Implementation of Variable Rate CPM Modulator

Spectrum is a non-renewable resource, and the spectrum resources of telemetry system are increasingly scarce. However, the demand for high bit-rate transmission is increasing. Continuous phase modulation (CPM), an efficient bandwidth modulation method, can alleviate this contradiction. This paper focuses on the implementation of CPM modulation with variable rate sampling technology based on Farrow structure, and proposes a variable rate sampling method for shaped offset quadrature phase-shift keying signal(SOQPSK). When the phase correlation length is greater than 1, it is called SOQPSK- TG. SOQPSK-TG has better power spectrum characteristics. According to the SOQPSK-TG signal model, the integer rate sampling is realized by interpolating baseband and interpolating phase. Combined with the analysis of demodulation results, it is concluded that the interpolating phase has the advantages of lower demodulation error rate and less hardware implementation.