Research On Compact Microwave Filters And Antennas As Well As Their Memristor-based Characteristics

With the ever-increasing rapid development and stringent requirement of the wireless communication systems, the research on compact broadband/multi-band microwave filters and antennas has become an important and hot topic in the area of electromagnetics recently. Combining research projects and practical engineering requirement, this dissertation has explored some new high-performance structures and technique, and proposed a series of compact planar filters and antennas based on microstrip resonators. Moreover, the memristor, as the fourth fundamental passive electrical element, has been studied through theoretical analysis and SPICE modeling. Also, the characteristics of the memristor-based microwave devices have been studied deeply. The whole dissertation is summarized as follows:Firstly, based on the stub-loaded half-wavelength open-loop resonators and one-wavelength ring resonators, a series of new resonators and new coupling types were proposed to achieve the design of the compact high-performance filters. Starting from the study on stub-loaded half-wavelength open-loop resonators, in Chapter II, dual- and tri-band bandpass filters(BPFs) were designed where the odd-mode and even-mode of the short stub-loaded dual-mode resonator(SSLDMR) were utilized to generate only one passband. In addition, the circular stub-loaded dual-mode resonator, circular stub-loaded tri-mode resonator, short stub-loaded stepped-impedance resonator(SSL-SIR), pie-section truncated semi-circle/quarter-circle resonator, and stub-loaded composite right/left-handed(SL-CRLH) resonator were proposed to apply in the design of the filters. In the terms of feed lines, a new coupling type with both capacitive and inductive source-load(S-L) coupling was presented for the first time and applied in the filters to obtain multiple transmission zeros and good harmonic suppression.Secondly, studying on one-wavelength ring resonators in Chapter III, a planar improved dual-mode ring resonator loaded by four mushroom-shaped stubs using a simple feed scheme was presented for design of dual- and tri-band BPFs. Then, based on some design methods of tri-mode filters in the literature, two new microstrip tri-mode modified ring resonators were presented to design a radial stub-loaded tri-mode filter and a center-frequency-fixed tri-mode filter. The characteristic difference between these two filters is that the center frequency of the latter one is still the same as that of traditional dual-mode ring resonator filter, which greatly facilitates the design of tri-mode filter. Moreover, a quad-T-stub-loaded ring resonator was proposed and applied in a compact ultra-wideband(UWB) BPF. Also, notch-band UWB BPFs using interdigital-coupled feed-line structures were presented. The proposed interdigital lines are used not only to realize strong coupling as feed lines, but also create an adjustable rejection band in the UWB passband without adding any other circuits, which make the overall size of the filter super miniaturized.Thirdly, a quad-T-shaped stub-loaded ring-resonator(SLRR) slot etched on the ground plane or on the radiating patch was theoretically analyzed, and its physical and electrical parameters were extracted in the required resonant frequencies. To validate the design concept, a tri-band printed antenna and a dual band-notched ultra-wideband(UWB) antenna using the SLRR-slot on the ground plane and radiating patch, respectively, were presented. The experimental results including reflection coefficients, peak gains, radiation patterns, and efficiencies of both antennas were measured.Fourthly, a mathematical model of the memristor and three features to determine if a device may be properly categorized as a memristor were briefly introduced. Then, a current-controlled memristive macro-model and a voltage-controlled memristive macro-model using SPICE were proposed to capture the double-loop hysteresis behaviors. Moreover, according to memristor’s mathematical modeling equations presented by Hewlett-Packard Lab, two simple memristor SPICE models were proposed in order to explore the unique characteristics and applications of the memristor in microwave devices. A reconfigurable microstrip bandpass filter based on a memristor was realized, and a memristor as a carrier-wave modulator was used into the microstrip patch antenna for signal modulation and its characteristics were analyzed.Finally, the research of the whole dissertation was summarized, and future work was suggested.