HARDWARE IMPLEMENTATION OF A DIFFERENTIAL QAM MODEM

In this paper a QAM modem based on certain modifications of the CCITT Recommendation V.29, is presented. A predominantly digital implementat ion without the use of DSP devices is given. Although the implementati on is for telephone bandwidth the idea can be expanded to be able to a chieve higher rates. In this design approach the modulation is based o n ROM-stored symbols while the demodulation is based on a symbol-by-sy mbol determination for the recovery of the original information bits. Specifically, the paper refers to a D16QAM design. Most of the stages are digital, a feature that simplifies the VLSI implementation. The sy nchronisation (timing recovery) is based on modified Phase Locked Loop .