Ultra-wideband Planar Magic-T using Interlayer Coupling 3 dB Directional Coupler and Branch-loaded Phase Shifter

In this paper, we propose an ultra-wideband magic-T operating in the frequency band from 1.2 to 4 GHz with a relative bandwidth of 108%, which is based on an interlayer coupling 3 dB directional coupler and a branch-loaded 90∘ phase shifter. Compared to traditional magic-T structures, it can operate within an ultra-wideband range and has the advantages of a simple structure and easy processing. Simulation and experimental results demonstrate excellent amplitude and phase stability. When the input is at the sum port, the phase error at each output port is less than 2.8∘. For the difference port input, the phase error at each output port is less than 7.6∘. Furthermore, the overall amplitude imbalance is less than 2.1 dB, the transmission coefficient is below −7.4 dB, and the isolation is greater than 11 dB. It can be used in ultra-wideband phased array systems to generate sum-and-difference beams for direction finding.