GB1439747A - Switchable multi-stage electrical attenuator devices - Google Patents

Abstract

1439747 Electrical switching device; electric component assemblies SOLARTRON ELECTRONIC GROUP Ltd 12 June 1973 [13 June 1972] 27574/72 Headings H1N and H1R [Also in Division H3] A switchable multistage electric attenuator device has microswitches located on the one side of a common metal earth sheet with their terminals passing through holes in the sheet and has stripline interconnections and attenuator cells located on the other side. The microswitches are of conventional design with retractive changeover contacts and are series connected for operative switching between a direct channel and an attenuation channel, Fig. 1, and each attenuator cell, Fig. 5, comprises a ceramic thick film chip 80 in which three resistors 81, 82, 83 form a # network anchored by earth-end connection tabs 92, 93 of a sheet metal holder screwed to the aforementioned other side of a U-shaped common earth sheet 50, Fig. 6, and which includes a capacitance spike 91 of suitable dimensions to compensate for the inherent inductance of the cell. The microswitches mounted on the one side of the earth sheet 50 are housed in pairs, Fig. 7, one switch of each pair belonging to adjacent stages, in cavities 111, 112 in a cast block 101 formed by the dividing wall 109, the side closure plates 102, 103 and the earth sheet 50 the gaps in the cavities adjacent the sides of the switches being filled with plastics liners 121, 222 having integral locating pegs 131 ... 136, all the dimensions including that of the capacitance spike 91 being determined and maintained to ensure that all stages are physically similar and that, with suitable resistance values, each will approximate to part of a transmission line having the required overall characteristic impedance, usually 50 ohms at radio frequency. The two mioroswitches of each stage are jointly actuated by a solenoid 140 via a spring-biased plate 153 holding an adjusting screw 154 and all the solenoids are mounted on a common base plate 51. A T-configuration can be used for the attenuator cell in which case there would preferably be two capacitance spikes.