(1)(Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers
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(2) (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. Passive RADAR DVB-T receiver for SDR. Why passive RADAR • Emitting is strongly regulated • The radiofrequency spectrum is already congested • RADAR range resolution ∆R = c0 /(2B) requires broadband (B) signals • returned power ∝ d −4. Aller Funkverkehr ist Landesverrat All radio traffic is high treason A. Price, Instruments of Darkness – The History of Electronic Warfare. GNURadio Multi-receiver synchronization Static targets: buildings Moving targets: planes Moving targets: ships Moving targets: cars. ⇒ use existing radiofrequency emissions and analyze their reflections on targets Demonstrated: GRAVES RADAR, France (47.3480◦ N, 5.5151◦ E), 143.05 MHz CW, 0.4 MW broadcast FM station 1 , Wifi2 , GSM3 , analog TV4 , DAB5 , Digital TV Question: can it be done with low-cost DVB-T receivers used as general purpose SDR ? 1. Multi-frequency. C.L. Zoeller & al., Passive coherent location radar demonstration, Proc. 34th Southeastern Symp. on System Theory, pp. 358–362 (2002), or J. Zhu & al., Adaptive beamforming passive radar based on FM radio transmitter, (2007): 13-13. Conclusion. K. Chetty & al., Through-the-wall sensing of personnel using passive bistatic wifi radar at standoff distances, IEEE Trans. on Geosci. & Remote Sensing 50.4 (2012): 1218-1226. 2. 3 R. Zemmari & al., GSM passive radar for medium range surveillance IEEE EuRAD (2009) 4 P.E. Howland & al., Target tracking using television-based bistatic radar, IEE Proc. Radar Sonar Navig., 1999, 146, pp. 166–174 5 M. Daun & al., Tracking in multistatic passive radar systems using DAB/DVB-T illumination, Signal Processing, 2012, 92(6), 1365-1386.. 2 / 29.
(3) Passive RADAR DVB-T receiver for SDR. Why passive RADAR • Emitting is strongly regulated • The radiofrequency spectrum is already congested • RADAR range resolution ∆R = c0 /(2B) requires broadband (B) signals • returned power ∝ d −4. 0. 200. 400. 600. time (666/512 trace/s). (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. 800. 1000. 1200. 1400. GNURadio. ⇒ use existing radiofrequency emissions and analyze their reflections on targets GRAVES RADAR, France (47.3480◦ N, 5.5151◦ E), 143.05 MHz CW, 0.4 MW Demonstrated: 1 2 broadcast FM station , Wifi , GSM3 , analog TV4 , DAB5 , Digital TV Question: can it be done with low-cost DVB-T receivers used as general purpose SDR ? 1600. Multi-receiver synchronization Static targets: buildings Moving targets: planes Moving targets: ships Moving targets: cars Multi-frequency Conclusion. 1800. -300. -200. -100. 0. 100. 200. 300. Doppler shift (Hz). 1. C.L. Zoeller & al., Passive coherent location radar demonstration, Proc. 34th Southeastern Symp. on System Theory, pp. 358–362 (2002), or J. Zhu & al., Adaptive beamforming passive radar based on FM radio transmitter, (2007): 13-13. 2. K. Chetty & al., Through-the-wall sensing of personnel using passive bistatic wifi radar at standoff distances, IEEE Trans. on Geosci. & Remote Sensing 50.4 (2012): 1218-1226. 3 R. Zemmari & al., GSM passive radar for medium range surveillance IEEE EuRAD (2009) 4 P.E. Howland & al., Target tracking using television-based bistatic radar, IEE Proc. Radar Sonar Navig., 1999, 146, pp. 166–174 5 M. Daun & al., Tracking in multistatic passive radar systems using DAB/DVB-T illumination, Signal Processing, 2012, 92(6), 1365-1386.. 3 / 29.
(4) (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. Passive RADAR DVB-T receiver for SDR. Low cost DVB-T receivers for SDR • low-cost DVB-T receivers (10.38 US$=1165 yens) • Linux driver port discovered that RTL2832U-based DVB-T receivers are general purpose software defined radio (SDR) receivers • various RF frontends, now R820T2 (50–1600 MHz, 35 dB RF gain) • 8-bit I and Q output on USB at max 2.4 MS/s • GNURadio real time processing framework 6. GNURadio Multi-receiver synchronization Static targets: buildings Moving targets: planes Moving targets: ships Moving targets: cars Multi-frequency Conclusion. 6 E4k. and RTL2832U based SDR @ http://jmfriedt.free.fr/en_sdr.pdf 4 / 29.
