a lightweight, ultra-wideband polarimetric w-band radar with high resolution for environmental...
TRANSCRIPT
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 ?