Space systems — Spacecraft system level radio frequency (RF) performance test in compact range

This document specifies the verification test activities for assessing the RF performance of integrated spacecraft, including test items, test requirements, and typical test procedures, test facility and chamber environment, with respect to the testing using compact range. This document is applicable to the RF performance test for spacecraft at system level using compact range.

Systèmes spatiaux — Essai de performance des radiofréquences (RF) dans une gamme compacte au niveau du système de l'engin spatial

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Published
Publication Date
29-Nov-2021
Current Stage
6060 - International Standard published
Start Date
30-Nov-2021
Completion Date
30-Nov-2021
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INTERNATIONAL ISO
STANDARD 23569
First edition
2021-11
Space systems — Spacecraft
system level radio frequency (RF)
performance test in compact range
Systèmes spatiaux — Essai de performance des radiofréquences (RF)
dans une gamme compacte au niveau du système de l'engin spatial
Reference number
ISO 23569:2021(E)
© ISO 2021
---------------------- Page: 1 ----------------------
ISO 23569:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on

the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below

or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
© ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 23569:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction .................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms and definitions .................................................................................................................................................................................... 1

4 Abbreviated terms ............................................................................................................................................................................................. 1

5 Test facility ........................................................................................................................................... ......................................................................2

6 Test requirement ................................................................................................................................................................................................. 4

6.1 System level RF performance test ......................................................................................................................................... 4

6.2 RF performance test in compact range ............................................................................................................................ 5

7 Test item ....................................................................................................................................................................................................................... 6

8 RF performance test methods ...............................................................................................................................................................7

8.1 EIRP test ....................................................................................................................................................................................................... 7

8.1.1 Test purpose ........................................................................................................................................................................... 7

8.1.2 Test principle ......................................................................................................................................................................... 7

8.1.3 Illustrative test procedure ........................................................................................................................................ 7

8.2 G/T-test .......................................................................................................................................................................................................... 8

8.2.1 Test purpose ........................................................................................................................................................................... 8

8.2.2 Test principle ......................................................................................................................................................................... 8

8.2.3 Illustrative test procedure ........................................................................................................................................ 9

8.3 SPFD test ...................................................................................................................................................................................................... 9

8.3.1 Test purpose ........................................................................................................................................................................... 9

8.3.2 Test principle ......................................................................................................................................................................... 9

8.3.3 Illustrative test procedure ..................................................................................................................................... 10

8.4 AFR test ...................................................................................................................................................................................................... 10

8.4.1 Test purpose ........................................................................................................................................................................ 10

8.4.2 Test principle ...................................................................................................................................................................... 10

8.4.3 Illustrative test procedure ..................................................................................................................................... 10

8.5 Group delay test .................................................................................................................................................................................. 10

8.5.1 Test purpose ........................................................................................................................................................................ 10

8.5.2 Test principle ...................................................................................................................................................................... 10

8.5.3 Illustrative test procedure ..................................................................................................................................... 11

8.6 PIM test....................................................................................................................................................................................................... 11

8.6.1 Test purpose ........................................................................................................................................................................ 11

8.6.2 Test principle ...................................................................................................................................................................... 11

8.6.3 Illustrative test procedure ..................................................................................................................................... 11

9 Test report ...............................................................................................................................................................................................................11

Annex A (informative) Illustrative procedures for EIRP test.................................................................................................12

Annex B (informative) Illustrative procedures for G/T-test ....................................................................................................16

Annex C (informative) Illustrative procedures for SPFD test ................................................................................................23

Annex D (informative) Illustrative procedures for AFR test ..................................................................................................27

Annex E (informative) Illustrative procedures for group delay test ..............................................................................32

Annex F (informative) Illustrative procedures for PIM test ....................................................................................................34

Annex G (informative) Derivation for G/T formula ...........................................................................................................................38

Bibliography ............................................................................................................................................................................................................................ 44

iii
© ISO 2021 – All rights reserved
---------------------- Page: 3 ----------------------
ISO 23569:2021(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to

the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see

www.iso.org/iso/foreword.html.

This document was prepared by Technical Committee ISO/TC 20, Aircraft and space vehicles,

Subcommittee SC 14, Space systems and operations.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www.iso.org/members.html.
© ISO 2021 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 23569:2021(E)
Introduction

System level test for RF performance of spacecraft, which is the test for spacecraft expected

performance on orbit, includes test of EIRP, G/T, SPFD, AFR, group delay, PIM, etc. In some conditions, it

also includes verification of the antenna pattern on two crossed planes (normally the antenna pattern

is measured in unit level and subsystem level; if it is necessary to measure in system level, the antenna

pattern on two crossed planes would be chosen for verification purpose). Compact range is suitable for

spacecraft full-link RF performance test, which includes uplink and downlink.