(5) (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. Passive RADAR DVB-T receiver for SDR GNURadio Multi-receiver synchronization Static targets: buildings Moving targets: planes Moving targets: ships. Basics • A “random” signal is emitted, e.g. by DVB-T tower 7 8 • This signal is recorded on a reference channel (direct path from emitter to reference receiver) • A measurement channel, ideally hidden from the direct wave, records reflections. • Search of the reference pattern in the measurement signal (time delayed) will give distance to target • Matched filter: cross-correlation will give the strongest probability that a delayed copy of the reference is found in the signal.. non−cooperative emitter. target. Moving targets: cars Multi-frequency Conclusion. ref. meas. 7 J. Raout & al., Passive bistatic noise radar using DVB-T signals IET radar, sonar & navigation 4.3 (2010): 403-411 8 J.E. Palmer & al., DVB-T passive radar signal processing, IEEE Trans. Signal Proc. 61.8 (2013): 2116-2126 5 / 29.
(6) (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. Real time correlation computation in GNURadio From convolution to correlation: • Convolution: Z. Passive RADAR. s(t)r (τ − t)dt. conv (s, r )(τ ) =. DVB-T receiver for SDR GNURadio. • Practical computation of convolution:. Multi-receiver synchronization. FT (conv (s, r )) = FT (s) · FT (r ). Static targets: buildings Moving targets: planes Moving targets: ships Moving targets: cars Multi-frequency. • Correlation:. Z corr (s, r )(τ ) =. s(t)r (t + τ )dt. • Convolution → correlation: time reversal • since exp(jωt)∗ = exp(−jωt), we conclude. Conclusion. FT (corr (s, r )) = FT (s) · FT ∗ (r ) 6 / 29.
(7) (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. Real time correlation computation in GNURadio. Passive RADAR DVB-T receiver for SDR GNURadio Multi-receiver synchronization Static targets: buildings Moving targets: planes Moving targets: ships Moving targets: cars Multi-frequency Conclusion. GNURadio: • collect N-sample long vectors • compute (i)FFT, • multiply with complex conjugate, • and 6 iFFT with fftshift to get 0-delay correlation at center of graph • or use waterfall sink for last 6 iFFT 7 / 29.
(8) (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. Passive RADAR DVB-T receiver for SDR GNURadio Multi-receiver synchronization Static targets: buildings Moving targets: planes Moving targets: ships Moving targets: cars Multi-frequency Conclusion. Challenge of DVB-T data collection • each DVB-T dongle is clocked by its own quartz oscillator • each DVB-T dongle communicates on the USB-bus at its own rate • each DVB-T dongle generates LO with its own (oscillator-locked) PLL • How can we make sure the datastream is continuous, the sampling rate equal and the phase coherent on the two dongles ? • Same clock solves the clock reference issue, but dithering must be deactivated + thermal coupling of PLL multipliers generating LO. • For RADAR application, phase coherence is only needed for the duration of the measurement (=maximum range). Experimental setup 8 / 29.
(9) (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. Passive RADAR DVB-T receiver for SDR. Challenge of DVB-T data collection • each DVB-T dongle is clocked by its own quartz oscillator • each DVB-T dongle communicates on the USB-bus at its own rate • each DVB-T dongle generates LO with its own (oscillator-locked) PLL. GNURadio Multi-receiver synchronization Static targets: buildings Moving targets: planes Moving targets: ships Moving targets: cars Multi-frequency Conclusion. • How can we make sure the datastream is continuous, the sampling rate equal and the phase coherent on the two dongles ? • Same clock solves the clock reference issue, but dithering must be deactivated + thermal coupling of PLL multipliers generating LO. • For RADAR application, phase coherence is only needed for the duration of the measurement (=maximum range). Need to de-activate PLL dithering in librtlsdr (superkuh.com/rtlsdr.html) 9 / 29.
(10) Passive RADAR DVB-T receiver for SDR GNURadio Multi-receiver synchronization Static targets: buildings Moving targets: planes Moving targets: ships Moving targets: cars Multi-frequency Conclusion. Challenge of DVB-T data collection • each DVB-T dongle is clocked by its own quartz oscillator • each DVB-T dongle communicates on the USB-bus at its own rate • each DVB-T dongle generates LO with its own (oscillator-locked) PLL 1. • How can we make sure the datastream is continuous, the sampling rate equal and the phase coherent on the two dongles ? • Same clock solves the clock reference issue, but dithering must be deactivated + thermal coupling of PLL multipliers generating LO. • For RADAR application, phase coherence is only needed for the duration of the measurement (=maximum range). experiment 1 experiment 2 experiment 3 experiment 4 experiment 5. 0.8. normalized xcorr (a.u.). (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. 0.6. 0.4. 0.2. 0. -400. -200. 0. 200. 400. time (us). Cross-correlation peak position for 5 experiments (400 µs @ 2 MS/s=800 sample offset) 10 / 29.
