Publication: Magyar Közlöny
Issue: MK-2009-104 (Year: 2009, Number: 104)
Era: 2004-2010
Section: 
Paragraph Index: 2247

b) the amplitude of these signals is nominally 71 dB below 1 mW, with limits between 69 dB and 77 dB below 1 mW. 3.1.1.7.5.2 The reply and suppression characteristics shall apply over a received amplitude of P1 between minimum triggering level and 50 dB above that level. 3.1.1.7.5.3 The variation of the minimum triggering level between modes shall not exceed 1 dB for nominal pulse spacings and pulse widths. 3.1.1.7.6 Pulse duration discrimination. Signals of received amplitude between minimum triggering level and 6 dB above this level, and of a duration less than 0.3 microsecond, shall not cause the transponder to initiate reply or suppression action. With the exception of single pulses with amplitude variations approximating an interrogation, any single pulse of a duration more than 1.5 microseconds shall not cause the transponder to initiate reply or suppression action over the signal amplitude range of minimum triggering level (MTL) to 50 dB above that level. 3.1.1.7.7 Echo suppression and recovery. The transponder shall contain an echo suppression facility designed to permit normal operation in the presence of echoes of signals-in-space. The provision of this facility shall be compatible with the requirements for suppression of side lobes given in 3.1.1.7.4.1. 3.1.1.7.7.1 Desensitization. Upon receipt of any pulse more than 0.7 microsecond in duration, the receiver shall be desensitized by an amount that is within at least 9 dB of the amplitude of the desensitizing pulse but shall at no time exceed the amplitude of the desensitizing pulse, with the exception of possible overshoot during the first microsecond following the desensitizing pulse. Note.— Single pulses of duration less than 0.7 microsecond are not required to cause the specified desensitization nor to cause desensitization of duration greater than permitted by 3.1.1.7.7.1 and 3.1.1.7.7.2. 3.1.1.7.7.2 Recovery. Following desensitization, the receiver shall recover sensitivity (within 3 dB of minimum triggering level) within 15 microseconds after reception of a desensitizing pulse having a signal strength up to 50 dB above minimum triggering level. Recovery shall be at an average rate not exceeding 4.0 dB per microsecond. 3.1.1.7.8 Random triggering rate. In the absence of valid interrogation signals, Mode A/C transponders shall not generate more than 30 unwanted Mode A or Mode C replies per second as integrated over an interval equivalent to at least 300 random triggers, or 30 seconds, whichever is less. This random triggering rate shall not be exceeded when all possible interfering equipments installed in the same aircraft are operating at maximum interference levels. 3.1.1.7.8.1 Random triggering rate in the presence of low-level in-band continuous wave (CW) interference. The total random trigger rate on all Mode A and/or Mode C replies shall not be greater than 10 reply pulse groups or suppressions per second, averaged over a period of 30 seconds, when operated in the presence of non-coherent CW interference at a frequency of 1 030 ±0.2 MHz and a signal level of –60 dBm or less. ± 3.1.1.7.9 REPLY RATE 3.1.1.7.9.1 The transponder shall be capable of at least 1 200 replies per second for a 15-pulse coded reply, except that, for transponder installations used solely below 4 500 m (15 000 ft), or below a lesser altitude established by the appropriate Annex 10 — Aeronautical Telecommunications Volume IV 22/11/07 3-6 authority or by regional air navigation agreement, transponders capable of at least 1 000 replies per second for a 15-pulse coded reply shall be permitted. 3.1.1.7.9.2 Reply rate limit control. To protect the system from the effects of transponder over-interrogation by preventing response to weaker signals when a predetermined reply rate has been reached, a sensitivity reduction type reply limit control shall be incorporated in the equipment. The range of this control shall permit adjustment, as a minimum, to any value between 500 and 2 000 replies per second, or to the maximum reply rate capability if less than 2 000 replies per second, without regard to the number of pulses in each reply. Sensitivity reduction in excess of 3 dB shall not take effect until 90 per cent of the selected value is exceeded. Sensitivity reduction shall be at least 30 dB for rates in excess of 150 per cent of the selected value. 3.1.1.7.9.3 Recommendation.— The reply rate limit should be set at 1 200 replies per second, or the maximum value below 1 200 replies per second of which the transponder is capable. 