Pathak, Sumant; Perrins, Erik; University of Kansas, Electrical Engineering & Computer Science Department (International Foundation for Telemetering, 2018-11)
      Amplitude Phase Shift Keying (APSK) is an attractive alternative to continuous phase non-linear modulations in telemetry systems with its low Peak-to-Average Power Ratio (PAPR). Since the PAPR is not exactly unity, we use APSK paired with Low-Density Parity Check (LDPC) codes to compensate for loss in power efficiency due to the power amplifier operating with backoff. In this paper we consider the adjacent channel spacing of a system with multiple configurations using LDPC coded APSK and SOQPSK-TG. We consider different combinations of 16 and 32-APSK and SOQPSK-TG and find the minimum spacing in frequency between the respective waveforms that does not distort system performance.