Slide 1 The radar CoE at Stellenbosch The group aims to support RADAR and EW in the country through: • Promoting Radar/EW awareness amongst students • Supporting Radar/EW research • Student bursary support • Interaction with Armscor / SA industry
Slide 1
The radar CoE at Stellenbosch
The group aims to support RADAR and EW in the country through:
• Promoting Radar/EW awareness amongst students
• Supporting Radar/EW research
• Student bursary support
• Interaction with Armscor / SA industry
© 2008 www.csir.co.zaSlide 2
2008 key activities
1. Radar system design course
2. Investigate properties of Chaff, cocktail analysis GUI tool
3. Sparse array radar project
4. Upgrade of HF radar at SANAE
5. High performance X-band radar antenna for CWFM radars
6. Designing large direct radiating aperture arrays
7. Passive microwave imaging
Ultra compact FMCW HF radarISAR imaging for cooperative targetsLow cost transponder tracking with sparse array radar
Slide 3
1. 2008 radar system design course
© 2008 www.csir.co.zaSlide 4
2. Properties of Chaff
© 2008 www.csir.co.zaSlide 5
3. Sparse array radar project
1. Simple hardware makes staring (“To look directly and fixedly”)
radars attractive in a wide range of applications
2. Working partnership with RRS
3. Principle of operation:
1. Sparse arrays have many sharp beams – angle
resolution
2. Resolution of target in a particular beam – ambiguity
3. Resolve ambiguity using multi-antenna
amplitude/phase data
© 2008 www.csir.co.zaSlide 6
Radiation Pattern of Tx Antenna
Slide 7
Filled Array64 element
Sparse Array4 element
A sparse antenna array
6λ
1λ
Slide 8
Detections in Range-Doppler map
Slide 9
Combined Radiation Patterns, Two Antennas
Slide 10
Three Antenna pattern
‘Difference’‘Sum’
Slide 11
4. Upgrade of HF radar at SANAE
Slide 12
Specifications of radar at SANAE
• Measures ionospheric plasma convection over polar regions
• OTH RADAR operating between 8 – 20MHz
• Range 3300km, resolution 15km and 45km
• Azimuth resolution between 3 and 6 degrees
• 16 beam field of view, 2 minutes for full scan
• Higher azimuth and range resolution
• Investigation of fast changing phenomenon i.e. higher time resolution
• Improve SNR
• Reconfigurable for different experiments
• Compatibility
Requirements
Slide 13
• Use independent receivers and transmitters on each antenna
• Increase azimuth resolution
• Apply array imaging techniques to data
• Increase range resolution
• Use pulse compression
• Use Nallatech FPGA module• 105MSa/s ADC and 160MSa/s DAC, PCI interface, Virtex 2 FPGA with embedded
PPC processor
• Requires low noise variable gain amplifier ~90dB
• Acquisition, interfacing and processing software
Implementation
© 2008 www.csir.co.zaSlide 14 Taken at midnight after storm
Slide 15
5. X-band radar antenna for CWFM
Along with RRS there are two focus points on this
system
• Low TX to RX coupling
• High cross polarisation purity
Coupling
loads
© 2008 www.csir.co.zaSlide 16
Low X-Polarisation
• Look at different slot
shapes in terms of:• Range of Conductance
• Bandwidth
• Cross-Polarization
• Normalize the results to
easily compare
arbitrarily shaped slots.
Slide 17
Conductance vs. Bandwidth Plots
© 2008 www.csir.co.zaSlide 18
Waveguides
• Determine the effect of the
waveguide shape on the
radiating properties of slots.
• Find a waveguide shape that
will:• Be simple to manufacture and
work with;
• Improve radiation properties of
slots.
Slide 19
6. Designing large active arrays
• Trend in high performance radar is to active arrays
• For large arrays, computer simulation Resource
hungry (CPU time and memory)
• Can be approximated as an infinite array problem• Commercial software eg CST/FEKO
• Based on Fourier analysis
• Can be used to find
• Element Coupling
• Input impedance
• Pattern properties
© 2008 www.csir.co.zaSlide 20
Example
2D Dipole Array:• Elements Y-directed
• Length = 0.4λ
• Frequency = 1.875 GHz
• a = b = 0.6λ
© 2008 www.csir.co.zaSlide 21
Calculating the Radiation Pattern
• Conventional Array Theory:
• Problem:
• Ignores effects of mutual coupling and scattering
• Rather use embedded element pattern:
• Def: “Pattern of infinite array, when only one element is excited and all
others are match terminated”
• Array Pattern of infinite array:
Slide 22
• Results
Slide 23
Radiation Pattern Results
Slide 24
7. All-Weather Passive Millimetre-Wave Imaging Petrie Meyer
110 GHzFrequency
210 510310 410 610
dB/k
mn
Att
enua
tio
310
010110
210
210110
610
m Wavelength
510 210410 310
-1-3S
rW
m
Rad
ianc
e
1510
010510
1010
1010510
• Desire to generate equivalent passive
images of a desired target area under
different weather conditions
• PMMW Advantages• Stealth
• Detects metallic and non-metallic objects
• Besides Military important commercial and
security applications
• Propagation windows at 35, 94, 140 and
220GHz
Slide 2525
Project Development
• Antenna System• 29-36 GHz Frequency-Scanned Waveguide
Antenna• Parallel Frequency Scan along longitudinal axis• Mechanical Scan/Object Movement on transverse
axis• Parabolic Reflector focuses beam on transverse
axis• Space-to-Frequency mapping inherent property of
antenna structure
• Analogue Design• Amplification of Low-Power Signal• Down-Conversion to 5-13GHz Range• Separation into Frequency Bins using Filter Bank
• Digital Design• Conversion to DC Digital Signals• Image Correction to improve image quality
(Kalman Filter)
start
end
z
slice
fLf
Hf
Lf
Hf
LNA RF40-24
Antenna RF37-29 Mixer
40-26.5
LO42
LNA IF18-2
LNA IF18-2
nmP
mP1
NmP
Filter Detector IntegratorrMultiplexe
Slide 2626
• Comparison of Day and/or Night Operation• Comparison of Visible Camera and MMW Camera
• Images taken of Simonsberg mountain at 12h00 and 21h00
Project Results
Slide 27
Project Future
• Mobility• Make System compatible for use on UAV
• Results in removal of Reflector
• Defocuses Antenna Pattern
• Increases reliance on Image Processor
Scanned Area ReconstructionImage• Image Resolution• Increase Image Resolution
• Increase in number of filters
(decrease in each filter’s
bandwidth)
• Increase in complexity of Filter
Bank
De-convolution with antenna pattern
© 2008 www.csir.co.zaSlide 28
Last word….
‘Thank you’ LEDGER for the
opportunity to focus student
work on radar applications