Microstrip coupler suitable for use as a 6-port reflectometer

The theory of a microstrip 6-port directional coupler suitable for use as a 6-port reflectometer for impedance measurements has been introduced by the authors in a previous paper. In the paper, the effect of dispersion, extra coupling beyond the uniformly coupled region and finite strip thickness on the coupler performance are discussed. The practical performance of an experimental coupler is compared with a theoretical prediction based on the information in an earlier paper by the authors and including the previously mentioned effects. The application of this coupler as a reflectometer is briefly described and practically tested at its centre frequency of 5 GHz.