Voon Chet Koo

AN INTRODUCTION TO SYNTHETIC APERTURE RADAR (SAR)

This paper outlines basic principle of Synthetic Aperture Radar (SAR). Matched filter approaches for processing the received data and pulse compression technique are presented. Besides the SAR radar equation, the linear frequency modulation (LFM) waveform and matched filter response are also discussed. Finally the system design consideration of various parameters and aspects are also highlighted.

A new unmanned aerial vehicle synthetic aperture radar for environmental monitoring

A new Unmanned Aerial Vehicle (UAV) Synthetic Aperture Radar (SAR) has been developed at Multimedia University, in collaboration with Agency of Remote Sensing Malaysia. The SAR operates at C-band, single V V -polarization, with 5m £ 5m spatial resolution. Its unique features include compact in size, light weight, low power and capable of performing real-time imaging. A series of fleld measurements and ∞ight tests has been conducted and good quality SAR images have been obtained. The system will be used for monitoring and management of earth resources such as paddy flelds, oil palm plantation and soil surface. This paper reports the system design and development, as well as some preliminary results of the UAVSAR.

Multimedia Learning Systems: A Future Interactive Educational Tool

Abstract The authors outline in this paper the enhancement of a learning technique by the deployment of a novel multimedia learning system (MMLS). An overview of MMLS starting from the content development flow to the implementation stage is discussed in detail. This project is currently being launched at the Multimedia University (MMU) Malaysia. Macromedia Dreamweaver and Macromedia Flash were used to develop the interactive environment within the two campuses in MMU. In addition, a borderless education scenario is proposed by accessing the MMLS web site at http://mmls.mmu.edu.my/ , through a T1 connection and Internet browser at the office as well as through slower connection speeds such as the common 28.8 kbps dial-up connection from off-campus sites.

FPGA-BASED CHIRP GENERATOR FOR HIGH RESOLUTION UAV SAR

This paper discusses the design and development of a FPGA-based chirp generator for high resolution Unmanned Aerial Vehicle (UAV) Synthetic Aperture Radar. The desired bandwidth of the chirp signal is 100MHz (combination of I and Q channels) with a chirp rate of 5MHz/s. Two algorithms based on the Memory-based architecture and the Direct Digital Synthesizer (DDS) architecture are presented. The measurement results indicate that the DDS chirp generator is a preferred choice for high-resolution SAR application.

SIDELOBES REDUCTION USING SIMPLE TWO AND TRI-STAGES NON LINEAR FREQUENCY MODULATION (NLFM)

The Linear Frequency Modulation (LFM) waveform is the most commonly and extensively used signal in practical radar system. However a compressed LFM signal at the receiver will produce the flrst sidelobe at a level of i13dB to the peak of the main lobe. A weighting function is needed to apply in order to reduce the sidelobes. However, the penalty of mismatch loss is clearly evident. It may reduce output SNR, typically by 1 to 2dB. Every single dB of additional SNR can have great efiects in reducing false alarm rates in target detection applications. In an efiort to achieve low autocorrelation sidelobe level without applying weighting function, Non-Linear Frequency Modulation (NLFM) signal has been investigated. This paper describes the sidelobe reduction techniques using simple two-stage FM waveform, modifled two-stage FM waveform and tri-stage FM waveform. Simulation results of the proposed NLFM signal are presented. Sidelobe reduction of more than i19dB can be achieved by this design without any weighting technique applied.

A SAR Autofocus Algorithm Based on Particle Swarm Optimization

In synthetic aperture radar (SAR) processing, autofocus techniques are commonly used to improve SAR image quality by removing its residual phase errors after conventional motion compensation. This paper highlights a SAR autofocus algorithm based on particle swarm optimization (PSO). PSO is a population-based stochastic optimization technique based on the movement of swarms and inspired by social behavior of bird flocking or fish schooling. PSO has been successfully applied in many different application areas due to its robustness and simplicity (1-3). This paper presents a novel approach to solve the low-frequency high-order polynomial and high- frequency sinusoidal phase errors. The power-to-spreading noise ratio (PSR) and image entropy (IE) are used as the focal quality indicator to search for optimum solution. The algorithm is tested on both simulated two-dimensional point target and real SAR raw data from RADARSAT-1. The results show significant improvement in SAR image focus quality after the distorted SAR signal was compensated by the proposed algorithm.

