Research On Key Techniques Of Multicarrier Complementary Phased-coded Radar

Multi-carrier Complementary Phase-coded (MCPC) radar signal which is based on Or-thogonal Frequency Division Multiplexing (OFDM) technique exhibits thumbtack ambigu-ity function. It is easy to be controlled, generated and compatible with modern communica-tion systems. By combining MCPC technique and wideband polarization radar technique, a simultaneous polarization frequency agility MCPC radar system is designed, and of which key techniques are intensive researched including MCPC radar signal waveform design, power amplifier nonlinear effects compensation and wideband frequency-dependent IQ im-balance compensation. The main work and contributions of this dissertation are listed as follows.1. An improved way to generate MCPC radar signal and a Doppler resisted signal de-tection method are proposed by combining oversampling technique. The proposed approach improved MCPC radar performance by modifying modulation sequences to adjust subcarrier spacing dynamically. Theory analysis and simulation results show that the proposed MCPC radar system has higher delay resolution, Doppler tolarence and immune to Foreign Contri-bution (FC) of phase noise between carriers, and the influences of DC offset are eliminated.2. By combining frequency agility technique and MCPC radar technique which is very suitable for simultaneous scattering matrix measurement technique implementation, a si-multaneous polarization frequency agility MCPC radar system is designed. Both these tech-niques improve system immunity to active jamming greatly. A frequency aigilty frequency synthesizer is designed and manufactured, which provides technique foundation for simul-taneous polarization frequency agility MCPC radar system implementation.3. By optimizing MCPC radar signal frequency weights, low signal Peak-to-Mean En-velope Power Ratio (PMEPR) and low auto-correlation sidelobe are realized. The optimiza-tion result shows that PMEPR of MCPC radar signal pulse train can be reduced to 66.7%, while mainlobe to sidelobe ratio can increase by 5dB. The signal structure of double trans-mitting single MCPC pulse and radar echoes self-correlation method are used for power amplifier nonlinear parameters extraction and compensation. The proposed approach can separate nonlinear effects and Doppler influence. The compensation procedures are immune to Doppler and noise. And the Doppler information can be reserved.4. By subdividing frequency spectrum and extracting IQ imbalance parameters from the cross-correlaiton function of radar echoes and original transmitted signal, a time domain IQ compensation approach is proposed for frequency-dependent IQ imbalance in wideband scenarios. In the compensation procedures, MCPC signal correlation properties are used for noise elimination and uncorrelated properties between MCPC signals are used to simplify calculation which increases with frequcny spectrum subdivision. Analysis and simulation results show that the proposed approach can compensate IQ imbalance effectively in wide-band and low Signal-to-Noise Ratio (SNR) scenarios.