Design Of Miniaturized Filter Based On Slow Wave Substrate Waveguide

Rapid development of the modern wireless communication systems has imposed an everincreasing demand for high-performance,low-cost,easy integrated compact devices.Microwave filters are indispensable components in communication systems,the performance of microwave filters is very important to the overall operation of the communication system Therefore,the design of miniaturized microwave filter with high performance,low cost and high integration has become the current research hotspot.Substrate waveguide transmission line fabricated on the printed circuit board(PCB),such as substrate integrated waveguide(SIW)and substrate integrated groove gap waveguide(SIGGW),are widely adopted in the design of microwave filter due its advantages of high Q-factor,low losses,high power capacity,low cost and high integration.Compared with SIW,SIGGW can effectively avoid energy leakage caused by possible poor electric contacts due its contactless and self-packaging characteristics.It's convenient to design microwave components,especially stacked BPF composed of multi-layer dielectric substrates.However,the drawback of these filters based on the above two substrate waveguides is that the dimension is bulky,limiting its values in future much more compact device platform.Thus,it is of great significance to study the miniaturization of substrate waveguide filters.Based on the design of miniaturized substrate integrated waveguide filters,the following works are carried out in this paper:Firstly,a dual-mode resonator and a series of filters with miniaturized dimension and controllable transmission zeros are presented based on the slow-wave substrate integrated waveguide(SW-SIW).Compared with normal SIW,the SW-SIW has shorter guided wavelength,providing convenience to realize miniaturized resonator and filters.Based on the SW-SIW,a dual-mode SW-SIW resonator is proposed.The dual-mode resonator realized by two stacked substrates consists of a SW-SIW cavity and a grounded central circular patch inside.Two cavity modes of TE102 mode and TE103 mode can be simultaneously excited in the SW-SIW cavity.By changing the diameter of the central circular patch,the resonant frequency of TE103 mode can be adjusted,even lower than the TE102 mode.Two cavity modes of TE102 mode and TE103 mode are coupled to the source and load using the Doublet scheme,thus,a transmission zero is generated.Two second-order SW-SIW filters with the TZs either below or above the passband are designed,proving the transmission zero can be controlled flexibly.Finally,a fourth-order filter with transmission zeros on both sides of the passband realized by cascading the two second-order SW-SIW filters is simulated.Compared with the normal fourth-order SIW filter,the proposed SW-SIW filter achieves 75% area reduction and shows advantages of compactness.Secondly,an ultra-compact stacked band-pass filter(BPF)realized by a novel slow-wave substrate integrated groove gap waveguide(SW-SIGGW)is presented.A SW-SIGGW is designed firstly.Compared with SIGGW without slow wave structure,the cut-off frequency and guided wavelength of the designed SW-SIGGW are reduced by 51.6% and 52.8%respectively,A dual-band resonator and a cascaded second-order SW-SIGGW BPF are designed based on the proposed SW-SIGGW transmission line.Compared with the conventional second-order SIGGW BPF,the SW-SIGGW BPF achieves 62.6% area reduction.By adopting vertical stacking technology,the area of the SW-SIGGW BPF is further miniaturized.The final area of the stacked SW-SIGGW BPF is only 18.7% of the conventional SIGGW BPF.The stacked SW-SIGGW BPF obtains 5.4% and 7.4% fractional bandwidth at11.8GHz and 18 GHz.Finally,the stacked SW-SIGGW BPF is fabricated and measured,good agreement between the measured and simulated results verifies the validity of the proposed design.