ETSI EN 303 363-1 V1.1.1 (2022-02)

Final draft ETSI EN 303 363-1 V1.0.4 (2021-12)

HARMONISED EUROPEAN STANDARD
Air Traffic Control Surveillance Radar Sensors;
Secondary Surveillance Radar (SSR);
Harmonised Standard for access to radio spectrum;
Part 1: SSR Interrogator
2 Final draft ETSI EN 303 363-1 V1.0.4 (2021-12)
Reference
DEN/ERM-TGAERO-30-1
Keywords
aeronautical, harmonised standard, radar, radio

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ETSI
3 Final draft ETSI EN 303 363-1 V1.0.4 (2021-12)
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 . 12
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 . 13
4.2.1.1.3 Conformance . 13
4.2.1.2 Transmitter power . 13
4.2.1.2.1 Definition. 13
4.2.1.2.2 Limits . 13
4.2.1.2.3 Conformance . 13
4.2.1.3 Transmitter power control . 13
4.2.1.3.1 Definition. 13
4.2.1.3.2 Limits . 14
4.2.1.3.3 Conformance . 14
4.2.1.4 Spectrum mask . 14
4.2.1.4.1 Definition. 14
4.2.1.4.2 Limits . 14
4.2.1.4.3 Conformance . 15
4.2.1.5 Emissions in idle mode . 15
4.2.1.5.1 Definition. 15
4.2.1.5.2 Limits . 15
4.2.1.5.3 Conformance . 15
4.2.1.6 Transmitted waveforms . 15
4.2.1.6.1 Definition. 15
4.2.1.6.2 Limits . 16
4.2.1.6.3 Conformance . 16
4.2.2 Receiver requirements . 16
4.2.2.1 Receiver sensitivity and flatness . 16
4.2.2.1.1 Definition. 16
4.2.2.1.2 Limits . 16
4.2.2.1.3 Conformance . 17
4.2.2.2 Receiver Saturation Level and Dynamic Range . 17
4.2.2.2.1 Definition. 17
4.2.2.2.2 Limits . 17
4.2.2.2.3 Conformance . 17
4.2.2.3 Receiver blocking . 18
4.2.2.3.1 Definition. 18
4.2.2.3.2 Limits . 18
4.2.2.3.3 Conformance . 18
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4 Final draft ETSI EN 303 363-1 V1.0.4 (2021-12)
4.2.2.4 Receiver selectivity . 18
4.2.2.4.1 Definition. 18
4.2.2.4.2 Limits . 18
4.2.2.4.3 Conformance . 18
4.2.2.5 Inter-modulation response rejection . 19
4.2.2.5.1 Definition. 19
4.2.2.5.2 Limits . 19
4.2.2.5.3 Conformance . 19
4.2.2.6 Receiver co-channel rejection . 19
4.2.2.6.1 Definition. 19
4.2.2.6.2 Limits . 19
4.2.2.6.3 Conformance . 19
4.2.2.7 Receiver Noise Figure . 19
4.2.2.7.1 Definition. 19
4.2.2.7.2 Limits . 19
4.2.2.7.3 Conformance . 19
5 Testing for compliance with technical requirements . 20
5.1 General requirements . 20
5.1.1 Standard operation mode for testing . 20
5.2 Environmental conditions for testing . 20
5.2.1 General Requirements . 20
5.2.2 Test Conditions . 20
5.2.2.1 Normal temperature and humidity . 20
5.2.2.2 Normal test power supply . 20
5.3 Test specifications . 21
5.3.1 Transmitter related tests . 21
5.3.1.0 General requirements . 21
5.3.1.1 Maximum frequency deviation . 21
5.3.1.1.1 Test conditions . 21
5.3.1.1.2 Procedure . 21
5.3.1.2 Transmitter power . 21
5.3.1.2.1 Test conditions . 21
5.3.1.2.2 Procedure . 21
5.3.1.3 Transmitter power control . 22
5.3.1.3.1 Test conditions . 22
5.3.1.3.2 Procedure . 22
5.3.1.4 Spectrum mask . 23
5.3.1.4.1 Test conditions . 23
5.3.1.4.2 Procedure . 23
5.3.1.5 Emissions in idle mode . 24
5.3.1.5.1 Test conditions . 24
5.3.1.5.2 Procedure . 25
5.3.1.6 Transmitted Waveforms . 25
5.3.1.6.1 Test conditions . 25
5.3.1.6.2 Procedure . 25
5.3.2 Receiver related tests . 26
5.3.2.0 General requirements . 26
5.3.2.1 Receiver sensitivity and flatness . 26
5.3.2.1.1 Test conditions . 26
5.3.2.1.2 Procedure . 26
5.3.2.2 Receiver Saturation Level and Dynamic Range . 27
5.3.2.2.1 Test conditions . 27
5.3.2.2.2 Procedure . 28
5.3.2.3 Receiver blocking . 28
5.3.2.3.1 Test conditions . 28
5.3.2.3.2 Procedure . 28
5.3.2.4 Receiver selectivity . 30
5.3.2.4.1 Test conditions . 30
5.3.2.4.2 Procedure . 30
5.3.2.5 Inter-modulation response rejection . 31
5.3.2.5.1 Test conditions . 31
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5 Final draft ETSI EN 303 363-1 V1.0.4 (2021-12)
5.3.2.5.2 Procedure . 32
5.3.2.6 Receiver co-channel rejection . 33
5.3.2.6.1 Test conditions . 33
5.3.2.6.2 Procedure . 33
5.3.2.7 Receiver Noise Figure . 33
5.3.2.7.1 Test conditions . 33
5.3.2.7.2 Procedure . 33
Annex A (informative): Relationship between the present document and the essential
requirements of Directive 2014/53/EU . 35
Annex B (normative): Measurement setups . 37
B.1 Setup 1 . 37
B.2 Setup 2 . 38
B.3 Setup 3 . 38
B.4 Setup 4 . 40
B.5 Setup 5 . 41
Annex C (informative): Checklist . 43
Annex D (informative): Maximum Measurement Uncertainty . 44
History . 45

