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In this article, a class of wideband bandpass filters (BPFs) using triple-mode coaxial resonators has been introduced. Each triple-mode resonator is utilized with TM010 mode, TE- mode, and TE+ mode orthogonal to each other. Two L-shaped feeding probes and a loading disk are adopted to implement the miniaturization of these wideband BPFs. To observe the degree of miniaturization, we set a design specification of the same fractional bandwidth (FBW) of 40% at the same central frequency of 2.5 GHz. After employing the L-shaped feeding probes and loading disk, the efficient circuit size without cavity thickness is reduced by 80% compared with the triple-mode wideband filter without L-shaped feeding probes and loading disk. In contrast, the unloaded quality factors are slightly changed. In addition, another advantage of this work is that the upper stopband is extended to 2.5f-{0}. Three experimental wideband BPFs in the large, medium, and small sizes are designed, manufactured, and tested for demonstration. Good agreements are obtained between simulation and experiment.

In this paper, a 7th-order cavity filtering crossover with three intersecting channels is presented. Three fundamental modes in one cavity resonator, namely TE011, TE101, and TM110, are adopted to control three frequency channels, respectively. Each channel of proposed crossover resonates at 3 GHz with the fractional bandwidth of 24%. Due to the modal orthogonality of three fundamental modes, good isolation among channels can be easily achieved with the level of 50 dB. Finally, the proposed design can be extended into 3times 3times 3 crossover array.

Waveguide components have been widely explored for several decades, due to their inherent merits of low insertion losses, high quality (Q) factors, and a significant power-handling capacity. Historically, cavity-based narrowband filters and multiplexers have been explored and designed for base stations and satellite applications. Compared with using single-mode resonators (SMRs), the implementation of multiple-mode resonators (MMRs) in waveguide structures is a promising solution to dramatically reduce the circuit volume and improve the frequency selectivity. Taking advantage of MMR techniques, various innovative waveguide structures have been proposed for a wide range of application scenarios. This article presents an overview of advances in microwave multiple-mode waveguide components, including narrow-, wide-, and multiband filters; multiplexers; three-state diplexers; crossovers; and balanced/unbalanced elements. Representative examples and their results are comprehensively discussed and summarized.

In this article, a series of filtering cavity slot arrays using high-order modes are investigated. It is found that each unit of the cavity slot arrays in the proposed high-order mode resonator is in phase with the same amplitude, which helps enhance the antenna gain and reduce the sidelobe level. Meanwhile, the filtering function is integrated into the design for frequency selectivity and harmonic mode suppression. The higher order response can be achieved by cascading more high-order mode resonators with required external quality factor (Qₑ) and coupling coefficient (K). The fractional bandwidth (FBW) and out-of-band suppression of proposed designs are also discussed. For proof-of-concept, a single-band third-order 4 x 5 filtering cavity slot array using a TM₄₅₀ mode resonator and a dual-band dual-polarized third-order 4 x 3 filtering cavity slot array, using TM₄₃₀ and TM₃₄₀ mode resonators, are fabricated and tested. The good agreement between the simulated and measured results verifies that the proposed design methodology is feasible for designing high-order mode filtering cavity slot array antennas.

A broadband high-gain slot grid array antenna (SGAA) is proposed in this paper. Based on the electromagnetic complementarity principle, the metal elements in the traditional microstrip grid array antenna (GAA) are replaced by a wide slot element. Compared with the GAA, the proposed SGAA achieves broadband and high-gain performance. In order to demonstrate this concept, a prototype with 9-element SGAA is designed using wide slot radiation elements and fabricated on Rogers 5880 printed circuit board (PCB) substrates, which is fed by a 50 Ω coaxial probe. The measured and simulated results show a good agreement. The proposed SGAA achieves a measured peak gain of 14.8 dBi at 26.0 GHz, a 10-dB impedance bandwidth from 22.2 to 28.5 GHz with a fractional bandwidth of 24.9%. These results indicate that the SGAA is with high performance and it is suitable for the fifth-generation (5G) millimeter wave (mmW) wireless communication system.

