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

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  • 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. State of the Art Coherent Pulsed Radar Modulation State of the Art Radars are Stupid! 2 Institut für Hochfrequenztechnik IHE und Elektronik
  • 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. Motivation – Basic Idea Communication Radar targets RadCom 4 Institut für Hochfrequenztechnik IHE und Elektronik
  • 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. “RadCom” Verification by Measurements by Christian Sturm and Werner Wiesbeck Forschungszentrum Karlsruhe Universität Karlsruhe (TH) in der Helmholtz - Gemeinschaft Research University•founded 1825
  • 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. 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. 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. 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. 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. 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. 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. 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. Summary Virtual Drive Radio detection Mobile and ranging Communications RadCom one transmission one spectrum one code 31 Institut für Hochfrequenztechnik IHE und Elektronik