Patent ID: 7265459

Claim:
A variable capacitor circuit to control the capacitance of a variable capacitor in a linear mode through a tuning voltage and to achieve a high Q-factor at the same time; comprising: a set of individual small capacitors; a set of capacitor switching stages, each stage comprising: a switching device allowing a steady ramp-up/ramp-down phase between the points of being fully switched on and fully switched off, and where said switching device is connected in series with one of said small capacitors; a switch control circuit to control the switching operation of said switching device in a steady ramp-up/ramp-down manner by generating a controlling signal, directly depending on a tuning voltage input, one for each of said capacitor switching stages; a threshold circuit to generate a set of threshold values, one for each of said capacitor switching stages; and a circuit to provide said tuning voltage, dedicated for the voltage controlled capacitance change.