A Nonuniform Sampler for Wideband Spectrally-Sparse Environments

TLDR

Nonuniform sampling can reduce the average sample rate by more than an order of magnitude compared to Nyquist when the signal spectrum is sparse, and the presented NUS system serves as a general‑purpose digital receiver. The study introduces a wide‑band compressed‑sensing nonuniform sampling system that exploits low average sampling rates. The system uses an Indium‑Phosphide heterojunction bipolar transistor sample‑and‑hold chip paired with an off‑the‑shelf ADC to digitize 800 MHz–2 GHz with 100 MHz of noncontiguous spectral content at 236 Ms/s, and reconstructs signals via a nonlinear compressed‑sensing algorithm. Measured GSM channel bit‑error‑rate data show the NUS system performs comparably to a conventional 4.4 Gs/s wideband ADC.

Abstract

We present a wide bandwidth, compressed sensing based nonuniform sampling (NUS) system with a custom sample-and-hold chip designed to take advantage of a low average sampling rate. By sampling signals nonuniformly, the average sample rate can be more than a magnitude lower than the Nyquist rate, provided that these signals have a relatively low information content as measured by the sparsity of their spectrum. The hardware design combines a wideband Indium-Phosphide heterojunction bipolar transistor sample-and-hold with a commercial off-the-shelf analog-to-digital converter to digitize an 800 MHz to 2 GHz band (having 100 MHz of noncontiguous spectral content) at an average sample rate of 236 Ms/s. Signal reconstruction is performed via a nonlinear compressed sensing algorithm, and the challenges of developing an efficient implementation are discussed. The NUS system is a general purpose digital receiver. As an example of its real signal capabilities, measured bit-error-rate data for a GSM channel is presented, and comparisons to a conventional wideband 4.4 Gs/s ADC are made.