ETSI EN 303 363-2 V1.1.1 (2023-10)

HARMONISED EUROPEAN STANDARD
Air Traffic Control Surveillance Radar Sensors;
Secondary Surveillance Radar (SSR);
Harmonised Standard for access to radio spectrum;
Part 2: Far Field Monitor (FFM)

2 ETSI EN 303 363-2 V1.1.1 (2023-10)

Reference
DEN/ERM-TGAERO-30-2
Keywords
aeronautical, harmonised standard, radar, radio
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ETSI
3 ETSI EN 303 363-2 V1.1.1 (2023-10)
Contents
Intellectual Property Rights . 6
Foreword . 6
Modal verbs terminology . 7
Introduction . 7
1 Scope . 8
2 References . 8
2.1 Normative references . 8
2.2 Informative references . 8
3 Definition of terms, symbols and abbreviations . 9
3.1 Terms . 9
3.2 Symbols . 12
3.3 Abbreviations . 13
4 Technical requirements specifications . 13
4.1 Environmental profile . 13
4.2 Conformance requirements . 13
4.2.1 Transmitter requirements . 13
4.2.1.1 Maximum frequency Deviation . 13
4.2.1.1.1 Definition. 13
4.2.1.1.2 Limits . 14
4.2.1.1.3 Conformance . 14
4.2.1.2 Transmitter power . 14
4.2.1.2.1 Definition. 14
4.2.1.2.2 Limits . 14
4.2.1.2.3 Conformance . 14
4.2.1.3 Spectrum mask . 14
4.2.1.3.1 Definition. 14
4.2.1.3.2 Limits . 14
4.2.1.3.3 Conformance . 14
4.2.1.4 Emissions in idle mode . 14
4.2.1.4.1 Definition. 14
4.2.1.4.2 Limits . 15
4.2.1.4.3 Conformance . 15
4.2.1.5 Transmitted Waveform . 15
4.2.1.5.1 Definition. 15
4.2.1.5.2 Limits . 15
4.2.1.5.3 Conformance . 15
4.2.2 Receiver requirements . 15
4.2.2.1 Receiver sensitivity and dynamic range . 15
4.2.2.1.1 Definition. 15
4.2.2.1.2 Limits . 16
4.2.2.1.3 Conformance . 16
4.2.2.2 Receiver selectivity . 16
4.2.2.2.1 Definition. 16
4.2.2.2.2 Limits . 16
4.2.2.2.3 Conformance . 16
4.2.2.3 Receiver immunity to interference . 16
4.2.2.3.1 Definition. 16
4.2.2.3.2 Limits . 17
4.2.2.3.3 Conformance . 17
4.2.2.4 FFM unwanted replies. 17
4.2.2.4.1 Definition. 17
4.2.2.4.2 Limits . 17
4.2.2.4.3 Conformance . 18
4.2.2.5 FFM SLS Effectiveness . 18
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4 ETSI EN 303 363-2 V1.1.1 (2023-10)
4.2.2.5.1 Definition. 18
4.2.2.5.2 Limits . 18
4.2.2.5.3 Conformance . 18
4.2.2.6 Receiver RF intermodulation response rejection . 18
4.2.2.6.1 Definition. 18
4.2.2.6.2 Limits . 18
4.2.2.6.3 Conformance . 18
5 Testing for Compliance with technical requirements . 19
5.1 General Requirements . 19
5.1.1 Standard operation mode for testing . 19
5.2 Environmental conditions for testing . 19
5.2.1 Introduction. 19
5.2.2 Temperature and humidity . 19
5.2.3 Power supply . 19
5.3 Test specifications . 20
5.3.1 Transmitter related tests . 20
5.3.1.1 Maximum Frequency Deviation . 20
5.3.1.1.1 Test conditions . 20
5.3.1.1.2 Procedure . 20
5.3.1.2 Transmitter power . 20
5.3.1.2.1 Test conditions . 20
5.3.1.2.2 Procedure . 20
5.3.1.3 Spectrum mask . 20
5.3.1.3.1 Test conditions . 20
5.3.1.3.2 Procedure . 21
5.3.1.4 Emissions in idle mode . 21
5.3.1.4.1 Test conditions . 21
5.3.1.4.2 Procedure . 21
5.3.1.5 Transmitted Waveform . 21
5.3.1.5.1 Test conditions . 21
5.3.1.5.2 Procedure . 22
5.3.2 Receiver related tests . 22
5.3.2.1 Receiver sensitivity . 22
5.3.2.1.1 Test conditions . 22
5.3.2.1.2 Procedure . 22
5.3.2.2 Receiver dynamic range . 22
5.3.2.2.1 Test conditions . 22
5.3.2.2.2 Procedure . 22
5.3.2.3 Receiver selectivity . 22
5.3.2.3.1 Test conditions . 22
5.3.2.3.2 Procedure . 23
5.3.2.4 Receiver immunity to interference . 23
5.3.2.4.1 Test conditions . 23
5.3.2.4.2 Procedure . 23
5.3.2.5 FFM unwanted replies. 25
5.3.2.5.1 Test conditions . 25
5.3.2.5.2 Procedure . 25
5.3.2.6 FFM SLS Effectiveness . 25
5.3.2.6.1 Test conditions . 25
5.3.2.6.2 Procedure . 26
5.3.2.7 Receiver RF intermodulation response rejection . 26
5.3.2.7.1 Test conditions . 26
5.3.2.7.2 Procedure . 26
Annex A (informative): Relationship between the present document and the essential
requirements of Directive 2014/53/EU . 28
Annex B (normative): Measurement setups . 30
B.1 Setup 1 . 30
B.2 Setup 2 . 30
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5 ETSI EN 303 363-2 V1.1.1 (2023-10)
B.3 Setup 3 . 31
B.4 Setup 4 . 32
B.5 Setup 5 . 32
B.6 Setup 6 . 33
Annex C (normative): FFM test equipment characteristics . 34
Annex D (informative): Reference Waveforms . 35
Annex E (informative): Checklist . 37
Annex F (informative): Maximum Measurement Uncertainty . 39
History . 40

