A 3-D Printed X-Band Waveguide Folded Filter

This paper presents an X-band bandpass filter that utilizes folded rectangular waveguide resonators. The folded resonator is derived from a conventional rectangular waveguide resonator, in which the two ends are folded 90 degrees upward or downward, along the direction of the electric fields propagating. The adjacent resonators are connected through an inductive iris at their folded ends, resulting in a more compact configuration of the entire filter. Compared to conventional rectangular waveguide bandpass filters, the proposed filter has a smaller footprint and wider stopband. A 4th-order filter prototype with a targeted central frequency of 10 GHz, a fraction bandwidth of 3%, and a return loss of 20 dB is proposed, simulated, and manufactured using 3-D printing technology. Measurements show excellent agreement with simulations.