3.1.1.7.10 Reply delay and jitter. The time delay between the arrival, at the transponder receiver, of the leading edge of P3 and the transmission of the leading edge of the first pulse of the reply shall be 3 plus or minus 0.5 microseconds. The total jitter of the reply pulse code group, with respect to P3, shall not exceed 0.1 microsecond for receiver input levels between 3 dB and 50 dB above minimum triggering level. Delay variations between modes on which the transponder is capable of replying shall not exceed 0.2 microsecond. 3.1.1.7.11 TRANSPONDER POWER OUTPUT AND DUTY CYCLE 3.1.1.7.11.1 The peak pulse power available at the antenna end of the transmission line of the transponder shall be at least 21 dB and not more than 27 dB above 1 W, except that for transponder installations used solely below 4 500 m (15 000 ft), or below a lesser altitude established by the appropriate authority or by regional air navigation agreement, a peak pulse power available at the antenna end of the transmission line of the transponder of at least 18.5 dB and not more than 27 dB above 1 W shall be permitted. Note.— An extended squitter non-transponder device on an aerodrome surface vehicle may operate with a lower minimum power output as specified in 5.1.1.2. 3.1.1.7.11.2 Recommendation.— The peak pulse power specified in 3.1.1.7.11.1 should be maintained over a range of replies from code 0000 at a rate of 400 replies per second to a maximum pulse content at a rate of 1 200 replies per second or a maximum value below 1 200 replies per second of which the transponder is capable. 3.1.1.7.12 REPLY CODES 3.1.1.7.12.1 Identification. The reply to a Mode A interrogation shall consist of the two framing pulses specified in 3.1.1.6.1 together with the information pulses (Mode A code) specified in 3.1.1.6.2. Note.— The Mode A code designation is a sequence of four digits in accordance with 3.1.1.6.6. 3.1.1.7.12.1.1 The Mode A code shall be manually selected from the 4 096 codes available. 3.1.1.7.12.2 Pressure-altitude transmission. The reply to Mode C interrogation shall consist of the two framing pulses specified in 3.1.1.6.1 above. When digitized pressure-altitude information is available, the information pulses specified in 3.1.1.6.2 shall also be transmitted. 3.1.1.7.12.2.1 Transponders shall be provided with means to remove the information pulses but to retain the framing pulses when the provision of 3.1.1.7.12.2.4 below is not complied with in reply to Mode C interrogation. Chapter 3 Annex 10 — Aeronautical Telecommunications 3-7 22/11/07 3.1.1.7.12.2.2 The information pulses shall be automatically selected by an analog-to-digital converter connected to a pressure-altitude data source in the aircraft referenced to the standard pressure setting of 1 013.25 hectopascals. Note.— The pressure setting of 1 013.25 hectopascals is equal to 29.92 inches of mercury. 3.1.1.7.12.2.3 Pressure-altitude shall be reported in 100-ft increments by selection of pulses as shown in the Appendix to this chapter. 3.1.1.7.12.2.4 The digitizer code selected shall correspond to within plus or minus 38.1 m (125 ft), on a 95 per cent probability basis, with the pressure-altitude information (referenced to the standard pressure setting of 1 013.25 hectopascals), used on board the aircraft to adhere to the assigned flight profile. 3.1.1.7.13 Transmission of the special position identification (SPI) pulse. When required, this pulse shall be transmitted with Mode A replies, as specified in 3.1.1.6.3, for a period of between 15 and 30 seconds. 3.1.1.7.14 ANTENNA 3.1.1.7.14.1 The transponder antenna system, when installed on an aircraft, shall have a radiation pattern which is essentially omnidirectional in the horizontal plane. 3.1.1.7.14.2 Recommendation.— The vertical radiation pattern should be nominally equivalent to that of a quarter-wave monopole on a ground plane. 3.1.1.8 TECHNICAL CHARACTERISTICS OF GROUND INTERROGATORS WITH MODE A AND MODE C CAPABILITIES ONLY 3.1.1.8.1 Interrogation repetition frequency. The maximum interrogation repetition frequency shall be 450 interrogations per second. 3.1.1.8.1.1 Recommendation.— To minimize unnecessary transponder triggering and the resulting high density of mutual interference, all interrogators should use the lowest practicable interrogator repetition frequency that is consistent with the display characteristics, interrogator antenna beam width and antenna rotation speed employed. 3.1.1.8.2 RADIATED POWER Recommendation.— In order to minimize system interference the effective radiated power of interrogators should be reduced to the lowest value consistent with the operationally required range of each individual interrogator site. 3.1.1.8.3 Recommendation.— When Mode C information is to be used from aircraft flying below transition levels, the altimeter pressure reference datum should be taken into account. Note.