(11) (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. Result. Passive RADAR DVB-T receiver for SDR GNURadio Multi-receiver synchronization Static targets: buildings Moving targets: planes Moving targets: ships Moving targets: cars Multi-frequency Conclusion. github.com/jmfriedt/gr-oscilloscope. 11 / 29.
(12) (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. Experimental setup GNURadio output:. Passive RADAR DVB-T receiver for SDR GNURadio Multi-receiver synchronization Static targets: buildings Moving targets: planes Moving targets: ships Moving targets: cars. Reference antenna. Multi-frequency Conclusion. Initial calibration by connecting the reference antenna to the measurment channel, and then keep the system running.. Measurement antenna. • Never stop the data stream since the time delay is unknown at first, but constant • Slow down datarate so as to capture one cross-correlation curve every 8 seconds, enough time to move the antenna 12 / 29.
(13) (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. Experimental setup GNURadio output:. Passive RADAR DVB-T receiver for SDR GNURadio Multi-receiver synchronization Static targets: buildings Moving targets: planes. Real time time-domain signal and cross-correlation display for assessing signal quality. Moving targets: ships Moving targets: cars. Reference antenna. Multi-frequency Conclusion. Measurement antenna. • Never stop the data stream since the time delay is unknown at first, but constant • Better: stream data to external application which grabs measurements when needed (ZeroMQ pipe) 13 / 29.
(14) (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. ZeroMQ • Stream from data recorder to signal processing tool (e.g. Matlab) • Separate recording from processing: intermadiate step between offline prototyping and integrated GNURadio processing. Passive RADAR DVB-T receiver for SDR GNURadio Multi-receiver synchronization Static targets: buildings Moving targets: planes Moving targets: ships Moving targets: cars Multi-frequency Conclusion. 14 / 29.
(15) (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. Result DVB-T: 2 MHz bandwidth = 1 sample every 500 ns or 150 m 75. 0. 75. 150. 225. 300 m. Passive RADAR DVB-T receiver for SDR GNURadio Multi-receiver synchronization Static targets: buildings Moving targets: planes Moving targets: ships Moving targets: cars Multi-frequency Conclusion. 15 / 29.
(16) (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. Result oscilloscope: 200 MHz bandwidth = 1 sample every 5 ns or 1.5 m. Passive RADAR DVB-T receiver for SDR GNURadio Multi-receiver synchronization Static targets: buildings Moving targets: planes Moving targets: ships Moving targets: cars Multi-frequency Conclusion. (200 ns wide autocorrelation peak) 16 / 29.
(17) Passive RADAR DVB-T receiver for SDR GNURadio Multi-receiver synchronization Static targets: buildings Moving targets: planes Moving targets: ships Moving targets: cars. Moving target: planes • Range measurement feasibility study demonstrated • Range-Doppler: for a moving target, try all possible Z xcorr (τ, fD ) = r (t) · s(t + τ ) · exp(j2πfD t)dt • Measurement duration ? • pulse compression ratio (SNR gain) given by the number of samples (B × T = N if whole bandwidth B = 1/fs is used) • Doppler resolution is 1/T Doppler-range ambiguity function • plane flying at 360 km/h =100 m/s introduces fD = f × 2v /c0 = 333 Hz @ 500 MHz ⇒ analyze 250 ms-long chunks of data (4 Hz Doppler resolution =9 km/h velocity resolution) • 250 ms=25 m @ 100 m/s • use of DVB-T receiver for Doppler shift (Hz) continuous data-stream & post-process: 2 MHz bandwidth=75 m range resolution 9 -150. -100. -50. distance (km). (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. 0. 50. 100. Multi-frequency Conclusion. 150 -300. -200. -100. 0. 100. 200. 9 kaira.sgo.fi/2013/09/passive-radar-with-16-dual-coherent.html. 300. 17 / 29.
