Novel rotary vane attenuator and variable directional coupler including methods for their precision calibration

Two new 4-port precision waveguide components are proposed. Both consist of a rotary part connected between two stationary orthomode transducers. In the attenuator version the rotary part is identical with the rotary part of the conventional rotary vane attenuator. In the directional-coupler version the rotary part is a 180¿¿ differential-phase-shift section. The coupling factor of the directional coupler can be continuously varied from ¿¿ 1 to + 1 and it is assumed that the directivity can be kept better than 30 dB over most of the coupling range and over a 20% bandwidth. In both cases it is swhown that the errors in the wanted transmission factors can be calculated from in situ measurements of much more easily measurable reflection and transmission factors. It seems likely that all the systematic errors athat are due to nonideal parts can be essentially corrected for. The only remaining errors are mechanical errors and errors due to higher modes which can be reduced arbitrarily. Fitted with external matched loads the rotary directional coupler may find application as a continuously variable precision attenuator for high continuous were power. Finally by combining the rotary directional coupler witha rotary phase shifter, essentially any complex coupling factor within the unit circle can be established.