ETSI ETS 300 332 ed.1 (1994-12)

Satellite Earth Stations and Systems (SES); Transmit/receive Very Small Aperture Terminals (VSATs) used for data communications operating in the Fixed Satellite Service (FSS) 6 GHz and 4 GHz frequency bands

DE/SES-02004

Satelitske zemeljske postaje in sistemi (SES) - Oddajno-sprejemni satelitski terminali z zelo majhno antensko odprtino (VSATs), ki se uporabljajo za podatkovne komunikacije v frekvenčnih pasovih 6 GHz in 4 GHz fiksne satelitske storitve (FSS)

General Information

• Status: Published
• Publication Date: 14-Dec-1994
• Technical Committee: SES 2 - RF and IF Equipment
• Current Stage: 12 - Completion
• Due Date: 28-Nov-1994
• Completion Date: 15-Dec-1994
• Ref Project: SIST ETS 300 332 E1:2006 - Satellite Earth Stations and Systems (SES); Transmit/receive Very Small Aperture Terminals (VSATs) used for data communications operating in the Fixed Satellite Service (FSS) 6 GHz and 4 GHz frequency bands

Standards Content (Sample)

SLOVENSKI STANDARD
SIST ETS 300 332 E1:2006
01-februar-2006
6DWHOLWVNH]HPHOMVNHSRVWDMHLQVLVWHPL6(62GGDMQRVSUHMHPQLVDWHOLWVNL
WHUPLQDOL]]HORPDMKQRDQWHQVNRRGSUWLQR96$7VNLVHXSRUDEOMDMR]D
SRGDWNRYQHNRPXQLNDFLMHYIUHNYHQþQLKSDVRYLK*+]LQ*+]ILNVQHVDWHOLWVNH
VWRULWYH)66
Satellite Earth Stations and Systems (SES); Transmit/receive Very Small Aperture
Terminals (VSATs) used for data communications operating in the Fixed Satellite Service
(FSS) 6 GHz and 4 GHz frequency bands
Ta slovenski standard je istoveten z: ETS 300 332 Edition 1
ICS:
33.060.30 Radiorelejni in fiksni satelitski Radio relay and fixed satellite
komunikacijski sistemi communications systems
SIST ETS 300 332 E1:2006 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------

SIST ETS 300 332 E1:2006

---------------------- Page: 2 ----------------------

SIST ETS 300 332 E1:2006
EUROPEAN ETS 300 332
TELECOMMUNICATION December 1994
STANDARD
Source: ETSI TC-SES Reference: DE/SES-02004
ICS: 33.060.30
VSAT, FSS
Key words:
Satellite Earth Stations and Systems (SES);
Transmit/receive Very Small Aperture Terminals (VSATs)
used for data communications
operating in the Fixed Satellite Service (FSS)
6 GHz and 4 GHz frequency bands
ETSI
European Telecommunications Standards Institute
ETSI Secretariat
F-06921 Sophia Antipolis CEDEX - FRANCE
Postal address:
650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE
Office address:
c=fr, a=atlas, p=etsi, s=secretariat - [e-mail]
X.400: Internet:
Tel.: [phone] - Fax: [phone]
Copyright Notification: No part may be reproduced except as authorized by written permission. The copyright and the
foregoing restriction extend to reproduction in all media.
© European Telecommunications Standards Institute 1994. All rights reserved.
New presentation - see History box

---------------------- Page: 3 ----------------------

SIST ETS 300 332 E1:2006
Page 2
ETS 300 332: December 1994
Whilst every care has been taken in the preparation and publication of this document, errors in content,
typographical or otherwise, may occur. If you have comments concerning its accuracy, please write to
"ETSI Editing and Committee Support Dept." at the address shown on the title page.

