Implementation of Radar Algorithms on an Acoustic Array

IMPLEMENTATION OF RADAR

ALGORITHMS ON AN ACOUSTIC

ARRAYSarah Middleton

Supervised by: Anton van Wyk, Jacques Cilliers, Pascale Jardin and Florence Nadal

3 December 2010

OVERVIEW1. Introduction to Phased Array Radar

versus MIMO Radar.2. Project Objectives.3. The Acoustic Array Hardware System.4. Testing Procedures.5. Beampattern Measurements.6. Target Parameter Estimation Results.7. 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

2

L-2

L-1

wavefront

ΔτL-1

ΔτL-2

Δτ2

Δτ1

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.

INCREASED ARRAY APERTURE

PROJECT OBJECTIVES

• Design and build a transmitter array which can be used to demonstrate radar array techniques.

Transmitter Array

• Compare the patterns that can be formed with phased array and MIMO techniques.

Beampattern Design

• Compare the accuracy and resolution of phased array and MIMO target range and angle estimation techniques.

Parameter Estimation

Literature Review -> Simulation -> Hardware Design -> Testing -> Results Analysis

Approach

THE HARDWARE SYSTEM

Receiver ArrayTransmitter Array

Master Control Unit (MCU)Implemented on an FPGA.

PCC application receives Ethernet packets from MCU.

Matlab applications perform signal processing.

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)

Finish

Transmit 400 samples on 16 channels.

Receive 800 samples on 16 channels.

Send received signal over Ethernet.

Start

Xilinx Virtex 5 on an ML505 development board.

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 andMIMO patterns are verysimilar, but the power ofthe phased array pattern isapproximately 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

ALGORITHM COMPARISONPhased Array Rank MIMO RankConventional Beamformer + Capon Beamformer +

Capon Beamformer + Amplitude and phase estimation (APES)

-

Music Algorithm + Generalised Likelihood Ratio Test (GLRT)

+

Deterministic Maximum Likelihood (DML)

- Approximate Maximum Likelihood (AML)

?

Transmitter Beamforming on Reception

++

MIMO Transmitter Beampattern Design RankOmnidirectional Pattern -

Maximum Power Design --Pascales Design +Beampattern Matching Design +

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.

THANK YOU!

ANY QUESTIONS?