Performance of N-tone sigma-delta modulators for UWB-OFDM
Due to the spectrum gap between subcarriers in an UWB-OFDM system, an N-tone sigma-delta modulator can be used to introduce appropriately placed nulls into the noise spectrum of such systems. The resulting performance is evaluated in terms of in-band quantization noise and excess resolution gained. Moreover, we relate the performance of our system to that of a traditional oversampled sigma-delta modulator operating in a lowpass system. A higher-order N-tone sigma-delta modulator having better noise shaping ability is also introduced for use in UWB-OFDM systems.