Recent Improvements to the UK National Microwave Attenuation Standards

The equipments that have been used in the United Kingdom throughout the last decade for the highest echelon microwave attenuation measurements are approaching obsolescence. To modernize them, two microwave synthesized sources have recently been purchased, and this paper describes five different configurations that have been developed for use with them, namely, a) 0.05-18-GHz parallel 50-kHz substitution system, containing an inductive voltage divider as the reference standard; b) a very low drift series 50-kHz substitution system; c) a series substitution system, employing coherent detection, which has a dynamic range of 150 dB; d) a 0.05-18 GHz-voltage ratio system for the automatic calibration of programmable attenuators; e) a very stable microwave bridge for the precise measurement of waveguide wall loss.