A Comparison of Autofocus Algorithms for SAR Imagery

A challenge in SAR system development involves compensation for nonlinear motion errors of the sensor platform. The uncompensated along-track motions can cause a severe loss of geometry accuracy and degrade SAR image quality. Autofocus techniques improve image focus by removing a large part of phase errors present after conventional motion compensation. It refers to the computer-automated error estimation and subsequent removal of the phase errors. Many autofocus algorithms have been proposed over the years, ranging from quantitative measurement of residual errors to qualitative visual comparison. However, due to the fact that different data sets and motion errors were employed, it is difficult to perform comparative studies on various algorithms. This paper compares and discusses some practical autofocus algorithms by using a common data set. Standard focal quality metrics are defined to measure how well an image is focused. Their implementation schemes and performance are evaluated in the presence of various phase errors, which include polynomial-like, high frequency sinusoidal, and random phase noise.

Performance evaluation of fuzzy-based decision system for pool

An important step in any machine intelligence is to automatically and reliably decide on a solution/outcome based on the inputs given. The mapping of the inputs to an output decision often follows a set of critical rules that mimic the decision that would often be decided by a human being. In this paper, the performance of a fuzzy-based decision system for playing a game of pool is presented by comparing the results involving direct hit with two known systems. The performance is also compared to the decision that would be made by the human players. The design steps for the fuzzy-based decision system are presented using the fuzzy logic approach by employing a three-input one-output fuzzy inference system based on a set of 24 rules. The results have shown that fuzzy logic is able to accurately decide on the best move, which is as good as the human players themselves.

Autofocus Algorithms Performance Evaluations Using an Integrated SAR Product Simulator and Processor

The design and development of synthetic aperture radar (SAR) system for a particular application often requires redesign of software and hardware to optimize the system performance. In addition, evaluations of the performance of existing autofocus and image formation algorithms are required for the SAR system designers to select a most suitable algorithm for a given image quality requirements. This is a time-consuming taskwithout a reconfigurable and comprehensive software package. Thus, a comprehensive SAR integrated simulator and processor software is needed to aid the system designers in optimizing all the system parameters and performance. This paper presents an integrated SAR simulator and processor (iSARSIMP) software package and the performance of three selected SAR autofocus algorithms has been evaluated as examples to demonstrate the usefulness of the iSARSIMP for SAR system designers. In the performance evaluation, simulated and actual SAR raw data were used for further analysis and comparison of the three selected autofocus algorithms.

Multitemporal C-Band Radar Measurement on Rice Fields

This paper investigates the relationship between C-Band backscatter measurement on the physical structure of rice flelds and its growth stages. The study is based on a ground- based scatterometer experiment conducted on rice flelds at Sungai Burung site in Malaysia for the year 2005 growing season. Seven C-band scatterometer acquisitions at full polarization, namely Horizontal-Horizontal, Horizontal Vertical, Vertical-Horizontal, Vertical-Vertical polar- ization with incidence angle from 0 - to 60 - , were measured. At the same time, ground truth data for an entire rice growing season were obtained at 12-day intervals from September to December 2005. The dates were chosen so as to coincide with RADARSAT-1 image acquisitions. The paper describes the experiment and investigates the radar sensitivity to the physical structures of rice at difierent polarization and incident angles for difierent rice growth stages. Based on the result, a close agreement of backscattering coe-cient between the scatterometer and RADARSAT-1 was obtained. DOI: 10.2529/PIERS060904212430