ETSI
6 ETSI EN 303 363-2 V1.1.1 (2023-10)
Intellectual Property Rights
Essential patents
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pertaining to these essential IPRs, if any, are publicly available for ETSI members and non-members, and can be
found in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to
ETSI in respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the
ETSI Web server (https://ipr.etsi.org/).
Pursuant to the ETSI Directives including the ETSI IPR Policy, no investigation regarding the essentiality of IPRs,
including IPR searches, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not
referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become,
essential to the present document.
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Foreword
This Harmonised European Standard (EN) has been produced by ETSI Technical Committee Electromagnetic
compatibility and Radio spectrum Matters (ERM).
The present document has been prepared under the Commission's standardisation request C(2015) 5376 final [i.2] to
provide one voluntary means of conforming to the essential requirements of Directive 2014/53/EU on the harmonisation
of the laws of the Member States relating to the making available on the market of radio equipment and repealing
Directive 1999/5/EC [i.1].
Once the present document is cited in the Official Journal of the European Union under that Directive, compliance with
the normative clauses of the present document given in Table A.1 confers, within the limits of the scope of the present
document, a presumption of conformity with the corresponding essential requirements of that Directive, and associated
EFTA regulations.
The present document is part 2 of a multi-part deliverable covering ATC Secondary Surveillance Radar systems for
civil air navigation operating in the frequencies 1 030 MHz and 1 090 MHz, as identified below:
Part 1: "SSR Interrogator";
Part 2: "Far Field Monitor (FFM)".

National transposition dates
Date of adoption of this EN: 26 September 2023
Date of latest announcement of this EN (doa): 31 December 2023
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 30 June 2024
Date of withdrawal of any conflicting National Standard (dow): 30 June 2025

ETSI
7 ETSI EN 303 363-2 V1.1.1 (2023-10)
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
Introduction
The SSR system provides ground-based surveillance of transponder fitted aircraft and, in addition, may allow data link
communication between ground stations and aircraft, where both are fitted with appropriate equipment.
Secondary Radar surveillance is exploited through two essential elements: the SSR interrogator, normally
ground-based, and the aircraft SSR transponder.
The Far Field Monitor (FFM) is a ground-installed device that is intended to monitor the uplink and/or downlink
performance of a Mode S interrogator system from a site located at a suitable distance from the radar interrogator (far
field).
By its fixed location, the Far Field Monitor provides a fixed geo-referenced position with respect to which the SSR
interrogator can keep aligned its azimuthal reference with the geographical north.
While a Far Field Monitor has many characteristics in common with a Mode S transponder, there are a number of
important differences required to allow monitoring and to ensure that FFM will not impact Air Traffic safety and have
only minimal impact on Radio Frequency Interference and SSR channel Loading.
An FFM interrogated by the SSR radar in Mode A, C, S and intermode formats, replies with matching Mode A, C, S
reply. The replies are evaluated by the SSR interrogator to ensure correct operation. In addition, the replies may contain
data about certain interrogation parameters as seen by the monitor.
As far as Mode S is concerned, it is assumed that the FFM can process interrogations in uplink format UF11, UF4 and
UF5 and can transmit the corresponding replies in downlink format DF11, DF4, DF20, DF5 and DF21.
As far as Intermode is concerned, it is assumed that the FFM having Mode-S capabilities will only reply to intermode
interrogations of type Mode A only all-call and Mode C only all-call. As far as intermode interrogations of type Mode
A/C/S all-call are concerned, the FFM will not reply to them. Table 1 sums up the FFM capabilities.
Table 1: FFM capabilities
Mode Interrogation processing Reply Transmission
Mode A Yes Yes
Mode C Yes Yes
Mode S Yes for at least UF11, UF4 and UF5 Yes for at least DF11, DF4, DF20, DF5 and DF21 replies
interrogations
Intermode Yes No in case of Mode A/C/S all interrogations (long P4)

