Results of using a varactor emphasizing charge storage effects in a high power VHF multiplier

It is possible, and in some cases advantageous, to obtain high efficiency from a varactor showing a minimal capacity versus voltage variation. By utilizing charge storage effects a varactor with only between a 1/5 to 1/6th power capacity law yielded over 70% efficiency in a tripler with 150 mc output. In addition, this varactor can handle power inputs well in excess of 50 watts. These results are accomplished by a specially designed impurity distribution which enables the attainment of high voltage breakdown with a minimum of extraneous body resistance in the semiconductor. At the same time the impurity distribution constrains the injected charge to the vicinity of the junction enhancing the stored charge contribution to the generation of harmonic currents. One of the most attractive features of a multiplier utilizing this varactor is the relative linearity of power output versus power input. This permits multiplication of amplitude modulated signals with low resultant distortion. It is believed that the emphasis of charge storage effects instead of capacity-voltage variation explains the linear power characteristic.