circuit and a plurality of capacitors connected to the switches sw 0 through sw n u2212 1 respectively the capacitance of the switched capacitor unit 130 is the sum of the capacitances of the selected capacitors connected vco by the switched digital switches sw 0 through sw n u2212 1 the overall whole capacitance of the vco depends on the capacitance of the switched capacitor unit 130 and the other capacitances as described herein as shown in the embodiments of fig2 binary weights are applied to capacitance values of the capacitors of the switched capacitor unit 130 and thus their capacitance values are c sw 2 1 c sw 2 n u2212 1 c sw as such c sw denotes the capacitance value of the lowest rank capacitor the switched varactor unit 140 includes a plurality of digital switches sw 0 through sw n u2212 1 and a plurality of varactors connected to the digital switches sw 0 through sw n u2212 1 respectively a change in the control voltage v cnt results in a change in the capacitances of the varactors the capacitance of the switched varactor unit 140 is determined by a sum of the capacitances of the.