Some rules for the choice of the C(V) characteristic for the design of frequency triplers with symmetrical varactors

In this paper we consider multipliers designed with varactors that have a symmetric C(V) capacitance-voltage characteristic, i.e. triplers, quintuplers, ... We show that for a tripler the optimal C(V) characteristic is not the most abrupt one, as stated in much works, but rather a cosine-like one. Our work is validated with the design of a frequency tripler based on the use of HBVs non-linear transmission lines. We obtained a significant improvement for the maximum conversion efficiency when a cosine C(V) is used instead of an abrupt one, for a 15 HBVs NLTL frequency tripler.