© 1982-2012 IEEE. In this paper, a series of designs for cavity balanced and unbalanced diplexer are proposed. The balanced and unbalanced designs can be categorized into four groups - unbalanced-to-unbalanced, unbalanced-to-balanced, balanced-to-unbalanced (B2U), and balanced-to-balanced. First, two approaches to achieve out-of-phase characteristics of three fundamental modes, namely TE011, TE101, and TM110 in a single triple-mode resonator, are proposed for balun filter designs. Second, four types of unbalanced and balanced diplexers are presented by adopting these three fundamental modes, of which the Butterworth response applies with specific external quality and coupling coefficient. To the authors' best knowledge, full-metal cavity balun diplexer and balanced diplexer are not reported in the open literature. For proof of concept, the design of a B2U diplexer is fabricated and measured. Good matching between simulated and measured results shows the accuracy of the proposed design and methodology, which would be attractive in the high-power radio frequency (RF) front-end systems.

© 2019 Wiley Periodicals, Inc. A novel band-stop filter (BSF) using coaxial-fed slotted substrate integrated waveguide (SIW) is proposed in this article. The proposed BSF is designed using coaxial-fed line with extended probes penetrating through the substrate and connecting each other, instead of using the main transmission line to dispose the resonators. The SIW cavities perform the resonators excited by the probes to produce a stopband. Then, two BSFs with one and two SIW cavities are firstly designed, both of them have SIW cavity resonator modes and lower-band reflection zeroes. Then, two types of third-order BSFs using two cavity resonators and one slot resonator are presented, the high selectivity is achieved by the RZs at both sides of the stopband. Finally, one of the proposed third-order BSFs is fabricated and measured to verify the design method.

© 2013 IEEE. In this paper, a novel design of frequency-selective surface (FSS) based on coupled stubs-loaded ring resonators (SLRRs) is proposed. The proposed FSS exhibits quasi-elliptic bandpass filtering characteristic at C-band. And each unit cell of the structure is composed of two SLRRs coupled by a circular aperture. A novel method of transmission line (TL) model is proposed to investigate the operating principle of a single SLRR under normal incidence plane wave. Moreover, the operating mechanism of the proposed FSS is further researched with the aid of the equivalent circuit model (ECM) analysis method. Due to the symmetric and low-profile physical structure, the FSS keeps stable frequency response under oblique incident plane wave for both transverse electric (TE) and transverse magnetic (TM) polarizations. Finally, the designed FSS is fabricated and measured. The measured results agree well with the simulated results. The measured results indicate that the proposed FSS exhibits a dual-polarized and stable bandpass frequency response with two transmission zeros (TZs) at around 5.71 and 6.87 GHz under different incident angles up to 40°.

© 2019 The Institution of Engineering and Technology. A class of triple-band and triplex cavity-backed slot antenna is proposed by using three fundamental modes in a single metal cavity: TE011, TE101, and TM110 modes, simultaneously. These three resonant modes can be excited by changing the position of the feeding slot without any extra components configured inside the cavity. By opening a single radiation slot, a single band triple-mode cavity-backed slot antenna is achieved. By opening three slots at three side walls of the cavity, a triple-band cavity-backed slot antenna is realised with three different radiation directions at three different operation frequencies. Moreover, a triplex triple-band antenna can be formed by combining a single slot antenna and three input ports in the proposed rectangular cavity. Finally, a triple-band multi-directional cavity-backed slot antenna prototype and a triplex triple-band cavity-backed single slot antenna prototype are fabricated and tested. The tested results are in good agreement with the simulated results, which indicates the feasibility of the proposed design methodology.

© 2019 IEEE. In this paper, a design of balanced-to-unbalanced magic-T with filtering response is proposed for the first time. The function of the proposed magic-T is composed of an in-phase balanced-to-unbalanced power divider and an out-of-phase balanced-to-unbalanced power divider. Three fundamental modes, namely, TE011, TE101, and TM110, of the triple-mode resonators (TMRs) are excited to provide the odd- and even-symmetric field distributions so that in-phase and out-of-phase responses can be achieved. It is noteworthy that the common-mode suppression can be achieved at the balanced ports, while high isolation is achieved at the single-end ports. To verify the concept, the proposed balanced-to-unbalanced magic-T structure is fabricated and measured. Good matching between simulated and measured results shows the validity and accuracy of the proposed design methodology.

