Digital processing of today’s radar signals

High Resolution Surveillance Radar Patrick Beasley, Tom Leonard, Tim Lamont-Smith A presentation to: BMEA 20 th October 2010 QinetiQ Proprietary

Content
1 Introduction
2 PILOT radar
3 Tarsier® radar
4 Cheddar reservoir
5 Recent advances
6 Future radar
7 Conclusions

1 Introduction
The use of high range resolution radar for harbour and coastal surveillance
Background to the World’s first production marine navigation radar – PILOT
Tarsier®, an example of a state-of–the-art high resolution radar
Trials results from Cheddar reservoir
Current technology
Future harbour and coastal radar
Conclusions

The World’s first FMCW production marine navigation radar (1987)
Developed by Philips Research Laboratories and Hollandse Signaal Apparaten
Designed to have equivalent performance to ZW06 pulsed radar
Detection performance
1m 2 Swerling 1 target at 7.2km (P d = 50%, P fa = 10 -6 )
Instrumented to 36km, minimum range 9m
Range resolution 4.5m to 36m
Dual antenna to minimise transmit – receive leakage
Later versions used reflected power canceller for single antenna operation
Frequency linearity derived from YIG oscillator limited effective range resolution
2 PILOT

2 PILOT – technology demonstrator

2 PILOT
Advantages
Solid state transmitter
Reliability
Low voltage supplies
Very good range resolution
Low probability of intercept
Waveform mismatched to ESM
Disadvantages
Frequency linearity challenging to achieve
Phase noise requirement
Inconvenience of separate Tx and Rx antennas
Can’t cancel reflected noise from very large targets
Range-Doppler coupling

2 PILOT PPI recorded in the strait between Sweden’s mainland and the island of Oland with a bridge approx 50m high at 15nm. Range rings every 4nm Note phase noise flash from large target

2 PILOT
Scout Mark 2 Squire Page
courtesy Thales Marine navigation Battlefield surveillance Air surveillance

3 Tarsier®

3 Tarsier® - parameters
Centre frequency 94.5GHz
Transmit power 100mW
Frequency sweep 600MHz
Antenna gain 47dB
Azimuth beamwidth 0.2 °
Elevation beamwidth 2°
Polarisation Circular
Noise figure 8dB
Detects a 2” bolt at 1 mile.

3 Tarsier® - The effect of phase noise from large targets

3 Tarsier® - Providence RI

3 Tarsier® - Providence zoomed in

3 Tarsier® - rain at Malvern, 90s intervals

3 Tarsier® Floodlights Houses Trees Phase noise flash Ground clutter

4 Cheddar Reservoir
High resolution clutter map of intensity, collected staring into wind
Dark pixels show high intensity (dB scale)
Lines remain visible over ~100 s

4 Cheddar Reservoir

4 Cheddar Reservoir
Zoomed in image
Waves are modulated (faint lines)
Individual waves travel at phase velocity, modulation envelope propagates at half that velocity
Higher RCS of waves at peak of modulation envelope

4 Cheddar Reservoir – Raytheon display

4 Cheddar Reservoir - Geese

5 Recent Advances – Harbour / Coastal surveillance requirement
Traditionally, a safety aid
Recent requirement for anti-terrorism
Jet skis, swimmers, divers, RHIBs
Small targets vs. sea clutter
Choice of RF frequency
Cost
Size
Weather
Transmit power and noise figure
Licensing and available bandwidth
Coastal surveillance very challenging for a CW based radar
High CW transmit power
Ultra low phase noise
High Tx/Rx antenna isolation

5 Recent Advances
Non-coherent
Fast scan rate (60rpm)
Good update for tracking algorithms
Minimises clutter cell (sea, land, rain)
Excellent range resolution, 10cm
Two target discrimination based on range resolution
Excellent geolocation, especially if used in multistatic mode
Coherent
Low scan rate (12rpm)
Slow update but additional Doppler information for tracker
Rejects clutter based on Doppler
Sub-clutter visibility
Very good range resolution, 1m
Target discrimination based on range resolution and Doppler
Very good geolocation, especially if used in multistatic mode
Optimal solution is to adapt the mode to the environment

5 Recent Advances – coherent operation
Provides phase and Doppler information
Traditionally exploited for military applications
Now low cost, high stability oscillators and DDS make coherent operation viable
Advantages of coherent integration
Integration of thermal noise improves sensitivity
Target discrimination based on range resolution and Doppler
Provision of target Doppler
Improves tracking
Aid to target classification
Rejection of sea and land clutter
Sub-clutter visibility
Rejection of rain backscatter – important at higher RF frequencies

6 Future radar Parameter PILOT (military only) 24GHz harbour radar (military or civil) Range resolution 4.5m to 36m (range scale dependent) 1.5m (all range settings) Clutter rejection Poor (non-coherent) Very good (coherent and non-coherent) Phase noise -110dBc/Hz at 166kHz -135dBc/Hz at 166kHz (COTS) -160dBc/Hz (custom) Instrumented range 36km 24km Antenna size 1.8m 0.7m Interference Susceptible in highly populated band – uses frequency diversity Sparsely populated band

6 Conclusions
High range resolution radar is achievable and affordable.
Excellent detection of small targets.
Coherent processing has many benefits.
Advantages in moving to a higher RF frequency.

Digital processing of today’s radar signals

by British Marine Electronic Association on Dec 15, 2010

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