Abstract: A device determines the propagation time of an acoustic signal by cross-correlation analysis between a transmission signal and a reception signal. The device determines the propagation time by cross-correlation analysis between the transmission signal and the reception signal from which reverberation has yet to be removed, removes, from the reception signal, as the reverberation, a signal component at and after a time point based on the determined propagation time, and redetermines a propagation time by cross-correlation analysis between the transmission signal and the reception signal from which the reverberation has been removed.

Abstract: A device determines a propagation time of an acoustic signal through cross-correlation analysis between a transmission signal and a reception signal. The device generates the transmission signal to satisfy (1) a ratio of a height of a peak other than a maximum peak in an autocorrelation function of the transmission signal to a height of the maximum peak being 0.8 or less and (2) a duration of the transmission signal being at least five times a shortest period of the transmission signal or at least 20 times a half width at half maximum of the autocorrelation function of the transmission signal.

Abstract: A drive circuit includes a GaN FET having a source connected to an anode of an LD and a drain connected to a power source of the LD, a gate drive having an output port connected to a gate of the GaN FET and a negative voltage port connected to the source of the GaN FET to receive an input voltage at a positive voltage port and output the input voltage from the output port in response to a signal with a predetermined level, a capacitor between the positive and negative voltage ports of the gate drive, a diode on a power source line connecting the positive voltage port of the gate drive and a VDD power source for outputting a voltage less than the breakdown voltage at a voltage Vgs of the GaN FET, and a semiconductor switch between the source of the GaN FET and the ground.