© 2019 IEEE. This paper proposes a novel miniaturized microwave filter based on circular spiral resonators (CSRs) embedded in a single metal cavity. The spiral structure is used to design filters in planar circuits with compact size, but not applied in cavity filters. The proposed CSR is firstly presented and analyzed, which has obvious size reduction compared to traditional cavity resonators, and still remain high filtering performance. Then, a second order filter using two CSRs sharing a metal cavity is designed, and it has two transmission zeroes (TZs) produced by the source-load coupling without additional coupling structure, which can improve the nearby stopband-rejection. The circuit size is 0.049λ0∗0.026λ0∗0.047λ0. Finally, the proposed second order filter is fabricated and measured, the measured results are in good agreement with the simulated results.

© 2019 IEEE. This paper presents our recently proposed multi-state diplexers (MSDs) implemented on different structures. The proposed MSDs have inherent property of multiple frequency channels, two of which can be used for duplexing mechanism by exciting one port as the input in each state. The MSDs have an attractive application in frequency hopping communication systems with miniaturization in their overall sizes. Then, three approaches to design the MSDs using different structures (planar triple-mode resonator, triple-mode cavity resonator and uniform/stepped impedance stub-loaded resonators) are presented. All the MSDs are finally fabricated and measured, the measurement are in good agreement with the simulation.

© 2019 IEEE. This paper presents the proposal and design of multistate diplexer on uniform- A nd stepped stub-loaded resonators, that is, a three-state diplexer (TSD) and a four-state diplexer (FSD). The two proposed diplexers have an attractive application in a frequency-hopping system with miniaturization in their overall size. Next, three and four sets of second-order bandpass filters are applied to form the three and four filtering channels, respectively. These filtering channels are then used to comprise these multiple-state diplexers. In this way, compact size and high-frequency selectivity have been well achieved. For the purpose of demonstration, the prototypes of TSD and FSD are fabricated and measured. The measured results are found in good agreement with the simulated results.

© 1963-2012 IEEE. In this paper, the design of a cavity crossover with three intersecting channels is presented. The three fundamental modes of a cavity resonator, namely, TE011, TE101, and TM110 modes, are adopted to resonate at each of three channels, respectively. Due to the modal orthogonality of these fundamental modes, high isolation among three channels can be achieved. Two kinds of crossovers, for narrowband and broadband applications, are presented. For the narrowband case, the proposed crossover resonates at 2.91 GHz with the fractional bandwidth of 1.4%. For the broadband case, the proposed crossover resonates at 3 GHz with the fractional bandwidth of 24%. The isolations of both designs reach more than 50 dB. For a proof of concept, the broadband example of the cavity crossover structures is fabricated and measured. A good agreement between the simulated and the measured results verifies the accuracy of the proposed design methodology.

© 2001-2012 IEEE. Corrugated metal with period grooves supports spoof surface plasmons polariton (SSPP) wave in microwave and terahertz ranges. In this letter, a four-way SSPP splitter/combiner with oval-ring periodic structures is presented by using a single connection junction. Up to the authors' best knowledge, a four-way SSPP splitter/combiner is never reported in the literature. In order to verify the performance of the mentioned SSPP splitter/combiner, we have manufactured and tested the presented SSPP splitter/combiner. The simulation and measurement results demonstrate that the designed conversion between a single coplanar waveguide junction and four SSPP waveguides is high efficiency. The SSPP splitter equally separates the electromagnetic wave into four paths. Hence, the proposed four-way splitter is expected to develop the SSPP active and passive components and relative integrated circuits.

© 1963-2012 IEEE. A highly integrated three-state diplexer (TSD) on a single planar elliptical structure is for the first time presented in this paper. Three resonant modes are investigated in a planar elliptical resonator, e.g., two TM11 degenerate modes and one TM21 mode. These three resonant modes are designed to form three filtering channels, which are further combined to generate three states of a diplexer, namely, TSD. The planar elliptical triple-mode resonator is fed by three microstrip lines to form a triple-mode TSD. In order to validate the concept, the designed planar TSD is fabricated and measured. The measured results are in good agreement with the simulated ones.

© 2018 IEEE. A triple-mode cavity filter with narrow passband realized in a single rectangular metal cavity without any tune crews, coupling apertures, iris, and corner cuts is proposed in this paper, while three resonant modes are classified as a TM mode and a pair of TE modes, which are excited by two metal probes in one single cavity. At both the upper and lower stop-bands, two transmission zeros are created to achieve a considerable out-of-band suppression. To prove the concept, a prototype is fabricated by using the silver plated aluminum technology demonstrating a measured fractional bandwidth of 3.6% at the center frequency of 2.53 GHz. The measured and simulated results are presented in good agreement.

