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 TE
₂₀
mode field of rectangular waveguide to generate two out-of-phase TE
₁₀
modes in the outputs. Purity of TE
₂₀
mode 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 TE
₁₀
to TE
₂₀
as a figure of merit (F.O.M). To improve the performance of design, here a filtering section with good rejection for TE
₁₀
mode and low insertion loss for TE
₂₀
mode 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.