Sigma-delta modulator for bandpass signal

The sigma-delta modulator (SDM) is an excellent choice for high resolution analog to digital converters. Recently a bandpass SDM was desired to convert an IF signal into a digital bit stream directly. In this paper, we propose a new bandpass architecture of an SDM based on MASH topology, which is called a bandpass MASH. Similar to the conventional MASH, bandpass MASH is always stable because all its poles are zeros. Further, since the loop coefficients of the proposed architecture are ones, the circuit is simple to design and easy to implement via VLSI technology. Behavior simulation shows that the proposed bandpass MASH achieves 17 bits resolution for an IF signal at 455 kHz. In addition, it also performs better than several other bandpass SDM´s