---------------------- Page: 4 ----------------------

SIST ETS 300 332 E1:2006
Page 3
ETS 300 332: December 1994
Contents
Foreword .5
1 Scope .7
2 Normative references.7
3 Definitions and abbreviations .8
3.1 Definitions .8
3.2 Abbreviations .9
4 Test report.9
5 Safety .9
5.1 Mechanical construction .9
5.2 Electrical safety.11
5.2.1 Power voltages.11
5.2.2 Lightning.11
5.2.3 Radio frequency radiation protection.12
5.2.4 Solar radiation protection .12
6 Radio Frequency (RF).12
6.1 Spurious radiation.12
6.2 On axis spurious radiation (outside the nominated bandwidth) .13
6.3 Transmit carrier centre frequency stability.14
6.4 Off-axis EIRP emission density (co-polar and cross-polar) within the band 5,850 to
6,425 GHz.14
6.5 Transmit polarisation discrimination (linear) or axial ratio (circular) .15
6.6 Carrier on-off (inside the nominated bandwidth).16
6.7 Electromagnetic immunity.16
7 Mechanical .16
7.1 Pointing stability .16
7.2 Antenna pointing accuracy capability.17
7.3 Linear polarisation angle alignment capability .17
8 Antenna transmit gain pattern (co-polar and cross-polar).17
9 Antenna receive gain pattern (co-polar and cross-polar) .18
10 Transmit polarisation discrimination.19
11 Receive polarisation discrimination.20
12 Electromagnetic immunity .20
13 Terrestrial interfaces .20
14 Control and monitoring.20
Annex A (normative): Spurious radiation outside main-beam - test procedure.21
A.1 Introduction.21
A.2 Measuring method.21
A.3 Equipment Under Test (EUT).22

---------------------- Page: 5 ----------------------

SIST ETS 300 332 E1:2006
Page 4
ETS 300 332: December 1994
A.4 Operating mode signal generation. 22
A.5 Test site and test set-up . 22
A.6 Measuring procedure below cut-off frequency . 22
History. 23

---------------------- Page: 6 ----------------------

SIST ETS 300 332 E1:2006
Page 5
ETS 300 332: December 1994
Foreword
This European Telecommunication Standard (ETS) has been produced by the Satellite Earth Stations and
Systems (SES) Technical Committee of the European Telecommunications Standards Institute (ETSI).
Transposition dates
Date of latest announcement of this ETS (doa): 31st March 1995
Date of latest publication of new National Standard 30th September 1995
or endorsement of this ETS (dop/e):
Date of withdrawal of any conflicting National Standard (dow): 30th September 1995

---------------------- Page: 7 ----------------------

SIST ETS 300 332 E1:2006
Page 6
ETS 300 332: December 1994
Blank page

---------------------- Page: 8 ----------------------

SIST ETS 300 332 E1:2006
Page 7
ETS 300 332: December 1994
1 Scope
This European Telecommunication Standard (ETS) provides specifications for the standardisation of the
characteristics of transmit/receive Very Small Aperture Terminals (VSATs) operating as part of a satellite
network used for the distribution and/or exchange of data between users.
In such a network a Centralised Control and Monitoring Function (CCMF) is responsible for the monitoring
and control of remote VSATs.
These VSATs have the following characteristics:
- operating in the shared part of the C band allocated to the Fixed Services (FS) and to the Fixed
Satellite Services (FSS), 5,850 to 6,425 GHz (Earth-Space), 3,625 to 4,200 GHz (Space-Earth);
- in these frequency bands circular polarisation is normally used and the system operates through
satellites at 3° spacing;
- designed for unattended operation;
- limited to the reception and transmission of baseband digital signals;
- equipped with one, or several terrestrial ports but the total aggregate information bit rate transmitted
towards the satellite through these ports shall be limited to 2 048 Mbit/s;
- antenna diameter not exceeding normally 7,3 m, or equivalent corresponding aperture.
The equipment considered in this ETS comprises both the "outdoor unit", usually composed of the
antenna subsystem with the associated power amplifier and Low Noise Block (LNB), and the "indoor unit"
composed of the remaining part of the communication chain, including the cable between these two units.
This ETS does not contain any requirement, recommendation or information about the installation of the
VSATs, nor is this ETS intended to apply to VSAT network hub stations.
This ETS deals with two types of specification:
- specifications defined in order to protect other users of the frequency spectrum, both satellite and
terrestrial, from unacceptable interference. In addition, these specifications are specified for the
purposes of electrical safety, structural safety and solar radiation protection as well as protection
from harmful interference;
- specifications related to characteristics which contribute to the quality of reception by providing the
VSAT with minimum interference protection from other radio systems.
2 Normative references
This ETS incorporates, by dated or undated reference, provisions from other publications. These
normative references are cited at the appropriate places in the text and the publications are listed
hereafter. For dated references, subsequent amendments to or revisions of any of these publications
apply to this ETS only when incorporated in it by amendment or revision. For undated references the latest
edition of the publication referred to applies.
[1] IEC 950 (1991): "Safety of information technology equipment including electrical
business equipment".
[2] IEC 81 (Co) 6 (1981): "Standards for Lightning Protection of Structures".
[3] CISPR Publication No. 22 (1992): "Limits and methods of measurement of radio
interference characteristics of information technology equipment".
[4] CISPR Publication No. 16 (1987): "Specifications for radio interference
measuring apparatus and measurement methods".

