Research On The Orthogonal Frequency Division Signal Waveform And The Range Sidelobe Suppression Techniques For MIMO Radar

As a new active radar detection radar system, MIMO radar is becoming a hotresearch issue in recent years. It has been developed into two regimes since its emerging,one is statistical MIMO radar, and the other is coherent MIMO radar. The former canimprove the detection performance of fluctuating targets through the spatial diversity,while the latter which is based on the traditional phased array, utilizes waveformdiversity by transmitting orthogonal waveforms to form a low gain wide beam in thespatial domain, achieving higher spatial resolution, and better parameter discriminationcapacity, etc. The orthogonal waveforms for MIMO radar mainly include frequencydivision waveform and code division waveform. Since the orthogonal frequencydivision linear frequency modulation signal is easy to generate and implement inengineering, it is commonly used in MIMO radar. However, this kind of signal possesesa high-level range sidelobe, thus, it cannot be effectively restrained by traditionalwindowing techniques. This dissertation is mainly about orthogonal frequency divisionwaveform design and related sidelobe suppression techniques for MIMO radar. Specificcontents are as follows:1. The signal model of the orthogonal frequency division MIMO radar with sparsearray and the deduction of the ambiguity function of orthogonal frequency divisionsignal as well as the method to build or remove the range-angle coupling are provided.2. The classification and the cause of high range sidelobe of ULA-MIMO radarwhen the emitting signal is SFDLFM signal are provided. Moreover, a method ispresented for suppressing the range sidelobe, which is realized by designing an iterationweighted pulse compression sidelobe suppression filter. The simulation results showthat this method can effectively reduce the sidelobe of the SFDLFM signal andorthogonal-phase codes signal with a good performance.3. According to the spectrum properties of the SFDLFM, a spectra modificationtechnique is presented in this dissertation, which has a good performance on sidelobesuppression. Moreover this technique can effectively reduce the complexity of thesystem and the computation load. 4. Several other orthogonal frequency division signals’ design methods are putforward and analyzed, including LFM signal with highly superposed frequencyspectrum, frequency division NLFM signal, and orthogonal polyphase codes-LFMproduct type hybrid-signal. It is shown by theoretical analysis and simulation that thefrequency LFM signal with highly superposed spectrum has a high mainlobe to peaksidelobe ratio (MPSR), but with a broaden mainlobe. And the frequency division NLFMsignal’s sidelobe can reach below-40dB except the high sidelobe in near region.Compared to the frequency division chirp signal with the same parameters, the Dopplertolerance becomes poor. However, compared with the orthogonal polyphase codessignal and the OFDM-LFM signal respectively, the codes-FM hybrid signal has betterrange resolution and the higher MPSR.