Research And Implementation Of Continuous Phase Modulation

In the ground-air communication system, such as Joint Tactical Information Distribution System (JTIDS), continuous phase modulation (CPM) is usually employed for its attractive power and spectral efficiency. CPM signals maintain continuous phase and constant amplitude which make them appropriate for non-linear channels. This thesis restricts attention to the research and implementation of CPM on software radio platform.Firstly, the common expression of CPM signals is introduced. Based on it, the power spectral density (PSD) is simulated, whose result shows that the spectral properties were influenced by all the modulation parameters. Then, several receiver constructers are outlined. The optimum maximum likelihood sequence detector (MLSD) in an additive white Gaussian noise channel consists of a filter bank followed by Viterbi decoder (VD). To reduce the high complexity of MLSD, two improvements are introduced, including a reduced stated sequence detector (RSSD) which combines decision feedback with Viterbi decoding and a reduced stated differential sequence detection (RSDSD). Specially, considering full response CPM, the maximum likelihood block estimation (MLBE) was also derived with emphasis on simplification of the receiver structures. Through numerical simulations, the performance of these demodulators is presented.Finally, the design and implementation schemes of modulator and demodulator, which conform to the software platform, are proposed. With the algorithms introduced, the modulator and demodulator of the MSK and 4CPM are completed respectively with FPGA.