Currently there are well-defined requirements for acceptance test of integrated spacecraft as final RF

performance verification tests, especially for commercial communication spacecraft. RF performance

test for the payload system (including the transponder and Tx/Rx antennas) is becoming more and more

important and should be verified before launch. At present, the system level RF performance test has

become one important step listed in the spacecraft production flow. It is carried out to verify whether

there is unexpected variation during the assembling of the spacecraft and whether the RF performance

in coverage area (footprint) can satisfy the specification.

According to ISO 15864, the system level RF performance test items have been identified as necessary

functional performance parameters in acceptance tests, so they can be tailored to the test requirement

for each kind of spacecraft or test plan.
© ISO 2021 – All rights reserved
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 23569:2021(E)
Space systems — Spacecraft system level radio frequency
(RF) performance test in compact range
1 Scope

This document specifies the verification test activities for assessing the RF performance of integrated

spacecraft, including test items, test requirements, and typical test procedures, test facility and

chamber environment, with respect to the testing using compact range. This document is applicable to

the RF performance test for spacecraft at system level using compact range.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
nominal plane wave axis of compact range
NPA

axis of propagation of a single plane wave generated by the compact range reflector

3.2
effective free space distance in compact range
equivalent distance from the feed, where spherical attenuation exists
4 Abbreviated terms
AFR amplitude-frequency response
AM amplitude modulation
ALC automatic level control
CR compact range
DUT device under test
EIRP effective isotropically radiated power
EM electrical model
FM frequency modulation

G/T ratio of gain-to-noise temperature (quality factor of spacecraft receiving system)

© ISO 2021 – All rights reserved
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ISO 23569:2021(E)
PIM passive intermodulation
QZ quiet zone
RBW resolution bandwidth
RF radio frequency
Rx receive
SERAP serration radiation protection structure
SPFD saturated power flux density
Tx transmit
CW continuous wave
5 Test facility

According to Reference [1], the compact range is one in which the test antenna is illuminated by the

collimated energy in the aperture of a larger point or line focus antenna. For example, a precision

paraboloidal antenna can be used to collimate the energy, as shown schematically in Figure 1, it is more

suitable for test antenna; a precision dual reflector antenna can be used to collimate the energy also,

like Cassegrain dual reflector antenna which is more suitable for the spacecraft system level test, as

shown schematically in Figure 2.
Key
1 quiet zone (QZ)
2 test antenna
3 range Tx/Rx feed
4 focal point

Figure 1 — Schematic representation of a compact range using a reflector and feed

© ISO 2021 – All rights reserved
---------------------- Page: 7 ----------------------
ISO 23569:2021(E)
Key
1 quiet zone (QZ)
2 spacecraft
3 Tx/Rx antenna
4 Tx/Rx antenna
5 range Tx/Rx feed
6 focal point
7 main reflection
8 subreflector

Figure 2 — Schematic representation of a compact range using a dual reflector and feed

The test facility is mainly composed of a range illuminating subsystem, a positioner subsystem, an

anechoic chamber and RF test instruments.

The range illuminating subsystem, which includes the range reflector and the range feeds, shall be

able to provide the plane wave with flatter amplitude and phase distribution in the QZ. The alignment

between the range reflector and the range feed can be done annually or biennially; the nominal plane

wave axis of compact range (NPA) direction can be shown (by cubic mirror or others). The reflector

shall have sufficient accuracy.

The positioner subsystem, which includes the DUT positioner and the range feed positioners, shall be

able to rotate the DUT and range feeds with sufficient accuracy. Due to the heft of the DUT, the DUT

positioner can be equipped with counter weight for balance.

The anechoic chamber, which is covered with several types of absorbing material, can provide test

environment with low reflectivity.

As part of the test facility, related RF instruments shall be provided, to produce uplink RF signal and

to measure downlink RF radiating signal of the DUT, the standard RF instruments are listed in Table 1.

