3D sonar system based on mills cross antenna configuration

A special aperture for a 3D sonar system is the so called Mills Cross antenna configuration. The Mills Cross arrangement looks like a "T" in which both antennas have a special function. In our work one antenna, consisting of 128 piezoelectric transducer elements, is used to transmit sound into a volume of interest. The second one, also made of 128 piezoelectric transducers, is used for receiving the reflections from objects or surfaces in the vicinity of the antennas. Each transducer element has a convex curvature to cover at least 30° of the elevational direction. With that a volume defined by sector angles of 30° × 30° can be measured. To achieve fast volumetric imaging a frequency coding is used to transmit signals in different directions at the same time. The received signals are decoded to determine the different signals coming from the different directions. In this work we present the basic working principals of the system and the first measurement results.