ETSI
8 ETSI EN 303 363-2 V1.1.1 (2023-10)
1 Scope
The present document specifies technical characteristics and methods of measurements for the following equipment
used in ground-based ATC Secondary Surveillance Radar systems for civil air navigation:
Far Field Monitors (FFM) operating on the frequencies as indicated in Table 2.
Table 2: FFM operating frequencies
Mode Operating frequencies
FFM Receive 1 030 MHz
FFM Transmit 1 090 MHz
NOTE: The relationship between the present document and essential requirements of article 3.2 of
Directive 2014/53/EU [i.1] is given in Annex A.
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
https://docbox.etsi.org/Reference/.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
Not applicable.
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] Directive 2014/53/EU of the European Parliament and of the Council of 16 April 2014 on the
harmonisation of the laws of the Member States relating to the making available on the market of
radio equipment and repealing Directive 1999/5/EC.
[i.2] Commission Implementing Decision C(2015) 5376 final of 4.8.2015 on a standardisation request
to the European Committee for Electrotechnical Standardisation and to the European
Telecommunications Standards Institute as regards radio equipment in support of Directive
2014/53/EU of the European Parliament and of the Council.
[i.3] ETSI EG 203 336: "Guide for the selection of technical parameters for the production of
Harmonised Standards covering article 3.1(b) and article 3.2 of Directive 2014/53/EU".
ETSI
9 ETSI EN 303 363-2 V1.1.1 (2023-10)
th
[i.4] ICAO Annex 10, Volume IV: "Surveillance Radar and Collision Avoidance Systems", 5 edition,
July 2014 including amendments up to amendment 91 dated 22-03-2021.
[i.5] ERC Recommendation 74-01 (2019): "Unwanted emissions in spurious domain".
[i.6] ITU-R Radio Regulations (2020).
[i.7] Eurocontrol Specification for European Mode S Station (EMS) (EUROCONTROL-SPEC-189)
Ver 4.0, September 2021.
[i.8] EUROCAE ED-73F: "Minimum Operational Performance Specification for Secondary
Surveillance Radar Mode S Transponders", December 2020.
nd
[i.9] ICAO Annex 10, Volume III: "Communication Systems", 2 Edition, 2007.
3 Definition of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the following terms apply:
all-call: intermode interrogations (Mode A/C/S all-call) or Mode S interrogations (Mode S only all-call) or Mode S
only all-call replies
Binary Pulse Position Modulation (BPPM): modulation used in the reply data block of a Mode S reply
NOTE: Within a Mode S reply data bit interval, a pulse transmitted in the first half of the interval represents a
binary ONE and a pulse transmitted in the second half represents a binary ZERO.
carrier frequency: radio frequency, i.e. 1 030 MHz for an SSR Interrogator, which has no "modulation" imposed on it
(yet)
chip: carrier interval in a Mode S interrogation within the pulse P6 with a duration of 0,25 microseconds and located
after the synchro phase reversal
control: RF path between the SSR interrogator and the SSR antenna allowing sidelobe suppression
NOTE: Control path is also called OMNI or OMEGA path and identified with Greek letter Ω.
Differential Phase Shift Keying (DPSK): phase modulation used in the P6 pulse of Mode S interrogations
NOTE: The aforementioned modulation uses phase reversal preceding chips to code binary ONEs and the
absence of phase reversal to code binary ZEROs.
downlink: direction of the signals transmitted on the 1 090 MHz frequency band from Mode A, C and S capable device
Downlink Format (DF): data coding format of a Mode S reply
NOTE: DF11 denotes the format of a Mode S all-call reply.
DF4 denotes the format of a Mode S selective reply of type "surveillance altitude reply".
DF5 denotes the format of a Mode S selective reply of type "surveillance identity reply".
DF20 denotes the format of a Mode S selective reply of type "Comm-B altitude reply".
DF21 denotes the format of a Mode S selective reply of type "Comm-B identity reply".
Comm-B denotes a Mode S selective reply containing supplementary data.
Far Field Monitor (FFM): system which monitors the uplink and/or downlink performance of an SSR or Mode S
system from a site located at a specified distance from the radar (far field)
NOTE 1: The monitor is interrogated by the radar, and its replies can be evaluated on the radar site. In addition, the
replies may contain data about certain interrogation parameters as seen by the monitor.
NOTE 2: A Mode S FFM supports Mode A, C and S.
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10 ETSI EN 303 363-2 V1.1.1 (2023-10)
NOTE 3: FFM is also referred to as "Remote Field Monitor" (RFM), "Position Adjustable Range Reference
Orientation Transponder" (PARROT) or "Site Monitor".
FFM test equipment: equipment to simulate Mode A, C and S interrogations to enable the testing of the performance
of Mode A, C and S based transponder and similar devices
FRUITs: replies received by an interrogator which are not triggered by own interrogations
NOTE: They overlap to requested replies and are to be considered as interfering signals.
idle state: entire period between transmissions, less 10-microsecond transition periods preceding the first pulse and
following the last pulse of the transmission
NOTE: The word "inactive" instead of "idle" is used in ICAO Annex 10, Volume IV [i.4] and EUROCONTROL-
SPEC-189 [i.7].
intermode: interrogation triggering replies from SSR transponders and eventually replies from Mode S transponders in
case of Mode A/C/S all-call interrogations
NOTE: Two types of intermode interrogations exist. The first type consists of Mode A or Mode C only all-call
interrogations to which transponders with Mode A and Mode C capabilities only reply and to which
Mode S transponders do not reply. The second type consists of Mode A/C/S all-call interrogations to
which all transponders reply. Intermode interrogations consist of P1, P3 and P4 pulses transmitted on the
sum port of the SSR interrogator and a P2 pulse transmitted on the control port of the SSR interrogator.
lockout: status in which the FFM is prevented from replying to All-Call interrogations
NOTE: This status is triggered by the interrogator using its own IC code, via a specific "lockout" protocol. This
status will last 18 seconds, unless renewed by the interrogator.
Minimum Triggering Level (MTL): minimum input power level that results in a 90 % reply ratio
mode A: type of interrogation, triggering a reply from Mode A capable devices for identity and surveillance allowing
the identification of the device
NOTE 1: A Mode A interrogation is defined by the pulse separation between the two P1 and P3 pulses, and
consists of P1 and P3 pulses transmitted via a high gain main beam antenna and a P2 pulse (P2 is called a
sidelobe - SLS- suppression pulse) via a separate antenna pattern with a different antenna gain.
NOTE 2: A Mode A reply consists of framing pulses (F1 and F2), up to 12 pulses between F1 and F2 and an
optionally manually activated and transmitted Special Identification pulse (SPI). The absence or presence
of each of the 12 identification pulses between F1 and F2 determines the Mode A reply code.
