A Feasibility Study on Frequency Domain ADC for Impulse-UWB Receivers

A feasibility study of frequency domain ADCs for an Impulse-UWB receiver is presented. A frequency domain ADC consists of a bank of narrow band bandpass filters and integrators, followed by a conventional ADC. The filter bank produces the ´spectrum samples´ (Fourier series coefficients) at frequencies corresponding to the center frequencies of the bandpass filters in the filter bank. The Fourier series coefficients are sampled and quantized by a conventional time domain ADC. In the baseband of the I-UWB receiver, the digitized Fourier series coefficients can be processed in the frequency domain or the pulse can be reconstructed and processed in the time domain. Sampling in the frequency domain, avoids the need for an ADC with a wide bandwidth and a high sampling rate for an I-UWB receiver. Simulation results on a mathematical model of a frequency domain ADC show that spacing the center frequencies of the bandpass filters at 200 MHz over the band of interest leads to a pulse reconstruction error of ~ 10% for a 5-bit ADC. Practical implementation issues in integrated circuit realization of the frequency domain ADC are described as well.