Planar Magic-Tee Using Substrate Integrated Waveguide Based on Mode-Conversion Technique

In this letter we present a planar magic-tee using mode-conversion technique. The device is fabricated using substrate integrated waveguide (SIW) technology. Using the presented design approach, it is possible to develop a planar magic tee without the need for multi-variable optimization. In this letter we use intrinsic odd symmetry of TE20mode field of rectangular waveguide to generate two out-of-phase TE10modes in the outputs. Purity of TE20mode in the waveguide guarantees low phase and amplitude imbalance of output signals. To investigate phase and amplitude imbalance of output signals, we define the ratio of residual TE10to TE20as a figure of merit (F.O.M). To improve the performance of design, here a filtering section with good rejection for TE10mode and low insertion loss for TE20mode is used to improve performance. Finally, measured data are presented for the fabricated prototype, which shows less than 1° phase imbalance and operation bandwidth between 10.75 to 11.4 GHz.