Implementationof CPM Modem In Frequency Hopping And Research On OFDM-CPM Technique

Continuous Phase Modulation is a kind of modulation signal with constant amplitude and continuous phase. In addition to its spectral characteristics, CPM possesses two other appealing characteristics. Firstly, CPM maintains a constant amplitude signal, which is appropriate for non-linear channels, as it will experience fewer adverse effects than a non-constant envelope signal. Hence, a non-linear high power amplifier in the signal path is acceptable. Secondly, the continuous phase in a CPM signal cause a little out-of-band emissions that affects very little to adjacent frequency bands. This paper describes a frequency hopping implementation of a CPM system. A novel orthogonal frequency-division multiplexing (OFDM) transmission systems based on CPM is studied in this paper. Firstly, we introduced the hardware and software development environment. Secondly, we introduced the FH-CPM implementation based on DDS in details and presented the steps. At last, an investigation of OFDM-CPM over non-linear system is presented. The peak-to-average power ratio (PAPR) performance of these signals is also presented, and an algorithm to reduce PAPR is proposed that is based on soft-envelope limitation (SEL). It is shown through numerical simulations that the proposed algorithm reduces the PAPR with fewer out-of-band emissions.