Voltage-controlled oscillator and communication device using the same

A voltage-controlled oscillator, comprising:

• a differential alternating current generator including a resonator capable of varying resonant frequency according to an input control voltage, for generating a pair of differential alternating current each of which having the same frequency with the resonant frequency of the resonator yet being 180 degrees out of phase in mutual;
• a pair of transformer each of which having a primary inductor and a secondary inductor, for conducting the alternating current to the primary inductor;
• and
• an impedance-matching circuit connected to the secondary inductor of the pair of transformers that outputs an output signal,
• wherein the differential alternating current generator, the transformers, and the impedance-matching circuit are formed on a common Si substrate, and
• wherein an output signal is outputted from the secondary inductors of the pair of transformers.

A communication device, comprising:

• a substrate;
• a voltage-controlled oscillator provided on the substrate;
• a signal processor provided on the substrate;
• and
• a bonding line provided on the substrate for connecting the voltage-controlled oscillator with the signal processor,
• wherein the voltage-controlled oscillator comprising:
• a differential alternating current generator including a resonator capable of varying resonant frequency according to an input control voltage, for generating a pair of differential alternating current each of which having the same frequency with the resonant frequency of the resonator yet being 180 degrees out of phase in mutual;
• a pair of transformers each of which having a primary inductor and a secondary inductor, for conducting the alternating current to the primary inductor;
• and
• an impedance-matching circuit connected to the secondary inductor of the transformers,
• wherein a high frequency output signal is outputted from the secondary inductors of the pair of the transformers, and
• wherein the signal processor operates in response to the high frequency output signal from the voltage-controlled oscillator.