Abstract: A plurality of relatively prime excitation waveforms are generated and applied to an object to be measured. Data of the excitation waveforms and a response waveform from the object are extracted by one frame every n frames and subjected to Fourier transform, thereby computing an input auto spectral matrix and an input-output cross spectral matrix. A frequency response function of the object is calculated from averaged spectral matrices obtained by adding and averaging corresponding elements of the corresponding spectral matrices a predetermined number of times. Readout start addresses for multiple waveforms, each stored in one of a plurality of waveform memories and having continuity at both ends, are shifted relative to each other every n frames, thereby obtaining the plurality of relatively prime excitation waveforms.

Abstract: A method for testing and measuring distortion in electrical devices is provided. For signal processing and carrying devices, a signal generator generates a signal having known phase, amplitude and frequency, which is provided both to a device under test and a measuring unit. The measuring unit measures the amplitude, frequency and phase rotation of an output of the device under test and provides these measured values to a suppression signal generator. The suppression signal generator generates a suppression signal which is added to the output signal from the device under test for suppressing the fundamental wave of the output signal. This suppressed signal is then provided to the measuring unit, for comparison with the original output signal from the device under test for determining distortion factors.

Abstract: In an AD converting device in which an analog random noise is added by analog adding means to an analog signal to be converted and the added output is converted by an AD converter to a digital signal, an analog offset voltage, whose level variation is around (1 to 7) times the quantization step size .DELTA. of the AD converter, is generated by offset generating means and is also applied to the analog adding means. A random noise waveform is stored in a memory, the read-out output of which is converted by DA converting means to an analog random noise having an amplitude about (1/2 to 6).DELTA., and the converted output is used as the above-said random noise. A digital value of the offset voltage and the digital noise waveform are subtracted from the output of the AD converter, as required.