Radar Systems Unit, Division of C4ISR Swedish Defence ... och... · Passive Radar, an overview Lars Ulander, Prof.1 Radar Systems Unit, Division of C4ISR Swedish Defence Research

Passive Radar, an overview

Lars Ulander, Prof.1Radar Systems Unit, Division of C4ISRSwedish Defence Research Agency (FOI)

1Part-time at Chalmers University of Technology

Contents

• Principles and Terminology• What’s on the market?• Some research results• International cooperation• Conclusions

Bistatic vs. Monostatic radar

• Monostatic radar: Self-contained but sensitive to ECM• Bistatic radar: Receiver is silent, but relies on suitable transmitters

Different types of Passive Radar

• Passive Coherent Location (PCL)• Passive Covert Radar (PCR)• Parasitic Radar• Hitchhiking Radar

Taxonomy

RadarMonostatic Bistatic

Cooperativetransmitter

Non-cooperativetransmitter

Taxonomy

RadarMonostatic Bistatic

Cooperativetransmitter

Non-cooperativetransmitter

Passive Radar

Taxonomy

RadarMonostatic Bistatic

Cooperativetransmitter

Non-cooperativetransmitter

Radar signal

Broadcast com signal

Taxonomy

RadarMonostatic Bistatic

Cooperativetransmitter

Non-cooperativetransmitter

Radar signal

Broadcast com signal

Passive Coherent Location (PCL) orPassive Covert Radar (PCR)

Taxonomy

RadarMonostatic Bistatic

Cooperativetransmitter

Non-cooperativetransmitter

Radar signal

Broadcast com signal

Parasitic Radar or Hitchhiking Radar

WWII Parasitic Radar

German Kleine Heidelberg(parasitic radar)

British Chain Home Radar(radar transmitter of opportunity)

f = 20-30 MHz, P = 750 kW

Passive radar: How does it work?

When direct signal is not available, Doppler-onlytracking from multiple receiving stations can be used

Correlationprocessing

DVB-T signal: Range-Doppler processing

(from Christiansen, thesis, NTNU)

Passive radar: Positioning

Positioning based on multiple receiving sites or receiver antenna array

Ambiguous position

Transmitters

• FM Radio 87.5-108 MHz– High power; Wide elevation antenna beam– Disadvantage: Bandwidth depends on program content

• Digital TV 170-230 MHz, 470-694 (790) MHz– High power; Narrower elevation antenna beam– DVB-T standard (OFDM) provides a good signal since

bandwidth is independent on program content• Other possibilities

– Satellite broadcasting, communication signals

Industrial developments

Silent Sentry (1999)

Other examples: AULOS (2011), Airbus Defence and Space (2012)

ERA Silent Guard (2014)

THALES HA-100 (2007)

Typical performance: 100-300 km range

A

FOI research: Passive radar ground imaging

Imaged ground area

High-resolution passive radar imaging of ground by synthetic-aperture radar (SAR) processing

FOI research: Passive SAR trials 2012

• Airborne receiver with digital TV as transmitter• Gotland island, the Baltic Sea (Follingbo TV mast)

FOI research: Passive SAR images of ships

200 400 600 800 1000 1200 1400 1600 1800 2000

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600

800

1000

1200

1400

1600

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Size 99m x 14m

Size 190m x 32m

Ships located on eastern side of Gotland (Slite harbour) at 40 km and identified by AIS logs

FOI research: Passive SAR image of Gotland

Resolution: ca 5 m x 20 m (limited by a single DVB-T channel)

Artifacts due to TV transmitter tower at Follingbo

FOI research: International cooperation

• NATO SET-186 (closed 2014)– APRA - Airborne Passive Radar Applications– Poland is lead nation

• NATO SET-207 (on-going since 2014)– Advanced situation-specific modeling, sensing and

vulnerability mitigation using passive radar technology– Germany is lead nation

Conclusions

• Passive radar is emerging technology, withsome production and prototype systems

• The main advantage is that system is passive (silent) and does not transmit signals

• The main disadvantage is that system dependson the availability of suitable transmitters

• Passive SAR for ground surveillance is a new research area, with first successful flight trials in 2012 by FOI. New flights conducted in 2016.