Air Traffic Systems Air Traffic Systems SECONDARY SURVEILLANCE RADAR INTRODUCTION AND BASIC PRINCIPLES Basic Primary Radar Transmitter Pulses TX Timing & Control RX & PROCESSING Received Signal Radar Picture.
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Air Traffic Systems Air Traffic Systems SECONDARY SURVEILLANCE RADAR INTRODUCTION AND BASIC PRINCIPLES Basic Primary Radar Transmitter Pulses TX Timing & Control RX & PROCESSING Received Signal Radar Picture DISADVANTAGES OF PRIMARY RADAR High Power Clutter Permanent Echo's Weather i.e. Rain etc. Identification Basic Secondary Radar Tx 1030 MHz SSR Rx 1090 MHz RX TX & PROCESSING Timing & Control Decoder Secondary returns 123 ABC Radar Picture Modes and Pulse Spacing 3µs Military A/C Ident - Mode 1 5 µs Military Mission Ident - Mode 2 8 µs Joint Military & Civil A/C Ident - Mode 3/A Civil A/C Ident - Mode B Altitude Data - Mode C 17 µs 21 µs SSR Questions (Modes) Who are you ? (Mode 1 and 3/A) What is your altitude ? (Mode C) What is your mission number ? (Mode 2) Are you FRIEND or FOE ? (Mode 4) Mode Interlacing The ability of the system to automatically change modes. This enables more diverse information to be gathered. MODE INTERLACING Military transponder set to :Mode 1, code = 1100 Mode 3/A, code = 4170 Mode C, code = h1 Civil transponder set to :Mode 3/A, code = 2210 Mode C, code = h2 h2 h1 Mode interlace pattern 1, 3A, C 3/A C 2210 h2 No 2210 h2 Military 1100 4170 h1 1100 4170 h1 1100 4170 h1 1 Civil 3/A C 1 No 2210 h2 No 1 3/A C Coded Replies EMERGENCY REPLIES CIVILIAN EMERGENCY GENERAL EMERGENCY - 7700 RADIO FAILURE - 7600 HI-JACK - 7500 ADVANTAGES OF SSR OVER PRIMARY RADAR POSITIVE IDENTIFICATION CLUTTER ELIMINATION LOWER POWER FOR EQUIVALENT RANGE ACCURATE HEIGHT INFORMATION EMERGENCY INFORMATION DISADVANTAGES OF SSR INTERROGATIONS VIA SIDE LOBES FALSE REPLIES UNCORRELATED IN TIME (FRUIT) GARBLING TRACK WANDER Aircraft A 80 miles Aircraft C 200 Miles Aircraft B INTERROGATION SIDE LOBE SUPPRESSION Aircraft A 80 miles Aircraft C 200 Miles Aircraft B P2 P1 2s P3 Site B PRF 260Hz Site A PRF 250Hz F.R.U.I.T. Correct reply (Frame pulses + 2 information..) FRUIT Second PRP First PRP Replies Replies 1 PRF DELAY Coincidence Gate De-fruited video O/P DEFRUITER PRINCIPLE GARBLE Overlapping replies OVERLAPPING A4 B2 D2 D4 F2 End of pulse train from aircraft A Beginning of pulse train from aircraft B F1 C2 A2 C4 TRACK WANDER 1st sweep 2nd sweep 3rd sweep 4th sweep TRACK WANDER 1st sweep 2nd sweep sweep sweep track THE MONOPULSE SYSTEM ELIMINATES TRACK WANDER BECAUSE ONLY ONE PULSE FROM A REPLY TRAIN IS NEEDED TO OBTAIN AN ACCURATE BEARING. BORE SIGHT COMBINED SUM & DIFFERENCE PATTERNS Mono-pulse Secondary Surveillance Radar MSSR Cardion Secondary Surveillance Radar Antenna mounted on Tactical Watchman Mounted on T101 Air Defence Radar SSR SYSTEM APPLICATIONS MILITARY AIRCRAFT CIVIL AIRCRAFT AIR TRAFFIC CONTROL MARITIME AIRCRAFT MISSILE NAVAL SYSTEMS MODE S I am able to reply to your “ALL CALL” because I have Mode S Preamble 8.0 s 0.5 s This is my discrete address Data block 56 s or 112 s Bit 1 Bit 2 Bit 3 Bit 4 Bit N 1 0 1 0 1 0 1 0 1 0 0.5 s The future of SSR Mode S – becoming compulsory under EASA rules CSSR and MSSR don’t support Mode S Airfield layout Any Questions