Algorithm Research Of CPM System With Low Complexity

Continuous phase modulation(CPM) is a kind of nonlinear digital modulation scheme with continuous phase. Its constant envelop makes CPM has high spectrum efficiency and power efficiency. So it has been widely used in telemetry, satellite and mobile communications. But memory between symbols makes the system receiver complex and difficult to synchronize. All of these limit the application of CPM in practical engineering.For high complexity of CPM system’s synchronization and reception, this thesis focused on the algorithm research which can reduce the complexity of the demodulation dramatically with litter loss of error performance. And then we proposed corresponding synchronization algorithm and system architecture. The main work and innovations are as follows:(1) Demodulate the CPM signals using pulse amplitude modulation decomposition algorithm based on maximum likelihood demodulation algorithm.General maximum likelihood demodulation requires a lot of matched filters, and need to backtrack based on a large number of grid state. So the thesis combined PAM decomposition algorithm with maximum likelihood demodulation algorithm to reduce the complexity of the demodulation and proposed a sub-optimal demodulation method.The computer simulation results showed that: suboptimal demodulation can make the number of matched filters and grid state greatly reduced with litter loss of error performance.(2) Proposed data aided synchronization algorithm based on maximum likelihood synchronization algorithm.This thesis combined the PAM decomposition algorithm with maximum likelihood CPM synchronization algorithm. Because frequency discriminator curve is unstable, we used an aided sequence and applied this sequence to the symbol timing and carrier phase synchronization. Simulation results showed that the synchronization method can effectively recover parameters of CPM.(3)Double-h CPM system designThe CPM signals with two modulation index have higher spectrum efficiency andmore complex receiver structures. In response to this phenomenon, this thesis determined a particular kind of signal considering the influences of modulated parameters on power spectrum density and performance. And then we designed the CPM system combining low complexity synchronous with demodulation algorithm and gave the structure of the frame, transmitters and receivers. Finally, we took the system simulation, analyzed and discussed the system performance.This thesis reduced the maximum-likelihood receiver complexity using PAM decomposition algorithm and enhanced the CPM system can be easily realized. We proposed a practical CPM system solution and offered the theoretical preparation for hardware implementation.