The frequency range, linearity and dynamic range of the RF measurement system shall satisfy the test

© ISO 2021 – All rights reserved
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ISO 23569:2021(E)

requirements. Part of the measurement equipment that makes up the test facility can be calibrated

periodically or in advance of the test by a national metrology institute.
Table 1 — Standard RF instruments
No. Name of instrument Function Applicated test item
EIRP, G/T, SPFD, AFR,
group delay.
1 Source Produce uplink transmitting signal.
Two sources are needed for PIM
test item.
Monitor the downlink receiving signal and
spectrum;
2 Spectrum analyser EIRP, G/T, SPFD, AFR, PIM
Measure the power of downlink receiving
signal.
Measure the power of downlink receiving
3 Power meter EIRP, SPFD
signal.
Reduce the power of downlink signal or
4 Fixed attenuator EIRP, G/T, SPFD, AFR, PIM
Reduce the power of uplink signal.
5 Coupler Couple a part of power from path. EIRP
Combine the signals of two paths with differ-
6 Power hybrid PIM
ent frequencies into one path.
Produce the AM or FM modulation signal
AM or FM modulation
7 which will be carried by uplink and downlink Group delay
signal generator
signal.
Convert the downlink signal to lower frequen-
8 Down converter Group delay
cy.
Demodulate the downlink signal to get the AM
9 Modem Group delay
or FM modulation signal.
Compare the two AM or FM modulation sig-
Modulation domain nal, one is carried by uplink signal, another is
10 Group delay
analyser carried by downlink signal, to get the related
time delay.
Data acquisition com- Run automatically controlled by computer
11 AFR
puter software to complete the data acquisition.
6 Test requirement
6.1 System level RF performance test

When the spacecraft system is very complex, system level RF performance test should be planned based

on the specifications and listed in the spacecraft production flow. The following preparations should be

considered:
a) DUT test scheme, such as which channel and how many channels will be tested;
b) goal budget of EIRP, G/T, SPFD for spacecraft system;

c) installation of the DUT self-alignment target which will be in accordance with the NPA;

d) installation of wind pipes for spacecraft heat dissipation, if necessary;

e) installation of additional humidifier/dehumidifier for special sensitive payload, if necessary;

f) provision of a suitable adapter as interface between spacecraft and the DUT positioner.

© ISO 2021 – All rights reserved
---------------------- Page: 9 ----------------------
ISO 23569:2021(E)
6.2 RF performance test in compact range

In order to verify whether the final RF performance can satisfy the specification, and to perform the RF

tests, the compact range system should fulfil the following conditions for either facility or customer's

equipment.
a) The QZ quality needs to consider the customer’s requirement.

b) The DUT positioner’s maximum bending moment shall be strong enough for spacecraft holding.

Based on the DUT’s weight and centre of gravity, the positioner’s counter weight can be calculated.

Both of the positioner’s elevation and azimuth axes should be balanced with counter weight, so as

to maintain the rotated angle accuracy.

c) The range reflection sources should be reduced. High-performance absorbing material should be

placed between the feed and the DUT to further reduce the effects of the diffraction from the feed

structure. It also helps to suppress any direct radiation from the feed antenna to the test region.

If the compact range has baffle or SERAP, position the baffle in the line-of-sight between the feed

and the QZ to reduce stray radiation directed to the QZ; and position the SERAP in an appropriate

place to prevent the feed from illuminating the main reflector serrations. The position of baffle or

SERAP in compact range is shown in Figure 3.
Key
1 quiet zone (QZ)
2 baffle
3 range Tx/Rx feed
4 focal point
5 SERAP
6 main reflector
7 subreflector
Figure 3 — Schematic of baffle and SERAP’s position

d) The spacecraft’s support structure shall be covered with absorbing material, so as to reduce

additional reflection as far as possible.
© ISO 2021 – All rights reserved
---------------------- Page: 10 ----------------------
ISO 23569:2021(E)

e) In the anechoic chamber, the range feed local area shall be covered with high power absorbing

material, because the spacecraft downlink is high power transmitting state, this area shall

withstand high power, if necessary. The temperature of this area shall be monitored during the

test.

Also, the range reflector local area shall be maintained in stable temperature state by running the

air-condition system continually if necessary, depending on manufacturer’s requirement, so as to

maintain stable QZ performance.

f) The capability of crane and hook need to consider the requirement of spacecraft lifting.

g) The electrical isolation / grounding should be available.

Normally, three grounding terminals isolated from each other can be prepared, and separately

connected to spacecraft surface, test instrument, and any other test equipment temporarily used in

the chamber.
h) The earth resistances need to consider the customer’s requirement.

i) Because of the high-power level in spacecraft system level test, the hazard areas should be

identified with warning plates and / or warning lamps at any personnel gate.
j) Calculate the RF link budget.

k) Do self-calibration for the RF equipment before each absolute value test if necessary, e.g. using a

power meter for absolute power test.
l) Do RF-cable loss calibration, if necessary.
m) Prepare the gain calibration data of the range feeds.

n) Prepare the antenna pattern data measured in subsystem level EM/RM (radiation mock-up).

