Defense and Security Research Center Passive Radar Krzysztof Kulpa Professor Scientific Director Defense and Security Research Center Institute of Electronic Systems Warsaw University of Technology Nowoiejska 15/19 00-665 Warsaw, Poland e-mail: k.kulpa@elka.pw.edu.pl Most recent, indicate, apologize

Outline Introduction to Passive Multistatic Radars Array antenna Tx Introduction to Passive Multistatic Radars Array antenna Direct signal and clutter cancelation Detection Tracking Applications Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Most recent, indicate, apologize Rx

WUT is the largest of 18 Polish technical universities Public state school Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Most recent, indicate, apologize

Warsaw University of Technology Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Most recent, indicate, apologize 19 faculties Over 30 thousand students ~2500 academic staff

WUT Radar Technology Lab Radar Modeling, Signal Processing, Applications Passive radar Noise radar FMCW radars Maritime radars ATC micro-Doppler NCTR THZ active imaging Active radars (inc. MIMO) Electronically Scanned Antenna T/R modules control and calibration SAR radars (X, W bands 15 m -> 5 cm res.) ISAR (ships, planes, ground targets) Radar signal simulations ECM/ECCM inc. DRFM Cooperation with: radar industry PITRADWAR Polish Army EDA NATO STO International labs Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Most recent, indicate, apologize

Active radar detection Advantage: Mature technology Reliable Independent Emission (illumination) Moving target Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Bi-static Echo return Disadvantage: Target warning High power consumption Limited accuracy Low Pd for low RCS targets Echo return Most recent, indicate, apologize Mono-static site Bi-static site

On board Man-made Emission DOA or TDOA On board Man-made Emission Advantage: Mature technology High Accuracy Covertness Moving target Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Disadvantage: Requires target man-made emissions High bandwidth data links needed Most recent, indicate, apologize Angle/time estimation sites Processing Site Data Link

Warsaw University of Technology Institute of Electronic Systems Passive Coherent Localization NOT PASSIVE !!! Advantage: No dedicated transmitters Covert High Accuracy No warning of target Different illuminators Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Disadvantage: Not mature technology High computational power High complexity of algorithms Not fully reliable Required illuminators of opportunity Most recent, indicate, apologize Mono- or multi-static receivers Warsaw University of Technology Institute of Electronic Systems Processing Site Data Link

Daventry Experiment Illuminator of opportunity: BBC - Empire Radio Station, 10 kW, wavelength 49m Introduction Coverage Sognals Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Most recent, indicate, apologize 26 February 1935 Arnold Wilkins (operator), A. P. Rowe & Robert Watson Watt. Signal processing and Visualisation using oscilloscope Detection range: 8 miles !

First operational passive radar Klein Heidelberg First operational passive radar Germany (1943) Target Illuminator: Chain Home radar (GB) Introduction Coverage Sognals Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions C Most recent, indicate, apologize Receiver antenna France

PCL Radar principles Bi-static detection equation Bi-static detection range Received signal Introduction Coverage Sognals Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Target rR rT Detection: Cross-ambiguity function (matched filtering) rB Transmitter Receiver rB= rR + rT - rB

PCL Detection range Air surveillance (long range) TV FM Urban Introduction Coverage Sognals Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Urban operations DAB/DVB-T WIMAX/LAN GSM/GPRS Wi-Fi

FM Signal spectrum Introduction Coverage Sognals Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions

FM Signal ambiguity Introduction Coverage Sognals Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions

DVB-T Signal spectrum Introduction Coverage Sognals Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions

DVB-T Signal ambiguity Introduction Coverage Sognals Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions

GSM Signal spectrum Introduction Coverage Sognals Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions

GSM Signal ambiguity Introduction Coverage Sognals Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions

PCL Scenario Ideal case Target echo Reference signal Main antenna Introduction Coverage Sognals Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Reference signal Transmitting antenna Reference antenna

Coverage prediction P = 10 kW Bi-static detection range Airliner receiver transmitter [km] Detection RCS (theoretical) [dBsm] -200 -150 -100 -50 50 100 150 200 -20 -15 -10 -5 5 10 Airliner Introduction Coverage Signals Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Fighter Missile

Array Antenna 8 element FM circular array antenna Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions 3 directional TV antennas

8 element FM circular array antenna Digital beamforming 8 element FM circular array antenna 8 x λ/2 dipoles Rectangular window 12 dB gain, -7dB sidelobes dB Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Lin - polar deg

8 element FM circular array antenna Digital beamforming 8 element FM circular array antenna 8 x λ/2 dipoles C windows set 11 dB gain, -28 sidelobes dB Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Lin - polar deg

Digital beamforming 8 element FM circular array antenna 8 x λ/2 dipoles Multi-beam beamforming 8 beams, -3dB crossing Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions

Digital beamforming 8 element FM circular array antenna 8 x λ/2 dipoles Multi-beam beamforming 16 beams, -1dB crossing Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions

