Microstrip coupler suitable for use as a 6-port reflectometer

Abstract

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.

Six‐port reflectometer based on four 0°/180° microstrip ring couplers

“…The purpose of the calibration is to calculate these unknowns (calibration constants). By using three positions of a sliding short circuit with a matched load (calibration procedure [4,11]), the above unknowns are obtained.…”

“…2), and the solution is given by the (ideally) common intersection of the three circles derived from the measured data [1]. There are different methods to implement the six-port reflectometer, such as using two directional couplers and two voltage probes [2], and using three-coupled lines (coaxial lines, stripline, waveguide, or microstrip lines) [3,4]. Another way is by using a five-port junction (ring or disc) and a directional coupler [5].…”