mode C: interrogation elicit from Mode C capable devices replies allowing SSR interrogator automatic
pressure-altitude transmission and surveillance
NOTE 1: A Mode C interrogation is defined by the pulse separation between the two P1 and P3 pulses. The Mode
C interrogation is transmitted via a narrow high gain main beam antenna. A third P2 Side Lobe
Suppression Pulse (SLS) is transmitted via a separate antenna pattern having a different gain.
NOTE 2: A Mode C reply consists of up to 15 pulses, two framing pulses (F1 and F2), up to 12 pulses transmitted
between F1 and F2. The absence or presence of each of the 12 pulses determines the Mode C code.
mode S: enhanced SSR mode allowing the addressing of individual aircraft and the retrieving of information with
higher integrity
NOTE 1: A Mode S interrogation consists of P1, P2 and P6 pulses transmitted via a directional high gain antenna
pattern while the P5 SLS pulse is transmitted via a separate antenna pattern having a different antenna
gain (P5 is called sidelobe suppression pulse).
A Mode S reply consists of a four-pulse preamble followed by a 56 or 112 pulse reply data block using
PPM.
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11 ETSI EN 303 363-2 V1.1.1 (2023-10)
NOTE 2: Mode S stands for "Mode Select" to allow selective addressing the unique 24 bit address allocated to a
Mode S based device replying or squittering on 1 090 MHz e.g. aircraft transponder, non transponder
devices or FFM. SSR Mode S address is defined in Annex 10, Volume III Part 1, chapter 9 [i.9] to be one
of 16 777 214 twenty-four-bit aircraft addresses allocated by ICAO to the State of Registry or common
mark registering authority and assigned as prescribed in the Appendix to the same chapter [i.9].
necessary bandwidth: width of the frequency band which is just sufficient to ensure the transmission of information at
the rate and with the quality required under specified conditions
out-of-band domain: frequency range, immediately outside the necessary bandwidth but excluding the spurious
domain, in which out-of-band emissions generally predominate
NOTE 1: Out-of-band emissions, defined based on their source, occur in the out-of-band domain and, to a lesser
extent, in the spurious domain. Spurious emissions likewise may occur in the out-of-band domain as well
as in the spurious domain.
NOTE 2: This definition is taken from ITU Radio Regulation [i.6].
out-of-band emissions: emission on a frequency or frequencies immediately outside the necessary bandwidth which
results from the modulation process but excluding spurious emissions
NOTE: This definition is taken from ITU Radio Regulation [i.6].
peak envelope power: average power supplied to the antenna transmission line by a transmitter during one radio
frequency cycle at the crest of the modulation envelope taken under normal operating conditions
NOTE: This definition is taken from ITU Radio Regulation [i.6].
phase overlay: technique to increase the data throughput by adding an additional phase modulation to each Mode-S
Data pulse transmitted on 1 090 MHz
phase reversal: 180-degree change of the phase of the uplink frequency carrier
NOTE: Phase reversal is a characteristics of the Differential Phase Shift Keying (DPSK) modulation used for the
uplink transmission of the Mode S signals.
Pulse Amplitude Modulation (PAM): type of pulse generation, where amplitude is changed between pulses
NOTE: SLS pulses P2 and P5 are PAM pulses, the Mode-S preamble and the Mode-A and Mode-C replies are
made with PAM pulses.
pulse decay time: time taken for the trailing edge of the pulse to decrease from 90 % to 10 % of the maximum
amplitude (voltage)
pulse duration: time between the 50 % amplitude (voltage) points on the leading and trailing edge of the pulse
envelope
pulse position modulation: pulse modulation of the 56 or 112 data pulses used by the Mode S reply and ADS-B
formats, by either transmitting the pulse in the first or second half of a microsecond
pulse rise time: time taken for the leading edge of the pulse to increase from 10 % to 90 % of the maximum amplitude
(voltage)
reply ratio: ratio between expected replies, corresponding to a given interrogation rate, and received replies
roll-call: selective Mode S interrogations addressed to an individual aircraft or selective Mode S replies received from
an individual aircraft
Secondary Surveillance Radar (SSR): radio-determination system based on the comparison of reference signals with
radio signals retransmitted from the position to be determined
NOTE 1: This definition is taken from ITU Radio Regulation [i.6].
NOTE 2: The SSR provides ground-based radar surveillance of targets equipped with transponder, and of far field
monitors.
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12 ETSI EN 303 363-2 V1.1.1 (2023-10)
Side Lobe Suppression (SLS): technique to use specific pulses P2 in Mode A and C, P5 in Mode S, dedicated for reply
suppression, which are transmitted via a separate antenna pattern with a different antenna gain
NOTE 1: The pulse amplitude of the received interrogation and SLS pulse are used to decide if SLS is activated or
not.
NOTE 2: P5 is used for Mode S-only all-call interrogation (UF = 11) to prevent replies from aircraft in the side and
back lobes of the antenna.
spurious domain: frequency range beyond the out-of-band domain in which spurious emissions generally predominate
NOTE: This definition is taken from ITU Radio Regulation [i.6].
spurious emissions: emission on a frequency or frequencies which are outside the necessary bandwidth and the level of
which may be reduced without affecting the corresponding transmission of information
NOTE 1: Spurious emissions include harmonic emissions, parasitic emissions, intermodulation products and
frequency conversion products, but exclude out-of-band emissions.
NOTE 2: This definition is taken from ITU Radio Regulation [i.6].
uplink: direction of the interrogation and data signals transmitted on the 1 030 MHz frequency band from SSR
interrogator to aircraft transponder or FFM
Uplink Format (UF): data coding format of a Mode S interrogation
NOTE: UF11 denotes the format of a Mode S only all-call interrogation.
UF4 denotes the format of a Mode S selective interrogation of type "surveillance altitude request".
UF5 denotes the format of a Mode S selective interrogation of type "surveillance identity request".
3.2 Symbols
For the purposes of the present document, the following symbols apply:
B -40 dB bandwidth
-40
B Necessary bandwidth
N
B 3 dB resolution bandwidth of transceiver
res
dB decibel
dB/dec dB per decade
dBm dB with respect to 1 milliwatt
dBpep dB with respect to peak envelope power
k Boltzmann's constant
kW Kilowatt
NF Noise Figure
NM Nautical mile
ns nano second
Pd Probability of detection
Pd Probability of detection at 1 090 MHz
Pd Probability of detection at a frequency offset from 1 090 MHz
offset
P Pulse power of transmission
t
RF Radio Frequency
t Time
t Pulse duration
p
t Pulse rise time
r
T Temperature in Kelvin
λ Wavelength
Ω Ohm
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13 ETSI EN 303 363-2 V1.1.1 (2023-10)
3.3 Abbreviations
For the purposes of the present document,
...

