Digital Modulation Method of Directional Loudspeaker

An digital modulation method of directional loudspeaker is proposed.A square wave whose frequency is the same with the resonant frequency of ultrasonic transducer is used to control the bridge power switch,while the original audio signal with a DC bias is amplified by the Class D amplifier and power to the bridge power switch.The output of the bridge power switch drives ultrasonic transducer after matching and filtering.Theoretical analysis and experimental results show that: the proposed digital modulation method of directional loudspeaker can reduce the power consumption of 58%~67% while ensuring the quality of output signal.It's a good solution to the directional loudspeaker power amplifier problem.