(18) (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. Passive RADAR DVB-T receiver for SDR GNURadio Multi-receiver synchronization. Moving target: planes. • Continuous stream: 32 MB/s=1.92 GB/min 2 channels×I/Q×4 bytes/measurement×2 MS/s. • Planes landing at Sendai airport, using the DVB-T emission at 473 MHz (NHK, 3 kW) • range-Doppler map: 3 minute acquisition requires several hours processing time on general purpose CPU/interpreted language (GNU/Octave). Static targets: buildings Moving targets: planes Moving targets: ships Moving targets: cars Multi-frequency Conclusion. 18 / 29.
(19) (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. Passive RADAR DVB-T receiver for SDR GNURadio Multi-receiver synchronization. Moving target: planes. • Continuous stream: 32 MB/s=1.92 GB/min 2 channels×I/Q×4 bytes/measurement×2 MS/s. • Planes landing at Sendai airport, using the DVB-T emission at 473 MHz (NHK, 3 kW) • range-Doppler map: 3 minute acquisition requires several hours processing time on general purpose CPU/interpreted language (GNU/Octave) -5. Static targets: buildings. tra jec. 10. y. tor. Multi-frequency. ne. Moving targets: cars. cars ?. 5. pla. Moving targets: ships. 0. bistatic range (km). Moving targets: planes. 15. Conclusion. 20 -200. -100. 0. 100. Doppler frequency shift (Hz). 200 19 / 29.
(20) (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. Passive RADAR DVB-T receiver for SDR GNURadio. Autocorrelation • Since some of the reference signal is in the measurement signal, autocorrelation will also identify Doppler shifted targets • All targets will match some resemblance with all others: in our case only 1 target • Avoids synchronizing two receivers, but lower signal to noise ratio due to the weak reference signal. Multi-receiver synchronization Static targets: buildings Moving targets: planes Moving targets: ships Moving targets: cars Multi-frequency Conclusion. 20 / 29.
(21) (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. Passive RADAR on ships Measurement from the sea shore near the port of Sendai. Passive RADAR DVB-T receiver for SDR GNURadio Multi-receiver synchronization Static targets: buildings Moving targets: planes Moving targets: ships Moving targets: cars Multi-frequency Conclusion. fD ' 12 Hz' 3.6 m/s' 13 km/h' 7 knot, consistent with AIS transmissions ('12 knot max. speed) 21 / 29.
(22) (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. Passive RADAR on cars x(τ, fD ) =. R +∞ ∞. ref (t + τ ) ·mes ∗ (t) · exp(j2πfD · t) ·dt {z } | {z } | τ =range. Passive RADAR DVB-T receiver for SDR GNURadio Multi-receiver synchronization Static targets: buildings Moving targets: planes Moving targets: ships Moving targets: cars Multi-frequency Conclusion. fD =speed. • No range resolution ⇒ τ = 0 and compute FFT (ref (t) · mes(t)∗ ) providing the Doppler shift spectrum • Data size: 2048 kS/s×4 bytes/S×I,Q×2 channels =33 MB/s=2 GB/min ⇒ max record size is 3 min (6 GB RAMfs) • Use first second of data to estimate (constant) time offset between ref. and meas. channels • Apply this offset to all subsequent dataset (400 µs 0.5 s segment) 22 / 29.
(23) (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. Short range targets: cars. -60. -40. DVB-T receiver for SDR GNURadio Multi-receiver synchronization Static targets: buildings Moving targets: planes Moving targets: ships. Doppler consistent with car velocity at a corner: fD = 2fc. v = 33 Hz c0. @ 500 MHz & 10 m/s. Doppler shift (Hz). -20. Passive RADAR. 0. 20. 40. 60. 0. 50. time (s). 100. 150. Moving targets: cars Multi-frequency Conclusion. Movie → 1 picture/s, keep only pictures with cars and one white line for each time a picture appears 23 / 29.
(24) (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. Short range targets: cars -60. -40. DVB-T receiver for SDR GNURadio Multi-receiver synchronization Static targets: buildings Moving targets: planes Moving targets: ships. Doppler consistent with car velocity at a corner: fD = 2fc. Doppler shift (Hz). -20. Passive RADAR. 0. 20. v = 33 Hz 40 c0. @ 500 MHz & 10 m/s. 60. 0. Moving targets: cars Multi-frequency. bike. 50. time (s). 100. 150. car leaving parking. Conclusion. 24 / 29.