SLOVENSKI STANDARD
01-december-2023
Radarski senzorji za nadzor zračnega prometa - Sekundarni nadzorni radar (SSR) -
Harmonizirani standard za dostop do radijskega spektra - 2. del: Antenski
nadzorni sistem (FFM)
Air Traffic Control Surveillance Radar Sensors - Secondary Surveillance Radar (SSR) -
Harmonised Standard for access to radio spectrum - Part 2: Far Field Monitor (FFM)
Ta slovenski standard je istoveten z: ETSI EN 303 363-2 V1.1.1 (2023-10)
ICS:
03.220.50 Zračni transport Air transport
33.060.99 Druga oprema za radijske Other equipment for
komunikacije radiocommunications
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

HARMONISED EUROPEAN STANDARD
Air Traffic Control Surveillance Radar Sensors;
Secondary Surveillance Radar (SSR);
Harmonised Standard for access to radio spectrum;
Part 2: Far Field Monitor (FFM)

2 ETSI EN 303 363-2 V1.1.1 (2023-10)

Reference
DEN/ERM-TGAERO-30-2
Keywords
aeronautical, harmonised standard, radar, radio
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ETSI
3 ETSI EN 303 363-2 V1.1.1 (2023-10)
Contents
Intellectual Property Rights . 6
Foreword . 6
Modal verbs terminology . 7
Introduction . 7
1 Scope . 8
2 References . 8
2.1 Normative references . 8
2.2 Informative references . 8
3 Definition of terms, symbols and abbreviations . 9
3.1 Terms . 9
3.2 Symbols . 12
3.3 Abbreviations . 13
4 Technical requirements specifications . 13
4.1 Environmental profile . 13
4.2 Conformance requirements . 13
4.2.1 Transmitter requirements . 13
4.2.1.1 Maximum frequency Deviation . 13
4.2.1.1.1 Definition. 13
4.2.1.1.2 Limits . 14
4.2.1.1.3 Conformance . 14
4.2.1.2 Transmitter power . 14
4.2.1.2.1 Definition. 14
4.2.1.2.2 Limits . 14
4.2.1.2.3 Conformance . 14
4.2.1.3 Spectrum mask . 14
4.2.1.3.1 Definition. 14
4.2.1.3.2 Limits . 14
4.2.1.3.3 Conformance . 14
4.2.1.4 Emissions in idle mode . 14
4.2.1.4.1 Definition. 14
4.2.1.4.2 Limits . 15
4.2.1.4.3 Conformance . 15
4.2.1.5 Transmitted Waveform . 15
4.2.1.5.1 Definition. 15
4.2.1.5.2 Limits . 15
4.2.1.5.3 Conformance . 15
4.2.2 Receiver requirements . 15
4.2.2.1 Receiver sensitivity and dynamic range . 15
4.2.2.1.1 Definition. 15
4.2.2.1.2 Limits . 16
4.2.2.1.3 Conformance . 16
4.2.2.2 Receiver selectivity . 16
4.2.2.2.1 Definition. 16
4.2.2.2.2 Limits . 16
4.2.2.2.3 Conformance . 16
4.2.2.3 Receiver immunity to interference . 16
4.2.2.3.1 Definition. 16
4.2.2.3.2 Limits . 17
4.2.2.3.3 Conformance . 17
4.2.2.4 FFM unwanted replies. 17
4.2.2.4.1 Definition. 17
4.2.2.4.2 Limits . 17
4.2.2.4.3 Conformance . 18
4.2.2.5 FFM SLS Effectiveness . 18
ETSI
4 ETSI EN 303 363-2 V1.1.1 (2023-10)
4.2.2.5.1 Definition. 18
4.2.2.5.2 Limits . 18
4.2.2.5.3 Conformance . 18
4.2.2.6 Receiver RF intermodulation response rejection . 18
4.2.2.6.1 Definition. 18
4.2.2.6.2 Limits . 18
4.2.2.6.3 Conformance . 18
5 Testing for Compliance with technical requirements . 19
5.1 General Requirements . 19
5.1.1 Standard operation mode for testing . 19
5.2 Environmental conditions for testing . 19
5.2.1 Introduction. 19
5.2.2 Temperature and humidity . 19
5.2.3 Power supply . 19
5.3 Test specifications . 20
5.3.1 Transmitter related tests . 20
5.3.1.1 Maximum Frequency Deviation . 20
5.3.1.1.1 Test conditions . 20
5.3.1.1.2 Procedure . 20
5.3.1.2 Transmitter power . 20
5.3.1.2.1 Test conditions . 20
5.3.1.2.2 Procedure . 20
5.3.1.3 Spectrum mask . 20
5.3.1.3.1 Test conditions . 20
5.3.1.3.2 Procedure . 21
5.3.1.4 Emissions in idle mode . 21
5.3.1.4.1 Test conditions . 21
5.3.1.4.2 Procedure . 21
5.3.1.5 Transmitted Waveform . 21
5.3.1.5.1 Test conditions . 21
5.3.1.5.2 Procedure . 22
5.3.2 Receiver related tests . 22
5.3.2.1 Receiver sensitivity . 22
5.3.2.1.1 Test conditions . 22
5.3.2.1.2 Procedure . 22
5.3.2.2 Receiver dynamic range . 22
5.3.2.2.1 Test conditions . 22
5.3.2.2.2 Procedure . 22
5.3.2.3 Receiver selectivity . 22
5.3.2.3.1 Test conditions . 22
5.3.2.3.2 Procedure . 23
5.3.2.4 Receiver immunity to interference . 23
5.3.2.4.1 Test conditions . 23
5.3.2.4.2 Procedure . 23
5.3.2.5 FFM unwanted replies. 25
5.3.2.5.1 Test conditions . 25
5.3.2.5.2 Procedure . 25
5.3.2.6 FFM SLS Effectiveness . 25
5.3.2.6.1 Test conditions . 25
5.3.2.6.2 Procedure . 26
5.3.2.7 Receiver RF intermodulation response rejection . 26
5.3.2.7.1 Test conditions . 26
5.3.2.7.2 Procedure . 26
Annex A (informative): Relationship between the present document and the essential
requirements of Directive 2014/53/EU . 28
Annex B (normative): Measurement setups . 30
B.1 Setup 1 . 30
B.2 Setup 2 . 30
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5 ETSI EN 303 363-2 V1.1.1 (2023-10)
B.3 Setup 3 . 31
B.4 Setup 4 . 32
B.5 Setup 5 . 32
B.6 Setup 6 . 33
Annex C (normative): FFM test equipment characteristics . 34
Annex D (informative): Reference Waveforms . 35
Annex E (informative): Checklist . 37
Annex F (informative): Maximum Measurement Uncertainty . 39
History . 40

