Multi-frequency transmission/reception apparatus

An ultrasonic transducer array comprising:

• a plurality of transducer elements, each transducer element further comprising:
• a radiating surface;
• two electrode surfaces coupled to the radiating surface, wherein transmit signals are applied to said electrode surfaces;
• and
• an additional surface coupled to the two electrode surfaces,
• wherein each transducer element vibrates, in response to said transmit signals, at a predetermined plurality of resonant frequencies based upon dimensions of an edge of the radiating surface that is not in common with the electrode surface and an edge of the electrode surface that is not in common with the radiating surface, further wherein the dimensions are selected so that a combination vibration mode does not occur,
• wherein the radiating surface transmits an acoustic wave resonating at the predetermined plurality of resonant frequencies and propagates with a predetermined angle of directivity, further wherein the angle of directivity is based upon a dimension of an edge common to the radiating surface and the electrode surface,
• wherein the dimension of the edge common to the radiating surface and the electrode surface is set to be larger than at least the edge of the radiating surface that is not in common with the electrode surface, and the edge of the electrode surface that is not in common with the radiating surface, to a degree that does not influence resonance in either a fundamental vibration mode or a harmonic vibration mode,
• wherein the transducer elements are arranged in an array so that each radiating surface lies in a common surface.