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 2 © 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 radar ISAR imaging for cooperative targets Low cost transponder tracking with sparse array radar

Slide radar system design course

Slide 4 © Properties of Chaff

Slide 5 © 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

Slide 6 © Radiation Pattern of T x Antenna

Slide 7 Filled Array 64 element Sparse Array 4 element A sparse antenna array 6λ6λ 1λ1λ

Slide 8 Detections in Range-Doppler map

Slide 9 Combined Radiation Patterns, Two Antennas

Slide 10 Three Antenna pattern ‘Difference’ ‘Sum’

Slide 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

Slide 14 © Taken at midnight after storm

Slide 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

Slide 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

Slide 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 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

Slide 20 © Example 2D Dipole Array: Elements Y-directed Length = 0.4 λ Frequency = GHz a = b = 0.6 λ

Slide 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 All-Weather Passive Millimetre-Wave Imaging Petrie Meyer 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 Project Development Antenna System 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)

Slide 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 AreaReconstructionImage 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

Slide 28 © Last word…. ‘Thank you’ LEDGER for the opportunity to focus student work on radar applications