The proposal of connecting several varactor wafers in series to obtain higher breakdown voltages without loss of cutoff frequency is explored theoretically and experimentally. Calculations indicate that for a common wafer and junction geometry, the cutoff frequency of series stacked varactors will vary approximately as VB-12 instead of the more rapid VB-1 or VB-32 variation characteristic of a single wafer. The virtue of this scheme has been demonstrated in a 4-to-12-GHz multiplier using varactors consisting of 1, 2, 3, and 4 series-connected, epitaxial GaAs, surface-barrier wafers. As anticipated, the varactor breakdown voltages increased directly with the number of wafers employed and the power capability as the square of that number, while efficiency decreased only slightly. A maximum power output of 1.21 watts at 12 GHz was obtained with 62 efficiency in a tripler circuit. The report summarizes the results achieved during the three years work on this contract on a variety of diode types for microwave applications. The principles involved in their design and application are discussed. The report reviews broadly the suitability of these principles for particular classes of applications.
Final rept. 10 Jun 62-9 Jun 65,
Prepared in cooperation with Bell Telephone Labs., Inc.