Digital Encoding of Phase Shift Keying Voiceband Data Signals

Computer simulation was used to evaluate the performance of eleven coder/decoders (CODEC´s) with phase shift keying (PSK) and differential PSK(DPSK) voiceband data signals. The CODEC´s were PCM, differential PCM and delta modulation systems designed for speech and operating at bit rates from 16 to 64 kbits/s. The voiceband data signals processed by these CODEC´s were demodulated to determine the phase error caused by the CODEC. The phase error introduced by the CODEC´s is a function of the phase of the CODEC sampling clock relative to the data modem bit clock. Some of the statistics of the phase error are presented. Three performance metrics were used to evaluate the performance of these CODEC´s-signal to quantizing noise ratio, variance of the phase error and maximum value of the phase error.