ETSI
6 Final draft ETSI EN 303 363-1 V1.0.4 (2021-12)
Intellectual Property Rights
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Foreword
This final draft Harmonised European Standard (EN) has been produced by ETSI Technical Committee
Electromagnetic compatibility and Radio spectrum Matters (ERM), and is now submitted for the Vote phase of the
ETSI standards EN Approval Procedure.
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 1 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)".
Proposed national transposition dates
Date of latest announcement of this EN (doa): 3 months after ETSI publication
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 6 months after doa
Date of withdrawal of any conflicting National Standard (dow): 18 months after doa

ETSI
7 Final draft ETSI EN 303 363-1 V1.0.4 (2021-12)
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. When aircraft are within the antenna beam of the ground station, its
interrogations elicit replies from transponders.
Civil use systems have different modes of interrogation/reply: Mode A, Mode C, Mode S and intermode. Mode A,
Mode C and Intermode interrogations consist of Pulse Amplitude Modulated (PAM) signals, Mode-S interrogations
have an additional pulse, with Differential Phase Shift Keying (DPSK) modulation.
Ground stations will be either Mode A/C ground stations, which can interrogate and receive replies on Mode A/C only,
or Mode S ground stations, for which the present standard founds its applicability, which can interrogate and receive
replies on all modes. On the other side, there are two classes of transponders: Mode A/C transponders, which can
respond to Mode A, Mode C and Intermode interrogations only, and Mode S transponders, which can respond to all
modes. Mode-S interrogation/replies have different data block depending on the information they have to support.
As far as Mode S is concerned, for the purpose of the present document it is assumed that the SSR can transmit
interrogations at least in the uplink formats (UF) UF11, UF4 and UF5 and can process replies in the downlink formats
(DF) DF11, DF4, DF20, DF5 and DF21.
The replies to all modes of interrogation are used to determine aircraft 2D position by measurement of the range and
bearing of the reply. The performance towards the radar parameters are determined on the basis of the number of
correct and validated replies received and decoded, in the operating environment.
Performances are affected by interference effects, which can result in a degradation of the signal causing lost or wrong
information. RF signals on either uplink or downlink can be distorted by other overlapping RF signals, which can make
correct decoding of wanted signals impossible. The degree of degradation is a function of the channel loading.
The SSR system requires a 3 dB receiver bandwidth of approximately 8 MHz centered on 1 030 MHz and 1 090 MHz
for the airborne transponder and ground SSR receiver respectively. This bandwidth is sufficient to permit significant
co-channel interference from transmitters operating on adjacent frequencies.
This interference can be minimized by ensuring adequate frequency or spatial separation between the interfering
transmitters and the SSR receivers. In this specific case, two air traffic service systems, DME and primary radars, can
be the cause of interference.
ETSI
8 Final draft ETSI EN 303 363-1 V1.0.4 (2021-12)
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.
Secondary Surveillance Radar (SSR) with Mode S capabilities which includes mode A/C, transmitting in the
1 030 MHz band with a power not exceeding 4 kW (66 dBm), and receiving in the 1 090 MHz band, used for air traffic
control and connected to a rotating antenna. The SSR Interrogator transmits interrogations to aircraft equipped with
transponder, receives the corresponding replies, and operates in the frequency bands as indicated in Table 1.
Table 1: SSR interrogator service frequency bands
Signals Service frequency bands
Transmitted signals 1 030 MHz
Received signals 1 090 MHz
NOTE 1: 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.
NOTE 2: Systems making use of an electronic scanned antenna are not covered by the present document.
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).
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.
ETSI
9 Final draft ETSI EN 303 363-1 V1.0.4 (2021-12)
[i.3] ECC/Recommendation (02)05 (2012): "Unwanted emissions".
[i.4] 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".
th th
[i.5] ICAO Annex 10, Volume IV: "Surveillance and Collision Avoidance Systems", 5 edition, 16
July 2018, including amendments up to amendment 90.
[i.6] Eurocontrol SUR/MODES/EMS/SPE-01: "European Mode S Station Functional Specification",
th
edition 3.11, 9 May 2005.
[i.7] ERC/Recommendation 74-01 (2019): "Unwanted emissions in spurious domain".
[i.8] ITU Radio Regulations (2020).
