I. INTRODUCTION
Underwater sonar transducers are widely used in different types of acoustic backscatter systems to measure velocity and/or distance along narrow acoustic beams. A class of these sonars employ the four independent piston transducers each inclined at 20 or 30 degrees to generate the four beams. Another approach is to employ the phased array techniques to from a single flat transducer to produce four beams. The advantages of the phased array sonar over the piston configuration are the reduced size and long range, especially at low frequencies below 200 kHz. The planar phased array transducer forms multiple beams at a single frequency along the two axes of a single two-dimensional phased array transducer [1]. The electrodes are connected orthogonally to the top and bottom of the individual ceramic element in the transducer to obtain the phased array transducer. The transmit and receive beam formers are used to simultaneously generate two pairs of independent beams in each X and Y axis.