Improved efficiency in the parametric transmitting array

It is shown that the efficiency of the parametric transmitting array may be improved over that obtained where two equal amplitude‐frequency components are employed in the primary wave. Through suitable periodic shaping of the envelope of the primary wave, available improvements in the output at the ’’difference’’ frequency of between 2.1 and 6.0 dB are possible in principle. The degree of available improvement depends upon whether the transmitter is peak power or average power limited and whether finite‐amplitude attenuation of the primary wave is significant. It is proposed that the on–off modulation of a single‐frequency carrier provides a simple, practical method through which near optimum efficiencies may be obtained under most circumstances. A bandwidth greater than the ’’difference’’ frequency is required at the transducer in order to achieve this improvement.Subject Classification: 25.35; 30.75.