Microwave switch device

1,003,758. Electric analogue calculating. MULLARD Ltd. July 23, 1962, No. 28243/62. Heading G4G. [Also in Division H1] A microwave attenuating device which produces an output dependent upon the level of the input signal comprises a silicon point-contact diode arranged in an arm of a three- or four-arm junction, e.g. a hybrid junction or a circulator. As shown in Fig. 2, two diodes R are arranged in two of the arms of a 3 db. directional coupler. At low input power levels the diodes effectively short-circuit the arms and power from input A is reflected to the output D. At higher values, the diodes have an impedance equal to that of the arms and the input power is absorbed. Where a hybrid ring or hybrid-T is used, it is necessary to insert a quarter-wave section between one of the diodes and the junction. The circuit of Fig. 5 uses a 3-arm circulator, the impedance of diode R determining the amount of power coupled from input arm A to output arm C. If a 4-arm circulator is used, the remaining arm is terminated in its characteristic impedance.