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Research And Implementation Of Modulation And Demodulation Technology Of Continuous Phase Signals

Posted on:2014-06-18Degree:MasterType:Thesis
Country:ChinaCandidate:D Y LiFull Text:PDF
GTID:2268330401964579Subject:Signal and Information Processing
Abstract/Summary:PDF Full Text Request
Continues phase modulation (CPM) is a large class of constant amplitudemodulation schemes with both continues phase and memory. Due to the continuity of itsbaseband signal phase, CPM signals exhibit a narrow spectral main lobe and low sidelobes,which makes CPM signals both bandwidth and power efficient; meanwhile theconstant amplitude allow nonlinear amplifiers to operate efficiently and the memoryintroduced within the modulation scheme makes CPM signals achieve better errorperformance than that of other modulation schemes.Because of the very reason of its phase continuity, the phase of CPM basebandsignals does not change obviously whit the alternating input symbols, which makes thedemodulation and synchronization process of CPM signals much more complexcompared with others modulation schemes and limite the practical use of CPM signals.With the aim of implementing the modulation and demodulation process of CPMsignals, in this thesis we reviewed the modulation and demodulation theory of CPMsignals, and then design and implement the relative process with FPGA logic.First, we reviewed the modulation theory of CPM signals, analyzed its phasecharacteristic whit phase tree, phase trellis and phase state; and then analyzed frequencyspectral of CPM baseband signals and its error probability in the sense of MaximumLikelihood Sequence Detection (MLSD).Then, we implemented the CPM modulation theory using the all digital CPMmodulator structure with FPGA. Then we verified the behavioral of modulation FPGAlogic with computer simulation. Logic simulation results proved the correctness of ourlogic design.We reviewed the demodulation and synchronization theory of CPM signals, andpropose a demodulation receiver structure that suitable for CPM signals in the sense ofSoftware Defined Radio (SDR) quadrature receiver. In the proposed receiver we imple-mented the synchronization of CPM signals by estimating the synchronization paramet-ers and modifying the received signal with them. We implemented the demodulation forCPM signals in the sense of MLSD using Viterbi decode structure, and for full-response CPM signals, the Viterbi decoder become a symbol-by symbol decoder.At last we designed the FPGA logic of the proposed CPM demodulation receiver,and verified the behavioral of each part of the logic structure by simulation, tested thedesigned logic with input data and analyzed the output data, the simulation resultsproved the correctness of our logic design.
Keywords/Search Tags:CPM, modulation, demodulation, synchronization, FPGA logic design
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