A sub-Nyquist sampling signal processing sonar receiver

Abstract

Sub-Nyquist bandpass sampling offers an attractive approach to reducing the complexity of multi-channel sonar receivers also reducing costly duplication of analogue hardware. Digital frequency down-conversion following high-rate sampling is an established method for economic multiple-channel receiver design. This paper describes an architecture, design procedure and prototype multi-channel receiver where direct sub-Nyquist sampling replaces the separate digital down-conversion stage. The prototype design discussed combines multiplexing of multiple channels to fewer sub-Nyquist samplers to achieve second-order quadrature bandpass sampling while maintaining a simple uniform overall sample rate. Design equations for the sampling-rate reduction enabling the decrease in complexity are included. In more traditional jargon, the prototype implements uniform quadrature second-order integer-positioned bandpass sampling combined with a multiplexer to provide multiple channels.