| With the rapid development of wireless communication technology and integrated circuit,the modern electronic systems not only have high performance but also get the tendency of highly integration,miniaturization,multi-band/multi-mode,multifunction,low cost,etc.As the key parts of microwave and millimeter-wave circuit and systems,the high performance and miniaturized passive components play an important role for the whole systems realizing highly integration,and has become the popular and difficult problems in the research area of passive components.In this dissertation,the applications of substrate integrated waveguide(SIW)and liquid crystal(LC)material technologies in the design of miniaturization microwave and millimeter-wave passive components are systematically researched,and a series of miniaturization,frequency tunable passive components such as bandpass filters and power dividers are implemented.The main research works and innovation achievements in this dissertation are summarized as follows:1.Design of compact SIW and half mode substrate integrated waveguide(HMSIW)passive components based on novel defected ground structure(DGS)Novel DGSs have been proposed in order to reduce the sizes of SIW and HMSIW passive components.Firstly,a novel SIW-DGS unit structure is built by using a pair of U-shaped slot nested with a pair of E-shaped slot.Compared to the traditional dumbbell DGS,this DGS effectively enlarges its equivalent inductance and equivalent capacitance,and has better sideband selectivity and wide stopband suppression performances.Furthermore,by using the size reduction feature of HMSIW and folded improvement for the ends of the U-shaped slots,a novel HMSIW-DGS unit structure with high sideband selectivity is built.Then,combining the high-pass characteristic of SIW/HMSIW and the low-pass characteristic of DGS,a wide stopband SIW bandpass filter and a high selectivity HMSIW bandpass filter are realized.Owing to the slow-wave effect produced by DGS can reduce the longitudinal transmission length of SIW/HMSIW,the designed filters have compact circuit sizes.Finally,making use of the multimode resonant characteristic produced by the HMSIW structure loaded with U-shaped slots,a compact wideband power divider with filtering function is designed,which has 80% size reduction compared with traditional HMSIW resonator power divider.2.Design of high frequency selectivity and compact millimeter-wave filters based on substrate integrated folded waveguide(SIFW)A novel controllable mixed electric and magnetic coupling structure with the SIFW technology has been proposed,and it has been applied to high frequency selectivity and compact millimeter-wave filters design.This novel structure is built by a meandered slot-line(MSL)combined with an inductive via-hole in a SIFW cavity.Owing to the disturbance of the MSL etched on the middle metal septum in the SIFW cavity,two closely-spaced resonator modes can be obtained,and then a more compact two poles filter can be designed using only one SIFW cavity in place of two.Meanwhile,between the two closely-spaced resonator modes,the MSL can create the electric coupling and the inductive window formed by the inductive via-hole can create the magnetic coupling.Therefore,the proposed SIFW structure achieves a mixed electric and magnetic coupling.Moreover,by adjusting the length of the MSL and the width of the inductive window,the electric and magnetic coupling can be separately controlled and a controllable transmission zero(TZ)can be produced below or above the passband.Based on the proposed SIFW mixed coupling structure,a number of high frequency selectivity and compact filters have been implemented at Ka-band.Compared to traditional SIW resonator filters,utilizing the proposed SIFW mixed coupling structure can contribute to size reduction over 50%.3.Design of compact LC tunable passive components based on inverted-microstrip structuresBased on the electric controllable dielectric anisotropy of LC material,a design method of compact LC tunable passive components with dual-mode inverted-microstrip resonant structures has been proposed.The LC material is packaged in the inner of multilayer substrates,and the size reduction of whole components and the amount decreasing of LC material can be realized by using the dual-mode inverted-microstrip resonators.Consequently,the tunable characteristics of the circuit can be achieved by using the electric controllable permittivity of the LC material.On the basis of the proposed method,a compact LC tunable filter with dual-mode inverted-microstrip square loop resonator and a compact LC tunable filtering power divider with dual-mode inverted-microstrip open loop resonator have been implemented.The experimental results indicate that the LC tunable filter and power divider have central frequency tuning range of 500 MHz and 520 MHz,respectively,and the circuit size reduce about 65% compared to utilizing ordinary resonance unit.4.Design of compact LC tunable filters based on SIW and substrate integrated coaxial line(SICL)The design technology of compact LC tunable filters based on SIW and SICL cavity resonators has been proposed.Firstly,a electrical biasing scheme is constructed to solve the inherent short-circuit characteristic of LC-based SIW resonator,which is realized by encapsulating LC material within the SIW cavity combined with the patch electrode embedded in the SIW cavity.Then,a three-order SIW tunable bandpass filter with electrical biasing is developed,which verifies the application feasibility of the use of LC material in planar SIW tunable filters.Furthermore,to overcome the large size shortcoming of SIW structure applying in microwave frequency band,a half wavelength LC-based SICL tunable cavity resonator is built and it has been applied to compact LC tunable filters design.Owing to the miniaturization property of SICL structure,the LC-based SICL tunable filters have over 55% sizes reduction compared with the LC-based SIW tunable filter,and have good transmission response and sideband selectivity. |
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