To reduce noise which may be generated in switching of GND, by eliminating switching of GND.
A communication apparatus A(10A) includes: a piezoelectric element unit 18A in which, two terminals are formed by serially connecting an even number of ultrasonic vibrators 62, each ultrasonic vibrator 62 being configured to convert a first high frequency signal into a transmitting wave and radiate the transmitting wave when the first high frequency signal is inputted, and to convert a receiving wave into a second high frequency signal and output the second high frequency signal when the receiving wave is detected, and a connecting part of a transmitting/receiving element equally dividing the even number of ultrasonic vibrators 62 is defined as a reference potential; a transmitting unit 14A for generating the first high frequency signal based on an inputted first information signal and outputting the generated first high frequency signal to the two terminals as a differential signal; a receiving unit 22A for combining second high frequency signals outputted from the two terminals, inputting a combined signal as a single end signal and extracting a second information signal contained in the inputted second high frequency signal; and a changeover switch 66A for connecting the two terminals to any one of the transmitting unit 14A and the receiving unit 22A.
Osamu Suzawa
Kazuhiko Miyasaka
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