slide 1 the radar coe at stellenbosch the group aims to support radar and ew in the country through:...

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

1. 2008 radar system design course


2. Properties of Chaff


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


Radiation Pattern of Tx Antenna

Filled Array64 element

Sparse Array4 element

A sparse antenna array

6λ

1λ

Detections in Range-Doppler map

Combined Radiation Patterns, Two Antennas

Three Antenna pattern

‘Difference’‘Sum’

4. Upgrade of HF radar at SANAE

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

• 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

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


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.

Conductance vs. Bandwidth Plots


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.

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


Example

2D Dipole Array:• Elements Y-directed

• Length = 0.4λ

• Frequency = 1.875 GHz

• a = b = 0.6λ


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:

• Results

Radiation Pattern Results

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

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

• 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

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


Last word….

‘Thank you’ LEDGER for the

opportunity to focus student

work on radar applications

slide 1 the radar coe at stellenbosch the group aims to support radar and ew in the country through:...

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