Spectral regrowth reduction for CCSDS 8-D 8-PSK TCM

A constant envelope modulation technique called the Smooth Phase Interpolated Keying (SPIK) is investigated. Its performance is studied in the context of Consultative Committee for Space Data Systems (CCSDS) 8-D 8-PSK Trellis Coded Modulation (TCM). It is observed that SPIK is highly spectrally efficient for nonlinear channels compared to linear modulations that use the conventional square root raised cosine (SRRC) filtering. An optimal receiver structure is described and suboptimal versions are investigated. The optimal receiver achieves excellent bit error rate (BER) performance. The performance of SPIK is studied for both travelling wave tube amplifier (TWTA) and solid state power amplifier (SSPA) models. It is observed that for nonlinear channels, SPIK based CCSDS provides significant benefits in spectral performance at the cost of nearly 1 dB in the BER performance over the SRRC based CCSDS, when the latter assumes perfect phase tracking. Further improvement in the BER performance of SPIK is possible at the cost of computational complexity, whereas an improvement in the SRRC approach involves more complexity and accurate parameter tracking of the nonlinear channel.