A lightweight, ultra-wideband polarimetric W-band radar with high resolution for environmental applications Richard Holliday, Matt Rhys-Roberts and Duncan.

A lightweight, ultra-wideband polarimetric W-band radar with high resolution for environmental applications

Richard Holliday, Matt Rhys-Robertsand Duncan A. Wynn

Q-par Angus LtdBarons Cross Laboratories

LeominsterHerefordshire HR6 8RS

UK www.q-par.com

Tel: +44(0) 1568 612138

Fax: +44(0) 1568 616373 EuRAD 2006European Radar Conference

Manchester, UK 14th September 2006

Outline

• Background• Review of suitable radar waveforms• Ultra-wideband (UWB) and random signal radar• Cross-ambiguity function analysis• Outline description

TransmitterBinary random phase codingRF spatial power combiner

AntennaProcessing

• Performance• Applications• Summary

Background

• A major threat to global stability is the change in the Earth’s climate

• Extremes of heat and drought, storms, wind, rain and more intense cold

• Unpredictable environmental behaviour- Temperature rises are likely to be non-uniform across the globe

• Uncertainty of the impact is incorporated into long-term national and international decision-making

- reflected in environmental standards and targets including :

- protection of people, homes and business from risk of flood- ensure availability of suitable water for drinking and bathing- prevention of destruction of natural habitats and extinction of animal species

- There is a very wide breadth of environmental issues …..

• Better understanding of the complex interaction between the Earth’s surface and atmosphere is essential

• Accurate descriptions of local and regional surface features and associated phenomena with timely monitoring are vital

• There are disadvantages associated with existing methods such as LIDAR and airborne/space-based SAR

• Millimetre wave radar offers an all-weather remote sensing solution with the benefits of compactness and high resolution -

Electromagnetic compatibility and tolerance to EMIwith reduced Size, Weight and Power (SWAP)are becoming more affordable

Background

Review of radar waveforms:

• Uncoded CW• Linear FMCW• Pulse compression waveforms • Phase shift / frequency shift coding • Coherent pulse trains/pulsed Doppler

• Ultra wideband (UWB) and Random Signal Radar (RSR)• Noise-like / chaotic waveforms• Sine plus noise FMCW• Noise FMCW• Compound noise FMCW• Dual-random quasi-CW• Correlation RSR / spectrum analysis RSR / anti-correlation RSR• random phase coded• Random pulse radar• Binary random phase coded

Binary random phase coded CW

Time domain sequence of binary random phase coded CWfc=94 GHz, chip rate=3 GHz

Binary random phase coded CW

Power spectrum of binary random phase coded CW (unfiltered)fc=94 GHz, chip rate=3 GHz

Cross-ambiguity function performance analysis :

• For a complex signal,

where is the complex envelope

• The cross-ambiguity function is defined as

where

• The time-reversed complex envelope for the output of a filter that is matched for a signal but receives the signal that is time-delayed with a frequency shift imposed upon it

• The time of arrival of the signal is considered to be unchanged by the frequency shift.

tfjtuts .2.exp. 00

tu0

2, Df

dttfjtutuf DD ..2.exp.., *010

Cross-ambiguity function for binary random phase modulated waveform:

94 GHz carrier with 3 GHz chip rate

Delay (ns)Doppler offset

frequency (Hz)

|(

,)|

Cross-ambiguity function performance analysis

0 Hz

-18.5 ns(-2.77 m)

+18.5 ns(2.77m)

0 ns

3.7 GHz

Cross-ambiguity function performance analysis

Doppler offset frequency spectrum and cross correlation responses

• Mean square sidelobe level (MSSL) supports range sidelobe supppression > 20 dB rms

• Range (along) resolution (unprocessed) better than 0.045 m

0

-20

-40

-60

Cross correlation

(dB)

0 2 4 6 8 10 12 14 16 18 20 Delay (ns)

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

S(f) (dB

)

0

-20

-40

-60

-80

Doppler offset frequency (Hz)

• Mean square sidelobe level (MSSL) supports Doppler sidelobe suppression > 21 dB rms

• Velocity (radial) resolution better than 0.0016 m.s-1

• Optically activated waveguide-based millimetre wave phase modulator with sub-nanosecond switching speed