ETSI
6 ETSI EN 303 363-2 V1.1.1 (2023-10)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The declarations
pertaining to these essential IPRs, if any, are publicly available for ETSI members and non-members, and can be
found in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to
ETSI in respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the
ETSI Web server (https://ipr.etsi.org/).
Pursuant to the ETSI Directives including the ETSI IPR Policy, no investigation regarding the essentiality of IPRs,
including IPR searches, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not
referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become,
essential to the present document.
Trademarks
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ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no
right to use or reproduce any trademark and/or tradename. Mention of those trademarks in the present document does
not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks.
DECT™, PLUGTESTS™, UMTS™ and the ETSI logo are trademarks of ETSI registered for the benefit of its

Members. 3GPP™ and LTE™ are trademarks of ETSI registered for the benefit of its Members and of the 3GPP
Organizational Partners. oneM2M™ logo is a trademark of ETSI registered for the benefit of its Members and of the ®
oneM2M Partners. GSM and the GSM logo are trademarks registered and owned by the GSM Association.
Foreword
This Harmonised European Standard (EN) has been produced by ETSI Technical Committee Electromagnetic
compatibility and Radio spectrum Matters (ERM).
The present document has been prepared under the Commission's standardisation request C(2015) 5376 final [i.2] to
provide one voluntary means of conforming to the essential requirements of Directive 2014/53/EU on the harmonisation
of the laws of the Member States relating to the making available on the market of radio equipment and repealing
Directive 1999/5/EC [i.1].
Once the present document is cited in the Official Journal of the European Union under that Directive, compliance with
the normative clauses of the present document given in Table A.1 confers, within the limits of the scope of the present
document, a presumption of conformity with the corresponding essential requirements of that Directive, and associated
EFTA regulations.
The present document is part 2 of a multi-part deliverable covering ATC Secondary Surveillance Radar systems for
civil air navigation operating in the frequencies 1 030 MHz and 1 090 MHz, as identified below:
Part 1: "SSR Interrogator";
Part 2: "Far Field Monitor (FFM)".

National transposition dates
Date of adoption of this EN: 26 September 2023
Date of latest announcement of this EN (doa): 31 December 2023
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 30 June 2024
Date of withdrawal of any conflicting National Standard (dow): 30 June 2025

ETSI
7 ETSI EN 303 363-2 V1.1.1 (2023-10)
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
Introduction
The SSR system provides ground-based surveillance of transponder fitted aircraft and, in addition, may allow data link
communication between ground stations and aircraft, where both are fitted with appropriate equipment.
Secondary Radar surveillance is exploited through two essential elements: the SSR interrogator, normally
ground-based, and the aircraft SSR transponder.
The Far Field Monitor (FFM) is a ground-installed device that is intended to monitor the uplink and/or downlink
performance of a Mode S interrogator system from a site located at a suitable distance from the radar interrogator (far
field).
By its fixed location, the Far Field Monitor provides a fixed geo-referenced position with respect to which the SSR
interrogator can keep aligned its azimuthal reference with the geographical north.
While a Far Field Monitor has many characteristics in common with a Mode S transponder, there are a number of
important differences required to allow monitoring and to ensure that FFM will not impact Air Traffic safety and have
only minimal impact on Radio Frequency Interference and SSR channel Loading.
An FFM interrogated by the SSR radar in Mode A, C, S and intermode formats, replies with matching Mode A, C, S
reply. The replies are evaluated by the SSR interrogator to ensure correct operation. In addition, the replies may contain
data about certain interrogation parameters as seen by the monitor.
As far as Mode S is concerned, it is assumed that the FFM can process interrogations in uplink format UF11, UF4 and
UF5 and can transmit the corresponding replies in downlink format DF11, DF4, DF20, DF5 and DF21.
As far as Intermode is concerned, it is assumed that the FFM having Mode-S capabilities will only reply to intermode
interrogations of type Mode A only all-call and Mode C only all-call. As far as intermode interrogations of type Mode
A/C/S all-call are concerned, the FFM will not reply to them. Table 1 sums up the FFM capabilities.
Table 1: FFM capabilities
Mode Interrogation processing Reply Transmission
Mode A Yes Yes
Mode C Yes Yes
Mode S Yes for at least UF11, UF4 and UF5 Yes for at least DF11, DF4, DF20, DF5 and DF21 replies
interrogations
Intermode Yes No in case of Mode A/C/S all interrogations (long P4)