[i.9] ICAO DOC-9924: "Aeronautical Surveillance Manual", edition 2, 2017.
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 (as it is derived from an omnidirectional antenna beam) or OMEGA
path and identified with Greek letter Ω.
difference: RF path between the SSR interrogator and the SSR antenna allowing the monopulse function
NOTE: Monopulse difference path is also called DELTA path and identified with Greek letter Δ.
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 aircraft transponder or FFM to
SSR
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.
ETSI
10 Final draft ETSI EN 303 363-1 V1.0.4 (2021-12)
Far Field Monitor (FFM): fixed ground based system allowing the monitoring of the uplink and/or downlink
performance of an SSR system, located at a pre-determined position from the radar (far field)
NOTE: The FFM is interrogated by the SSR, and its replies are evaluated by the secondary radar for calibration
and self-test purposes. A FFM with Mode S capability has Mode A and Mode C capabilities too.
fruits: replies received by an interrogator but not triggered by own interrogations. 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.5] and Eurocontrol
SUR/MODES/EMS/SPE-01 [i.6].
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.
mode A: interrogation triggering a Mode A reply allowing the identification of aircraft
NOTE 1: A Mode A interrogation consists of P1 and P3 pulses transmitted on the sum port of the SSR interrogator
and a P2 pulse transmitted on the control port of the SSR interrogator (P2 is called a sidelobe suppression
pulse). The interval between P1 and P3 determines the Mode A interrogation type.
NOTE 2: A Mode A reply consists of framing pulses (F1 and F2) and up to 12 pulses between F1 and F2. The
absence or presence of each of the 12 pulses determines the Mode A code.
mode C: interrogation triggering a Mode C reply containing encoded pressure-altitude information
NOTE 1: A Mode C interrogation consists of P1 and P3 pulses transmitted on the sum port of the SSR interrogator
and a P2 pulse transmitted on the control port of the SSR interrogator. The interval between P1 and P3
determines the Mode C interrogation type.
NOTE 2: A Mode C reply consists of framing pulses (F1 and F2) and up to 12 pulses 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 on the sum port of the SSR
interrogator and a P5 pulse transmitted on the control port of the SSR interrogator (P5 is called a sidelobe
suppression pulse). A Mode S reply consists of a four-pulse preamble followed by a reply data block.
NOTE 2: Mode S stands for "Mode Select".
NOTE 3: The addressing method consists of a unique 24 bit Mode-S address for each individual aircraft
transponder, assigned by ICAO and using a country prefix scheme. The Mode S address is used by SSR
Interrogator in the interrogations, and by transponders and FFM in their correlated replies.
monopulse: technique used to determine the direction of a RF signal by comparison of different RF antenna paths
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.
ETSI
11 Final draft ETSI EN 303 363-1 V1.0.4 (2021-12)
NOTE 2: This definition is taken from ITU Radio Regulation [i.8].
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.8].
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.8].
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): modulation used for Mode A, Mode C, intermode interrogations, pulses P1 and
P2 of Mode S interrogations as well as Mode A, Mode C replies and the preamble pulses of Mode S replies
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 rise time: time taken for the leading edge of the pulse to increase from 10 % to 90 % of the maximum amplitude
(voltage)
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.8].
NOTE 2: The SSR provides ground-based radar surveillance of targets equipped with transponder, and of far field
monitors.
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.8].
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.8].
sum: RF path between the SSR interrogator and the SSR antenna allowing the transmission and reception of RF signals
through the main directional beam of the SSR antenna
NOTE: Monopulse sum path is also called SIGMA path and identified with Greek letter Σ
uplink: direction of the 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 in
...

HARMONISED EUROPEAN STANDARD
Air Traffic Control Surveillance Radar Sensors;
Secondary Surveillance Radar (SSR);
Harmonised Standard for access to radio spectrum;
Part 1: SSR Interrogator
2 ETSI EN 303 363-1 V1.1.1 (2022-02)

Reference
DEN/ERM-TGAERO-30-1
Keywords
aeronautical, harmonised standard, radar, radio
ETSI
650 Route des Lucioles
F-06921 Sophia Antipolis Cedex - FRANCE

Tel.: +33 4 92 94 42 00  Fax: +33 4 93 65 47 16

Siret N° 348 623 562 00017 - APE 7112B
Association à but non lucratif enregistrée à la
Sous-Préfecture de Grasse (06) N° w061004871