---------------------- Page: 9 ----------------------

SIST ETS 300 332 E1:2006
Page 8
ETS 300 332: December 1994
[5] EN 55011 (1986): "Limits and methods of measurements of radio interference
characteristics of industrial, scientific and medical (ISM) radio-frequency
equipment".
[6] IEC 510-2-1 (1978): "Methods of measurement for radio equipment used in
satellite earth stations Part 2".
[7] IEC 510-1-2 (1984): "Methods of measurement for radio equipment used in
satellite earth station Part 1".
[8] IEC 801-3 (1984): "Electromagnetic compatibility for industrial process
measurement and control equipment Part 3".
[9] ETS 300 160: "Satellite Earth Stations (SES) - Control and monitoring functions
at a VSAT".
[10] ETS 300 161: "Satellite Earth Stations (SES) - Centralised control and
monitoring functions for VSAT networks".
[11] ITU-R Recommendation 732 (1992): "Method for statistical processing of Earth
station antenna side-lobe peaks".
3 Definitions and abbreviations
3.1 Definitions
For the purposes of this ETS, the following definitions apply.
outdoor unit: Is the part of the terminal installed in a position within line of sight to the satellite and it is
intended to be operated in outdoor environmental conditions.
It usually comprises three main parts:
1) the antenna sub-system which converts the incident radiation field into a guided wave and vice
versa;
2) the LNB, which is a device that amplifies, with very low internal noise, the received signals in the
Radio Frequency (RF) band and converts them to intermediate frequencies;
3) the power amplifier which amplifies the low level RF signals for transmission through the antenna
subsystem.
NOTE 1: The installation equipment (means of attachment) is not included in this ETS.
However, the antenna structures and other components directly mounted on the
antenna and forming an integral part of it, are subject to the specifications of this ETS.
indoor unit: Is composed of the remaining part of the equipment. It is generally installed inside the
buildings and is connected to the outdoor unit. The connection cable between the outdoor and indoor unit
belongs to the indoor unit.
nominated bandwidth: The bandwidth of the VSAT radio frequency transmission is nominated by the
manufacturer. The nominated bandwidth is wide enough to encompass all spectral elements of the
transmission which have a density greater than the specified spurious levels, and to take account of the
transmit carrier frequency stability.
NOTE 2: This parameter is to allow flexibility regarding adjacent channel interference levels
which will be taken into account by operational procedures depending on the exact
transponder carrier assignment situation.
spurious radiation: Is any radiation outside the nominated bandwidth.

---------------------- Page: 10 ----------------------

SIST ETS 300 332 E1:2006
Page 9
ETS 300 332: December 1994
3.2 Abbreviations
For the purposes of this ETS, the following abbreviations apply:
CCMF Centralised Control and Monitoring Functions
CISPR Comité International Spécial des Perturbations Radioélectriques
CSPDN Circuit Switched Public Data Network
EIRP Equivalent Isotropically Radiated Power
EUT Equipment Under Test
FS Fixed Service
FSS Fixed Satellite Service
IEC International Electrotechnical Commission
ITU International Telecommunication Union
ITU-R ITU Radiocommunication Sector
LNB Low Noise Block (low noise amplifier and down converter)
RF Radio Frequency
VSAT Very Small Aperture Terminal
4 Test report
The test report shall contain:
- the value of the nominated bandwidth declared by the manufacturer;
- the results of the tests.
5 Safety
5.1 Mechanical construction
Purpose:
Protection of operating personnel, the public and goods from insecure structures.
Specification:
This specification applies to the outdoor unit only.
The outdoor unit, including mounted and structural components, (but excluding the means of attachment)
shall be designed to support the following main loads due to:
- the weight of the antenna and structural components;
- the wind speed.
Loading due to snow and ice is not considered.
At wind speeds up to 180 km/h, referred to standard atmosphere temperature and pressure (293 K and
5
1,013 x 10 Pa (1 013 mbar)), none of the components shall be torn away.
Verification:
Two alternative methods are given for verification.
a) Wind tunnel testing.
A wind tunnel shall be used for the purpose of conformance testing. The wind tunnel tests shall be
performed on the outdoor unit, or alternatively on a scale-model of the outdoor unit. The data
obtained for the scale-model shall be computed in order to obtain data for the true antenna size.