7 Test item

RF performance test items described in this document refer to tests of EIRP, G/T, SPFD, AFR, group

delay and PIM.

RF performance test items are tailored to the test requirement for each kind of spacecraft or test plan.

The channels selected to be tested depend on the test requirement.

To verify the spacecraft’s uplink performance, G/T and SPFD shall be tested. The spacecraft body

together with the Rx antennas shall be located in the QZ, while the Tx range feed shall be located at the

focus of the range reflector.

To verify the spacecraft’s downlink performance, EIRP shall be tested. The spacecraft body together

with the Tx antennas shall be located in the QZ, while the Rx range feed shall be located at the focus of

the range reflector.

To verify the spacecraft’s full link performance, AFR and group delay shall be tested. For the AFR

test, the spacecraft body together with the Tx antennas or the spacecraft body together with the Rx

antennas shall be located in the QZ, while the Rx or the Tx range feed shall be located at the focus of the

range reflector, depending on whether output AFR or input AFR will be tested. For the group delay test,

the spacecraft body together with the Tx antennas and Rx antennas shall be located in the QZ, if the size

of the QZ is not enough to support the full link wireless test, this group delay test item will be tailored.

For a spacecraft antenna system which shares Rx/Tx signals, the PIM components of the spacecraft’s

downlink transmitting signal may go directly to the uplink channels. If PIM frequencies are within the

spacecraft’s uplink receiving frequency band, PIM shall be tested. The spacecraft body together with

the Tx antennas shall be located in the QZ, while the Rx range feed shall be located at the focus of the

range reflector.
© ISO 2021 – All rights reserved
---------------------- Page: 11 ----------------------
ISO 23569:2021(E)

The EIRP, SPFD and PIM test need to be done in saturation state, which means spacecraft’s uplink is

saturated. The saturation point can be determined by several methods, such as power/gain method, AM

number method, and by monitoring the telemetry parameters of spacecraft’s amplifier.

8 RF performance test methods
8.1 EIRP test
8.1.1 Test purpose

The purpose of the EIRP test is to measure and to evaluate EIRP values at the beam peak and/or at

a typical point in the spacecraft downlink coverage area (footprint), and to verify whether the EIRP

values can satisfy the goal budget and specifications. By combining the antenna pattern measured in

subsystem level EM/RM (radiation mock-up) and the system level measured EIRP values at the beam

peak and/or at a typical point, the EIRP coverage pattern can be obtained.

If necessary, a verification of the spacecraft’s Tx or Tx/Rx antenna radiation pattern can also be done on

two crossed planes in coverage area by using the downlink EIRP setup.
8.1.2 Test principle

In compact range, the spherical wave from the range feed is reflected by the reflector, as a plane wave,

to the QZ, wherein the spacecraft is located, then the equivalent spacecraft to earth RF link can be used

for system level RF performance test. The distance from the range feed to the reflector and then to the

QZ, is the effective free space distance in compact range, R; this value depends on the design of compact

range.

Based on the reciprocity of compact range, spacecraft’s downlink signal, Tx, is reflected by the range

reflector and goes back to the range feed, wherein R is the same. The EIRP can be obtained by measuring

the Rx signal received by the range feed. The EIRP can be calculated by Formulae (1), (2) and (3).

QG= ·P (1)
EIRP Tx,,satTxsat
PL·
Rx CR p,down
Q = (2)
EIRP
Rx,CR
 4πR 
L = (3)
p,down  
 
down
where
L is the free space loss for the downlink signal;
p,down
R is the effective free space distance in compact range, m;
P is the received power measured at the output port of the range feed, W;
Rx,CR
G is the gain of Rx range feed.
Rx,CR
8.1.3 Illustrative test procedure

Two illustrative procedure examples for the EIRP test are provided in Annex A. The EIRP can be

measured by two methods: with full wireless link setup or with wireless downlink setup. The procedure

to be used depends on the test requirement and whether the size of QZ can satisfy the full link setup.

© ISO 2021 – All rights reserved
---------------------- Page: 12 ----------------------
ISO 23569:2021(E)
8.2 G/T-test
8.2.1 Test purpose

The purpose of the gain-to-noise temperature ratio, G/T, test is to measure and to evaluate G/T values

at the beam peak and/or at a typical point in the spacecraft’s uplink coverage area (footprint). The test

results show whether the G/T values can satisfy the goal budget and specifications. The G/T coverage

pattern can be obtained by combining the antenna pattern measured in subsystem level EM/RM

(radiation mock-up) and the system level measured G/T values at the beam peak and/or at a typical

point.
8.2.2 Test principle

As described in 8.1.2, the spacecraft is located in the QZ and illuminated by the plane wave. R is known

and depends on the design of the compact range.