Important notice
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ETSI
3 ETSI EN 303 363-1 V1.1.1 (2022-02)
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 . 12
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 . 13
4.2.1.1.3 Conformance . 13
4.2.1.2 Transmitter power . 13
4.2.1.2.1 Definition. 13
4.2.1.2.2 Limits . 13
4.2.1.2.3 Conformance . 13
4.2.1.3 Transmitter power control . 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 Spectrum mask . 14
4.2.1.4.1 Definition. 14
4.2.1.4.2 Limits . 14
4.2.1.4.3 Conformance . 15
4.2.1.5 Emissions in idle mode . 15
4.2.1.5.1 Definition. 15
4.2.1.5.2 Limits . 16
4.2.1.5.3 Conformance . 16
4.2.1.6 Transmitted waveforms . 16
4.2.1.6.1 Definition. 16
4.2.1.6.2 Limits . 16
4.2.1.6.3 Conformance . 16
4.2.2 Receiver requirements . 17
4.2.2.1 Receiver sensitivity and flatness . 17
4.2.2.1.1 Definition. 17
4.2.2.1.2 Limits . 17
4.2.2.1.3 Conformance . 17
4.2.2.2 Receiver Saturation Level and Dynamic Range . 17
4.2.2.2.1 Definition. 17
4.2.2.2.2 Limits . 18
4.2.2.2.3 Conformance . 18
4.2.2.3 Receiver blocking . 18
4.2.2.3.1 Definition. 18
4.2.2.3.2 Limits . 18
4.2.2.3.3 Conformance . 18
4.2.2.4 Receiver selectivity . 19
ETSI
4 ETSI EN 303 363-1 V1.1.1 (2022-02)
4.2.2.4.1 Definition. 19
4.2.2.4.2 Limits . 19
4.2.2.4.3 Conformance . 19
4.2.2.5 Inter-modulation response rejection . 19
4.2.2.5.1 Definition. 19
4.2.2.5.2 Limits . 19
4.2.2.5.3 Conformance . 19
4.2.2.6 Receiver co-channel rejection . 19
4.2.2.6.1 Definition. 19
4.2.2.6.2 Limits . 20
4.2.2.6.3 Conformance . 20
4.2.2.7 Receiver Noise Figure . 20
4.2.2.7.1 Definition. 20
4.2.2.7.2 Limits . 20
4.2.2.7.3 Conformance . 20
5 Testing for compliance with technical requirements . 20
5.1 General requirements . 20
5.1.1 Standard operation mode for testing . 20
5.2 Environmental conditions for testing . 21
5.2.1 General Requirements . 21
5.2.2 Test Conditions . 21
5.2.2.1 Normal temperature and humidity . 21
5.2.2.2 Normal test power supply . 21
5.3 Test specifications . 21
5.3.1 Transmitter related tests . 21
5.3.1.0 General requirements . 21
5.3.1.1 Maximum frequency deviation . 21
5.3.1.1.1 Test conditions . 21
5.3.1.1.2 Procedure . 21
5.3.1.2 Transmitter power . 22
5.3.1.2.1 Test conditions . 22
5.3.1.2.2 Procedure . 22
5.3.1.3 Transmitter power control . 23
5.3.1.3.1 Test conditions . 23
5.3.1.3.2 Procedure . 23
5.3.1.4 Spectrum mask . 23
5.3.1.4.1 Test conditions . 23
5.3.1.4.2 Procedure . 24
5.3.1.5 Emissions in idle mode . 25
5.3.1.5.1 Test conditions . 25
5.3.1.5.2 Procedure . 25
5.3.1.6 Transmitted Waveforms . 26
5.3.1.6.1 Test conditions . 26
5.3.1.6.2 Procedure . 26
5.3.2 Receiver related tests . 26
5.3.2.0 General requirements . 26
5.3.2.1 Receiver sensitivity and flatness . 26
5.3.2.1.1 Test conditions . 26
5.3.2.1.2 Procedure . 26
5.3.2.2 Receiver Saturation Level and Dynamic Range . 28
5.3.2.2.1 Test conditions . 28
5.3.2.2.2 Procedure . 28
5.3.2.3 Receiver blocking . 29
5.3.2.3.1 Test conditions . 29
5.3.2.3.2 Procedure . 29
5.3.2.4 Receiver selectivity . 31
5.3.2.4.1 Test conditions . 31
5.3.2.4.2 Procedure . 31
5.3.2.5 Inter-modulation response rejection . 32
5.3.2.5.1 Test conditions . 32
5.3.2.5.2 Procedure . 32
ETSI
5 ETSI EN 303 363-1 V1.1.1 (2022-02)
5.3.2.6 Receiver co-channel rejection . 33
5.3.2.6.1 Test conditions . 33
5.3.2.6.2 Procedure . 33
5.3.2.7 Receiver Noise Figure . 34
5.3.2.7.1 Test conditions . 34
5.3.2.7.2 Procedure . 34
Annex A (informative): Relationship between the present document and the essential
requirements of Directive 2014/53/EU . 35
Annex B (normative): Measurement setups . 37
B.1 Setup 1 . 37
B.2 Setup 2 . 38
B.3 Setup 3 . 38
B.4 Setup 4 . 40
B.5 Setup 5 . 41
Annex C (informative): Checklist . 43
Annex D (informative): Maximum Measurement Uncertainty . 44
History . 45

ETSI
6 ETSI EN 303 363-1 V1.1.1 (2022-02)
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
The present document may include trademarks and/or tradenames which are asserted and/or registered by their owners.
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 1 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: 14 February 2022
Date of latest announcement of this EN (doa): 31 May 2022
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 30 November 2022
Date of withdrawal of any conflicting National Standard (dow): 30 November 2023

