Accelerated Target Detection Using Fractional Fourier Transform

Abstract

The word “RADAR” was originally an acronym, for “Radio Detection and Ranging.” Today, the technology is so common that the word has become a Standard English noun. In early days, the radar functionality was confined to detecting the target and determining the range. As the advancement of science and technology, there has been a remarkable evolution in the radar technology. Modern communication systems and signal processing has been playing a vital role for detecting the targets with a background of active clutters. Thus, traditional techniques have been playing a key role in order to achieve modern techniques in radar. The nonlinearities that arise in radar cause large interference by affecting the small desired signal and it is difficult to resolve the target from the interference. Some Time-Frequency analysis methods can be implemented in the radar, so that the parameters of the targets can be estimated with good accuracy. Linear frequency modulated (LFM) signal is widely used for radar system, acoustic communication and sonar system. In a noisy environment detection and estimation of the LFM signal are extremely important, and they gain considerable attention in recent years. Radar transmitted signal is modulated as LFM signal due to the relative motion between radar and target, and nonlinearity exists due to the acceleration of target. Nonlinearity in the signal makes the spectrum aberrant. Target detection using a conventional FFT (Fast Fourier Transform) decreases the performance due to nonlinearity. The aberrant spectrum contains the information of radial acceleration. In the field of military, radar did not provide acceleration information because in the early time aircrafts have low mobility. In these days with the help of advancement in technology, the mobility of aircrafts have increased, therefore the effect of acceleration on signal spectrum of FFT could not be neglected. This dissertation work is concerned with the study of RADAR signals processing with the ultimate goal of parameter estimation of Accelerated Radar Target. The technique is based on the Fractional Fourier Transform (FrFT), which is better suited for radar applications. The parameter estimation accuracy of system is also analysed with different values of signal to noise ratio (SNR).