The G/T can be measured in two different modes: the fixed gain mode and the automatic level control

(ALC) mode. The ALC mode requires one more step in the data acquisition compared with the fixed

gain mode. The major difference between these two modes is that the output power level varies with

the input power level in the fixed gain mode, whereas the output power level is constant in the ALC

mode.

a) G/T in the fixed gain mode is obtained from three sequential power level measurements:

1) noise power level, P , of the receiving test equipment, while the spacecraft transponder is

turning off, the RF output of range source is turning off also;

2) noise power level, P , of the receiving test equipment, including the spacecraft noise level, while

the spacecraft transponder is turning on, the RF output of range source is turning off;

3) power level, P , of the receiving test equipment, inc
...

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 23569
ISO/TC 20/SC 14
Space systems — Spacecraft
Secretariat: ANSI
system level radio frequency (RF)
Voting begins on:
2021­09­02 performance test in compact range
Voting terminates on:
Systèmes spatiaux — Essai de performance des radiofréquences (RF)
2021­10­28
dans une gamme compacte au niveau du système de l'engin spatial
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
ISO/FDIS 23569:2021(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN­
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. ISO 2021
---------------------- Page: 1 ----------------------
ISO/FDIS 23569:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH­1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/FDIS 23569:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Abbreviated terms .............................................................................................................................................................................................. 1

5 Test facility .................................................................................................................................................................................................................. 2

6 Test requirement .................................................................................................................................................................................................. 4

6.1 System level RF performance test .......................................................................................................................................... 4

6.2 RF performance test in compact range .............................................................................................................................. 5

7 Test item ........................................................................................................................................................................................................................ 6

8 RF performance test methods ................................................................................................................................................................ 7

8.1 EIRP test ....................................................................................................................................................................................................... 7

8.1.1 Test purpose ........................................................................................................................................................................ 7

8.1.2 Test principle ...................................................................................................................................................................... 7

8.1.3 Illustrative test procedure ....................................................................................................................................... 7

8.2 G/T ­test ........................................................................................................................................................................................................ 8

8.2.1 Test purpose ........................................................................................................................................................................ 8

8.2.2 Test principle ...................................................................................................................................................................... 8

8.2.3 Illustrative test procedure ....................................................................................................................................... 9

8.3 SPFD test ...................................................................................................................................................................................................... 9

8.3.1 Test purpose ........................................................................................................................................................................ 9

8.3.2 Test principle ...................................................................................................................................................................... 9

8.3.3 Illustrative test procedure ....................................................................................................................................10

8.4 AFR test ......................................................................................................................................................................................................10

8.4.1 Test purpose .....................................................................................................................................................................10

8.4.2 Test principle ...................................................................................................................................................................10

8.4.3 Illustrative test procedure ....................................................................................................................................10

8.5 Group delay test ..................................................................................................................................................................................10

8.5.1 Test purpose .....................................................................................................................................................................10

8.5.2 Test principle ...................................................................................................................................................................10

8.5.3 Illustrative test procedure ....................................................................................................................................11

8.6 PIM test .......................................................................................................................................................................................................11

8.6.1 Test purpose .....................................................................................................................................................................11

8.6.2 Test principle ...................................................................................................................................................................11

8.6.3 Illustrative test procedure ....................................................................................................................................11

9 Test report ................................................................................................................................................................................................................11

Annex A (informative) Illustrative procedures for EIRP test ...................................................................................................12

Annex B (informative) Illustrative procedures for G/T-test......................................................................................................16

Annex C (informative) Illustrative procedures for SPFD test ...................................................................................................23

Annex D (informative) Illustrative procedures for AFR test .....................................................................................................27

Annex E (informative) Illustrative procedures for group delay test .................................................................................32

Annex F (informative) Illustrative procedures for PIM test ......................................................................................................34

Annex G (informative) Derivation for G/T formula ............................................................................................................................38

Bibliography .............................................................................................................................................................................................................................44

© ISO 2021 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO/FDIS 23569:2021(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non­governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 20, Aircraft and space vehicles,

Subcommittee SC 14, Space systems and operations.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
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ISO/FDIS 23569:2021(E)
Introduction

System level test for RF performance of spacecraft, which is the test for spacecraft expected

performance on orbit, includes test of EIRP, G/T, SPFD, AFR, group delay, PIM, etc. In some conditions, it

also includes verification of the antenna pattern on two crossed planes (normally the antenna pattern

is measured in unit level and subsystem level; if it is necessary to measure in system level, the antenna

pattern on two crossed planes would be chosen for verification purpose). Compact range is suitable for

spacecraft full­link RF performance test, which includes uplink and downlink.