ETSI
7 ETSI EN 303 363-1 V1.1.1 (2022-02)
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. When aircraft are within the antenna beam of the ground station, its
interrogations elicit replies from transponders.
Civil use systems have different modes of interrogation/reply: Mode A, Mode C, Mode S and intermode. Mode A,
Mode C and Intermode interrogations consist of Pulse Amplitude Modulated (PAM) signals, Mode-S interrogations
have an additional pulse, with Differential Phase Shift Keying (DPSK) modulation.
Ground stations will be either Mode A/C ground stations, which can interrogate and receive replies on Mode A/C only,
or Mode S ground stations, for which the present standard founds its applicability, which can interrogate and receive
replies on all modes. On the other side, there are two classes of transponders: Mode A/C transponders, which can
respond to Mode A, Mode C and Intermode interrogations only, and Mode S transponders, which can respond to all
modes. Mode-S interrogation/replies have different data block depending on the information they have to support.
As far as Mode S is concerned, for the purpose of the present document it is assumed that the SSR can transmit
interrogations at least in the uplink formats (UF) UF11, UF4 and UF5 and can process replies in the downlink formats
(DF) DF11, DF4, DF20, DF5 and DF21.
The replies to all modes of interrogation are used to determine aircraft 2D position by measurement of the range and
bearing of the reply. The performance towards the radar parameters are determined on the basis of the number of
correct and validated replies received and decoded, in the operating environment.
Performances are affected by interference effects, which can result in a degradation of the signal causing lost or wrong
information. RF signals on either uplink or downlink can be distorted by other overlapping RF signals, which can make
correct decoding of wanted signals impossible. The degree of degradation is a function of the channel loading.
The SSR system requires a 3 dB receiver bandwidth of approximately 8 MHz centered on 1 030 MHz and 1 090 MHz
for the airborne transponder and ground SSR receiver respectively. This bandwidth is sufficient to permit significant
co-channel interference from transmitters operating on adjacent frequencies.
This interference can be minimized by ensuring adequate frequency or spatial separation between the interfering
transmitters and the SSR receivers. In this specific case, two air traffic service systems, DME and primary radars, can
be the cause of interference.
ETSI
8 ETSI EN 303 363-1 V1.1.1 (2022-02)
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.
Secondary Surveillance Radar (SSR) with Mode S capabilities which includes mode A/C, transmitting in the
1 030 MHz band with a power not exceeding 4 kW (66 dBm), and receiving in the 1 090 MHz band, used for air traffic
control and connected to a rotating antenna. The SSR Interrogator transmits interrogations to aircraft equipped with
transponder, receives the corresponding replies, and operates in the frequency bands as indicated in Table 1.
Table 1: SSR interrogator service frequency bands
Signals Service frequency bands
Transmitted signals 1 030 MHz
Received signals 1 090 MHz
NOTE 1: 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.
NOTE 2: Systems making use of an electronic scanned antenna are not covered by the present document.
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).
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.
ETSI
9 ETSI EN 303 363-1 V1.1.1 (2022-02)
[i.3] ECC/Recommendation (02)05 (2012): "Unwanted emissions".
[i.4] 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".
th th
[i.5] ICAO Annex 10, Volume IV: "Surveillance and Collision Avoidance Systems", 5 edition, 16
July 2018, including amendments up to amendment 90.
[i.6] Eurocontrol SUR/MODES/EMS/SPE-01: "European Mode S Station Functional Specification",
th
edition 3.11, 9 May 2005.
[i.7] ERC/Recommendation 74-01 (2019): "Unwanted emissions in spurious domain".
[i.8] ITU Radio Regulations (2020).
[i.9] ICAO DOC-9924: "Aeronautical Surveillance Manual", edition 2, 2017.
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 (as it is derived from an omnidirectional antenna beam) or OMEGA
