WE3.L10.2: COMMUNICATION CODING OF PULSED RADAR SYSTEMS

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WE3.L10.2: COMMUNICATION CODING OF PULSED RADAR SYSTEMS

  1. 1. “RadCom” The Intelligent Radar Signal Communication Coding of Pulsed Radar Systems by Werner Wiesbeck Forschungszentrum Karlsruhe Universität Karlsruhe (TH) in der Helmholtz - Gemeinschaft Research University•founded 1825
  2. 2. State of the Art Coherent Pulsed Radar Modulation State of the Art Radars are Stupid! 2 Institut für Hochfrequenztechnik IHE und Elektronik
  3. 3. State of the Art Coherent Pulsed Radar Modulation Radar type Time domain Frequency domain A A τp T Pulsed-CW t f A fTx FM-Chirp t t fTx A Frequency Coded t f A A Stagger ... t f 3 Institut für Hochfrequenztechnik IHE und Elektronik
  4. 4. Motivation – Basic Idea Communication Radar targets RadCom 4 Institut für Hochfrequenztechnik IHE und Elektronik
  5. 5. Basic Idea reflected signal communication RadCom Tx signal targets Car equipped with RadCom system Interference interferer signal Intelligent Transportation 2D Radar Imaging System (ITS) Communications by digital Diversity, MIMO beam-forming Driver Assistance •range Congestion Avoidance •traffic information •speed Dynamic Route Planning •road condition •azimuth PreCrash Detection •C2C communication 7 Institut für Hochfrequenztechnik IHE und Elektronik
  6. 6. Radar and Communication Ranges Radar equation: Com. range: PTx " GTx " GRx R " #2 " $ PTx " GTx " GRx C " #2 PRxRadar = PRxCom = (4 % ) 3 " R 4 (4 $ ) 2 " R 2 4# " R 2 PRxCom = PRxRadar " ! ! $ 8 Institut für Hochfrequenztechnik IHE und Elektronik !
  7. 7. Coding of Radar Signals Well known Radar coding for EW purposes: Pulse Radar Linear FM Chirp FMCW M-Sequence Example: Multicarrier Signals ...... OFDM Coding in communications: Single carrier BPSK, QPSK OFDM CDMA DSSS ...... 9 Institut für Hochfrequenztechnik IHE und Elektronik
  8. 8. OFDM Signal Spectrum -10 OFDM spectrum sub-carrier rel. power spectral density in dB OFDM pulse shape: rectangular 0 (-13dB first order sidelobes for single sub-carrier) -10 N sub-carriers, e.g. 16 -20 complex orthog. sampling in FD -30 -1 -0.5 0 0.5 1 normalized frequency 10 Institut für Hochfrequenztechnik IHE und Elektronik
  9. 9. OFDM Transmit Signal x(t,f) Nc-1 n=0 carrier .... .... f envelopes µ=0 ... ... bo ls .... sy m Nsym-1 t TOFDM Δf B 11 Institut für Hochfrequenztechnik IHE und Elektronik
  10. 10. OFDM Multi Carrier Transmit Scheme Orthogonal(FDM) scheme as a digital multi-carrier method cyclic prefix pilots guards N data QAM 1:N OFDM signal symbols IFFT N:1 source modulator symbols formation stream Frequency Domain Time Domain Dividing data Each sub-carrier is Total data rates similar to into parallel data modulated at a low single-carrier schemes streams symbol rate 12 Institut für Hochfrequenztechnik IHE und Elektronik
  11. 11. Joint Radar and Communication System Concept communication partner Advantages of OFDM signals: high data rate for payload data (no spreading required) high processing gain low range side lobes possibility of Doppler processing (orthogonal to range) Beam-forming capability 13 Institut für Hochfrequenztechnik IHE und Elektronik
  12. 12. OFDM System Parameters for 24 GHz ISM Band Symbols Parameter Value fc Carrier frequency 24 GHz Nc Number of subcarriers 1024 f Subcarrier spacing 90.909 kHz TOFDM Elementary OFDM symbol duration 11 µs TG Cyclic prefix length 1.375 µs B Total signal bandwidth 93.1 MHz R Radar range resolution 1.61 m Rmax Unambiguous range 1650 m vrel,max Unambiguous velocity ± 284 m/s Nsym Number of evaluated symbols 256 ∆vrel Velocity resolution 2.22 m/s GP Processing Gain 54.2 dB 16 Institut für Hochfrequenztechnik IHE und Elektronik
  13. 13. OFDM Coded Radar System Simulation Signal: OFDM coded BPSK Targets: {X,Y}, v, RCS Tx: G, PTx, Nsym Propagation: ray-tracing OFDM-Tx channel Radar OFDM-Rx processing Radar image Binary data 17 Institut für Hochfrequenztechnik IHE und Elektronik
