Robust Transceiver Design and Waveform Synthesis for Wideband MIMO Radar

Licentiatavhandling, 2012

This thesis deals with the problem of designing and synthesizing waveforms that are optimal, both in a signal-to-noise-and-interference ratio (SNIR), and in a system hardware design perspective, i.e., to synthesize time domain waveforms with a low peak-to-average power ratio (PAPR), or even constant modulus. In the first part of the thesis, we investigate the possibility to suppress interference for wideband multiple-input multiple-output radar, by exploiting the spectral properties of the transmit signals. The idea is to use tunable filters at the transmitter and receiver sides, and to derive the optimal power spectral density that enhances the system performance in terms of the SNIR, for a given scenario. Herein, the focus is to suppress active jamming interference, and especially deceptive jamming. The proposed method is extended to invoke imperfections in the given scenario. Two robust optimization methods are evaluated: one that utilizes a Taylor series expansion of the SNIR, and one that exploits a worst-case SNIR maximization. In the second part of the thesis, we utilize the results obtained in the first part to synthesize time domain signals that achieve certain hardware restrictions. By using the technique of partial transmit sequence, we synthesize signals that achieve optimal spectral properties and that experience a low PAPR. Finally, we show that if we allow the power spectrum to deviate somewhat from its desired shape, a further reduction of the PAPR, or even a constant modulus signal is possible. The proposed method can be used to design a time domain signal with any predefined power spectrum, if there is no design restriction except for the PAPR on the time domain signal waveform.