Patent ID: 8305136

Claim:
A switchable capacitive element (SKE), comprising n parallel-connected paths (PF) with a respective capacitor (K) of capacitance C, per path n semiconductor switches (SW), cascaded in the path, with a respective source connection (S), gate connection (G) and drain connection (D), wherein the switchable capacitive element (SKE) has a frequency-dependent quality factor Q S on (ω) when the semiconductor switches (SW) are open and has a frequency-dependent quality factor Q S off (ω) when the semiconductor switches (SW) are closed, R G is the nonreactive resistance of a resistive element connected to the gate connection, R GS is the nonreactive resistance between the gate connection (G) and the source connection (S), R GD is the nonreactive resistance between the gate connection (G) and the drain connection (D), R D is the nonreactive resistance of a capacitive element connected between the drain connection (D) and the source connection (S), r DS is the nonreactive resistance between the drain connection (D) and the source connection (S), C GD is the capacitance between the gate connection (G) and the drain connection (D), C GS is the capacitance between the gate connection (G) and the source connection (S), C DS is the capacitance between the drain connection (D) and the source connection (S), wherein the values C, R MIM , R ON , R G , R GS , R GD , R D , r DS , C GD , C GS , C DS are optimized according to the equation Q ON S = 1 ω · ( R MIM + n · R ON ⁢ R a n · R ON + R a ) · C when the semiconductor switches (SW) are open and according to the equation Q OFF S = ⁢ 1 ω · ( R MIM + n ⁢ ⁢ R d + n ω 2 ⁢ C d 2 ⁢ R e + n 3 ω 2 ⁢ C d 2 ⁢ R a ) · ⁢ C ⁢ d ⁢ C ⁢ C d + n ⁢ ⁢ C when the semiconductor switches (SW) are closed, wherein R a = R G · C GD + C GS C GD R d = R c ( 1 + C DS C c ) 2 ⁢ ⁢ C d = C DS + C c ⁢ ⁢ R e = r DS ⁢ R D r DS + R D ⁢ ⁢ R c = R GD 1 + ( ω ⁢ ⁢ R GD ⁢ C GD ) 2 + R GS 1 + ( ω ⁢ ⁢ R GS ⁢ C GS ) 2 - 1 ω 2 ⁢ R G ⁢ C GD ⁢ C GS ⁢ ⁢ C c = C GD ⁢ C GS C GD + C GS and n is a natural number ≧1.