Multistandard and echo cancelling modem using front end processor

A new front end processor (FEP), containing an analog-to-digital converter (ADC), a digital-to-analog converter (DAC) and a digital signal processor (DSP), has been developed to achieve digital implementation of the whole modem system. The paper describes the multistandard and echo cancelling modem system using this type of FEP. The chip consists mainly of two blocks, the ADC and DAC block and the DSP block. In the ADC and DAC block, the oversampling delta-sigma modulation technique is adopted to obtain a wide dynamic range (80 dB) and high resolution (equivalent to 13 bits)