Currently there are well-defined requirements for acceptance test of integrated spacecraft as final RF

performance verification tests, especially for commercial communication spacecraft. RF performance

test for the payload system (including the transponder and Tx/Rx antennas) is becoming more and more

important and should be verified before launch. At present, the system level RF performance test has

become one important step listed in the spacecraft production flow. It is carried out to verify whether

there is unexpected variation during the assembling of the spacecraft and whether the RF performance

in coverage area (footprint) can satisfy the specification.

According to ISO 15864, the system level RF performance test items have been identified as necessary

functional performance parameters in acceptance tests, so they can be tailored to the test requirement

for each kind of spacecraft or test plan.
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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 23569:2021(E)
Space systems — Spacecraft system level radio frequency
(RF) performance test in compact range
1 Scope

This document specifies the verification test activities for assessing the RF performance of integrated

spacecraft, including test items, test requirements, and typical test procedures, test facility and

chamber environment, with respect to the testing using compact range. This document is applicable to

the RF performance test for spacecraft at system level using compact range.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
nominal plane wave axis of compact range
NPA

axis of propagation of a single plane wave generated by the compact range reflector

3.2
effective free space distance in compact range
equivalent distance from the feed, where spherical attenuation exists
4 Abbreviated terms
AFR amplitude-frequency response
AM amplitude modulation
CR compact range
DUT device under test
EIRP effective isotropically radiated power
EM electrical model
FM frequency modulation

G/T ratio of gain-to-noise temperature (quality factor of spacecraft receiving system)

PIM passive intermodulation
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ISO/FDIS 23569:2021(E)
QZ quiet zone
RBW resolution bandwidth
RF radio frequency
Rx receive
SERAP serration radiation protection structure
SPFD saturated power flux density
Tx transmit
CW continuous wave
5 Test facility

According to Reference [1], the compact range is one in which the test antenna is illuminated by the

collimated energy in the aperture of a larger point or line focus antenna. For example, a precision

paraboloidal antenna can be used to collimate the energy, as shown schematically in Figure 1, it is more

suitable for test antenna; a precision dual reflector antenna can be used to collimate the energy also,

like Cassegrain dual reflector antenna which is more suitable for the spacecraft system level test, as

shown schematically in Figure 2.
Key
1 quite zone (QZ)
2 test antenna
3 range Tx/Rx feed
4 focal point

Figure 1 — Schematic representation of a compact range using a reflector and feed

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ISO/FDIS 23569:2021(E)
Key
1 quite zone (QZ)
2 spacecraft
3 Tx/Rx antenna
4 Tx/Rx antenna
5 range Tx/Rx feed
6 focal point
7 main reflection
8 subreflector

Figure 2 — Schematic representation of a compact range using a dual reflector and feed

The test facility is mainly composed of a range illuminating subsystem, a positioner subsystem, an

anechoic chamber and RF test instruments.

The range illuminating subsystem, which includes the range reflector and the range feeds, shall be

able to provide the plane wave with flatter amplitude and phase distribution in the QZ. The alignment

between the range reflector and the range feed can be done annually or biennially; the nominal plane

wave axis of compact range (NPA) direction can be shown (by cubic mirror or others). The reflector

shall have sufficient accuracy.

The positioner subsystem, which includes the DUT positioner and the range feed positioners, shall be

able to rotate the DUT and range feeds with sufficient accuracy. Due to the heft of the DUT, the DUT

positioner can be equipped with counter weight for balance.

The anechoic chamber, which is covered with several types of absorbing material, can provide test

environment with low reflectivity.

As part of the test facility, related RF instruments shall be provided, to produce uplink RF signal and

to measure downlink RF radiating signal of the DUT, the standard RF instruments are listed in Table 1.

