Adv Antest Corporation

Takeda Riken Kogyo Kubushikikaisha

Masayuki Ogawa

Takahiro Yamaguchi

Toshiharu Kasahara

Hiromi Kosawa

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. For testing signal reproducing devices, such as compact disc players and video tape recorders, such a device reproduces a series of signals, for which a series of corresponding suppression signals is generated by the suppression signal generator. Each suppression signal is added to the corresponding original signal and eliminates the fundamental wave in each signal in the series. The suppressed signals are then compared with the orginal corresponding signals for determining distortion factors of the signal reproducing device.

Distortion measuring system method utilizing signal suppression

A frequency range of measurement is divided into a plurality of regions. For each region a test signal suitable for measurement of the region is generated independently, and the test signal is supplied to a device under test. The output of the device under test is converted by an AD converter into a digital signal, which is then subjected to fast Fourier transform. For each region the sensitivity of the AD converter is set for optimal conversion of the signal level at its input side by the converter, and then the fast Fourier transform is carried out. On the basis of the sensitivity set for one of the regions, the magnitude of the fast Fourier transform output in each of the other regions is corrected according to the sensitivities set for the other regions.

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Gyoda, Japan

Masayuki Ogawa