UWB Mixed-Signal Transform-Domain Direct-Sequence Receiver

We consider a mixed-signal ultra wideband (UWB) direct-sequence spread-spectrum (DS-SS) receiver. The receiver expands the signal over a basis set, and then operates on the basis coefficients. An analog computation of the basis coefficients efficiently parallelizes the signal for digital processing, relaxing the sampling requirements and enabling parallel digital processing at a much lower rate. Bit error rate (BER) performance is evaluated, as well as distortion due to basis truncation. The parallel processing also facilitates efficient interference mitigation. Various models for interference including adjacent multicarrier interference are developed and analyzed. Several simulation results confirm the analysis and provide insight into quantization error, basis truncation distortion, and the impact of the UWB channel. We show that in the AWGN uncoded case for SNR < 10 dB, the receiver can be operated at almost half the Nyquist rate with only 1 dB of performance loss. Moreover, when a common convolutional code is employed, the aggregate sampling rate can be 37.5% lower than Nyquist rate with little loss in receiver performance.