Ultrasonic sensor, and method for controlling a burst signal

An ultrasonic sensor comprising:

• a piezoelectric element for transmitting and receiving an ultrasonic signal, wherein the piezoelectric element has a reverberation frequency that is variable based on a variation in an environment of the ultrasonic sensor;
• a transmitter configured to drive the piezoelectric element;
• a burst signal sending circuit configured to deliver a burst signal of a burst wave frequency to the transmitter;
• a receiver configured to accept a reception signal received by the piezoelectric element;
• an amplification circuit configured to amplify the reception signal to output an amplified signal;
• and
• a signal processing circuit configured to assess the amplified signal output from the amplification circuit,
• wherein
• the signal processing circuit is configured to assess the reverberation frequency of a reverberation signal contained in the amplified signal or a reverberation time that depends on a difference of the reverberation frequency from the burst wave frequency, and to feed a result of assessment back to the burst signal sending circuit, and
• based on the result of assessment, the burst signal sending circuit is configured to adjust the burst wave frequency, wherein the burst signal sending circuit is configured to set the burst wave frequency, with the result of assessment reflected to follow variation of the reverberation frequency caused by the environment of the ultrasonic sensor.