Circuit configuration for DC-biased capacitors

Abstract

A capacitive element includes two or more voltage-variable capacitors (varactors). The varactors are configured so that they are coupled in series with respect to an applied AC signal and are coupled in parallel with respect to an applied DC bias voltage. The effective capacitance of the overall capacitive element can be tuned by varying the DC bias voltage.

What is claimed is:  
     
         1 . A voltage-variable capacitive element comprising: 
 a first DC bias node and a second DC bias node for receiving a DC bias voltage;    a first AC node and a second AC node for receiving an AC signal;    N varactors, wherein N is at least two and each varactor has a capacitance that varies according to a voltage applied across the varactor; and    wherein the N varactors are coupled in parallel between the DC bias nodes with respect to the DC bias voltage and are coupled in series between the AC nodes with respect to the AC signal.