---------------------- Page: 11 ----------------------

SIST ETS 300 332 E1:2006
Page 10
ETS 300 332: December 1994
b) Numerical analysis and simplified tests.
This method shall provide an alternative to the wind tunnel test. The effects of maximum wind load
shall be first computed on the overall outdoor unit using a numerical analysis method, e.g. finite
elements method by computer taking into account the intrinsic properties of the materials. In a
second step, the computed loads shall be applied to the structure.
The purpose of the numerical analysis is twofold:
1) to show compliance with the specification under nominated conditions;
2) to compute equivalent static loads (force and torque) applied to the critical attachment points
of the structure, e.g.:
- reflector - mounting legs fixing point;
- reflector - struts;
- struts - LNB.
Test procedure:
a) Wind tunnel.
The test object shall be mounted in such a way, that wind load can be applied from all horizontal
directions in steps of 45°. The tests shall be carried out with the elevation angle of the antenna at its
minimum and at its maximum in turn. The wind load shall be increased gradually in steps up to 180
km/h, each step lasting approximately one minute.
The tests may be performed at any atmosphere temperature and air pressure. If the atmospheric
5
conditions differ from standard conditions (temperature = 293°K, air pressure = 1,013 x 10 Pa),
then the test velocity shall be determined according to the formula:
5
VV××[(1,013 10 ) /P ]×[T / 293]
TS= T T
where: V = wind velocity in test;
T
V = wind velocity in standard conditions;
S
P = air pressure in test, (Pa);
T
T = temperature in test, (K).
T
During the load conditions the test object shall be observed and the distortions recorded.
The test report shall contain:
- description of the test equipment;
- description of the tests performed;
- results of the measurements or calculations on the mechanical loads transmitted from the
outdoor unit to the attachment devices.
For the pointing stability (see subclause 7.1):
- results of the measurements of the deviation of the antenna position, and components with
respect to each other.

---------------------- Page: 12 ----------------------

SIST ETS 300 332 E1:2006
Page 11
ETS 300 332: December 1994
b) Numerical analysis and tests.
The computations needed to derive the field of forces and torque and the equivalent static stresses
shall be carried out for the same wind directions and elevation as specified in the wind tunnel test
procedure a) above. Only the maximum 180 km/h shall be considered. The air related parameters,
namely the kinematic viscosity used to calculate drags at the rims of the structure shall be
calculated with the standard atmospheric environmental conditions given in a) above. It shall be
verified with the simulated results that break point limits are not exceeded for any self-contained
element. During the practical test the calculated equivalent static loads shall be applied at any
critical fixing point of the assembly.
During the load conditions, the outdoor unit shall be observed, and any distortion recorded.
The test report shall contain:
- the computation method used;
- description of the test equipment;
- description of the tests performed;
- results of the safety margin calculation;
- results of the measurements or calculations on the mechanical loads transmitted from the
outdoor unit to the attachment devices.
For the pointing stability (see subclause 7.1):
- results of the measurements or mechanical distortions.
5.2 Electrical safety
5.2.1 Power voltages
Purpose:
Protection of operating personnel and the public from electric shock.
Specification:
The electrical safety of the equipment shall be in accordance with the introduction and clauses 1 to 3
of IEC 950 [1]. These clauses deal with fundamental design requirements, wiring, connections and supply.
Verification:
Conformance shall be determined according to IEC 950 [1] verification methods.
5.2.2 Lightning
Purpose:
To avoid dangerous potential differences between the outdoor unit and any other conductive structure.
Specification:
Means shall be provided to permit the attachment of bonding conductors of dimension indicated in table 7
of IEC 81 (Co) 6 [2].
Verification:
Conformance shall be determined by inspection.

