Design of evanescent mode band-pass filters based on groove gap waveguide technology

This paper proposes for the first time a design method of Chebyshev band-pass filters based on groove gap waveguide (GGW) technology and evanescent mode. The evanescent mode GGW section has been implemented by decreasing the width of the groove area by means of two additional rows of metallic pins, and the filter structure has been obtained by inserting resonators of metallic pins along the central part of this narrower GGW section according to a coupling matrix synthesis method. The proposed method has allowed reducing the analysis number of this band-pass filter during the design process and the computation cost with the electromagnetic (EM) simulator, solving the discretization problem of the different lengths of the evanescent mode section. This design technique has been applied to a fourth-order Chebyshev band-pass GGW filter. The design has been performed in the recommended band of the WR75 standard (10 GHz - 15 GHz). The design specifications have been a central frequency f0 = 12 GHz, a fractional bandwidth FBW = 2.5 % and return loss RL = 20 dB. Measurement and electromagnetic (EM) simulation results have shown a good agreement. Return and insertion losses in the pass-band region of the measured prototype have been, respectively, RL = 20 dB and IL = 0.3 dB, while maximum attenuation in the stop-band regions reached ASB = 83 dB. A comparison has been performed between the measured prototype and other GGW band-pass filters. The proposed GGW band-pass filter has been shown to have reduced size and high-performance characteristics. Future emerging communications systems could benefit from this evanescent mode GGW Chebyshev band-pass filter.