© 2018 IEEE. The quasi-elliptic multi-mode bandpass cavity filters and duplexer with slot mixed-coupling structure are proposed in this paper. A single metal cavity embedded with a rectangular-shaped slot-cut metal plate is utilized to constitute a multi-mode bandpass filter with a few features including wide passband, low profile and controllable transmission zeros (TZs). In this paper, the slot-cut metal plane serves as the multi-mode resonators. In detail, the slot on the metal plane functions as the circuit element to move the higher order modes within the reasonable frequency-band, while serving as a mixed-coupling structure to generate out-of-band transmission zeros. To demonstrate the multiple-mode capability in filter design, the dual-mode, triple-mode, and quadruple-mode filters are developed by appropriately allocating a few TZs in the upper stopbands using the proposed slot mixed-coupling approach, namely, Type-I filters. Next, a quadruple-mode cavity filter with both lower and higher TZs is designed, namely, Type-II filter, which is further applied for the exploration of a duplexer. Finally, the filter and duplexer prototypes are fabricated and measured. The measurement results are found in good agreement with the simulated ones.

© 2017 IEEE. A variety of multiple-mode narrow-band bandpasss filer is designed, analyzed, and fabricated based on doublet and its properties. Three resonant modes: TE101, TE011 and TM110 modes in a single cavity are excited. The proposed filters use a microstrip line as a feeder then couple to a slot on one side of a single rectangular cavity. By rotating and offsetting two slots at the input port and output port of the rectangular cavity, three fundamental modes are implemented without any cross-coupling. The proposed structure also create two transmission zeros (TZs), by adjusting the positions of the two TZs near the passband, e.g., at lower or upper stopband, high rejection is achieved. Due to emergence of the three resonant modes and realization of a pair of TZs, a high attenuation and sharp filtering selectivity is achieved. Good agreement between measurement and simulation is achieved.

© 2013 IEEE. This paper presents a new class of second-order individually and continuously tunable dual- and triple-band bandpass filters in a single metal cavity. Each passband is realized by two identical metal posts. These dual- and triple-band tunable filters are achieved by putting two or three identical sets of metal-post pair in a single metal cavity. Metal screws are co-designed as a part of the metal posts to control their insertion depth inside the cavity. In this way, the resonant frequencies can be continuously controlled and designed at the desired frequency bands. Moreover, the distance between the two metal posts in a post pair can be freely tuned. Thus, the external quality factor (Qe) and coupling coefficient (k) between the adjacent modes can be easily adjusted to meet the specified requirement in synthesis design. At the bottom of the cavity, some grooves are used to extend the tunable frequency range and make the resonant frequency linearly varied with the height of the metal post. The center frequency of each passband can be independently tuned with a frequency range of 0.8-3.2 GHz and tunable ratio of 4. Finally, the continuously tunable dual- and triple-band bandpass filters prototypes with second order response are designed and fabricated, of which each passband can be individually tuned with a large tuning range.

© 2013 IEEE. On the basis of doublet and its properties, a class of multiple-mode narrow band bandpasss filter is designed and fabricated by simultaneously exploiting the three resonant modes in a single rectangular cavity: TE101, TE011, and TM110 modes. The input/output ports of the proposed filter are fed by coupling a microstrip line to a slot on the side wall of a rectangular cavity. Different modes are excited by changing the position and shape of the two slots at input and output of the rectangular cavity without any intra-cavity coupling. Besides three poles within the passband, a pair of transmission zeros (TZs) is achieved, which can be controlled independently by setting the positions of the two TZs at the lower and/or upper stopband. High stopband attenuation and high filtering selectivity are achieved by considerably allocating three transmission poles and two zeros. In order to verify the proposed theory, two filter prototypes are fabricated and measured.

A survey was made of gingival scrapings stained by the Papanicolaou method to assess the occurrence of Entamoeba gingivalis, a nonpathogenic-oral amoeba. Positive findings were recorded in 59% of 113 dental patients, and 32% of 96 healthy controls. These figures showed no significant changes during the last 20 years when compared with data published in 1960 and 1963. The existence of E. gingivalis and its rare appearance in the sputum should be known to cytologists because of the morphologic resemblance to Entamoeba histolytica, a pathogenic amoeba. Morphologic features are described to differentiate E. gingivalis from similar structures found in sputum.