Acoustic transducer

A matching network for an acoustic transducer, the acoustic transducer being operable to communicate at a centre-frequency and across an operational bandwidth, the acoustic transducer comprising a piezoelectric element having a dielectric constant which varies with temperature, the transducer having a natural frequency at a given temperature, and being operable to transfer a signal between an electrical load and the piezoelectric element, wherein the matching network comprises:

• a temperature compensating capacitor connected in parallel with the piezoelectric element, the temperature compensating capacitor being for counteracting temperature-induced changes to the dielectric constant of the piezoelectric element such that the natural frequency of the transducer is substantially constant over a range of temperatures;
• a first shunt inductor connected in parallel with the piezoelectric unit;
• and
• a second shunt inductor connected in parallel with the piezoelectric unit.

An acoustic transducer for communications within an operational bandwidth, the transducer comprising:

• a piezoelectric element having a dielectric constant that varies with temperature;
• a driving electrode at the surface of the piezoelectric element;
• and
• a matching network, having a natural frequency at a given temperature, and operable to transfer an input signal to the piezoelectric element, the matching network being connected to the driving electrode, wherein the matching network includes
• a temperature compensating capacitor connected in parallel with the piezoelectric element,
• a first shunt inductor connected in parallel with the piezoelectric element,
• a second shunt inductor connected in parallel with the piezoelectric element,
• a first series inductor operably connected across the first and second shunt inductors, and a series capacitor operably connected to the second shunt inductor.