Transmitter: Binary random phase modulator

Modulator RF input3 GHz

Constant amplitudeRF phase modulated output

< 0.3 ns

Binary random phase modulator

A, B and C are amplitude constants

• Performance

• Millimetre wave (W-band)• Wide tunable bandwidth 75-110 GHz• Wide instantaneous bandwidth > 4 GHz• High switching speed > 3 GHz• Linear passive RF component • Low insertion loss (< 0.5 dB)• High RF power handling (typ. > 1w mean)• Millimetre waveguide compatible

are phase constants

1sin. tAts inputinput ttCts inputoutput 3sin.

ttBts 22mod sin.

t

3,2,1

Transmitter: RF spatial power combiner

overmoded waveguidesecond harmonicgraded gap Gunn GaAs diode array

fundamental mode waveguide array

Input

90 – 98 GHz>100 mW

Output

90 – 98 GHz>500 mW

Antenna

W-band scalar feed

Modular 3-axis positioner

• Twin 0.75 m diameter reflectors with Cassegrain sub-reflectors• spun Aluminium and precision machine-finished • circularly symmetric scalar feed with WR-10 waveguide transition• plane polarisation - Tx (V, H, arbitrary polarisation planes)

- Rx (simultaneous orthogonal polarisation planes) • 75-110 GHz RF bandwidth (tunable)

• Radiation characteristics at 94 GHzInstantaneous RF bandwidth > 4 GHz Co-polar directive gain > 54 dBi 3 dB beamwidth 0.2 degreesMean-square sidelobe level (MSSL) better than –19 dBCross-polar response better than 30 dBRF isolation >50 dB Efficiency > 55 %

Processing

Pseudo-randomnoise generator

Bi-phasemodulator

StabPSU

StabPSU

StabPSU

StabPSU

Low Noise Amplifier

IReference

QReference

IV

IH

QV

QH

High conversion rate ADCAnti-aliassing

/ LPFLog amp

Referenceoscillator

Transmitterantenna

Receiverantenna

V channel

H channel

Masterclock

Magic-T

Spatial RF power combiner

X

X

X

X

X

X

X

Orthomode transducer

I/Q mixer

directional coupler

USB Port 1

USB Port 2

USB Port 3

Termination

Magic-T

Processing

6-channelanalogue

to digital converterNational Semiconductor

ADC08D

Attitude Heading ReferenceWatson Industries

AHRS

Global Positioning SystemGarmin

GPS

Modular 3-axisantenna positioner

USB

USB

USB

serial port

serial port

serial port

Sony Vaio lap-top PC

PCG-GRT896HP

Graphical User Interface

Performance : Signal to noise power ratio vs range

7ms dwell time 1s dwell time

Applications - Environmental• Surface mapping of local land and water levels

- observation and measurement of surface and near-surface water movements- measured water ripples can be resolved to infer flow rates, rates of change, flow direction and location of below-surface features

• Management of water resources- drainage and irrigation planning

Flood defence planning - Definition of flood plane areas - Monitoring 24 hour / 7 day with automatic triggering upon user-specified events to provide warning of flood escalation- Effective and timely deployment of limited and valuable defences/barriers- Planning, design and effective deployment of flood defence resources and structures such as bridge constructions, sandbags etc

Applications - Environmental • Pollution detection, localisation and monitoring

- pollution in the form of particulate debris or paints,oils causing changes of water surface characteristics

• Bathymetry- measurement of water current flow vectors (depth, water magnitude,

direction, flow rate and water surface topology) for monitoring and prediction in rivers, estuaries and inland waterways

• Agricultural crop monitoring

• Fish farming –salmon / trout fishing / deployment of fish spawn

• Monitoring of iceberg / “bergy bits” and glacier movements

• Traffic monitoring (speed, classification, traffic density, direction)

Summary

• Specifically designed for environmental applications

• An UWB polarimetric millimetre wave 94 GHz radar that uses binary random phase coding to provide a lightweight,all-weather remote measurement capability with high resolution

is under development by Q-par Angus Ltd

• Simplified radar architecture – readily extended to other applications via “plug and play”

• High performance at relatively low cost by exploiting COTS components

• Completed radar will be demonstrated operating in a proof-of-concept surface mapping mode in a representative environment later in 2006

Acknowledgements

UK DTI

Advantage West Midlands

UK Natural Environment Research Council

University of WorcesterDr John Fagg (Head of Dept. of Geography, Applied Sciences and Archaeology)

e2V Technologies LtdNigel Priestley and Martin Westmoreland

University of BirminghamProf. Peter Hall and Dr Edward Hoare

Thank you

Any questions ?