— Use of Mode C below transition levels is in accordance with the philosophy that Mode C can usefully be employed in all environments. 3.1.1.9 INTERROGATOR RADIATED FIELD PATTERN Recommendation.— The beam width of the directional interrogator antenna radiating P3 should not be wider than is operationally required. The side- and back-lobe radiation of the directional antenna should be at least 24 dB below the peak of the main-lobe radiation. Annex 10 — Aeronautical Telecommunications Volume IV 22/11/07 3-8 3.1.1.10 INTERROGATOR MONITOR 3.1.1.10.1 The range and azimuth accuracy of the ground interrogator shall be monitored at sufficiently frequent intervals to ensure system integrity. Note.— Interrogators that are associated with and operated in conjunction with primary radar may use the primary radar as the monitoring device; alternatively, an electronic range and azimuth accuracy monitor would be required. 3.1.1.10.2 Recommendation.— In addition to range and azimuth monitoring, provision should be made to monitor continuously the other critical parameters of the ground interrogator for any degradation of performance exceeding the allowable system tolerances and to provide an indication of any such occurrence. 3.1.1.11 SPURIOUS EMISSIONS AND SPURIOUS RESPONSES 3.1.1.11.1 SPURIOUS RADIATION Recommendation.— CW radiation should not exceed 76 dB below 1 W for the interrogator and 70 dB below 1 W for the transponder. 3.1.1.11.2 SPURIOUS RESPONSES Recommendation.— The response of both airborne and ground equipment to signals not within the receiver pass band should be at least 60 dB below normal sensitivity. 3.1.2 Systems having Mode S capabilities 3.1.2.1 Interrogation signals-in-space characteristics. The paragraphs herein describe the signals-in-space as they can be expected to appear at the antenna of the transponder. Note.— Because signals can be corrupted in propagation, certain interrogation pulse duration, pulse spacing and pulse amplitude tolerances are more stringent for interrogators as described in 3.1.2.11.4. 3.1.2.1.1 Interrogation carrier frequency. The carrier frequency of all interrogations (uplink transmissions) from ground facilities with Mode S capabilities shall be 1 030 plus or minus 0.01 MHz. 3.1.2.1.2 Interrogation spectrum. The spectrum of a Mode S interrogation about the carrier frequency shall not exceed the limits specified in Figure 3-2. Note.— The Mode S interrogation spectrum is data dependent. The broadest spectrum is generated by an interrogation that contains all binary ONEs. 3.1.2.1.3 Polarization. Polarization of the interrogation and control transmissions shall be nominally vertical. 3.1.2.1.4 Modulation. For Mode S interrogations, the carrier frequency shall be pulse modulated. In addition, the data pulse, P6, shall have internal phase modulation. 3.1.2.1.4.1 Pulse modulation. Intermode and Mode S interrogations shall consist of a sequence of pulses as specified in 3.1.2.1.5 and Tables 3-1, 3-2, 3-3, and 3-4. Chapter 3 Annex 10 — Aeronautical Telecommunications 3-9 22/11/07 Note.— The 0.8 microsecond pulses used in intermode and Mode S interrogations are identical in shape to those used in Modes A and C as defined in 3.1.1.4. 3.1.2.1.4.2 Phase modulation. The short (16.25-microsecond) and long (30.25-microsecond) P6 pulses of 3.1.2.1.4.1 shall have internal binary differential phase modulation consisting of 180-degree phase reversals of the carrier at a 4 megabit per second rate. 3.1.2.1.4.2.1 Phase reversal duration. The duration of the phase reversal shall be less than 0.08 microsecond and the phase shall advance (or retard) monotonically throughout the transition region. There shall be no amplitude modulation applied during the phase transition. Note.— The minimum duration of the phase reversal is not specified. Nonetheless, the spectrum requirements of 3.1.2.1.2 must be met. 3.1.2.1.4.2.2 Phase relationship. The tolerance on the 0 and 180-degree phase relationship between successive chips and on the sync phase reversal (3.1.2.1.5.2.2) within the P6 pulse shall be plus or minus 5 degrees. Note.— In Mode S a “chip” is the 0.25 microsecond carrier interval between possible data phase reversals. 3.1.2.1.5 Pulse and phase reversal sequences. Specific sequences of the pulses or phase reversals described in 3.1.2.1.4 shall constitute interrogations. 3.1.2.1.5.1 Intermode interrogation 3.1.2.1.5.1.1 Mode A/C/S all-call interrogation. This interrogation shall consist of three pulses: P1, P3, and the long P4 as shown in Figure 3-3. One or two control pulses (P2 alone, or P1 and P2) shall be transmitted using a separate antenna pattern to suppress responses from aircraft in the side lobes of the interrogator antenna. Note.