Use of noise signals for multi-mode operation of phased arrays

Abstract

A technique is described with which it is possible to simultaneously transmit and receive in different modes (directivity radiation patterns) of an array utilizing correlation detection and the unique properties of statistically independent noise signals. The feasibility of a particular application—phased arrays which scan simultaneously in more than one direction—is demonstrated by using a simple ultrasonic three transducer linear array and a random signal ultrasonic correlation system. Theory and experimental results are presented which evaluate the effects of clutter and variations in the system parameters on the system signal-to-noise ratio. Results show that multi-mode (multiple scan direction, multiple focal point, etc.) operation can improve phased array performance by decreasing the scanning time necessary to cover a desired volume of space even though extra correlation time may be needed in some cases to reduce the small amount of interference noise which exists between modes.