path and identified with Greek letter Ω.
difference: RF path between the SSR interrogator and the SSR antenna allowing the monopulse function
NOTE: Monopulse difference path is also called DELTA path and identified with Greek letter Δ.
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 aircraft transponder or FFM to
SSR
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.
ETSI
10 ETSI EN 303 363-1 V1.1.1 (2022-02)
Far Field Monitor (FFM): fixed ground based system allowing the monitoring of the uplink and/or downlink
performance of an SSR system, located at a pre-determined position from the radar (far field)
NOTE: The FFM is interrogated by the SSR, and its replies are evaluated by the secondary radar for calibration
and self-test purposes. A FFM with Mode S capability has Mode A and Mode C capabilities too.
False Replies Unsynchronized In Time (FRUITs): replies received by an interrogator but 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.5] and Eurocontrol
SUR/MODES/EMS/SPE-01 [i.6].
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.
mode A: interrogation triggering a Mode A reply allowing the identification of aircraft
NOTE 1: A Mode A interrogation consists of P1 and P3 pulses transmitted on the sum port of the SSR interrogator
and a P2 pulse transmitted on the control port of the SSR interrogator (P2 is called a sidelobe suppression
pulse). The interval between P1 and P3 determines the Mode A interrogation type.
NOTE 2: A Mode A reply consists of framing pulses (F1 and F2) and up to 12 pulses between F1 and F2. The
absence or presence of each of the 12 pulses determines the Mode A code.
mode C: interrogation triggering a Mode C reply containing encoded pressure-altitude information
NOTE 1: A Mode C interrogation consists of P1 and P3 pulses transmitted on the sum port of the SSR interrogator
and a P2 pulse transmitted on the control port of the SSR interrogator. The interval between P1 and P3
determines the Mode C interrogation type.
NOTE 2: A Mode C reply consists of framing pulses (F1 and F2) and up to 12 pulses 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 on the sum port of the SSR
interrogator and a P5 pulse transmitted on the control port of the SSR interrogator (P5 is called a sidelobe
suppression pulse). A Mode S reply consists of a four-pulse preamble followed by a reply data block.
NOTE 2: Mode S stands for "Mode Select".
NOTE 3: The addressing method consists of a unique 24 bit Mode-S address for each individual aircraft
transponder, assigned by ICAO and using a country prefix scheme. The Mode S address is used by SSR
Interrogator in the interrogations, and by transponders and FFM in their correlated replies.
monopulse: technique used to determine the direction of a RF signal by comparison of different RF antenna paths
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
ETSI
11 ETSI EN 303 363-1 V1.1.1 (2022-02)
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.8].
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.8].
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.8].
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): modulation used for Mode A, Mode C, intermode interrogations, pulses P1 and
P2 of Mode S interrogations as well as Mode A, Mode C replies and the preamble pulses of Mode S replies
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 rise time: time taken for the leading edge of the pulse to increase from 10 % to 90 % of the maximum amplitude
(voltage)
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.8].
NOTE 2: The SSR provides ground-based radar surveillance of targets equipped with transponder, and of far field
monitors.
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.8].
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.8].
sum: RF path between the SSR interrogator and the SSR antenna allowing the transmission and reception of RF signals
through the main directional beam of the SSR antenna
NOTE: Monopulse sum path is also called SIGMA path and identified with Greek letter Σ
uplink: direction of the signals transmitted on the 1 030 MHz frequency band from SSR interrogator to aircraft
transponder or FFM
ETSI
12 ETSI EN 303 363-1 V1.1.1 (2022-02)
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 interro
...