— The Mode A/C/S all-call interrogation elicits a Mode A or Mode C reply (depending on the P1-P3 pulse spacing) from a Mode A/C transponder because it does not recognize the P4 pulse. A Mode S transponder recognizes the long P4 pulse and responds with a Mode S reply. This interrogation was originally planned for use by isolated or clustered interrogators. Lockout for this interrogation was based on the use of II equals 0. The development of the Mode S subnetwork now dictates the use of a non-zero II code for communication purposes. For this reason, II equals 0 has been reserved for use in support of a form of Mode S acquisition that uses stochastic/lockout override (3.1.2.5.2.1.4 and 3.1.2.5.2.1.5). The Mode A/C/S all-call cannot be used with full Mode S operation since II equals 0 can only be locked out for short time periods (3.1.2.5.2.1.5.2.1). This interrogation cannot be used with stochastic/lockout override, since probability of reply cannot be specified. 3.1.2.1.5.1.2 Mode A/C-only all-call interrogation. This interrogation shall be identical to that of the Mode A/C/S all-call interrogation except that the short P4 pulse shall be used. Note.— The Mode A/C-only all-call interrogation elicits a Mode A or Mode C reply from a Mode A/C transponder. A Mode S transponder recognizes the short P4 pulse and does not reply to this interrogation. 3.1.2.1.5.1.3 Pulse intervals. The pulse intervals between P1, P2 and P3 shall be as defined in 3.1.1.4.3 and 3.1.1.4.4. The pulse interval between P3 and P4 shall be 2 plus or minus 0.05 microsecond. 3.1.2.1.5.1.4 Pulse amplitudes. Relative amplitudes between pulses P1, P2 and P3 shall be in accordance with 3.1.1.5. The amplitude of P4 shall be within 1 dB of the amplitude of P3. 3.1.2.1.5.2 Mode S interrogation. The Mode S interrogation shall consist of three pulses: P1, P2 and P6 as shown in Figure 3-4. Annex 10 — Aeronautical Telecommunications Volume IV 22/11/07 3-10 Note.— P6 is preceded by a P1 – P2 pair which suppresses replies from Mode A/C transponders to avoid synchronous garble due to random triggering by the Mode S interrogation. The sync phase reversal within P6 is the timing mark for demodulation of a series of time intervals (chips) of 0.25 microsecond duration. This series of chips starts 0.5 microsecond after the sync phase reversal and ends 0.5 microsecond before the trailing edge of P6. A phase reversal may or may not precede each chip to encode its binary information value. 3.1.2.1.5.2.1 Mode S side-lobe suppression. The P5 pulse shall be used with the Mode S-only all-call interrogation (UF = 11, see 3.1.2.5.2) to prevent replies from aircraft in the side and back lobes of the antenna (3.1.2.1.5.2.5). When used, P5 shall be transmitted using a separate antenna pattern. Note 1.— The action of P5 is automatic. Its presence, if of sufficient amplitude at the receiving location, masks the sync phase reversal of P6. Note 2.— The P5 pulse may be used with other Mode S interrogations. 3.1.2.1.5.2.2 Sync phase reversal. The first phase reversal in the P6 pulse shall be the sync phase reversal. It shall be the timing reference for subsequent transponder operations related to the interrogation. 3.1.2.1.5.2.3 Data phase reversals. Each data phase reversal shall occur only at a time interval (N times 0.25) plus or minus 0.02 microsecond (N equal to, or greater than 2) after the sync phase reversal. The 16.25-microsecond P6 pulse shall contain at most 56 data phase reversals. The 30.25-microsecond P6 pulse shall contain at most 112 data phase reversals. The last chip, that is the 0.25-microsecond time interval following the last data phase reversal position, shall be followed by a 0.5-microsecond guard interval. Note.— The 0.5-microsecond guard interval following the last chip prevents the trailing edge of P6 from interfering with the demodulation process. 3.1.2.1.5.2.4 Intervals. The pulse interval between P1 and P2 shall be 2 plus or minus 0.05 microsecond. The interval between the leading edge of P2 and the sync phase reversal of P6 shall be 2.75 plus or minus 0.05 microsecond. The leading edge of P6 shall occur 1.25 plus or minus 0.05 microsecond before the sync phase reversal. P5, if transmitted, shall be centred over the sync phase reversal; the leading edge of P5 shall occur 0.4 plus or minus 0.05 microsecond before the sync phase reversal. 3.1.2.1.5.2.5 Pulse amplitudes. The amplitude of P2 and the amplitude of the first microsecond of P6 shall be greater than the amplitude of P1 minus 0.25 dB. Exclusive of the amplitude transients associated with phase reversals, the amplitude variation of P6 shall be less than 1 dB and the amplitude variation between successive chips in P6 shall be less than 0.25 dB. The radiated amplitude of P5 at the antenna of the transponder shall be:

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