A reconfigurable CMOS VCO with an automatic amplitude controller for multi-band RF front-ends

A fully integrated reconfigurable 3.6-6.0 GHz 0.18μm CMOS VCO with an automatic amplitude controller (AAC) for multi-standard front-ends is proposed. Due to the wide tuning range, utilizing mixed tuning technique large amplitude variations over the band are observed. Thus a novel low noise AAC is implemented to stabilize the amplitude regardless of operation frequency. Measurements are performed both with and without the AAC loop active, showing that the AAC loops noise contributions are very small. The circuit displays phase noise levels of -124 dBc/Hz or less at 3 MHz offset within the entire frequency baud while consuming 7.7-12.2 mW of power. The relative amplitude variations over the frequency band are 100 mV.