Study On Non-recursive Continuous Phase Modulation And Its FPGA Implementation

Continuous phase modulation(CPM)signal has the characteristics of constant envelope and phase continuity,and thus has higher power and spectrum efficiency than traditional modulation schemes(such as the phase shift keying and quadrature amplitude modulation).CPM has been widely used in the high-speed mobile communications,remote sensing and other power and bandwidth limited wireless communication.In addition,CPM has recursive and non-recursive decomposition models.Among them,the non-recursive CPM is superior to the recursive CPM in correcting errors.Therefore,this paper mainly studies non-recursive CPM technology and its FPGA implementation.Firstly,this paper introduces the basic principle of CPM,and studies the decomposition model and the demodulation algorithm of CPM.The conversion matrix of recursive CPM to non-recursive CPM is then deduced.The error performance of the recursive CPM and non-recursive CPM are simulated by coherent and non-coherent demodulation algorithm,respectively.Secondly,based on the design of the data frame format,the frequency offset estimation and channel equalization technique of the LDPC-coded non-recursive CPM(LDPC-NRCPM)system are studied in the imperfect channel.Compared with the recursive CPM modulation,the error performance of non-recursive CPM modulation in the cascaded system is studied by the coherent and non-coherent demodulation algorithm.By these two demodulation algorithms,the non-recursive CPM has a performance gain of nearly 3 d B over the recursive CPM.Moreover,the influence of the frequency offset on the cascaded system is studied.Compared with the non-recursive cascaded CPM system with non-coherent demodulation algorithm,the cascaded system with coherent demodulation algorithm is more sensitive to frequency offset.Furthermore,a frequency offset estimation algorithm based on ML criterion is proposed.The frequency is compensated in the case of non-coherent demodulation algorithm with large frequency offset.Also,the influence of multipath fading and its equalization technique(MMSE)in terms of the bit error performance of the cascaded system is studied.The multi-path fading has a great influence on the error performance of the cascaded system,and the error performance of the cascaded system using MMSE equalization algorithm has been improved.Finally,the design and implementation of the non-recursive CPM modulator and demodulator are studied,respectively.And the structure of each main module is introduced in detail.The designed modulator takes the advantages of properties of NRCPM,thus it requires a simple realization with less hardware resource consumption.Similarly,based on the designed frame format,the designed demodulator requires small demodulation delay and less hardware resource consumption.