Isolation Loss

Isolation between Antenna ports is required to be measured by the subcontractor at commissioning. For True move we can measure the isolation to verify 2 things. Firstly to verify Antenna performance, and secondly, and most importantly, to check for feeders crossed between sectors.

Perform the test as follows: This is a two port Measurement

Turn on the Site Master and let stabilize for 5 minutes. From the ‘MODE’ function select ‘INSERTION LOSS(+6dBm)’. Set up the sweep frequencies ‘F1 & F2’, using table 2 Antenna Characteristics, for the

particular antennas installed. Calibrate the Site master as per the Operating manual. Using the two cables and

calibration devices. Connect feeder A1 and A2 and make measurement. Use the ‘AUTO SCALE’ function to ensure the whole sweep is displayed on the screen. Use the ‘MARKER’ function – markers 1 & 2 to highlight the peaks and valleys in the

display. Up to 4 markers may be used. Save the sweep using the ‘SAVE DISPLAY’ function. Use a file name such as

BKD059AI. Repeat measurement and save file for all sectors (B1-B2, C1-C2, etc.) for new sites. When any sectors have double cross- polar antennas for example sector1 in below

figure, the measurement between 1st and 2nd antennas belonging the same sector (A1-A'1, A'1-A'2) and of the existing ones (A1-A2, B1-B2, C1-C2) shall be performed.

Page 7 of 16 9/4/2023


When the additional sector is added, the measurement of new sector (D1-D2) shall be performed. For the case, if there are any changes (location of feeders) on the existing sectors, do the measurement and save file for those sectors as well.

Page 8 of 16 9/4/2023


5. TIPS AND TRICKS WITH THE SITE MASTER

5.1 Power Output

Always ensure that the RF output power for all measurements is set to maximum (+6dBm for S251B). This will ensure best accuracy and reduce interference from external sources.

5.2 Calibration

To remove the need to calibrate the Site Master for each different measurement, calibrate the instrument at power up for a 2 port test.

6. INTERPRETATION OF RESULTS

6.1 DTF (TDR) Measurement

Below is a typical result from a Bangkok Site

-50

-45

-40

-35

-30

-25

0 5 10 15 20 25 30 35 40

M1 M2M3

Distance-to-faultBKD059C1D

Model: S251B Serial #: 00124008 Prop.Vel:0.800Date: 01/13/2002 Time: 16:22:00 Ins.Loss:0.000dB/mBiasTee: OFF Output Power: 6.00 dBmResolution: 259 CAL: ON(COAX)

dB

Distance (0.0 - 40.0 Meter)

M1: -50.46 dB @ 2.02 m M2: -33.56 dB @ 31.94 m M3: -44.44 dB @ 18.91 m

From the Sweep display above we can conclude the following:

M2 shows a reflection at 32 metres. This is the reflection from the antenna. By using Table 1 Feeder Characteristics we can determine that 32 metre feeder length is OK when 7/8” feeder is used.

M1 shows a reflection at a distance of 2 metres. This is a reflection from the first connector after the bottom jumper which is well within specification and can be ignored.

M3 shows a reflection at 19 metres. Unexpected peaks in the reading such as this are to be investigated by visual inspection. This feeder checked OK visually.

Page 9 of 16 9/4/2023


The DTF measurement is an excellent way to isolate any faults along the length of the feeder, which would not otherwise show as part of a Return Loss sweep. Typical faults are loose connectors, over bent feeders, crushed feeders etc.

Investigate any unexpected peaks in the DTF sweep by visual inspection.

6.2 Insertion Loss

Below is a typical result from a Chang Mai Site.

In the plot above, we can see that Marker M2 is set to the valley, which relates to the frequency at which the insertion loss is the worst for the cable being tested. It should be noted that this is a peek measurement of insertion loss.

The acceptance value is equal to Calculate cable loss value plus 0.2 dB allowance including all jumpers connectors and surge arrestors. Where the calculated value is equal to “Length” multiply by cable loss spec. plus two jumper cable loss. “Length” cable can be found by DTF measurement.

Calculate Loss cable = Length (m) x Cable loss (dB/m.) + 2 jumper cable loss (dB)

= Length (m) x Cable loss (dB/m.) + 1.0 (dB)

Acceptance value = Calculate Cable loss (dB) + Allowance (dB)

= Calculate Cable loss (dB) + 0.2 (dB)

Page 10 of 16 9/4/2023


6.3 Return Loss

To simplify the interpretation of these results a single minimum return loss of better than 16dB must be achieved. As well as achieving this target the plot must show a reactive response characterised by sharp variations in level between 20 and 40 dB as per the plot below. If the plot is too flat it can mean that the system is resistive rather than reactive and hence faulty.Please note that sites with long feeders will appear to have a better return loss measurement than sites with short feeders due to the greater cable losses.

Below is a typical return Loss sweep from a Bangkok site.

