The Implementation of Chirp Scaling Algorithm Via Fast Fourier Transform

Abstract

It is necessary to use bulky aperture to produce high resolution images in optical systems. Since frequency in synthetic aperture radar is lower than that of optical systems then even obtaining mediocre resolution in synthetic aperture radar need a bulky antenna. For doing this, it needs antenna with hundreds meters' length [1]. An aerial radar can collect data while making advance of distance to few hundred meters and process data in such way that it seems to be obtained from a physically bulky antenna. Synthetic aperture is defined as distance through which a flying object goes to make synthetic antenna. As a synthetic aperture radar moves it sends a pulse to each target. Reflecting echoes are taken by the receiver and kept in an echo-accumulating space. Since relating to the ground the radar is moving, reflecting echoes take Doppler displacement [2]. Comparing Doppler displacement frequency to a referent frequency makes it possible that large number of reflecting echo concentrate on one point; as a result, the length of antenna capturing a particular point will be increased effectively [3]. To produce image from raw data four algorithms have been developed so far. Among these algorithms Chirp scaling with excellent power of the focusing on the target (higher resolution), optimized processing [4], and simple implementation has been cared for. In spite of the Range Migration and Range Doppler Algorithms this algorithm can be implemented without the need of inter-acquire easily, it can also be used to point and band capturing. In point capturing Range Migration Algorithm, Range Doppler Algorithm, and Chirp Scaling Algorithm are used but in point capturing Polar Algorithm, Range Doppler Algorithm, and Chirp Scaling Algorithm are used. Fourier Transform is used to both implement and phase-keeping effectively. Another advantage of using Chirp Scaling Algorithm in terms of Secondary Range Compression is to provide range for bilateral processing of adapting filter. Secondary Range Compression is an effective method for joining Range-Bearing, it increasingly can be applied to pass large radar beam, large beam width, and high Squint inclination. The structure of paper is as follow: section II present the chirp scaling algorithm. Section III demonstrate the results and conclusion is represented in section IV.