Study On Key Technologies For Digital Receiver For Constant Envelope Signals

In the current, the problem of shortage of bandwidth and increasingly complexcommunication environment has become more and more prominent; this paper mainlyhas a research on carrier synchronization and digital AGC, which are the keytechnologies of constant envelope digital receiver. First, two types of existing constantenvelope modulation techniques and principal modulation forms of them are introduced;Secondly, several classic data-aided frequency estimation algorithms based on MPSKsignals are simulated by MATLAB, and a comparison and analysis of their estimationaccuracy and the range of frequency offset is conducted. The result shows that theirestimation range of frequency offset is not big enough and they have a difficulty insynchronization at low signal-to-noise ratio. Based on this, a research and MATLABsimulation on FFT offset frequency offset estimation algorithm and a differential-basedfrequency offset estimation algorithm, which have a large range of estimated frequencyoffset, is conducted in this paper. Then, for the shortage of the above algorithms, threehigh-precision estimation algorithms for large frequency offset at low signal-to-noiseratio are proposed and simulated by MATLAB. The results show that the performanceof the estimation algorithms is good for a large frequency offset at low SNR. Finally, thedigital AGC technology and two digital AGC algorithms are discussed in this paper.MATLAB simulation of the two algorithms proves they are correct. On the basis of theabove, the digital AGC algorithm based on Newton iteration algorithm are implementedin DSP at last.