The frequency range, linearity and dynamic range of the RF measurement system shall satisfy the test

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ISO/FDIS 23569:2021(E)

requirements. Part of the measurement equipment that makes up the test facility can be calibrated

periodically or in advance of the test by a national metrology institute.
Table 1 — Standard RF instruments
No. Name of instrument Function Applicated test item
EIRP, G/T, SPFD, AFR
Group delay
1 Source Produce uplink transmitting signal.
Two sources are needed for PIM
test item.
Monitor the downlink receiving signal and
spectrum;
2 Spectrum analyser EIRP, G/T, SPFD, AFR, PIM
Measure the power of downlink receiving
signal.
Measure the power of downlink receiving
3 Power meter EIRP, SPFD
signal.
Reduce the power of downlink signal or
4 Fixed attenuator EIRP, G/T, SPFD, AFR, PIM
Reduce the power of uplink signal.
5 Coupler Couple a part of power from path. EIRP
Combine the signals of two paths with differ­
6 Power hybrid PIM
ent frequencies into one path.
Produce the AM or FM modulation signal
AM or FM modulation
7 which will be carried by uplink and downlink Group delay
signal generator
signal.
Convert the downlink signal to lower frequen­
8 Down converter Group delay
cy.
Demodulate the downlink signal to get the
9 Modem Group delay
AM or FM modulation signal.
Compare the two AM or FM modulation sig­
Modulation domain nal, one is carried by uplink signal, another is
10 Group delay
analyser carried by downlink signal, to get the related
time delay.
Data acquisition com­ Run automatically controlled by computer
11 AFR
puter software to complete the data acquisition.
6 Test requirement
6.1 System level RF performance test

When the spacecraft system is very complex, system level RF performance test should be planned based

on the specifications and listed in the spacecraft production flow. The following preparations should be

considered:
a) DUT test scheme, such as which channel and how many channels will be tested;
b) goal budget of EIRP, G/T, SPFD for spacecraft system;

c) installation of the DUT self-alignment target which will be in accordance with the NPA;

d) installation of wind pipes for spacecraft heat dissipation, if necessary;

e) installation of additional humidifier/dehumidifier for special sensitive payload, if necessary;

f) provision of a suitable adapter as interface between spacecraft and the DUT positioner.

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6.2 RF performance test in compact range

In order to verify whether the final RF performance can satisfy the specification, and to perform the RF

tests, the compact range system should fulfil the following conditions for either facility or customer's

equipment.
a) The QZ quality needs to consider the customer’s requirement.

b) The DUT positioner’s maximum bending moment shall be strong enough for spacecraft holding.

Based on the DUT’s weight and centre of gravity, the positioner’s counter weight can be calculated.

Both of the positioner’s elevation and azimuth axes should be balanced with counter weight, so as

to maintain the rotated angle accuracy.

c) The range reflection sources should be reduced. High-performance absorbing material should be

placed between the feed and the DUT to further reduce the effects of the diffraction from the feed

structure. It also helps to suppress any direct radiation from the feed antenna to the test region.

If the compact range has baffle or SERAP, position the baffle in the line-of-sight between the feed

and the QZ to reduce stray radiation directed to the QZ; and position the SERAP in an appropriate

place to prevent the feed from illuminating the main reflector serrations. The position of baffle or

SERAP in compact range is shown in Figure 3.
Key
1 quite zone (QZ)
2 baffle
3 range Tx/Rx feed
4 focal point
5 SERAP
6 main reflector
7 subreflector
Figure 3 — Schematic of baffle and SERAP’s position

d) The spacecraft’s support structure shall be covered with absorbing material, so as to reduce

additional reflection as far as possible.
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e) In the anechoic chamber, the range feed local area shall be covered with high power absorbing

material, because the spacecraft downlink is high power transmitting state, this area shall

withstand high power, if necessary. The temperature of this area shall be monitored during the

test.

Also, the range reflector local area shall be maintained in stable temperature state by running the

air-condition system continually if necessary, depending on manufacturer’s requirement, so as to

maintain stable QZ performance.

f) The capability of crane and hook need to consider the requirement of spacecraft lifting.

g) The electrical isolation / grounding should be available.

Normally, three grounding terminals isolated from each other can be prepared, and separately

connected to spacecraft surface, test instrument, and any other test equipment temporarily used in

the chamber.
h) The earth resistances need to consider the customer’s requirement.

i) Because of the high-power level in spacecraft system level test, the hazard areas should be

identified with warning plates and / or warning lamps at any personnel gate.
j) Calculate the RF link budget.

k) Do self-calibration for the RF equipment before each absolute value test if necessary, e.g. using a

power meter for absolute power test.
l) Do RF-cable loss calibration, if necessary.
m) Prepare the gain calibration data of the range feeds.

n) Prepare the antenna pattern data measured in subsystem level EM/RM (radiation mock-up).

7 Test item

RF performance test items described in this document refer to tests of EIRP, G/T, SPFD, AFR, group

delay and PIM.

