Pei-Hung Evan Tsai
B.Sc.Eng (Electrical Engineering), University of Cape Town
Background
I am currently doing my M.Sc.Eng and am Affiliated with the Radar and Remote Sensing group (RRSG) at the University of Cape Town.
Undergraduate Project (2008)
My undergraduate final year project topic was Broadcast Signal Direction Finding”. I was supervised by Professor Mike Inggs and Dr. Yoann Paichard. My project report can be found here.
Postgraduate Project (2009/2010)
The Radar and Remote Sensing Group (RRSG) at the University of Cape Town is currently developing a Passive Coherent Location (PCL) demonstration system using FM & TV transmitters located around Cape Town Airport. The novelty of this system is the use of several transmitters and several receivers in a netted or MIMO configuration. Such a configuration provides several advantages over traditional monostatic and bistatic configurations, i.e.:
Better coverage by increasing the signal to noise ratio (SNR)
angular diversity gain on the target's Radar Cross Section (angular fading compensation).
Better accuracy on the Angle of Arrival using multilateration techniques.
Better robustness of the tracking algorithms.
The receivers are designed at a low-cost by using hardware platforms originally designed for digital software defined wireless applications and are fully synchronised by GPS-disciplined oscillators clocks (GPSDO).
One of the main problems of PCL systems is that the power of the directed signal is much higher than the power of the signal reflected by the target, which can cause the receiver to be saturated. This effect can be minimised by steering a null in the direction of the transmitter, using beamforming techniques at the receiving antenna.
Analogue beamsteering (coherent phase shift) and beamforming techniques (combination of phase shift and amplitude weighting) have proven to be robust and easy to implement for a fixed beam. However, when the bean has to be formed dynamically, digital beamforming techniques can be preferred for their easier implementation over a wide bandwidth or over several frequencies. In a PCL context, this is the case when a null has to be steered both at TV and FM frequencies. Another Advantage of digital methods is their lower response time, which can be exploited to dynamically switch the radar operational mode from surveillance to target tracking in a region where the signal-to-noise (SNR) ratio is low (limit of coverage) or when a proper response to multiple jammers in a rapidly changing environment is required. It is now possible to implement these digital techniques at a low cost for a limited number of antenna elements using several synchronised Analog-to-Digital (ADC) coverters and programmable devices (FPGA).
Digital beamforming techniques have been known or more than 10 years, but little work has been done in the PCL context, so the objective of my M.Sc.Eng project is to:
compare the performances and limitations of digital v.s analogue techniques (response time, resolution, dynamic range, achievable bandwidth).
Find suitable algorithms to dynamically adapt the orientation of the beam with a null steered in the transmitter directions and over several frequency band
design and implement a digital beamformer in a PCL context using the Universal Software Radio Peripheral (USRP)
The results of this work will be easily transposable for future active radars in South Africa, in a civil or military context.
Contact Details:
Radar Lab (3)
7th Floor
Menzies Building
Upper Campus
University of Cape Town
Office: +27 21 6503756
Cell: +27 82 0509039
Alternative: +27 73 7537353
Email: tsai.evan.429@gmail.com