Method to increase the tuneability of varactors

A method of providing a tunable circuit or admittance arrangement comprising the steps of:

• providing a capacitive branch with at least one tunable first capacitor, providing a resonant branch with at least a tunable second capacitor and an inductor in series;
• connecting said capacitive and resonant branches in parallel;
• selecting the first or the second capacitor as a reference parameter capacitor;
• fixing a capacitance of the reference parameter capacitor;
• calculating a capacitance of the first or second capacitor not used as the reference parameter capacitor and an inductance of the inductor using the fixed capacitance value, an upper and lower frequency values defining a frequency range, and a maximum allowable tolerance/deviation;
• establishing the frequency range, while giving the maximum allowable tolerance or frequency dependent deviation of a varactor forming an equivalent varactor of the tunable circuit or admittance arrangement;
• and
• selecting a capacitance of the first and second capacitors and an inductance of the inductor in dependence of one another so that the frequency dependency of tunability of the equivalent varactor arrangement can be controlled.