Research On High Performance SIW Microwave Filter

With the development of the communication technology, demand of the high speedwireless mobile communication becomes more and more intense, and the spectrumresource is shortage increasingly. The filter, as the key device of band allocation andchannel isolation, is supposed to with stringent selectivity, low insertion, and potentialintegration into the circuit for high frequency and wide band application. Substrateintegrated waveguide (SIW) filter provides a low-cost, low-weight, easy for highfrequency and wide band application, simple fabrication with the PCB<CC andpossible integration scheme while maintaining high performance, which is satisfied withthe needs perfectly. But the discontinuities in the post wall of the SIW lead to poorstopband attenuation of SIW filter; the filter's I/O setting is limited by the rectangularwaveguide; substrate dissipation causes a loss in the SIW resonator Q value, higher thefrequency, lower the Q value, the Q descending make the filter selectivity to deteriorate;moreover, the position tolerance of plated via-holes is usually several times thetolerance of trace sizes in PCB or LTCC, the fabrication tolerance directly influencefilter designing, optimizing and final performance. These disadvantages limit theapplication of substrate integrated waveguide greatly.With the purpose of promoting SIW filters application in the wirelesscommunication, many improve SIW filter performance technology are studied in thisthesis. The main research works include as follows:1. Three popular I/O modes for SIW filter include microstrip, taper, slot couplingand their size sensitivity, and the dispersion characteristics of SIW are analyzed. Thetransmission characteristic of SIW and the size sensitivity features of the three I/Omodes are got. Furthermore, the broadband coupling resonant cavity filter synthesizetechnology is studied. The results can be used to facilitate the synthesizing of highperformance broadband coupling resonant cavity filter.2. The electromagnetic characteristics of substrate integrated circular waveguide(SICW) are presented in this thesis. In order to meet the needs of the system installationand integration, such as satellite communications and mobile equipment, based on the circular symmetry TM01mode in SICW, a high performance wideband filter the withflexibility I/O structure is designed. Additionally, the coupling structure of the dualmode in the SICW filter are researched also, and asymmetric responding filters withimprovement upper stopband performance are obtained.3. A method to improve filter upper stopband performance using bypass couplingsubstrate integrated circular cavity resonator (BC-SICCR) is presented. Using SICCR asthe bypass coupling resonator, its resonant frequency can be entirely controlled by theSICCR radius (when height is fixed) owing to theTM01mode is selected as only theoperating mode while the SICCR height h and the radius R meet with h/R <2.04. Dueto the operating mode is exclusivity in SICCR, this structure of the inverter with SICCRbrings the bypass coupling of the SICCR in the SIW is independent of frequency,transmission zeros can be set up at arbitrary place in filter stopband through theBC-SICCR. Besides, a technique of bypass cross coupling through higher/lower orderdual mode in one SIW to produce a transmission zero is presented, and it is verified bya oversized dual mode folded half mode SIW filter with bypass cross couplingtransmission zeros.4. The electromagnetic character of the elliptic substrate integrated waveguide isstudied. A novel half mode elliptic substrate integrated waveguide (HMESIW) filterwith a good performance in tolerance sensitivity is proposed and fabricated by usingstandard PCB technology. Due to the advantage of elliptical waveguide cavity, no modesplitting or rotation of the polarization plane at the condition of slight deformations incross section, the tolerance sensitivity of the filter sizes is reduced. The measured resultsdemonstrate the HMESIW filter has a superior performance in tolerance sensitivity.Through the above-mentioned researchs, the results can be boosted the design ofhigh performance SIW microwave filter.