Low insertion loss 61 GHz narrow-band filter implemented with Groove Gap Waveguides

This paper presents a 61 GHz narrow-band filter, implemented with Groove Gap Waveguide (GGW) coupled resonators. This structure does not require metal contact on the side walls and, therefore, is very suitable for mm-wave applications. At these frequencies, the manufacturing process imperfections become important, and an appreciable response deterioration can be found using classical microwave waveguides, such as the rectangular waveguide. The presented filter is a 5 pole Chebyshev filter, having 2,5% relative bandwidth. An important novelty in this design is the integration of the coaxial feeding in the bottom metal piece, which allows even more manufacturing flexibility. The remarkable good results in terms of insertion losses (15 dB), and return losses (13 dB), of the fabricated prototype endorse this technology as a serious solution for the mm-wave band.