Design Of Wide Band Bandpass Filters Using Substrate Integrated Waveguide Technology

Substrate integrated waveguide (SIW) is a device which integrates thetraditional media filled rectangular waveguide in dielectric substrate. It has thesimilar transmission characteristics with metal rectangular waveguide. So SIW hasthe advantages of metal rectangular waveguide, such as low radiation, low insertionloss and so on, besides SIW has low profile, and it is easy to integrate and process.Therefore SIW is widely used in modern wireless communication system. Design ofwide band bandpass filters using substrate integrated waveguide technology hasbecome a hot research topic.The working frequency of common substrate integrated waveguide bandpassfilter is usually very high, and its bandwidth is very narrow, which restrict itsdevelopment in mobile communication system. Three kinds of wide band bandpasssubstrate integrated waveguide filters with different defected ground structures areproposed in this thesis, and their working frequencies all cover1.8~2.6GHz withrelative bandwidth above36.4%. On this basis, two kinds of half mode substrateintegrated waveguide filters with different defected ground structures are designed.Under the same design index, size of half mode substrate integrated waveguide ishalf of full mode substrate integrated waveguide, thus the characteristic of goodminiaturization is realized. At the same time, according to the correspondingrelationship between waveguide slot and impedance (admittance) components, andthe dual relationship between symmetric oscillator and magnetic fluid, theequivalent lumped circuit model of substrate integrated waveguide filter withdefected ground structure loaded is proposed, which well explains the bandpasscharacteristic of the filter, and the reason why the filter`s size is large. In order tofurther reduce the size, a kind of evanescent mode substrate integrated waveguidebandpass filter with rectangular metal blocks loaded is proposed, and this bandpassfilter can also work in the frequency range of1.8-2.6GHz. According to theequivalent relationship between substrate integrated waveguide and transmissionline, the equivalent lumped circuit model of evanescent mode substrate integratedwaveguide bandpass filter with rectangular metal blocks loaded is finally deduced,and it explains the wideband bandpass characteristic of the filter.In this thesis, all the simulation work is implemented by CST MicrowaveStudio electromagnetic simulation software. According to the simulation results,the corresponding substrate integrated waveguide filters are fabricated. Theirreflection coefficient and transmission coefficient are test by Anritsu37247D vectornetwork analyzer, and the experimental results match well with the simulation ones,which proves the correctness of the design idea. The proposed filters all can be applied to the fourth generation mobile communication system.