Low power implementation of an N-Tone ΣΔ converter

The zeros of the noise transfer function (NTF) of a ΣΔ converter can be altered by modifying the loop filter. For example, a low-pass ΣΔ is converted into a band-pass ΣΔ by shifting the zeros of the NTF from zero to fs/4. In a similar fashion, an N-Tone ΣΔ 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 noise valleys being one - it reduces to the familiar band-pass ΣΔ converter. In this paper, we provide a system-level understanding of an N-Tone ΣΔ 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.