| || Hardware Implementation of a 16-QAM Modem using Waveform Switching Technique
Author : Nibandhe, Reena P. ;Roy, Kathika ;Bhat, K. P. M.
Source : Defence Science Journal ; Vol:56(5) ; 2006 ; pp 815-824
Subject : 621.38 Electronics;681.2 Instrumentation
Keywords : 16-QAM;8-PSK modulation;Waveform mapping;Programmable gain amplifier;Digital phase detector
Abstract : A new modem circuit technique is proposed for multilevel signal transmission to utilise the transmission bandwidth efficiently in bandwidth-constrained voice-band channels. Using this technique, a 16-level quadrature amplitude modulated (16-QAM ) signal is generated as a cascaded configuration of an 8-level phase-shift keying (8-PSK) and a 4-level amplitude-shift keying ( 4-ASK) using waveform mapping rules. The data detection procedure, which is based on the determination of each symbol one-by-one by inspection of their amplitude level and absolute phase information, is described.