© The Institution of Engineering and Technology
In this Letter, a new design scheme for wideband balun bandpass filter (BPF) is presented originating from the conventional Marchand-type balun prototype. The designed balun BPF is basically composed of three microstrip lines on the top side of the substrate and two half-wavelength slotline resonators etched in the ground plane. A distinctive wideband performance is attained by utilising the broadside coupling between these microstrip lines and slotline resonators. For demonstration, one fabricated prototype balun BPF operating at 3.75 GHz shows a broad bandwidth of 93% with nice in-band balanced performance. Final results from simulation and experiment are both recorded in good agreement.
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