---------------------- Page: 13 ----------------------

SIST ETS 300 332 E1:2006
Page 12
ETS 300 332: December 1994
5.2.3 Radio frequency radiation protection
Purpose:
Protection of operating personnel and the public from radio frequency radiation hazards.
Specification:
The equipment shall be fitted with a warning notice in a clearly visible position, indicating the region in
2
which a radio frequency radiation level in excess of 10 W/m may occur.
Verification:
By visual inspection.
5.2.4 Solar radiation protection
Purpose:
Protection of operating personnel and the public from solar radiation focusing effects.
Specification:
If, in conditions of sunshine, solar radiation is focused near the feed such that burning may occur, the
equipment shall be fitted with a warning notice in a clearly visible position.
Verification:
A statement shall be provided to indicate that the surface of the antenna has been treated to avoid the
situation, or otherwise by visual inspection to confirm the presence of warning notice.
6 Radio Frequency (RF)
6.1 Spurious radiation
Purpose:
To limit the level of interference to terrestrial and satellite radio services.
Specification:
1) The VSAT shall satisfy the limits for radiated interference field strength specified in CISPR
Publication No. 22 [3] over the frequency range from 30 MHz to 960 MHz, at a test distance of 10
m.
Table 1
Frequency range Quasi-peak at 10 m
(MHz)
(dB μμV/m)
Class B Class A
30 to 230 30 40
230 to 960 37 47
The lower limits shall apply at the transition frequency.
The applicable class A or B shall be designated by the manufacturer and indicated in the data sheet
of the test report.

---------------------- Page: 14 ----------------------

SIST ETS 300 332 E1:2006
Page 13
ETS 300 332: December 1994
2) For the carrier-off case, the off-axis spurious Equivalent Isotropically Radiated Power (EIRP) from
the VSAT, in any 100 kHz band, shall be below the following limits, for all off-axis angles greater
than 7°:
960,0 MHz to 10,7 GHz 48 dBpW;
10,7 GHz to 21,2 GHz 54 dBpW;
21,2 GHz to 40,0 GHz 60 dBpW.
The lower limits shall apply at the transition frequency.
3) For the carrier-on case, the off-axis spurious EIRP from the VSAT, shall be below the following
limits, for all off-axis angles greater than 7°:
49 dBpW in any 100 kHz band in the range 960,0 MHz to 3,4 GHz;
55 dBpW in any 100 kHz band in the range 3,4 GHz to 5,450 GHz;
78 dBpW in any 20 MHz band in the range 5,450 GHz to 6,825 GHz;
55 dBpW in any 100 kHz band in the range 6,825 GHz to 10,7 GHz;
61 dBpW in any 100 kHz band in the range 10,7 GHz to 21,2 GHz;
78 dBpW in any 20 MHz band in the range 10,9 GHz to 13,650 GHz;
67 dBpW in any 100 kHz band in the range 21,2 GHz to 40 GHz.
The lower limits shall apply at the transition frequency.
4) These limits are applicable to the complete VSAT equipment, comprising the indoor and outdoor
units and at least 10 m of connection cable between them.
Verification:
Measurement of spurious radiation generated by a VSAT terminal under operation.
Test procedure:
The full system shall be tested. The test procedure is given in annex A.
The environmental conditions of the test laboratory shall be within the range of those for which the indoor
unit is designed to operate.
6.2 On axis spurious radiation (outside the nominated bandwidth)
Purpose:
To limit the level of interference to satellite radio services.
Specification:
In the 5,850 to 6,425 GHz band the EIRP spectral density of the spurious radiation excluding inter-
modulation products and excluding the nominated bandwidth shall not exceed 4 - 10 log N dBW in any
100 kHz band with the carrier on.
The on axis spurious radiation, outside the 5,850 to 6,425 GHz band, are limited in subclause 6.1 by
taking into account the on axis antenna gain, i.e. on axis limit is equal to limit in subclause 6.1 minus
maximum off axis gain plus on axis gain.
N is the maximum number of VSATs which are expected to transmit simultaneously in the same carrier
frequency band. This number shall be indicated by the manufacturer.
When the carrier is off, the EIRP spectral density of the spurious radiation in the 5,850 to 6,425 GHz band
shall not exceed - 21 dBW in any 100 kHz band.
NOTE: Inter-modulation limits inside the band 5,850 to 6,425 GHz are to be determined by
system design, subject to satellite operator specifications.

