A Design Of Ka-band Band Pass Filter Based On Gap Waveguide

A new kind of transmission structure, called ridge gap waveguide(RGW), is promoted in 2009 for the first time. RGW is created upon the surface of a metal parallel-plate waveguide, with electromagnetic band gap(EBG) structure all around the metal ridge. When the gap between the upper metal plate and EBG upper surface is less than λ/4, because of the frequency band gap of the EBG structure, the propagation is forbidden in any direction, except in the gap between the upper plate and the transmission structure, where only a quasi-TEM mode is allowed to propagate in a relatively wide frequency band. Later, the groove gap waveguide is put forward, the only difference is that a groove takes the place of ridge structure. This new type of transmission structure restrains the dispersion mode but also makes the electromagnetic wave travels only in the air, so it can decrease the loss to a great deal, when compared to microwave strips. Besides, easy manufacturing is its another advantage. Moreover, when it comes to integrating with other components, the new structure needs no extra shielding cover or isolating parts, nor share we worry about the potential resonance effect, which maybe the case of a microwave strip. Therefore, the new structure can easily find its wide application upon millimeter wave or the higher frequency band.This paper mainly deals with analyzing the parameters of the mushroom-like and bed-of-nails EBG structures in details, and the influence of various parameters on the band gap frequency and bandwidth. Two different kinds of narrow band pass filter working in Ka-band with high out-of-band rejection based on groove gap waveguide techniques are researched and designed. Details are as follows:1. Two methods of calculating the frequency band gap, called waveguide transmission method and the dispersion pattern method, are introduced and studied. And the advantages and disadvantages of the two methods are analyzed. Waveguide transmission method is less demanding on computer performance, uses short simulation time, saves resources and improves the efficiency at the beginning. Dispersive mode method is relatively simple on modeling, gets accurate results, draws precise dispersion curve and can analyze any two-dimensional periodic structure.2. Parametric analysis on mushroom-like EBG structure is given. By increasing the length of patches, the period of units, the dielectric constant, the thickness of dielectric, and the radius of metallized vias, respectively, changes in the center frequency of the band gap, the band gap range and relative bandwidth are got.3. Parametric analysis on bed-of-nails EBG structure is done. By increasing the length of nails, the height of nails, the period of units and the thickness of air layer, respectively, changes in the center frequency of the band gap, the band gap range and relative bandwidth are summarized.4. Two types of Ka-band narrow band pass filter, based on gap waveguide technology are researched and designed. Simulated and optimized by Ansys HFSS, 3-order and 5-order filter are designed, and the simulated results are followed.5. In this paper, a new type of Ka-band narrow band pass filter, based on dielectric loaded gap waveguide technology, is presented and designed for the first time. Simulated and optimized by Ansys HFSS, the dielectric loaded filter is fabricated and measured, and the simulated and measured results are followed in the paper.