Abstract: A speed measuring apparatus including a transmitter for transmitting an acoustic reference wave toward a moving-target, the acoustic reference wave being generated based on a reference signal with a predetermined frequency. Also included is a receiver for receiving acoustic reflection waves which are generated by the transmitted acoustic reference wave being reflected by the moving-target, for converting the acoustic reflection waves to receiver signals, and for outputting the receiver signals therefrom. Further, a signal attenuating unit for selectively attenuating a signal component with the same frequency as the frequency of the reference signal in the receiver signals which are output from the receiver and outputting signals therefrom and a band pass filter unit for selecting at least one Doppler signal component from the signals output from the signal attenuating unit are included.

Abstract: In the A/D converter test method, the square wave pulse as the test signal is supplied to the A/D converter under test; said pulse is converted into the digital signal by said A/D converter; the waveform of said square wave pulse is reconstructed by converting the digital signal outputted from said A/D converter into the analog signal; the rise time of said A/D converter under test is measured from the reconstructed waveform of said square wave pulse; and the dynamic characteristics of said A/D converter is calculated from the measured rise time.

Abstract: A DA converter testing system for testing DA converters which convert digital information into analog information, particularly suitable for testing the dynamic characteristics of such DA converters. The DA converter testing system has an AD conversion means which receives the analog output signal of a test DA converter, operating at a conversion period greater than the waveform repetition period of the repetitive output waveform of the test DA converter. Accordingly, the fast repetitive output waveform of the test DA converter can be converted into corresponding digital codes at a high accuracy and hence the DA converter testing system is more suitable than the conventional DA converter testing system, for testing the dynamic characteristics of DA converters.