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A novel method for the development of a reconfigurable cavity bandpass filter using fluid dielectric is proposed. Dielectric material can produce an effective permittivity ϵeff of the resonant mode when it is loaded into the cavity. Thus, a tube filled with fluid dielectric, e.g., distilled water, can achieve controlled and reversible ϵeff by adjusting the amount of water in the tube. The same manner of resonant frequency can be achieved as the resonant frequency is related to ϵeff, and then frequency tuning is realized. The fluid property can realize easier and faster tuning mechanism than conventional solid dielectric. As ϵeff is affected by the loaded dielectric parallel to the electric field, a triple-mode resonator with resonant modes TE101, TE011, and TM110, which have orthogonal electric fields, is investigated to realize tri-band reconfiguration. The ϵeff, as well as the resonant frequencies, corresponding to each mode can be individually controlled by adjusting their related water posts. Then, reconfigurable single-band and tri-band bandpass filters are designed. A reconfigurable tri-band cavity filter using a triple-mode cavity resonator and fluid dielectric with individual and continuous frequency tuning is reported for the first time. Finally, the reconfigurable tri-band filter is fabricated and measured to validate the concept. [ABSTRACT FROM AUTHOR]

A class of bandwidth-enhanced full-metal cavity-backed slot filtenna is proposed in this communication. The design is constructed by three resonators. They are two resonance windows and one resonance cavity. As a consequence of that, three resonance modes are achieved using a single cavity. By using this resonance window, the 10 dB frequency bandwidth of the proposed cavity antenna has wide fractional bandwidth (FBW) of 20%. To the authors’ best knowledge, the proposed filtenna achieves the widest FBW among those published full-metal cavity-backed slot filtennas. Moreover, a fifth-order filtenna is also designed to further broaden the 10 dB FBW to 24%. Finally, an antenna prototype was fabricated and tested for experimental verification of the proposed design methodology. Good agreement between the measurement and simulation shows the feasibility of the proposed wideband full-metal filtenna using a resonance window approach. [ABSTRACT FROM AUTHOR]

A novel concept and approach for integration of a three-state diplexer (TSD) by utilizing the triple-mode cavity resonators is proposed in this paper. The proposed TSD has the inherent nature of three frequency channels, two of which can be utilized for duplexing channels by exciting one port as the input in each state. Meanwhile, three fundamental modes, namely, TE011, TE101, and TM110, are excited in the triple-mode resonators (TMRs) to control these three frequency channels. Without utilizing any junction networks for impedance matching, the required values of the external quality factors and coupling coefficients can be extracted to meet the relevant Chebyshev responses in the three bands of the TSD, simultaneously. Owing to the modal orthogonality among the three fundamental modes, high isolation among these three frequency channels can be effectively achieved. For proof of concept, two design examples of the TSD structures are presented with different topologies. For both examples, four and six TMRs are adopted, respectively, where the predicted three frequency channels of the TSD can be successfully excited with excellent channel isolations. The fabricated prototype shows good agreement between the simulated and measured results verifying the feasibility of the proposed design methodology. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

An integrated method of broadband duplex–filtenna based on a 3-D metallic cavity structure is proposed in this paper. In our design, two broadband filtennas with different operation frequency bands share the same metallic cavity-backed resonator. The two operation bands are realized with fractional bandwidths (FBWs) of 24% and 18%. The whole total FBW of two bands achieves 57%, and there are radiated nulls at the transition band showing a good filtering property. By integrating these two filtennas, a duplex–filtenna is formed with unidirectional radiation property. The radiation gain of these two filtennas exhibits good filtering property. The filtenna gain frequency responses have two transmission zeros near the lower and upper cutoff frequencies of both lower and upper operation bands. To validate the proposed concept, one cavity-backed duplex–filtenna with low-profile metallic cavity is designed and fabricated. The measured results have verified the simulation results well, and the isolation between the two wideband channels exceeds 30 dB as predicted in theory. [ABSTRACT FROM AUTHOR]

A novel concept for the two-in-one design with the integration of filters and antennas, using a single cavity, is presented in this communication. Basically, a triple-mode resonator (TMR) is utilized as a common feeder to achieve filtering and radiating functions at three different frequency bands. Each of the three bands adopts one of the three fundamental modes, namely, TE011, TE101, and TM110, in a single TMR to realize the relevant functions. Owing to the modal orthogonality of these fundamental modes, high isolation can be effectively realized among these three channels. Based on the proposed TMR, three different prototypes are designed for different applications. For the first prototype, the structure of a dual-band filter plus an antenna is presented using a second-order TMR. Based on the combination of a duplexer plus an antenna, the second prototype is attained. To further explore the function of the proposed TMR, the structure of a filter plus a dual-polarization antenna is depicted as the third prototype. For verification, the third prototype is fabricated and tested. Good agreement between the simulated and the measured results is achieved, which proves the feasibility of the proposed design methodology. [ABSTRACT FROM PUBLISHER]

