Broadband Slotline-to-Rectangular Waveguide Transition Using a Truncated Bow-Tie Antenna

In this paper, we propose a broadband slotline-to-rectangular waveguide transition using a truncated bow-tie antenna. Our design yields a single transition that has a 37% fractional bandwidth for which the return loss is larger than 20 dB, almost covering the whole X-band (8.2-12.4 GHz). Furthermore, in order to miniaturize the proposed transition, a stepped-impedance resonator (SIR) is used in the placement of the quarter-wavelength section in the transition. The resulting slotline-to-rectangular waveguide transition using the SIR not only greatly reduces 17% of physical size but also maintains the broadband performance, which possesses a 36.57% fractional bandwidth of 20-dB return loss. In order to verify these simulation results, back-to-back structures for both transitions are fabricated and measured where the measurement results are in good agreement with the simulation results.