High-speed A/D conversion for ultra-wideband signals based on signal projection over basis functions

The paper introduces techniques to perform analog-to-digital (A/D) conversion, based on the quantization of the coefficients obtained by the projection of a continuous-time signal over an orthogonal space. This framework for A/D conversion is motivated by the sampling of an input signal in domains which may lead to lower levels of signal distortion and significantly less demanding A/D conversion characteristics. The A/D conversion distortion is reduced by assigning optimal bit rates according to the variance distribution of the coefficients. Moreover, since the quantization of the coefficients is realized at the end of a time window during which the signal is projected, the speed of the quantizers can be much lower than the one needed in conventional time-domain ADCs. In particular, we study ADC in the frequency domain which overcomes some of the difficulties encountered with conventional time-domain A/D conversion of signals with very large bandwidths, such as ultra-wideband (UWB) signals.