Hardware Implementation of a 16-QAM Modem Using Waveform Switching Technique

A new modem circuit technique is proposed for multilevel signal transmission to utilisethe transmission bandwidth efficiently in bandwidth-constrained voice-band channels. Usingthis technique, a 16-level quadrature amplitude modulated (16-QAM ) signal is generated as acascaded configuration of an 8-level phase-shift keying (8-PSK) and a 4-level amplitude-shiftkeying ( 4-ASK) using waveform mapping rules. The data detection procedure, which is basedon the determination of each symbol one-by-one by inspection of their amplitude level andabsolute phase information, is described