Mitsubishi Denki Kabushiki Kaisha

Ken'ichi Tajima

Kenji Itoh

Akio Iida

Shuji Nishimura

In a receiving and transmitting apparatus, a frequency of a direct digital synthesizer provided in a local oscillating circuit is controlled in order to reduce a frequency error, based on data of a frequency error detecting circuit. The direct digital synthesizer includes a digital operation circuit for inputting data designating the frequency and outputting an amplitude value of a periodic signal synchronous with a reference clock, and digital-analog converter for converting the amplitude value of the periodic signal to an analog signal.

Method and apparatus for communication and signal synthesis

A frequency synthesizer having reduced spurious components for use in a receiving and transmitting apparatus. The frequency synthesizer includes a direct digital synthesizer (DDS) for generating a first signal having a first frequency determined by channel setting data. The first signal is applied to a frequency divider to generate a divided signal having a divided frequency. The divided signal is applied to a frequency converter for shifting the divided frequency by a shift frequency interval to provide a reference signal having a reference frequency. The reference signal is applied to a phase locked loop (PLL) for generating a final signal having a predetermined frequency characteristic.

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Kanagawa, Japan

Ken'ichi Tajima