Implementation of Radar Algorithms on an Acoustic Array Sarah Middleton Supervised by: Anton van Wyk, Jacques Cilliers, PascaleJardin and Florence Nadal 3 December 2010
Overview • Introduction to Phased Array Radar versus MIMO Radar. • Project Objectives. • The Acoustic Array Hardware System. • Testing Procedures. • Beampattern Measurements. • Target Parameter Estimation Results. • Conclusion.
Phased Array and MIMO • Phased array • The ith element transmits a base signal multiplied by a complex weight wi. • The signals sum constructively and destructively to form a high powered beam in a desired direction. • MIMO • Each element transmits a signal which is orthogonal to all of the other signals. • This allows an omnidirectional pattern to be transmitted, and increases the degrees of freedom. 0 1 Δτ1 2 Δτ2 wavefront ΔτL-2 L-2 ΔτL-1 L-1
Transmitter Beamforming on REception • If a set of orthogonal signals is transmitted, a matched filter bank can be used to extract the signals from the received signal. • Transmitter beamforming can then be applied to the signals, after they have been received. • This also has the effect of increasing the effective array aperture. • Also, the radar field of view can be scanned for targets after the transmission of a single burst.
Project objectives • Approach
The Hardware System PC C application receives Ethernet packets from MCU. Matlab applications perform signal processing. Master Control Unit (MCU) Implemented on an FPGA. Transmitter Array Receiver Array
Transmitter Array • 16 small speakers make up the transmitter array. • The transmitter analogue board consists of: • A digital to analogue converter. • A low-pass reconstruction filter. • A Class AB audio amplifier.
Receiver Array • 16 small microphones are configured as a ULA. • The receiver analogue electronics consists of: • An amplifier board. • An second amplifier stage. • A low-pass anti-aliasing filter. • An analogue to digital converter.
Master Control Unit (MCU) Xilinx Virtex 5 on an ML505 development board. Start Transmit 400 samples on 16 channels. Receive 800 samples on 16 channels. Send received signal over Ethernet. Finish
PC • The PC is responsible for • Designing the set of 16 signals which combine to give a desired pattern. • Receiving Ethernet packets from the MCU. • Converting the data in the Ethernet Packet into the voltages that it represents. • Calibrate the received signal. • Band-pass filtering, demodulating and low-pass filtering the signals. • Applying parameter estimation algorithms to determine the target locations.
Testing • Testing was performed in an anechoic chamber. • The sampling frequency was 40 kHz. • The chirp bandwidth or MIMO signal symbol frequency was 4 kHz. • The carrier frequency was 10 kHz. • Transmitted signal duration was 10 ms.
Patterns with One Main Lobe • The phased array and • MIMO patterns are very • similar, but the power of • the phased array pattern is • approximately 7 dB higher.
Patterns with Three Main Lobes • The side lobe levels of the measured signals are higher than the simulated signals.
Omnidirectional Pattern • Between -60° and 60°, the measured pattern has about 3.5 dB variation making it significantly more omnidirectional than the other patterns.
Parameter Estimation With One Target Phased Array MIMO
Parameter Estimationwith three targets Phased Array MIMO
Conclusion • An acoustic array hardware system has been successfully built and tested. • Beampatterns which transmit power omnidirectionally, in one direction and in three directions have been generated. • Target parameter estimation shows: • A corner reflector target can be detected. • MIMO techniques can provide higher angular resolution estimates.