Saleh AmplifierandDoppler Effect on PSK modulated signals in Inter- Satellite Communication

The paper brings out the cumulative effect of Doppler frequencies on Saleh type non-linearity for a PSK (Phase Shift Keying) modulated signal in Intersatellite communication link. The distortion introduced is measured by taking Error Vector Magnitude (EVM) as metric of evaluation. A PSK modulated signal is considered for study and the equation for the EVM is derived for the PSK signal affected with Doppler and Saleh type non-linearity. The Intersatellite links to be employed for the proposed constellation get affected with Doppler. The Doppler frequency changes with the frequency of operating signal. In this paper a time invariant Doppler is considered and its effect on the PSK signal is brought out. The PSK type considered is QPSK and the effect of amplifier linearity is first derived and then the effect of Doppler is applied onto it. The EVM expression derived is the power reference type. From the EVM expression results are presented for variation of EVM with doppler frequency.From the results it can be observed that a) The EVM variesnon-periodically with the Doppler frequency. b) The EVM value changes for different Saleh Parameters and changes with the Doppler frequency. The EVM values are found to worse for Saleh parameters that have higher values of slope in the amplifier characteristics.