An Optimized Planar MIMO Array Approach to In-Air Synthetic Aperture Sonar

Abstract

Modern three-dimensional (3-D) imaging sonar sensors are perfectly capable of creating awareness of the complete nearby environment with great accuracy. However, as range increases, these systems start to struggle with object detection as the poor attenuation of sound through air causes the signal-to-noise ratio to become too small. When looking at other sensing modalities, such as radar, this problem is tackled by using systems that utilize more than one element in the sending and/or receiving stage resulting in a greater effective detection range. At this further distance, the resolution of the obtained image will tend to decrease. Both radar and underwater sonar systems make use of synthetic aperture systems to increase the spatial imaging resolution. In this letter, we combine both techniques to create an in-air (simultaneous transmit) synthetic aperture beamforming (STSTAB) sensor, based on the eRTIS 3-D sonar sensor, that will increase the system's range and angular resolution without sacrificing the measurement rate. Different aspects of the emitter array will be addressed, such as the optimal placement of the elements of the emitter array, along with the coded signals that will be emitted simultaneously. The result will be a fast-measuring imaging sonar sensor with a narrow point-spread-function and improved range.