| 摘要 |
PURPOSE:To attenuate an image signal of an output signal with a 3dB 90 deg. power synthesizer by comparing signals of two voltage controlled oscillators at a phase detector, forming a phase locked loop in one voltage controlled oscillator with a phase detector output and controlling the loop so as to keep the phase difference between the oscillated signals of the two voltage controlled oscillators to 90 deg.. CONSTITUTION:An oscillated signal of the 1st VCO1 whose oscillating signal frequency is controlled by a channel selection voltage fed to a channel selection voltage terminal 20 is inputted to the phase detector 3 of the phase locked loop comprising the 2nd VCO2, the phase detector 3, a loop amplifier 4 and a loop filter 5. Since the local oscillating circuit is constituted by adding the 1st VCO1 to the phase locked loop and interlocking it with the 2nd VCO2 in the phase locked loop by means of the channel selection voltage, two signals phase-shifted by 90 deg. over a wide are applied and the cancellation of the image signals is attained even to an input signal over a wide range.
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