-50

-45

-40

-35

-30

-25

-20

1750 1800 1850 1900 1950

M1M2

Return LossBKD059B2R

Model: S251B Serial #: 00124008Date: 01/13/2002 Time: 16:48:04BiasTee: OFF Output Power: 6.00 dBmResolution: 259 CAL: ON(COAX)

dB

Frequency (1710.0 - 1990.0 MHz)

M1: -21.41 dB @ 1870.62 MHz M2: -50.46 dB @ 1728.44 MHz


M1 at the peak of the sweep shows that the minimum Return Loss is 21.4 dB. For a feeder length of 32 metres with Kathrein 739496 Antennas this is well within specification.M2 shows a null of 50 dB.

Page 11 of 16 9/4/2023


6.4 Isolation Loss

As mentioned earlier that purpose of this test is to verify antenna performance and check if there are any crossed feeders at the site.

All Antenna manufacturers quote figures of >30dB for isolation between Antenna ports however it is almost impossible to achieve isolation figures better than 55dB. To this end we can assume that if the worst point in the isolation plot is between –30dB and –55dB that the feeders are correctly installed. Or it the antenna feeders are crossed we would expect an isolation greater than 55dB.

For double-antenna BTS, the isolation between antennas depends on the distance separation between them as shown in table below. We would expect the isolation plot of TX-TX between 1st and 2nd antennas belonging the same sector (A1-A'1) is below –30 dB that antenna performance is proper.

Distance between 1st-2nd

Antennas30cm 50cm 80cm

Isolation loss (A1-A'1) 31.1 dB 35.5 dB 39.6 dB

Note: 1. Assume antenna 65 BW and Gain 17.5 dBi used in calculation2. Both antennas point to the same direction

Diagram showing 2 sectors with crossed feeders and one sector with correct feeders

Page 12 of 16 9/4/2023


The following sweep shows a normal port isolation curve.

-57.5

-55.0

-52.5

-50.0

-47.5

1750 1800 1850 1900 1950

M1M2

Gain/Insertion LossBKD059AI


dB

Frequency (1710.0 - 1990.0 MHz)

M1: -47.58 dB @ 1948.75 MHz M2: -61.26 dB @ 1770.77 MHz


M1 tells us that the minimum port isolation for this sector is 47dB. The 2 feeders are connected to the same AntennaM2 tells us that the Antenna null is at 1770.77MHz.

The Sweep below shows the port isolation from a site with crossed feeders.

-120

-110

-100

-90

-80

1750 1800 1850 1900 1950

M1 M2

Gain/Insertion LossBAD ISOL


dB

Frequency (1710.0 - 1990.0 MHz)

M1: -75.56 dB @ 1768.6 MHz M2: -107.13 dB @ 1869.53 MHz


M1 tells us that the Antenna port isolation is 75dB. The 2 feeders are not connected to the same Antenna.

Page 13 of 16 9/4/2023

Peak

Peak


7. USE OF SOFTWARE TOOLS

The Site Master has a comprehensive software tool, which gives the ability to upload sweep results to a PC. Using this facility is possible to save the sweep results to the hard drive or network server.

To install the software on an True move PC, the IT Department will need to be consulted, to enable the software installation to proceed.

Once installed it is simply a matter of connecting the Site Master to a PC and using the ‘CAPTURE’ function from the software menu. The selected sweeps will then be uploaded. Once uploaded sweeps can be modified. Changes can be made to titles, limit values and properties.

It is also possible to convert a Return Loss plot to VSWR plot.

Tip: For best results save files in Windows Metafile (*.wmf) format. Using this format, sweeps can easily be inserted into Documents for best presentation.

Page 14 of 16 9/4/2023


8. APPENDICES

For those who want to convert to VSWR, the following table shows Return Loss versus VSWR and Reflection Coefficient:

RL(dB) VSWR RL(dB) VSWR RL(dB) VSWR RL(dB) VSWR

46.0 1.01 0.00498 26.0 1.11 0.0521 17.7 1.30 0.130 8.0 2.32 0.398

40.0 1.02 0.00990 25.0 1.12 0.0566 17.0 1.33 0.141 7.0 2.61 0.445

37.0 1.03 0.0148 24.0 1.13 0.0610 16.0 1.38 0.158 6.02 3.01 0.500

34.0 1.04 0.0196 23.5 1.14 0.0654 15.0 1.43 0.178 5.0 3.56 0.562

32.0 1.05 0.0244 23.0 1.15 0.0698 14.0 1.50 0.200 4.0 4.42 0.631

30.4 1.06 0.0291 22.0 1.17 0.0783 13.0 1.58 0.224 3.01 5.85 0.707

29.0 1.07 0.0338 21.5 1.18 0.0826 12.0 1.67 0.250 2.0 8.72 0.794

28.0 1.08 0.0385 20.7 1.20 0.0909 11.0 1.78 0.282 1.0 17.39 0.891

27.0 1.09 0.0431 20.0 1.22 0.100 10.0 1.92 0.316 0.5 34.75 0.944

26.4 1.10 0.0476 19.0 1.25 0.112 9.0 2.10 0.355 0.0 Infinity 1.00

END OF DOCUMENT

Page 15 of 16 9/4/2023

basic site master & antenna system theory_v5.0

Documents

updated version

updated coordinate

updated isolation loss

updated isolation test

version document review

release date

self build project

personal signature date