| CPC H03F 1/565 (2013.01) [G01S 7/52 (2013.01); G01S 7/524 (2013.01); H03F 2200/387 (2013.01)] | 18 Claims |

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1. An amplifier circuit to be used in a sonar, the amplifier circuit comprising:
a transmission amplifier;
a transducer; and
a matching circuit arranged to connect the transmission amplifier to the transducer so as to form a series circuit,
wherein the transducer has a first impedance characteristic comprising a resonance frequency and an anti-resonance frequency higher than the resonance frequency, and
wherein the transducer connected to the matching circuit has a second impedance characteristic different from the first impedance characteristic, the second impedance characteristic comprising a first resonance frequency and a second resonance frequency higher than the first resonance frequency.
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