Modulation of microwave power with electron transfer diodes

An experimental study was made of a microwave amplitude modulator using AA 703B electron-transfer diodes, the object being to determine its performance characteristics and the mechanisms on which they depend. The test equipment included a microwave oscillator transmitting continuous signals through a rectifier, an attenuator, a frequency meter, a circulator, and a double-throw switch to either of two modulator cells. Modulated signals were either reflected through one circular arm, another rectifier, a directional coupler, and a high-precision attenuator to an oscillograph, or transmitted through the other circulator arm and a wideband detector to a millimeter. A modulator cell consisted of a rectangular waveguide segment 23 x 3.5 sq mm in cross section with a Gunn-effect diode inside and three tuning screws inserted through holes in one of the wide walls. Measurements over the 9.95-10.08 GHz operating frequency range have revealed an increase of the modulation factor with increasing microwave signal power at a constant microwave signal power.