(25) (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. Doubling the bandwith • • • •. Four DVB-T setup: two towards reference, two towards targets Each pair is set to two frequencies: adjacent frequencies = double bandwidth Challange: sub-sample resolution alignement of all datastreams Demonstration with ship detection. 5000. 0.5. 2000. 0.4. 0.7. Range (m). 0.6. 3000. 0.6 0.5. 2000. 0.2. 0.4 0.3. 1000. 0.2. 0.1. 0 -50. -40. -30. -20. -10. 0. 10. 20. 30. 40. 0.1. 0 -50. 50. Doppler frequency (Hz). -40. -30. -20. -10. 0. 10. 20. 30. 40. 50. Doppler frequency (Hz). 5000. Moving targets: ships. 1 0.9. 4000. 0.8 0.7. Range (m). Conclusion. 3000. 1000. Moving targets: planes. Multi-frequency. 0.8. 0.3. Static targets: buildings. Moving targets: cars. 0.9. 4000. 0.8 0.7. Range (m). Multi-receiver synchronization. 1. 0.9. 4000. DVB-T receiver for SDR GNURadio. 5000. 1. Passive RADAR. 3000. 0.6 0.5. 2000. 0.4 0.3. 1000. 0.2 0.1. 0 -50. -40. -30. -20. -10. 0. 10. 20. Doppler frequency (Hz). 30. 40. 50. 25 / 29.
(26) (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. Doubling the bandwith • Four DVB-T setup: two towards reference, two towards targets • Each pair is set to two frequencies: adjacent frequencies = double bandwidth • Challange: sub-sample resolution alignement of all datastreams • Demonstration with ship detection. DVB-T receiver for SDR. Multi-receiver synchronization Static targets: buildings Moving targets: planes Moving targets: ships Moving targets: cars. Normalized amplitude. GNURadio. 1. 1. 0.8. 0.8. Normalized amplitude. Passive RADAR. 0.6. 0.4. 0.2. 0 1500. 1750. 2000. 2250. Range (m). Range cross-section. 2500. 2750. 3000. 0.6. 0.4. 0.2. 0 -50. -40. -30. -20. -10. 0. 10. 20. 30. 40. 50. Doppler frequency (Hz). Doppler cross-section. Multi-frequency Conclusion. The two center frequencies can be widely separated: strong sidelobes but fringe period determined by center frequency difference 26 / 29.
(27) (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. Passive RADAR DVB-T receiver for SDR GNURadio Multi-receiver synchronization Static targets: buildings Moving targets: planes Moving targets: ships Moving targets: cars Multi-frequency Conclusion. Conclusion and perspectives • Demonstrated ability to detect static and moving targets using non-cooperative emitter ... • using low-cost DVB-T receivers acting as general purpose SDR. • GNURadio processing environment for fast prototyping and educational purposes (opensource) What next ? • array of DVB-T receivers for Direction of Arrival (DOA 10 ) analysis (azimuth by exploiting the phase of the correlation) • Real time correlation processing on the FPGA of the Redpitaya board ? (2× 125 MHz ADC for improved range resolution) Resources: Slides: http://jmfriedt.free.fr/fosdem2018.pdf Manuscript: http://jmfriedt.free.fr/URSI.pdf French article: GNU/Linux Magazine France 212 (Feb. 2018) Ship movies: http://jmfriedt.sequanux.org/ship6.mp4 (ship4..ship8) Plane movies: http://jmfriedt.sequanux.org/plane1.mp4 (plane1, plane2) 10 GRCon2017 program @ www.gnuradio.org/grcon-2017/program/grcon17-presentations/ and presentations @ www.youtube.com/playlist?list=PLbBQHMnVMR43mM18y4r8L7l8bbYMgloFx 27 / 29.
(28) (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. Short range targets: cars. -60. -40. DVB-T receiver for SDR GNURadio Multi-receiver synchronization Static targets: buildings Moving targets: planes Moving targets: ships Moving targets: cars. Doppler consistent with car velocity at a corner: fD = 2fc. Doppler shift (Hz). -20. Passive RADAR. v = 33 Hz c0. @ 500 MHz & 10 m/s. 0. 20. 40. 60. 0. 20. 40. 60. time (s). 80. 100. 120. Multi-frequency Conclusion. 28 / 29.
(29) (Yet another) DVB-T based passive radar demonstration using Software Defined Radio on low-cost DVB-T receivers. Geographical settings 1 0 1 2 3 4 km CNEAS 3.3 km. 12 km. port. Passive RADAR DVB-T receiver for SDR GNURadio. TV towers. Multi-receiver synchronization Static targets: buildings Moving targets: planes. 11.3 km. Moving targets: ships Moving targets: cars Multi-frequency Conclusion. airport 29 / 29.
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