Analysis of symmetric-varactor-frequency triplers

A simple analytical model for varactors that have a symmetric capacitance-voltage characteristic is introduced. This empirical but general model can be used to represent the reactance nonlinearity of quantum-barrier varactors, symmetric high-electron-mobility varactors, and back-to-back barrier-n-n/sup +/ diodes. Using this model, a generalized large-signal analysis of symmetric-varactor triplers is developed. The analysis yields an expression for the maximum efficiency. The results show that the optimized efficiencies at low input power levels are greater than those possible for conventional varactors having similar cutoff frequencies and breakdown voltages. It is further shown that a series-resonant circuit including a symmetric varactor can be described by Duffing´s equation. The solution of this equation predicts hysteresis effects.<>