SLOVENSKI STANDARD
01-april-2022
Radarski senzorji za nadzor zračnega prometa - Sekundarni nadzorni radar (SSR) -
Harmonizirani standard za dostop do radijskega spektra - 1. del: Bralnik SSR
Air Traffic Control Surveillance Radar Sensors - Secondary Surveillance Radar (SSR) -
Harmonised Standard for access to radio spectrum - Part 1: SSR Interrogator
Ta slovenski standard je istoveten z: ETSI EN 303 363-1 V1.1.1 (2022-02)
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 1: SSR Interrogator
2 ETSI EN 303 363-1 V1.1.1 (2022-02)

Reference
DEN/ERM-TGAERO-30-1
Keywords
aeronautical, harmonised standard, radar, radio
ETSI
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© ETSI 2022.
All rights reserved.
ETSI
3 ETSI EN 303 363-1 V1.1.1 (2022-02)
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 . 12
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 . 13
4.2.1.1.3 Conformance . 13
4.2.1.2 Transmitter power . 13
4.2.1.2.1 Definition. 13
4.2.1.2.2 Limits . 13
4.2.1.2.3 Conformance . 13
4.2.1.3 Transmitter power control . 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 Spectrum mask . 14
4.2.1.4.1 Definition. 14
4.2.1.4.2 Limits . 14
4.2.1.4.3 Conformance . 15
4.2.1.5 Emissions in idle mode . 15
4.2.1.5.1 Definition. 15
4.2.1.5.2 Limits . 16
4.2.1.5.3 Conformance . 16
4.2.1.6 Transmitted waveforms . 16
4.2.1.6.1 Definition. 16
4.2.1.6.2 Limits . 16
4.2.1.6.3 Conformance . 16
4.2.2 Receiver requirements . 17
4.2.2.1 Receiver sensitivity and flatness . 17
4.2.2.1.1 Definition. 17
4.2.2.1.2 Limits . 17
4.2.2.1.3 Conformance . 17
4.2.2.2 Receiver Saturation Level and Dynamic Range . 17
4.2.2.2.1 Definition. 17
4.2.2.2.2 Limits . 18
4.2.2.2.3 Conformance . 18
4.2.2.3 Receiver blocking . 18
4.2.2.3.1 Definition. 18
4.2.2.3.2 Limits . 18
4.2.2.3.3 Conformance . 18
4.2.2.4 Receiver selectivity . 19
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4 ETSI EN 303 363-1 V1.1.1 (2022-02)
4.2.2.4.1 Definition. 19
4.2.2.4.2 Limits . 19
4.2.2.4.3 Conformance . 19
4.2.2.5 Inter-modulation response rejection . 19
4.2.2.5.1 Definition. 19
4.2.2.5.2 Limits . 19
4.2.2.5.3 Conformance . 19
4.2.2.6 Receiver co-channel rejection . 19
4.2.2.6.1 Definition. 19
4.2.2.6.2 Limits . 20
4.2.2.6.3 Conformance . 20
4.2.2.7 Receiver Noise Figure . 20
4.2.2.7.1 Definition. 20
4.2.2.7.2 Limits . 20
4.2.2.7.3 Conformance . 20
5 Testing for compliance with technical requirements . 20
5.1 General requirements . 20
5.1.1 Standard operation mode for testing . 20
5.2 Environmental conditions for testing . 21
5.2.1 General Requirements . 21
5.2.2 Test Conditions . 21
5.2.2.1 Normal temperature and humidity . 21
5.2.2.2 Normal test power supply . 21
5.3 Test specifications . 21
5.3.1 Transmitter related tests . 21
5.3.1.0 General requirements . 21
5.3.1.1 Maximum frequency deviation . 21
5.3.1.1.1 Test conditions . 21
5.3.1.1.2 Procedure . 21
5.3.1.2 Transmitter power . 22
5.3.1.2.1 Test conditions . 22
5.3.1.2.2 Procedure . 22
5.3.1.3 Transmitter power control . 23
5.3.1.3.1 Test conditions . 23
5.3.1.3.2 Procedure . 23
5.3.1.4 Spectrum mask . 23
5.3.1.4.1 Test conditions . 23
5.3.1.4.2 Procedure . 24
5.3.1.5 Emissions in idle mode . 25
5.3.1.5.1 Test conditions . 25
5.3.1.5.2 Procedure . 25
5.3.1.6 Transmitted Waveforms . 26
5.3.1.6.1 Test conditions . 26
5.3.1.6.2 Procedure . 26
5.3.2 Receiver related tests . 26
5.3.2.0 General requirements . 26
5.3.2.1 Receiver sensitivity and flatness . 26
5.3.2.1.1 Test conditions . 26
5.3.2.1.2 Procedure . 26
5.3.2.2 Receiver Saturation Level and Dynamic Range . 28
5.3.2.2.1 Test conditions . 28
5.3.2.2.2 Procedure . 28
5.3.2.3 Receiver blocking . 29
5.3.2.3.1 Test conditions . 29
5.3.2.3.2 Procedure . 29
5.3.2.4 Receiver selectivity . 31
5.3.2.4.1 Test conditions . 31
5.3.2.4.2 Procedure . 31
5.3.2.5 Inter-modulation response rejection . 32
5.3.2.5.1 Test conditions . 32
5.3.2.5.2 Procedure . 32
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5 ETSI EN 303 363-1 V1.1.1 (2022-02)
5.3.2.6 Receiver co-channel rejection . 33
5.3.2.6.1 Test conditions . 33
5.3.2.6.2 Procedure . 33
5.3.2.7 Receiver Noise Figure . 34
5.3.2.7.1 Test conditions . 34
5.3.2.7.2 Procedure . 34
Annex A (informative): Relationship between the present document and the essential
requirements of Directive 2014/53/EU . 35
Annex B (normative): Measurement setups . 37
B.1 Setup 1 . 37
B.2 Setup 2 . 38
B.3 Setup 3 . 38
B.4 Setup 4 . 40
B.5 Setup 5 . 41
Annex C (informative): Checklist . 43
Annex D (informative): Maximum Measurement Uncertainty . 44
History . 45

ETSI
6 ETSI EN 303 363-1 V1.1.1 (2022-02)
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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ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no
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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 1 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: 14 February 2022
Date of latest announcement of this EN (doa): 31 May 2022
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 30 November 2022
Date of withdrawal of any conflicting National Standard (dow): 30 November 2023

