Research On Key Technology For CPM Transmitter And Receiver

With the increasing demand of the rate and quality of communication and the way and content of communication enriching, the signal spectrum is more and more intensive, the wireless spectrum resource is scarcer and scarcer and the power consumption of the terminal is higher and higher. Continuous Phase Modulation (CPM) is insensitive to non-linear distortion with constant envelope and high power efficiency and spectrum utilization, thus it has been already widely used in the special wireless communication field, such as the radio communication, the deep space communication, the high band communication and so on. Nowadays it has aroused extensively attention as a feasible way for60GHz Millimeter-wave wireless communication. With the increase of communication system bandwidth, the frequency and the complexity of the channel environment, channel distortion, frequency selective fading and the in-band group delay ripple follow, thus the traditional signal processing method for CPM is not very good to adapt to the bad channel changes, and in the design of CPM transceiver, finding out the effective methods to fight against the bad channel environment is very necessary. This paper includes:(1) The principles and models of CPM have been given out, and titled-phase CPM has also been brought in to reduce the phase state of CPM trellis. Then, the cause and actual meaning of the mobile communication channel model have been quantitatively analyzed and model. For the synchronization techniques of the CPM transmitters and receivers, we compared Maximum Likelihood (ML) based synchronization algorithm with the difference based one, including frame synchronization, frequency bias estimation, phase error and timing error estimation. After simulation under different multi-path fading channels, it can be derived that the performance of the ML based one is far better than that of the difference based one. Nevertheless, the former one has a higher complexity and has the problem of synchronization parameter error diffusion.(2) For the equalization techniques of the CPM transmitters and receivers, we firstly decompose the titled-phase CPM signal into discrete linear representation separately based on Laurent decomposition and orthogonal decomposition, and used the discrete linear representation for frequency domain equalization. We simulated and analyzed the equalization both with channel state information known and unknown, and achieved the results that the frequency domain equalization techniques have good anti-multipath fading ability and the Laurent decomposition based one worked a little better.(3) For the pre-compensation method, we show the impact of the in-band group-delay ripple typically existing in analog/RF filter in continuous-phase modulation (CPM) systems and propose a coefficients estimation based compensation method to rival against the group-delay ripple. The method employs a compensation filter to eliminate the in-band group-delay ripple, and the coefficients of the filter are determined by a recursive estimation method based on minimum mean square error (MMSE). The steps of the implementation of this method are also presented. Simulations demonstrate that an accurate filter can be achieved to efficiently compensate for the group-delay ripple, obtaining great performance improvements.