Slow-Wave Groove Gap Waveguide Bandpass Filter

Gap waveguide (GW) is a promising technology for its advantages of self-package and easy assembly without the requirement of contact. In this paper, a miniaturized groove GW (GGW) called slow-wave GGW (SW-GGW) is presented for the first time. The slow-wave feature is implemented by introducing symmetrical capacitive quasi-periodic corrugations inside the GGW. To obtain more design and manufacturing flexibility, all the four walls of the SW-GGW are separated utilizing the gap waveguide technology. A six-order iris SW-GGW band-pass filter is designed, whose length is reduced to 57.1% of the conventional iris rectangular waveguide filter with the same response. The irises of the SW-GGW filter are located on the broad-side walls in half-height form. This configuration not only reduces the manufacturing complexity but also makes it possible to implement filter with different responses by simply replacing the broad-side walls. The measured fractional bandwidth (FBW) of the SWGGW filter is around 3.88% at 11.87 GHz with the return loss better than 18 dB and minimum insertion loss of 0.5 dB.