RF performance test items are tailored to the test requirement for each kind of spacecraft or test plan.

The channels selected to be tested depend on the test requirement.

To verify the spacecraft’s uplink performance, G/T and SPFD shall be tested. The spacecraft body

together with the Rx antennas shall be located in the QZ, while the Tx range feed shall be located at the

focus of the range reflector.

To verify the spacecraft’s downlink performance, EIRP shall be tested. The spacecraft body together

with the Tx antennas shall be located in the QZ, while the Rx range feed shall be located at the focus of

the range reflector.

To verify the spacecraft’s full link performance, AFR and group delay shall be tested. For the AFR

test, the spacecraft body together with the Tx antennas or the spacecraft body together with the Rx

antennas shall be located in the QZ, while the Rx or the Tx range feed shall be located at the focus of the

range reflector, depending on whether output AFR or input AFR will be tested. For the group delay test,

the spacecraft body together with the Tx antennas and Rx antennas shall be located in the QZ, if the size

of the QZ is not enough to support the full link wireless test, this group delay test item will be tailored.

For a spacecraft antenna system which shares Rx/Tx signals, the PIM components of the spacecraft’s

downlink transmitting signal may go directly to the uplink channels. If PIM frequencies are within the

spacecraft’s uplink receiving frequency band, PIM shall be tested. The spacecraft body together with

the Tx antennas shall be located in the QZ, while the Rx range feed shall be located at the focus of the

range reflector.
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The EIRP, SPFD and PIM test need to be done in saturation state, which means spacecraft’s uplink is

saturated. The saturation point can be determined by several methods, such as power/gain method, AM

number method, and by monitoring the telemetry parameters of spacecraft’s amplifier.

8 RF performance test methods
8.1 EIRP test
8.1.1 Test purpose

The purpose of the EIRP test is to measure and to evaluate EIRP values at the beam peak and/or at

a typical point in the spacecraft downlink coverage area (footprint), and to verify whether the EIRP

values can satisfy the goal budget and specifications. By combining the antenna pattern measured in

subsystem level EM/RM (radiation mock-up) and the system level measured EIRP values at the beam

peak and/or at a typical point, the EIRP coverage pattern can be obtained.

If necessary, a verification of the spacecraft’s Tx or Tx/Rx antenna radiation pattern can also be done on

two crossed planes in coverage area by using the downlink EIRP setup.
8.1.2 Test principle

In compact range, the spherical wave from the range feed is reflected by the reflector, as a plane wave,

to the QZ, wherein the spacecraft is located, then the equivalent spacecraft to earth RF link can be used

for system level RF performance test. The distance from the range feed to the reflector and then to the

QZ, is the effective free space distance in compact range, R; this value depends on the design of compact

range.

Based on the reciprocity of compact range, spacecraft’s downlink signal, Tx, is reflected by the range

reflector and goes back to the range feed, wherein R is the same. The EIRP can be obtained by measuring

the Rx signal received by the range feed. The EIRP can be calculated by Formulae (1), (2) and (3).

QG= ·P (1)
EIRP Tx,,satTxsat
PL·
Rx CR p,down
Q = (2)
EIRP
Rx,CR
 4πR 
L = (3)
p,down  
 
down
where
L is the free space loss for the downlink signal;
p,down
R is the effective free space distance in compact range, m;
P is the received power measured at the output port of the range feed, W;
Rx,CR
G is the gain of Rx range feed.
Rx,CR
8.1.3 Illustrative test procedure

Two illustrative procedure examples for the EIRP test are provided in Annex A. The EIRP can be

measured by two methods: with full wireless link setup or with wireless downlink setup. The procedure

to be used depends on the test requirement and whether the size of QZ can satisfy the full link setup.

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8.2 G/T -test
8.2.1 Test purpose

The purpose of the gain­to­noise temperature ratio, G/T, test is to measure and to evaluate G/T values

at the beam peak and/or at a typical point in the spacecraft’s uplink coverage area (footprint). The test

results show whether the G/T values can satisfy the goal budget and specifications. The G/T coverage

pattern can be obtained by combining the antenna pattern measured in subsystem level EM/RM

(radiation mock-up) and the system level measured G/T values at the beam peak and/or at a typical

point.
8.2.2 Test principle

As described in 8.1.2, the spacecraft is located in the QZ and illuminated by the plane wave. R is known

and depends on the design of the compact range.

The G/T can be measured in two different modes: the fixed gain mode and the automatic level control

(ALC) mode. The ALC mode requires one more step in the data acquisition compared with the fixed

gain mode. The major difference between these two modes is that the output power
...

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