PCL Scenario Direct signal Target echo Direct signal Reference signal Main antenna Direct signal Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Reference signal Transmitting antenna Reference antenna

PCL Scenario Direct signal + clutter Ground Clutter Target echo Main antenna Direct signal Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Reference signal Transmitting antenna Reference antenna

PCL Scenario Direct signal + Clutter + multipatch Ground Clutter and targets in Reference signal Ground Clutter Target echo Main antenna Direct signal Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Reference signal Indirect Reference signal (multipath) Transmitting antenna Reference antenna

Bistatic Measurements Targets Range-Doppler correlation results Dynamic 120 dB Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Long observation time (~1s) Low/medium range resolution No angle resolution High Doppler resolution Measurement of R, V [,a] different illuminators of opportunity: FM, DAB, DBVT, GSM, WiMax and others Most recent, indicate, apologize

Masking effect Short range target signal masking effects – multiple targets Strong echo return can be assumed as a noise signal while detecting long-range targets Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Target1 rR rT Correlation based detection is optimal only for single target case Transmitter Receiver Target2

Direct power Direct power P = 100 kW R = 10 km p = -11 dBm kTB = -121 dBm pt = -146 dBm Required dynamic Range to noise = 110 dB to target = 135 dB Correlation gain 40-60 dB (only) 70-100 dB direct signal and clutter cancelation is required Pt=1MW Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Pt=10kW

Final coverage [km] Detection RCS - near target suppresed [dBsm] receiver transmitter -200 -150 -100 -50 50 100 150 200 -20 -15 -10 -5 5 10 Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions

Strong signal masking effect 10 -3 -2 -1 20 30 40 50 60 near/far range ratio Near range strong signal can be treated as an additional noise during long-range target detection To decrease long-range target detection loses strong target echo removal procedures must be apply Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions detection loses [dB]

Short distance target masking effect dBsm [km] Detection RCS - near target blinding effect [dBsm] receiver transmitter target -200 -150 -100 -50 50 100 150 200 -20 -15 -10 -5 5 10 Short distance strong echo masking effect Solution: Adaptive clutter/targets removal Requirements: Good channels match reference and main, low multi-path effects Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions

Strong echo removal procedure CLEAN STEP I - Strong echo estimation using maximum of range-Doppler correlation function STEP II - Strong echo removal Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions STEP III – long-range echo estimation using maximum of range-Doppler correlation function STEP IV – test: if strongest echo > limits -> continuation of strong echo removal ( go to STEP II )

Strong echo removal effect Direct signal masking effects and short distance strong echo masking effect taken into consideration Direct signal antenna base suppression [km] Detection RCS - near target suppresed [dBsm] receiver transmitter target -200 -150 -100 -50 50 100 150 200 -20 -15 -10 -5 5 10 Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions

Reference channel problems Refrence and Main Receiver response characteristic difference Multipath in reference channel |A| f Main antenna Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Reference signal Reference antenna Transmitting antenna Reference receiver DSP PCL processor Main receiver

Why good reference channel is required Low target side-lobes Good attenuation of direct signal Good attenuation of ground clutter Adaptive removal of strong targets Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions

Reference channel equalization methods Environment-based method Knowledge based equalization methods Constant amplitude method Methods based on signal structure Digital signal reconstruction Indirect path knowledge base Environment-based method Ground clutter based equalization DSP-based method Maximum contrast methods Reference point equalization Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions

Reference channel signal restoration A/C Digital decoder Digital coder Restored signal Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions For digital modulation (GSM, WiFi, DAB, DVBT) it is possible to restore original signal by: decoding the bit-stream apply the bit-error correction encode

Range-Doppler Correlation Single-antenna system A/C Digital decoder Digital coder Restored signal Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Plot extraction Clutter cancelation Range-Doppler Correlation

PCL localization Bistatic Multistatic For good performance several transmitters are needed Increase of sensitivity due to multistatic operation xmeas1(t) xmeas2(t) Bistatic Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Multistatic Single Transmitter/Receiver pair Range/Angle estimation Poor cross-range resolution Most recent, indicate, apologize Multi Transmitter/Receiver pair Range/Angle estimation + Ellipsoid cross-section estimation Good range & cross-range resolution

PCL localization Multistatic Single receiver blind zone possible zones of low Doppler or range resolution zones with reduced visibility towards the transmitters possibility of ghost targets Ghost targets Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Most recent, indicate, apologize Blind zones

PCL localization Multistatic Multi receiver Reduced blind zones High probability of detection/tracking Data exchange required Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Most recent, indicate, apologize

Tracking Two-stage tracker Single-stage tracker Combining bistatic measurements from different TxRx pairs Bistatic tracking Plot-track association Kalman filtering Calculating Cartesian coordinates of plots Cartesian Tracking Extended Kalman filtering Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Most recent, indicate, apologize Tracking Plot-track association Kalman filtering Track verification

