Design and Implementation of a Broadband Substrate Integrated Waveguide Magic-T

In this letter, a novel broadband magic-T using a stripline embedded hybrid substrate integrated waveguide (SIW) structure is proposed. A tapered transition is used to transform the TEM mode of the stripline to the waveguide modes of the vertically stacked SIWs. Due to the vertical symmetry of the structure, the input signal of the stripline can be naturally split into two equal and in-phase signals at the output ports on the top and bottom layers. An E-plane SIW power divider is utilized to realize the E-plane input/output port of the magic-T. Due to the wide bandwidth of the stripline-to-SIW transition, a significant bandwidth improvement with respect to conventional SIW magic-Ts is achieved. Measured results show that, the proposed magic-T has a fractional bandwidth of 49.1% (8.28-13.68 GHz) with return loss better than 15 dB, and the amplitude and phase imbalances are less than 0.24 dB and 3 degrees, respectively.