Analog to Digital Conversion of Ultra- Wideband Signals in Orthogonal Spaces

This paper introduces novel techniques to perform analog to digital (AID) conversion, based on the quantization of the coefficients obtained by the projection of a continuoustime signal over an orthogonal space. The new AID techniques proposed here are motivated by the sampling of the input signal in domains which may lead to lower levels of signal distortion and significantly less demanding A/D conversion characteristics. As a particular case, we study A/D conversion in the frequency domain where samples of the signal spectrum are taken such that no timealiasing occurs in the discrete-time version of the signal. We show that the frequency domain analog to digital converter (ADC) overcomes some of the dimcultiw encountered in conventional time-domain methods for AID conversion of signals with very large haudnidths, such as ultra-wideband (UWB) signals. The discrete frequency samples are then passed through a vector quantizer with relaxed characteristics, operating over D C levels that change with a speed that is much lower than that required for time-domain AID conversion. Fundamental Sgures of merit in AID conversion and important system trade-offs are discussed for the proposed frequency domain ADC. As an example of this approach, we consider a multi-camer UWB Communications s cb e m e.