Low power implementation of an n-tone ΣΔ converter

Abstract

The zeros of the noise transfer function (NTF) of a /spl Sigma//spl Delta/ converter can be altered by modifying the loop filter. For example, a low-pass /spl Sigma//spl Delta/ is converted into a band-pass /spl Sigma//spl Delta/ by shifting the zeros of the NTF from zero to f s/4. In a similar function, an n-tone /spl Sigma//spl Delta/ can be created by inserting multiple zeros in the NTF. If the signals are then placed only in these noise valleys, a high signal to noise ratio (SNR) can be achieved. In its most simplest form - the number of voice valleys being one - it reduces to the familiar band-pass /spl Sigma//spl Delta/ converter. In this paper, we provide a system-level understanding of an n-tone /spl Sigma//spl Delta/ converter and the resulting performance. We then provide a circuit design for a low power implementation of such a converter. We emphasize high operational speed and low power consumption as the focus of the design is for a UWB-OFDM receiver.