ETSI
8 ETSI EN 303 363-2 V1.1.1 (2023-10)
1 Scope
The present document specifies technical characteristics and methods of measurements for the following equipment
used in ground-based ATC Secondary Surveillance Radar systems for civil air navigation:
Far Field Monitors (FFM) operating on the frequencies as indicated in Table 2.
Table 2: FFM operating frequencies
Mode Operating frequencies
FFM Receive 1 030 MHz
FFM Transmit 1 090 MHz
NOTE: The relationship between the present document and essential requirements of article 3.2 of
Directive 2014/53/EU [i.1] is given in Annex A.
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
https://docbox.etsi.org/Reference/.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
Not applicable.
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] Directive 2014/53/EU of the European Parliament and of the Council of 16 April 2014 on the
harmonisation of the laws of the Member States relating to the making available on the market of
radio equipment and repealing Directive 1999/5/EC.
[i.2] Commission Implementing Decision C(2015) 5376 final of 4.8.2015 on a standardisation request
to the European Committee for Electrotechnical Standardisation and to the European
Telecommunications Standards Institute as regards radio equipment in support of Directive
2014/53/EU of the European Parliament and of the Council.
[i.3] ETSI EG 203 336: "Guide for the selection of technical parameters for the production of
Harmonised Standards covering article 3.1(b) and article 3.2 of Directive 2014/53/EU".
ETSI
9 ETSI EN 303 363-2 V1.1.1 (2023-10)
th
[i.4] ICAO Annex 10, Volume IV: "Surveillance Radar and Collision Avoidance Systems", 5 edition,
July 2014 including amendments up to amendment 91 dated 22-03-2021.
[i.5] ERC Recommendation 74-01 (2019): "Unwanted emissions in spurious domain".
[i.6] ITU-R Radio Regulations (2020).
[i.7] Eurocontrol Specification for European Mode S Station (EMS) (EUROCONTROL-SPEC-189)
Ver 4.0, September 2021.
[i.8] EUROCAE ED-73F: "Minimum Operational Performance Specification for Secondary
Surveillance Radar Mode S Transponders", December 2020.
nd
[i.9] ICAO Annex 10, Volume III: "Communication Systems", 2 Edition, 2007.
3 Definition of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the following terms apply:
all-call: intermode interrogations (Mode A/C/S all-call) or Mode S interrogations (Mode S only all-call) or Mode S
only all-call replies
Binary Pulse Position Modulation (BPPM): modulation used in the reply data block of a Mode S reply
NOTE: Within a Mode S reply data bit interval, a pulse transmitted in the first half of the interval represents a
binary ONE and a pulse transmitted in the second half represents a binary ZERO.
carrier frequency: radio frequency, i.e. 1 030 MHz for an SSR Interrogator, which has no "modulation" imposed on it
(yet)
chip: carrier interval in a Mode S interrogation within the pulse P6 with a duration of 0,25 microseconds and located
after the synchro phase reversal
control: RF path between the SSR interrogator and the SSR antenna allowing sidelobe suppression
NOTE: Control path is also called OMNI or OMEGA path and identified with Greek letter Ω.
Differential Phase Shift Keying (DPSK): phase modulation used in the P6 pulse of Mode S interrogations
NOTE: The aforementioned modulation uses phase reversal preceding chips to code binary ONEs and the
absence of phase reversal to code binary ZEROs.
downlink: direction of the signals transmitted on the 1 090 MHz frequency band from Mode A, C and S capable device
Downlink Format (DF): data coding format of a Mode S reply
NOTE: DF11 denotes the format of a Mode S all-call reply.
DF4 denotes the format of a Mode S selective reply of type "surveillance altitude reply".
DF5 denotes the format of a Mode S selective reply of type "surveillance identity reply".
DF20 denotes the format of a Mode S selective reply of type "Comm-B altitude reply".
DF21 denotes the format of a Mode S selective reply of type "Comm-B identity reply".
Comm-B denotes a Mode S selective reply containing supplementary data.
Far Field Monitor (FFM): system which monitors the uplink and/or downlink performance of an SSR or Mode S
system from a site located at a specified distance from the radar (far field)
NOTE 1: The monitor is interrogated by the radar, and its replies can be evaluated on the radar site. In addition, the
replies may contain data about certain interrogation parameters as seen by the monitor.
NOTE 2: A Mode S FFM supports Mode A, C and S.
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10 ETSI EN 303 363-2 V1.1.1 (2023-10)
NOTE 3: FFM is also referred to as "Remote Field Monitor" (RFM), "Position Adjustable Range Reference
Orientation Transponder" (PARROT) or "Site Monitor".
FFM test equipment: equipment to simulate Mode A, C and S interrogations to enable the testing of the performance
of Mode A, C and S based transponder and similar devices
FRUITs: replies received by an interrogator which are not triggered by own interrogations
NOTE: They overlap to requested replies and are to be considered as interfering signals.
idle state: entire period between transmissions, less 10-microsecond transition periods preceding the first pulse and
following the last pulse of the transmission
NOTE: The word "inactive" instead of "idle" is used in ICAO Annex 10, Volume IV [i.4] and EUROCONTROL-
SPEC-189 [i.7].
intermode: interrogation triggering replies from SSR transponders and eventually replies from Mode S transponders in
case of Mode A/C/S all-call interrogations
NOTE: Two types of intermode interrogations exist. The first type consists of Mode A or Mode C only all-call
interrogations to which transponders with Mode A and Mode C capabilities only reply and to which
Mode S transponders do not reply. The second type consists of Mode A/C/S all-call interrogations to
which all transponders reply. Intermode interrogations consist of P1, P3 and P4 pulses transmitted on the
sum port of the SSR interrogator and a P2 pulse transmitted on the control port of the SSR interrogator.
lockout: status in which the FFM is prevented from replying to All-Call interrogations
NOTE: This status is triggered by the interrogator using its own IC code, via a specific "lockout" protocol. This
status will last 18 seconds, unless renewed by the interrogator.
Minimum Triggering Level (MTL): minimum input power level that results in a 90 % reply ratio
mode A: type of interrogation, triggering a reply from Mode A capable devices for identity and surveillance allowing
the identification of the device
