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Abstract

A digital-analog shared circuit in dual mode radio equipment, which shares a local oscillator in a digital mode and analog mode. A first frequency synthesizer generates a first and a second local oscillation frequency in a digital and an analog receiving mode, respectively, in response to a control signal from a switching control. In the digital receiving mode, a quadrature demodulater including a first and a second demodulator in a demodulator section is enabled, and carries out quadrature detection of a received signal fed from an RF stage, thereby supplying the detected signal to a baseband signal processor stage. In the analog receiving mode, a buffer to which the second local oscillation frequency is supplied is enabled to deliver the second local oscillation frequency to the analog IF stage. A second frequency synthesizer generates a third local oscillation frequency in a digital transmitting mode and a fourth local oscillation frequency in an analog transmitting mode. In the digital transmitting mode, a quadrature modulator including a first and a second modulator is enabled to carry out quadrature modulation using the third local oscillation frequency. In the analog transmitting mode, the fourth local oscillation frequency undergoes frequency modulation by an analog modulating signal, and the modulated signal is in turn supplied to the RF stage through the second modulator.

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