Small-size ring coupler design method based on fully distributed composite right/left-handed approach

A new method to design a small-size ring coupler is proposed, showing that the coupler may be seen as consisting of fully distributed composite right/left-handed phase shifters. A 3 dB ring coupler is designed by using the proposed method. The coupler is analysed numerically and then experimentally characterised. It is shown that the experimental results are in very good agreement with the expected ones. For the designed and fabricated coupler, the area reduction is about 50 , compared to the conventional ring coupler.