Tuned circuit for sonar beam pattern optimization

A sonar system including an underwater transducer having interleaved separate piozoelectric projecting and receiving arrays wherein said projecting array is energized and said receiving array is connected to receive echo signals during alternate time periods, and

• tuned circuit means are included for inhibiting reflected energy from said projecting array during the time said receiving array is receiving echo signals characterized in that said projector array operates to transmit a plurality of selected discrete frequencies with adjoining frequencies differing from each other by less than approximately one percent and said tuned circuit is connected across said projector array and comprises an inductor connected in series with said projector array and a resonant circuit connected in series with said inductor, said resonant circuit including at least two parallel branches, one of which includes inductance means and the other of which contains resistance means, capacitance means and inductance means, values of said resistive, capacitive and inductive components being chosen such that said projector array becomes mechanically stiff at all of the operating frequencies of said receiver.