Patent ID: 7920030

Claim:
A multi-phase voltage-control oscillator (VCO), comprising: a first VCO circuit; and a second VCO circuit, wherein the second VCO circuit and the first VCO circuit have a plurality of 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, wherein the first VCO circuit comprises: a first NMOS transistor having a second source/drain electrode grounded; a second NMOS transistor having a second source/drain electrode grounded, and a gate electrode coupled to the first source/drain electrode of the first NMOS transistor; a first inductor for grounding a back gate electrode of the first NMOS transistor; a second inductor for grounding a back gate electrode of the second NMOS transistor; a first varactor for coupling a first source/drain electrode of the first NMOS transistor to a control voltage; a second varactor for coupling a first source/drain electrode of the second NMOS transistor to the control voltage; a third inductor for coupling the first source/drain electrode of the first NMOS transistor to a voltage source; and a fourth inductor for coupling the first source/drain electrode of the second NMOS transistor to the voltage source.