Cartesian Tracking Bistatic Trackers Bistatic Tracks Bistatic Plots Combining bistatic tracks from different TxRx pairs Time aligment Cartesian Tracking Extended Kalman filtering Calculating Cartesian coordinates of tracks Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Most recent, indicate, apologize Track fusion (for NTxRx>3) Track verification

Parallel updating All ellipsoids Extended Kalman filtering High dimension of measurement matrices Bistatic tracking – for primary plot selection If missing plot in single TxRx pair – Kalman prediction used instead of plot For asynchronous measurements - interpolation Filter equations dependant on the number of TxRx pairs Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Most recent, indicate, apologize

Serial updating one ellipsoid a time Extended Kalman filtering switch one ellipsoid a time Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Extended Kalman filtering Constant dimensionality (low) Bistatic tracking – for primary plot selection If missing plot in single TxRx pair – no action is taken ready for asynchronous measurements comparable computational power Most recent, indicate, apologize

Results Scenario: Rx - 1 Tx - 3 Targets - 3 Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Most recent, indicate, apologize

WUT PaRaDe PCL demonstrator Plot display Correlator display FM radio as illuminator of opportunity Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Track display Most recent, indicate, apologize

PARADE Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions

PARADE Real time processing Plot display Track display Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions

Long range tracking: 600-80 km bistatic PARADE Long range tracking: 600-80 km bistatic Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions XY display Bistatic display

Mobile PaRaDe (2007) Target PCL system on moving platform Transmitter of opportunity RS(t) RT(t) Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions L(t) Most recent, indicate, apologize Direct signal and clutter RT(t) RS(t) PCL platform Clutter

Airborne PaRaDe (2008) STAP processing First trials Data fusion Detected target Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Data fusion Hardware Antennas Multistatic coverage Most recent, indicate, apologize

PET-PCL GUNICA  PCL 4 mobile radar set Area: 40x40 km Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions 4 mobile radar set Area: 40x40 km PCL-PET Most recent, indicate, apologize PIT-RADWAR POLAND

Passive detection based on active radar illumination Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Most recent, indicate, apologize

Passive radar features (1) High update rate FM 1s DVB-T 0.1 s GSM 0.3 s SAT-TV 0.1-0.3 s High detection range FM 800 km bistatic DVB-T 400 km bistatic GSM 40 km bistatic No own emission (ARM missile - not a danger) Possible of exploitation pulse (radar) emitters Possible of exploitation of over-horizon far transmitters (up to 400 km range) Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions

Passive radar features (2) Continues illumination on target no range/Doppler ambiguity no blind speeds/ranges NCTR capabilities ISAR imaging micro-Doppler analysis detection of rotor flashes engine modulation detection Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions

Passive radar features (3) Detection coverage increase by: netted PCL radars data fusion on track level (classical) data fusion on bistatic track level data fusion on plot level data fusion on raw data level Data link requirements high data throughput – especially for raw data level fusion Time synchronization requirements track/plot level - 1 ms data level – 10 ns + frequency and phase coherency Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions

Passive radar features (4) Detection of low RCS targets: stealth targets drones /UAV missiles Detection of target behavior acceleration measurement target split shape changes Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions

Passive radar features (5) Multiband operation: FM radio (88-108 MHz) DAB (~200 MHz) DVB-T (450-850 MHz) GSM, LTE ..: 850, 950, 1800, 2100 and others DVB-S (C, X Ku band) Satellite radio (C band) Active radar exploitation VHF/UHF radar L band radars (including SSR) C band radars (including weather radars) S band radars Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions

Passive radar features (6) ECM resistant: wide bandwidth lack on knowledge where is (are) receivers high power jammer may be used as illuminator Jammer tracking DOA TDOA (high accuracy) No transmitter case Add own FM/DVB-T transmitter Add high power jammers (NOISE RADAR !) Relay on neighbors transmitters (up to 400 km range) Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions

Future of PCL Personal sensors Airborne sensors Mobile systems Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions Fixed systems Maritime sensors

Future conferences in POLAND SPS-2015 Signal Processing Symposium 10-12 June 2015 Poland, Warsaw/Debe Radar, remote sensing Biomedical signal processing Image processing Security Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions http://sps2015.ise.pw.edu.pl Important Dates Papers for reviewing (3 - 4 pages): February 10, 2015 Notification for Authors: March 10, 2015 Early participants ́ registration: April 01, 2015 Full paper submission: April 21, 2015 SPS 2015: June 10-12, 2015

Future conferences in POLAND mrw2016.org IRS 2016 17th International Radar Symposium May 10-12, 2016 Krakow, Poland Chaired by: Krzysztof Kulpa Hermann Rohling Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions http://mrw2016.org/en/irs2016/about-irs

Thank you Introduction Coverage Design Antennas Clutter CLEAN Tracking WUT PaRaDe Conclusions