Good code sets based on Piecewise Linear FM
Qazi, Farhan Aslam
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In this dissertation, classes of good analog and polyphase code sets, based on Piecewise Linear FM (PLFM) are introduced. The analog code sets, designed using pieces of Linear FM waveforms, have good autocorrelation and cross-correlation properties, i.e. they have small autocorrelation sidelobe peaks and cross-correlation peaks. They also possess the ability to both tolerate and detect Doppler shift. By concatenating sections of P3/P4 polyphase codes, new polyphase code sets are constructed, which can be considered as polyphase counterparts of the analog PLFM based code sets. Like the analog code sets, the polyphase PLFM code sets have good correlation properties and stand out in being the only class of polyphase code sets that can both tolerate and detect Doppler shift. The receiver is modeled as a matched filter, decomposed into two parallel parts, in order to extract information on the radial direction of a target in addition to its radial speed. At the cost of a slight degradation in the correlation properties and a small SNR loss, the Doppler properties of the proposed analog and digital code sets can be improved further by extending the matched filter parts in either direction.