Patent ID: 8502614
Filing Date: 2013-08-06
Classification: H03B,H03H,H03J

Abstract:
1. A communication system comprising: a low-noise amplifier that amplifies a receive signal received by an antenna; a mixer that converts a frequency of an output signal of said low-noise amplifier; an oscillator that generates a local oscillator signal for conversion of the frequency, and outputs the local oscillator signal to said mixer; a demodulator that takes out a receive base band signal from an output signal of said mixer; a modulator that modulates a transmit base band signal and outputs two signals orthogonal in phase to each other; an orthogonal modulator that modulates the two signals orthogonal in phase to each other by use of the local oscillator signal outputted by said oscillator to thereby output an orthogonal modulation signal a power amplifier that amplifies the orthogonal modulation signal; and a switch that supplies the receive signal received from the antenna to said low-noise amplifier at the time of receiving and supplies the orthogonal modulation signal outputted by said power amplifier to the antenna at the time of transmitting, wherein said oscillator comprises: a variable inductor whose inductance varies; and a first variable capacitor whose capacitance varies, the first variable capacitor being connected to the variable inductor in parallel, wherein said variable inductor comprises: a first inductor; a second inductor magnetically coupled to the first inductor through mutual inductance; and an inductance controller comprising a second variable capacitor, the inductance controller being connected to the second inductor, wherein the inductance controller has an inductance control terminal that receives a control signal to vary a device value of the second variable capacitor, and as a result of variation in the device value of the second variable capacitor, caused by the control signal, inductance of the first inductor varies, and wherein the entire range of the capacitance of the second variable capacitor due to which the inductance of the first inductor shows a value continuously changing from the highest to the lowest and with increase of the capacitance of the second variable capacitor is excluded from use as providing a degraded quality factor though the first variable capacitor and the second variable capacitor working in cooperation with each other so as to prevent degradation of the quality factor caused by the continuously changing value in the inductance from the highest to the lowest.