Miniaturized Slotted Bandpass Filter Design Using a Ridged Half-Mode Substrate Integrated Waveguide

This letter demonstrates significant miniaturization of slotted half-mode substrate integrated waveguide filters by incorporating a capacitive ridge. Based on this concept, two-pole and four-pole slotted bandpass filters are designed, fabricated and measured. Simulations are carried out using HFSS, and the prototypes are fabricated using a multi-layer printed circuit board process. The filters operate at 5.1 and 5.5 GHz and have a total width as small as 5.2 mm. The measured S-parameters of the slotted filters illustrate insertion loss of 0.8 dB and stopbands larger than 8 GHz. Compared to previously reported slotted half-mode substrate integrated waveguide filters, the proposed structure has a smaller footprint, lower insertion loss, and a larger stopband all at once.