  14. 14. OFDM Radar Processing x(t) ITx (n) Tx ~ fc ! y(t) ! IRx (n) Rx ! ! ! Standard approach: New, dedicated approach: Cross-correlation Tx-Rx Signals Complex division of symbols IRx (n) src (" ) = $ y(t)x(t # " ) dt Idiv (n) = ITx (n) , src (" ) = IFFT[ Idiv (n)]  dependent on signal (data) completely independent  unpredictable correlations from signal (data) !  high computational effort ! low computational effort 18 Institut für Hochfrequenztechnik IHE und Elektronik
  15. 15. OFDM-Radar Range-Doppler Processing IFFT ............. k=N-1 distance ............. . k=1 k=0 ν=0 . . . ν=M-1 Doppler 3. Step: Inverse Fourier trans- formation in frequency direction ............. FFT ............. frequency frequency n=N-1 n=N-1 . . n=1 n=1 ............. ............. n=0 n=0 µ=0 . . . µ=M-1 ν=0 . . . ν=M-1 time Doppler 2. Step: Fourier transformation in time direction 1. Step: I ( n) complex division I div (n) = Rx Processing gain: Nc·Nsym of symbols I Tx (n) 19 Institut für Hochfrequenztechnik IHE und Elektronik
  16. 16. Range and Doppler Resolution for 3 Targets Target Range R in m Speed v in m/s B = 93.1 MHz z1 33,2 10 Tsym = 12.375 µs z2 33,2 14 Nsym = 128 z3 35 10 fc = 24 GHz Distance R in m Unambiguous and independent resolution for distance and Doppler for an arbitrary number of objects Relative velocity v in m/s 20 Institut für Hochfrequenztechnik IHE und Elektronik
  17. 17. “RadCom” Verification by Measurements by Christian Sturm and Werner Wiesbeck Forschungszentrum Karlsruhe Universität Karlsruhe (TH) in der Helmholtz - Gemeinschaft Research University•founded 1825
  18. 18. Measurement System Setup at 24 GHz ISM Band A(f) Mixer creates two sidebands Ethernet HUB Only upper sideband is evaluated at the receiver frequency cable losses GRx = 22 dBi ≈ 3.5 dB (( ( FSQ26 @ 24.05 GHz GTx = 22 dBi PTx = 22 dBm Mixer SMR40 (( ( amp @ 23.85 GHz Reference + Trigger OFDM Signal SMJ 100A @ 200 MHz 22 Institut für Hochfrequenztechnik IHE und Elektronik
  19. 19. Measurement on Street Normalization to RCS = 1 m² in 10 m distance Radar image in dB 13.3 dBm² 8.1 dBm² v = -14.2 km/h Velocity ≈ 15.7 m/s = 56.7 km/h 23 Institut für Hochfrequenztechnik IHE und Elektronik
  20. 20. Digital Beam-forming for Azimuth Processing by Christian Sturm and Werner Wiesbeck Forschungszentrum Karlsruhe Universität Karlsruhe (TH) in der Helmholtz - Gemeinschaft Research University•founded 1825
  21. 21. Multi-beam DBF Radar Signal Processing Rx signal y1(t) Receive array signal vector Rx signal y2(t) Rx signal y3(t) # src,1 (" ) & Rx signal y4(t) src,4 (" ) % ( KKF KKF % src,2 (" )( ! = s (" ) KKF % src,3 (" ) ( rc Corr % ( Sendesignal x(t) Sendesignal x(t) $ src,4 (" )' ! Sendesignal x(t) Tx signal x(t) τ ! 4 3 1 2 ! d/λ d/ λ d/λ Azimuth Processing by Digital Beamforming 26 Institut für Hochfrequenztechnik IHE und Elektronik
  22. 22. Digital Beam-Forming for Multiple Targets Coverage unprocessed: coverage Tx = coverage Rx transmit beam ⇔multiple receive beams DBF processed multiple receive beams 27 Institut für Hochfrequenztechnik IHE und Elektronik
  23. 23. Radar und Communication with Digital Beam-forming Multiple antenna systems and coded signals for Super Resolution? V2V communication by codes range compression by correlation (PN-Codes, PPM, OFDM, MPSK...) angular compression by Digital Beam-forming or by Super-Resolution? 28 Institut für Hochfrequenztechnik IHE und Elektronik
  24. 24. Music Processing in OFDM Radar G T OFDM-Tx Channel OFDM-Rx Binary DATA Pow N_sym Radar AWGN V Performance azimuth processing {X,Y} RCS Image Data time MUSIC . ... s ot sh p na .s ! ... sc1 (n,m) 29 ! Institut für Hochfrequenztechnik IHE und Elektronik
  25. 25. Virtual Drive with Ray-Tracing DBF and Super Resolution Ray-Tracing Kanalmodell Radar Transmitter Ray-tracing (BPSK Modulation) Radar Receiver DBF with Super Resolution Range Correlation Azimuth Array Processing 30 Institut für Hochfrequenztechnik IHE und Elektronik
  26. 26. Summary Virtual Drive Radio detection Mobile and ranging Communications RadCom one transmission one spectrum one code 31 Institut für Hochfrequenztechnik IHE und Elektronik

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