Transient analysis of a varactor bridge doubler

A direct digital integration of circuit equations was used to study the transient behaviour of a varactor bridge doubler circuit. A suddenly-applied sine, wave was assumed for the fundamental drive. A piecewise-linear varactor characteristic was used. The calculations show that good efficiency and rapid transient response can be obtained for certain ranges of tuning and bias. Experimentally observed input-output power relations are reproduced remarkably well by theoretically calculated results. These include an abrupt increase from negligible output to high efficiency as output is increased, for fixed bias voltage. Also, instabilities are observed when the power is too high for a given bias. The calculations thus prove that sideeffects such as rectification and avalanche multiplication in the varactor diode are not necessary for the presence of spurious oscillations