Projects:2018s2-226 Software Library for Inverse Synthetic Aperture Radar

Abstract here

Introduction

Radar monitoring system is now widely used in signal processing and data analysis. With the development of military and civilian fields, detecting targets of a radar are no longer confined to be static, such as flights or ships. Under this situation, a new technique – ISAR – was engendered that uses a static antenna to detect moving targets, whose software library will be developed in this project.

Project team

Project students

• Alfred Lu
• Ting Jiang
• Nan Yang

Supervisors

• Dr Brian Ng
• Dr Hong Gunn Chew

Objectives

The purpose of Project 226: Software Library for Inverse Synthetic Aperture Radar is to write a signal processing software library to form images and implement a variety of algorithms, including converting analogue information into digital data, time and frequency domain analysis, and radar image generation. In addition, all evaluations will be performed in Matlab using both simulated and real data [1].

Background

Radar

Radar is an electrical system which transmits EM waves toward a region of interest and receives the reflected signal from the targets for detecting and ranging it. The major components in a radar include transmitter which generates EM waves, transmit antenna which transmit the signal into propagation medium, receive antenna which receive the EM waves reflected from the target, a detector which can demodulate the carrier signal and finally a signal processor which can sort and analyse the received signal.

SAR

Developed in 1950s, synthetic Aperture Radar (SAR), based on the principle of synthetic aperture, realises high-resolution microwave imaging. It has the characteristics of all-weather, high-resolution and wide-range etc. It was firstly mainly used in airborne and spaceborne platform. With the development of technology, missile-borne, ground-based SAR, UAV SAR, near-space platform SAR and hand-held SAR etc. have appeared. SAR equipped with various forms of platforms is widely used in military and civilian fields.

SAR transmits electromagnetic waves in turn. Radar antenna collects, digitalises and stores reflected echoes for later processing. As sending and receiving occur at different times, they are mapped to different locations. A good combination of received signals has constructed a virtual aperture which is much longer than the physical antenna length. This is why it is called “synthetic aperture”, giving it the attribute of imaging radar. The target direction is parallel to the flight path and perpendicular to the azimuth direction, also known as the orbit direction because it is in line with the position of the object in the antenna’s field of view.

ISAR

Inverse synthetic aperture radar (ISAR) is a radar technique using radar imaging to generate two-dimensional high resolution image pf a target, which is an important branch in the development of SAR. ISAR is capable of imaging long-range targets with high resolution, so it has great potential for long- range targets. To achieve ISAR imaging, motion compensation must be carried out [2].

The basic principles of SAR and ISAR imaging are the same, which is to obtain high range resolution by transmitting broadband signal and high azimuth resolution by large observation angles. However, different from SAR which is installed on a moving platform to detect static targets, ISAR is a ground-based system to form images for moving objects. Due to the non-cooperation of targets, the development of ISAR was relatively slower than SAR. In 1980, C. C. Chen and Andrew in the United States published the first real ISAR image for an aircraft and researched about signal pre-processing, distance bending and motion compensation. After that, more and more publicly reported ISAR images appeared including Boeing 727, DC-9 and even Venus. In recent years, V. C. Chen and Jian Li had introduced micro-Doppler analysis into ISAR imaging to analyse target moving components. With the in-depth and extensive research of ISAR technology, ISAR has been able to obtain the detailed images of most moving targets (such as aircraft, ships, missiles, satellites and other targets), and has become an extremely important means of target recognition in strategic defence systems [3].

References

[1] “Project Proposals”, the University of Adelaide, Adelaide, 2018. Available at: https://myuni.adelaide.edu.au/courses/35933/files/3348540/download?wrap=

[2] “Inverse synthetic-aperture radar”, Wikipedia. Available at: https://en.wikipedia.org/wiki/Inverse_synthetic-aperture_radar.

[3] L. Zhang, “Study of high resolution ISAR Imaging for mono- and bistatic radar”, Xidian University, p. 1, Sep. 2011.