Sequence and waveform set design for radar and communication systems
Abstract
Three topics involving sequence and waveform set design for radar and communication systems are considered. Fundamental properties of the ambiguity function and the uncertainty relation of Fourier transforms assert a fundamental limitation on the ability of any single radar waveform to simultaneously resolve two or more targets closely spaced in both time-delay and Doppler-shift. In the first topic, the problem of using multiple wave-form sets to make high-resolution delay-Doppler measurements is considered and the composite ambiguity function is introduced as a tool to measure the delay-Doppler resolution characteristics of a set of waveforms. The problem of designing optimal coded waveform sets under a time-bandwidth product constraint is also considered, and explicit optimal phase, frequency, and joint phase-frequency coded waveform sets having constant amplitude are presented, as well as algorithms for the construction of such sets of arbitrary size. In the second topic we propose a simple signaling technique that can significantly reduce the range ambiguity level in pulse-Doppler radar. Instead of transmitting identical pulses, we phase-modulate the pulses with an m-sequence. Because of its spectrum-spreading characteristics, when being modulated to a radar pulse train the m-sequence can spread the pulse train's range ambiguity evenly across the entire signal bandwidth. Since the performance of this signaling technique is most promising for very long pulse train, we further investigate its application to the Synthetic Aperture Radar in which thousands of pulses are usually used. In the third topic, a transmitter diversity wireless communication system over Rayleigh fading channel using Pilot Symbol Assisted Modulation (PSAM) is studied. Unlike conventional transmitter diversity system with PSAM that estimates the superimposed fading process, we are able to estimate each individual fading process corresponding to the multiple transmitters by using appropriately designed pilot symbol sequences. With such sequences being available, special coded modulation schemes can then be designed to avoid the use of interleaver.
Degree
Ph.D.
Advisors
Bell, Purdue University.
Subject Area
Electrical engineering
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