Patent ID: 7551038

Claim:
A multi-phase voltage-control oscillator (VCO), comprising: a first VCO circuit comprising: a first NMOS transistor, having a first source/drain electrode coupled to a voltage source; a second NMOS transistor, having a first source/drain electrode coupled to the voltage source; a first inductor, for coupling a gate electrode of the first NMOS transistor to a second source/drain electrode of the second NMOS transistor; a second inductor, for coupling a gate electrode of the second NMOS transistor to a second source/drain electrode of the first NMOS transistor; a first varactor, for coup 1 ing the second source/drain electrode of the first NMOS transistor to a control voltage; a second varactor, for coupling the second source/drain electrode of the second NMOS transistor to the control voltage; a third inductor, for grounding the second source/drain electrode of the first NMOS transistor: and a fourth inductor, for grounding the second source/drain electrode of the second NMOS transistor to ground: and a second VCO circuit, having a plurality of inductors corresponding to the first, second, third and fourth inductors, and the inductors in the second VCO circuit are respectively cross-coupled with the inductors in the first VCO circuit to generate a mutual inductance effect, so as to output a plurality of oscillating signals with different phases.