Quadrature VCO using symmetrical spiral inductors and differential varactors

摘要

A quadrature VCO includes two cross-coupled differential pairs, two parallel LC tank circuits, two LO units and a plurality of source followers, supplying by a tail current source and a tail capacitor. The LC tank circuit constitutes of symmetrical spiral inductors and differential varactors, which constitutes of common anode diodes. The quadrature VCO circuitry is implemented on a chip with 2.4 GHz operating frequency. The quadrature VCO generates quadrature LO signals with high phase accuracy and good gain match under low power, good phase noise and small chip area, thus it can be applied to a variety of integrated transceivers.