Sanyo Electric Co., Ltd.

Agilent Technologies, Inc.

Ryoji Sakiyama

Kazuhiro Kimura

A DA converter comprises a high-pass filter that outputs a multibit digital signal with a predetermined frequency or lower thereof attenuated if a signal level of the input multibit digital signal is less than a predetermined threshold, the high-pass filter outputting the multibit digital signal without attenuation if the signal level is at the threshold or higher; a &#x394;&#x3a3; modulator that performs &#x394;&#x3a3; modulation of the signal output from the filter unit; a dynamic element matching circuit that divides the signal output from the &#x394;&#x3a3; modulator to a plurality of signals; and a plurality of internal DA converters that convert the plurality of signals output from the dynamic element matching circuit to an analog signal.

Multibit &#x394;&#x3a3; modulation DA converter

An impedance measuring apparatus comprising an automatic balanced bridge has four numerically controlled oscillators that supply sine-wave signals and cosine-wave signals to the quadrature detector and vector modulator of the narrow-band amplifier inside the automatic balanced bridge. The frequency or phase of the output signals of the four numerically controlled oscillators are updated by numeric control from the outside. The four numerically controlled oscillators of the impedance measuring apparatus are oscillators whose frequency or phase is changed a pre-determined time after they have been controlled from the outside. Furthermore, the impedance measuring apparatus has control means with which the change in the frequency or the phase of the output signals of the four numerically controlled oscillators is synchronized.

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Kanagawa, Japan

Ryoji Sakiyama