---------------------- Page: 15 ----------------------

SIST ETS 300 332 E1:2006
Page 14
ETS 300 332: December 1994
Verification:
Conformance shall be determined by direct measurement.
Test procedure:
The measurement shall be performed by the following method.
The power of the spurious radiation at the interface point between the antenna and the remaining outdoor
unit shall be measured according to the measurement method in IEC 510-1-2 [7], section 2, subclause
5.2.2. The antenna on-axis gain shall be measured using one of the methods of IEC 510-2-1 [6], clause 8,
or any other method, that can be proved to give the same results. The EIRP of the spurious radiation shall
be calculated from the above two measurements. The environmental conditions of the test laboratory shall
be those for which the indoor unit is designed to operate.
NOTE: Definitions and methods of measurement for integrated equipment are under study.
6.3 Transmit carrier centre frequency stability
Purpose:
Protection of transmissions on the same satellite.
Specification:
The transmitted carrier centre frequency shall not deviate from its nominal value by more than an amount
which allows the carrier (and its close-in spectral components which have a spectral power density greater
than the specified spurious levels) to remain within its nominated bandwidth. This frequency tolerance
refers to the initial frequency adjustment plus long-term drift. Long-term drift shall be assumed to be at
least one month.
Verification:
Conformance shall be determined from documentary evidence.
6.4 Off-axis EIRP emission density (co-polar and cross-polar) within the band 5,850 to 6,425
GHz
Purpose:
Protection of other satellite (uplink) systems.
Specification:
The maximum EIRP in any 4 kHz band within the nominated bandwidth of the co-polarised component in
any direction Ø degrees from the antenna main beam axis shall not exceed the following limits:
32 - 25 log Ø - 10 log N dBW for 2,5° ≤ Ø ≤ 7°;
11 - 10 log N dBW for 7° < Ø ≤ 9,2°;
35 - 25 log Ø - 10 log N dBW for 9,2° < Ø ≤ 48°;
-7 - 10 log N dBW for  Ø > 48°.
In addition the cross-polarised component in any direction Ø degrees from the antenna main beam axis
shall not exceed the following limits:
22 - 25 log Ø - 10 log N dBW for 2,5° ≤ Ø ≤ 7°;
1 - 10 log N dBW for 7° < Ø ≤ 9,2°.
Where Ø is the angle, in degrees, between the main beam axis and the direction considered, and N is the
maximum number of VSATs which may transmit simultaneously in the same carrier frequency band. This
number shall be indicated by the manufacturer.

---------------------- Page: 16 ----------------------

SIST ETS 300 332 E1:2006
Page 15
ETS 300 332: December 1994
For Ø > 70° the values given above may be increased to 4 - 10 log N dBW over the range of angles for
which the particular feed system may give rise to relatively high levels of spillover.
For antennas designed for minimum off-axis gain in the direction of the geostationary orbit, the
specification for Ø between 2,5° and 20° need only be met within ± 3° of a plane bisected by the main
beam axis.
This plane shall be marked and identified on the antenna. There shall be an axis of rotation along the
main beam axis, with adjustment capability to an accuracy of 0,5°. The antenna shall be capable of having
the above plane aligned with the geostationary orbit plane.
Verification:
Conformance shall be determined from:
- measurement of maximum RF power density entering the antenna feed;
- measurement of the co-polar and cross-polar transmit gain patterns in four planes containing
the main beam axis with an angular separation of 45°. When linear polarisation is used, one
of these planes shall be the E-plane.
Test procedure:
The measurement of the RF power density shall be made in accordance with IEC 510-1-2 [7], subclause
5.2.2.2. The measurement of the transmit gain patterns shall be made in accordance to IEC 510-2-1 [6]
clause 8, or any other recognised method that can be proved to give similar results, at 5,855 GHz, 6,140
GHz and 6,420 GHz.
6.5 Transmit polarisation discrimination (linear) or axial ratio (circular)
Purpose:
Protection of signals on the orthogonal polarisation.
Specification:
When linear polarisation is used, the ratio of the on-axis co-polar gain to the cross-polar gain in any
direction in the transm
...