Design of mutually matching multiple-varactor array doubler for power

A design method is described in which properly designed λ/4 transmission line is used such that one varactor impedance is utilized to conjugately match that of another varactor at input frequency. Two such pairs are again connected by a properly designed transmission line such that they match each other at the second harmonic output frequency. Thus, a basic building block of four varactors without any external tuning circuit is obtained. Any number of these building blocks can be put together to obtain any desired output power.