NOTE 1: A Mode A interrogation is defined by the pulse separation between the two P1 and P3 pulses, and
consists of P1 and P3 pulses transmitted via a high gain main beam antenna and a P2 pulse (P2 is called a
sidelobe - SLS- suppression pulse) via a separate antenna pattern with a different antenna gain.
NOTE 2: A Mode A reply consists of framing pulses (F1 and F2), up to 12 pulses between F1 and F2 and an
optionally manually activated and transmitted Special Identification pulse (SPI). The absence or presence
of each of the 12 identification pulses between F1 and F2 determines the Mode A reply code.
mode C: interrogation elicit from Mode C capable devices replies allowing SSR interrogator automatic
pressure-altitude transmission and surveillance
NOTE 1: A Mode C interrogation is defined by the pulse separation between the two P1 and P3 pulses. The Mode
C interrogation is transmitted via a narrow high gain main beam antenna. A third P2 Side Lobe
Suppression Pulse (SLS) is transmitted via a separate antenna pattern having a different gain.
NOTE 2: A Mode C reply consists of up to 15 pulses, two framing pulses (F1 and F2), up to 12 pulses transmitted
between F1 and F2. The absence or presence of each of the 12 pulses determines the Mode C code.
mode S: enhanced SSR mode allowing the addressing of individual aircraft and the retrieving of information with
higher integrity
NOTE 1: A Mode S interrogation consists of P1, P2 and P6 pulses transmitted via a directional high gain antenna
pattern while the P5 SLS pulse is transmitted via a separate antenna pattern having a different antenna
gain (P5 is called sidelobe suppression pulse).
A Mode S reply consists of a four-pulse preamble followed by a 56 or 112 pulse reply data block using
PPM.
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11 ETSI EN 303 363-2 V1.1.1 (2023-10)
NOTE 2: Mode S stands for "Mode Select" to allow selective addressing the unique 24 bit address allocated to a
Mode S based device replying or squittering on 1 090 MHz e.g. aircraft transponder, non transponder
devices or FFM. SSR Mode S address is defined in Annex 10, Volume III Part 1, chapter 9 [i.9] to be one
of 16 777 214 twenty-four-bit aircraft addresses allocated by ICAO to the State of Registry or common
mark registering authority and assigned as prescribed in the Appendix to the same chapter [i.9].
necessary bandwidth: width of the frequency band which is just sufficient to ensure the transmission of information at
the rate and with the quality required under specified conditions
out-of-band domain: frequency range, immediately outside the necessary bandwidth but excluding the spurious
domain, in which out-of-band emissions generally predominate
NOTE 1: Out-of-band emissions, defined based on their source, occur in the out-of-band domain and, to a lesser
extent, in the spurious domain. Spurious emissions likewise may occur in the out-of-band domain as well
as in the spurious domain.
NOTE 2: This definition is taken from ITU Radio Regulation [i.6].
out-of-band emissions: emission on a frequency or frequencies immediately outside the necessary bandwidth which
results from the modulation process but excluding spurious emissions
NOTE: This definition is taken from ITU Radio Regulation [i.6].
peak envelope power: average power supplied to the antenna transmission line by a transmitter during one radio
frequency cycle at the crest of the modulation envelope taken under normal operating conditions
NOTE: This definition is taken from ITU Radio Regulation [i.6].
phase overlay: technique to increase the data throughput by adding an additional phase modulation to each Mode-S
Data pulse transmitted on 1 090 MHz
phase reversal: 180-degree change of the phase of the uplink frequency carrier
NOTE: Phase reversal is a characteristics of the Differential Phase Shift Keying (DPSK) modulation used for the
uplink transmission of the Mode S signals.
Pulse Amplitude Modulation (PAM): type of pulse generation, where amplitude is changed between pulses
NOTE: SLS pulses P2 and P5 are PAM pulses, the Mode-S preamble and the Mode-A and Mode-C replies are
made with PAM pulses.
pulse decay time: time taken for the trailing edge of the pulse to decrease from 90 % to 10 % of the maximum
amplitude (voltage)
pulse duration: time between the 50 % amplitude (voltage) points on the leading and trailing edge of the pulse
envelope
pulse position modulation: pulse modulation of the 56 or 112 data pulses used by the Mode S reply and ADS-B
formats, by either transmitting the pulse in the first or second half of a microsecond
pulse rise time: time taken for the leading edge of the pulse to increase from 10 % to 90 % of the maximum amplitude
(voltage)
reply ratio: ratio between expected replies, corresponding to a given interrogation rate, and received replies
roll-call: selective Mode S interrogations addressed to an individual aircraft or selective Mode S replies received from
an individual aircraft
Secondary Surveillance Radar (SSR): radio-determination system based on the comparison of reference signals with
radio signals retransmitted from the position to be determined
NOTE 1: This definition is taken from ITU Radio Regulation [i.6].
NOTE 2: The SSR provides ground-based radar surveillance of targets equipped with transponder, and of far field
monitors.
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12 ETSI EN 303 363-2 V1.1.1 (2023-10)
Side Lobe Suppression (SLS): technique to use specific pulses P2 in Mode A and C, P5 in Mode S, dedicated for reply
suppression, which are transmitted via a separate antenna pattern with a different antenna gain
NOTE 1: The pulse amplitude of the received interrogation and SLS pulse are used to decide if SLS is activated or
not.
NOTE 2: P5 is used for Mode S-only all-call interrogation (UF = 11) to prevent replies from aircraft in the side and
back lobes of the antenna.
spurious domain: frequency range beyond the out-of-band domain in which spurious emissions generally predominate
NOTE: This definition is taken from ITU Radio Regulation [i.6].
spurious emissions: emission on a frequency or frequencies which are outside the necessary bandwidth and the level of
which may be reduced without affecting the corresponding transmission of information
NOTE 1: Spurious emissions include harmonic emissions, parasitic emissions, intermodulation products and
frequency conversion products, but exclude out-of-band emissions.
NOTE 2: This definition is taken from ITU Radio Regulation [i.6].
uplink: direction of the interrogation and data
...