Investigations On Substrate Integrated Waveguide, Defected Ground Structure, And Their Applications For Filter Design

With the rapid development of electronic information systems to multifunction, miniaturization, and low cost, etc., there are more and more urgent demands on high-performance miniaturized microwave passive components for system on package (SoP) technology. Thus, it is necessary to develop new integration techniques for microwave passives in SoP with high performance, high integration density, good compatibility, low loss, and high power handling capability. For such a purpose, this dissertation investigates two new techniques of modified substrate integrated waveguide (SIW) and defected ground structure (DGS) systematically. Their theoretical models are analyzed, and various bandpass filters, phase shifter, and other passive components are developed based on them both with good performances and compact configurations.The main academic contributions of this dissertation are as follows.(1) An accurate, fast and efficient method is established to evaluate the average power handling capabilities of half- and quarter-wavelength stepped impedance microstrip filters, which is based on the coupled resonator circuit model of bandpass filter, the temperature rise model of microstrip line, and the transmission line theory for heat conduction. The proposed method can be used for the synthesis and optimization of microstrip filters together with their power handling consideration.(2) A novel type of bandpass filter are developed with quarter-folded SIW cavities, whose occupied areas are only 1/8 that of conventional SIW cavity-coupled filters. It is also found that there is no obvious hot spot inside the component, and its average power handling capability is much better than that of other planar structures.(3) A type of multilayer partial H-plane filter using folded SIW and evanescent coupling is proposed, with its performance not sensitive to the fabrication tolerance. Further, a new type of evanescent-mode SIW bandpass filters is investigated thoroughly. Its area is only about 1/10 that of the conventional SIW filters, and its spurious suppression characteristics is very attractive. It should be pointed out that cross coupling can also be introduced to improve the frequency features of evanescent-mode filters. To achieve large fractional bandwidth, a special SIW bandpass filter operating on the cutoff frequency of the waveguide is designed.(4) A bandpass filter is designed using the SIW cavity loaded with a dielectric rod. Compared with conventional SIW filters, it has the advantages of compactness, low insertion loss, and good harmonic suppression characteristics by using the tentative fabrication technique of loading high-quality dielectric rods into PCB, which has been indicated theoretically and experimentally.(5) The modal dispersion behavior of various periodically loaded half-mode SIWs are studied in detail by mathematical treatments and experiments. To further demonstrate their applications, an electrically tunable phase shifter is developed using a varactor-loaded structure, and two bandpass filters are also realized with the electromagnetic bandgap (EBG)-loaded waveguide. Then, by migrating the half-mode concept into T-septum SIWs, the first published ultra-wideband SIW filter is implemented, to the best of our knowledge.(6) The coupled resonator circuit model is proposed for a transmission line loaded with a DGS unit. And a continuous vector fitting method is developed for extracting the accurate model of DGSs. To achieve dual-bandgap characteristics, a dual-planar compact DGS circuit is built up and then applied to design a lowpass filter with sharp slope side. Further, we use the complementary split ring resonator (CSRR), a special DGS unit, to form a novel dual-mode zeroth-order ring bandpass filter, where the occupied area is reduced obviously, with its spurious suppression performance also improved.(7) An"extended doublet"bandpass filter is made up using an SIW cavity and a CSRR etched on its top metal plane with the merits of compact structure, easy fabrication, and good performances. The presented component is an example for hybrid integration of both SIW and DGS techniques to utilize the geometrical and behavioral complementarities between them. This is a successful case to develop high-performance miniaturized microwave passives in SoP.For the researches listed above, a number of different samples are designed and fabricated, with PCB or low temperature co-fire ceramic (LTCC) technologies adopted. The validity and efficiency of our investigations have been demonstrated by the good agreements between the measured, simulated and modeled results.