ETSI
7 ETSI EN 303 363-1 V1.1.1 (2022-02)
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. When aircraft are within the antenna beam of the ground station, its
interrogations elicit replies from transponders.
Civil use systems have different modes of interrogation/reply: Mode A, Mode C, Mode S and intermode. Mode A,
Mode C and Intermode interrogations consist of Pulse Amplitude Modulated (PAM) signals, Mode-S interrogations
have an additional pulse, with Differential Phase Shift Keying (DPSK) modulation.
Ground stations will be either Mode A/C ground stations, which can interrogate and receive replies on Mode A/C only,
or Mode S ground stations, for which the present standard founds its applicability, which can interrogate and receive
replies on all modes. On the other side, there are two classes of transponders: Mode A/C transponders, which can
respond to Mode A, Mode C and Intermode interrogations only, and Mode S transponders, which can respond to all
modes. Mode-S interrogation/replies have different data block depending on the information they have to support.
As far as Mode S is concerned, for the purpose of the present document it is assumed that the SSR can transmit
interrogations at least in the uplink formats (UF) UF11, UF4 and UF5 and can process replies in the downlink formats
(DF) DF11, DF4, DF20, DF5 and DF21.
The replies to all modes of interrogation are used to determine aircraft 2D position by measurement of the range and
bearing of the reply. The performance towards the radar parameters are determined on the basis of the number of
correct and validated replies received and decoded, in the operating environment.
Performances are affected by interference effects, which can result in a degradation of the signal causing lost or wrong
information. RF signals on either uplink or downlink can be distorted by other overlapping RF signals, which can make
correct decoding of wanted signals impossible. The degree of degradation is a function of the channel loading.
The SSR system requires a 3 dB receiver bandwidth of approximately 8 MHz centered on 1 030 MHz and 1 090 MHz
for the airborne transponder and ground SSR receiver respectively. This bandwidth is sufficient to permit significant
co-channel interference from transmitters operating on adjacent frequencies.
This interference can be minimized by ensuring adequate frequency or spatial separation between the interfering
transmitters and the SSR receivers. In this specific case, two air traffic service systems, DME and primary radars, can
be the cause of interference.
ETSI
8 ETSI EN 303 363-1 V1.1.1 (2022-02)
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.
Secondary Surveillance Radar (SSR) with Mode S capabilities which includes mode A/C, transmitting in the
1 030 MHz band with a power not exceeding 4 kW (66 dBm), and receiving in the 1 090 MHz band, used for air traffic
control and connected to a rotating antenna. The SSR Interrogator transmits interrogations to aircraft equipped with
transponder, receives the corresponding replies, and operates in the frequency bands as indicated in Table 1.
Table 1: SSR interrogator service frequency bands
Signals Service frequency bands
Transmitted signals 1 030 MHz
Received signals 1 090 MHz
NOTE 1: 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.
NOTE 2: Systems making use of an electronic scanned antenna are not covered by the present document.
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).
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.
ETSI
9 ETSI EN 303 363-1 V1.1.1 (2022-02)
[i.3] ECC/Recommendation (02)05 (2012): "Unwanted emissions".
[i.4] 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".
th th
[i.5] ICAO Annex 10, Volume IV: "Surveillance and Collision Avoidance Systems", 5 edition, 16
July 2018, including amendments up to amendment 90.
[i.6] Eurocontrol SUR/MODES/EMS/SPE-01: "European Mode S Station Functional Specification",
th
edition 3.11, 9 May 2005.
[i.7] ERC/Recommendation 74-01 (2019): "Unwanted emissions in spurious domain".
[i.8] ITU Radio Regulations (2020).
[i.9] ICAO DOC-9924: "Aeronautical Surveillance Manual", edition 2, 2017.
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 (as it is derived from an omnidirectional antenna beam) or OMEGA
path and identified with Greek letter Ω.
difference: RF path between the SSR interrogator and the SSR antenna allowing the monopulse function
NOTE: Monopulse difference path is also called DELTA path and identified with Greek letter Δ.
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 aircraft transponder or FFM to
SSR
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.
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10 ETSI EN 303 363-1 V1.1.1 (2022-02)
Far Field Monitor (FFM): fixed ground based system allowing the monitoring of the uplink and/or downlink
performance of an SSR system, located at a pre-determined position from the radar (far field)
NOTE: The FFM is interrogated by the SSR, and its replies are evaluated by the secondary radar for calibration
and self-test purposes. A FFM with Mode S capability has Mode A and Mode C capabilities too.
False Replies Unsynchronized In Time (FRUITs): replies received by an interrogator but 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.5] and Eurocontrol
SUR/MODES/EMS/SPE-01 [i.6].
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.
mode A: interrogation triggering a Mode A reply allowing the identification of aircraft
NOTE 1: A Mode A interrogation consists of P1 and P3 pulses transmitted on the sum port of the SSR interrogator
and a P2 pulse transmitted on the control port of the SSR interrogator (P2 is called a sidelobe suppression
pulse). The interval between P1 and P3 determines the Mode A interrogation type.
NOTE 2: A Mode A reply consists of framing pulses (F1 and F2) and up to 12 pulses between F1 and F2. The
absence or presence of each of the 12 pulses determines the Mode A code.
mode C: interrogation triggering a Mode C reply containing encoded pressure-altitude information
NOTE 1: A Mode C interrogation consists of P1 and P3 pulses transmitted on the sum port of the SSR interrogator
and a P2 pulse transmitted on the control port of the SSR interrogator. The interval between P1 and P3
determines the Mode C interrogation type.
NOTE 2: A Mode C reply consists of framing pulses (F1 and F2) and up to 12 pulses 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 on the sum port of the SSR
interrogator and a P5 pulse transmitted on the control port of the SSR interrogator (P5 is called a sidelobe
suppression pulse). A Mode S reply consists of a four-pulse preamble followed by a reply data block.
NOTE 2: Mode S stands for "Mode Select".
NOTE 3: The addressing method consists of a unique 24 bit Mode-S address for each individual aircraft
transponder, assigned by ICAO and using a country prefix scheme. The Mode S address is used by SSR
Interrogator in the interrogations, and by transponders and FFM in their correlated replies.
monopulse: technique used to determine the direction of a RF signal by comparison of different RF antenna paths
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
ETSI
11 ETSI EN 303 363-1 V1.1.1 (2022-02)
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.8].
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.8].
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.8].
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): modulation used for Mode A, Mode C, intermode interrogations, pulses P1 and
P2 of Mode S interrogations as well as Mode A, Mode C replies and the preamble pulses of Mode S replies
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 rise time: time taken for the leading edge of the pulse to increase from 10 % to 90 % of the maximum amplitude
(voltage)
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.8].
NOTE 2: The SSR provides ground-based radar surveillance of targets equipped with transponder, and of far field
monitors.
spurious domain: frequency range beyond the out-of-band domain in which sp
...