OFDM Based Orthogonal Radar Signal Design And Its Application In MIMO Radar Systems

Benefit from the progress of MIMO technology in communication system, the combination of it with radar leads to the birth of new concept of MIMO radar. Such radar can dramatically improve the performance of the system in that it can provide a higher resolution for locating a target, increase the degree of freedom and offer a stronger ability to resist the RCS fluctuation of target compared with conventional SISO radar. And the property of waveform for MIMO radar has a keen impact on the performance. For the collocated MIMO radar, mutually orthogonal waveforms are needed to avoid inter-interference and received signals can be separated from each other at the receiver. Thus, it has been a hot-spot to design the orthogonal signals to support simultaneous transmission from multiple antennas in the field of radar.In this dissertation, I design a set of mutually orthogonal signals for collocated MIMO radar based on the OFDM signal. Firstly, the mathematical model derivation is done for the Uniform Linear Array MIMO (ULA-MIMO) radar and expressed in the form of vector and matrix for convenience. Then the properties of ambiguity function is derived and presented. At the beginning of chapter 3, this dissertation investigates the ambiguity function of OFDM radar, the zero-delay cut and the zero-doppler cut. It shows that there is no range-doppler coupling in OFDM radar. Inspired by the characteristic of power spectrum, a set of mutually orthogonal signals are generated by interleaving the original OFDM signal with uniform frequency interval. Then the ambiguity function of I-OFDM signals in MIMO radar application is presented based on the statistical derivation, due to the stochastic feature of signals. Then the orthogonality feature is verified by theoretical analysis and the range profile, zero-delay cut and processing gain are also investigated. Finally, the Monte Carlo simulations are done on the platform of Matlab to validate the theoretical results presented before.In chapter 4 of the dissertation, a signal processing scheme is proposed to implement at the receiver part. In this scheme, the received signal is firstly transformed into frequency domain to do the Doppler compensation to keep orthogonal. Then the signals are separated by pulsed compression to obtain the range of target. In the last part of dissertation, a feasibility study is performed about the application of OFDM radar system on PSoC 5LP, which is a programmable system on chip. Here, attention is focused on the introduction of function and parameters setting to lay the foundation of implementation.