A reflectometer and power-ratio technique for the measurement of low values of waveguide attenuation

The device under test, which is terminated in a sliding short-circuit, is connected to the measurement plane of a tuned waveguide reflectometer and dc voltages, proportional to the incident and reflected power levels, are balanced, for various short positions, to yield the dissipative component of attenuation. Provision of a switched reference arm in the reflectometer enables the effects of thermal and mechanical changes to the apparatus during a measurement to be minimized. Remaining sources of error are due to power meter zero offset, power meter linearity and mismatch. 99.7-percent confidence levels for a component with a mean total attenuation of 0.1290 dB, at 7.3 GHz, are ±0.0014 dB; the maximum deviation, of the five results, from the mean is 0.0002 dB.