A novel approach for design of a miniaturized cavity triplexer is proposed in this paper by using triple-mode resonator (TMR) as a common feeder of three frequency channels in a triplexer. Three frequency channels are generated by three fundamental modes of a single rectangular triple-mode cavity resonator. Without installing any connection-oriented junction network, i.e., T-junction or star junction, only coupling slots are adopted herein to achieve required coupling coefficients and external quality factors toward the specified Chebyshev responses in the three passbands simultaneously. High isolation among these three separated bands can be effectively achieved owing to the modal orthogonality via sharing a common TMR structure as a feeder. Two triplexers are then designed and fabricated using varied topologies. The hybrid resonator triplexer method is presented as the first approach by using a TMR as a feeder to feed three sets of single-mode cavity bandpass filters. As the second approach, the triple-mode triplexer (TMT) method is developed by cascading a few TMRs to form a multistage higher order TMT. Finally, two fabricated triplexer prototypes are tested for experimental verification of the proposed design methodology. Good agreement between measurement and simulation is achieved. [ABSTRACT FROM PUBLISHER]

A class of UWB filter-antenna is proposed. The proposed filter-antenna is compact, high inband selectivity and insensitive to ground plane size. A via-fed monopole antenna is proposed with tapered shape between the radiator and ground plane. This tapered shape supports two resonant modes to provide wideband matching. Four shorting pins are added to this antenna to improve the selectivity of the filter-antenna performance. Furthermore, a shunt LC-resonator is used to generate the notched-band in the UWB band without extra circuit size. To verify the predicted results, two prototype filter-antennas with and without notched-band are fabricated and measured on a low-cost two-side printed circuit board. The measured results exhibit a good selectivity, the measured return loss is below -12.5 dB within the desired passband and the size is compact with overall dimension of 28.5\times 28\times 0.8\ mm^3. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]

Novel design concept of reconfigurable full-metal cavity-backed slot antennas (CBSAs) using movable metal posts is proposed in this article. It is found that the cavity mode with purely directional electric field is only affected by the metal post to be placed in parallel to its electric field. Thus, two orthogonal cavity modes TE101 and TE011 can be perturbed by two respective metal posts so as to independently tune the resonant frequencies of these two modes. Electromagnetic energy of the cavity modes can be radiated out through the slots on the top wall of the cavity. In this context, reconfigurable slot antennas with different functionalities, such as single-band, dual-band, dual-mode wideband, the tunable frequency with constant bandwidth, and tunable bandwidth with constant frequency, are thus constituted to demonstrate its attractive design feasibility. The frequency-reconfigurable cavity-back slot antenna with movable metal posts is proposed for the first time. The utilization of the metal posts allows us to achieve a continuous frequency tuning property, while the full-metal structure of the proposed antenna holds a high power-handling capacity and a high radiation efficiency. In final, a prototype of the dual-mode wideband slot antenna is designed, fabricated, and tested to reveal its total efficiency higher than 88% and stable radiation pattern over the tuning band. Good agreement between the measured and the simulated results well validates the presented design concept. [ABSTRACT FROM AUTHOR]

In this communication, an $S$ -band wide-bandwidth and wide-beamwidth full-metal circularly polarized (CP) cavity-backed slot antenna is proposed. A pair of triangular prisms placed at the corners of the cavity is introduced to produce TE101 and TE011 modes with orthogonal electric fields. These two modes are used to achieve the CP radiation and radiate the energy through a single-circular slot. By simultaneously varying the prisms’ size and slot radius, the axial ratio (AR) bandwidth (ARBW) improves. The ARBW is further improved by replacing the circular slot with an elliptical slot. As a result, the ARBW increases from 1.0% to 10.3% without complicating the antenna structure and without enlarging the antenna size. Besides, the antenna still operates at two degenerate modes to introduce stable radiation gain and pattern. In addition, the proposed CP slot antenna features a wide ARBW. The final measurement shows that the proposed CP antenna can achieve a 9.5% bandwidth, a stable gain of 7.65 dBic ± 0.15 dBic, and higher than 140° ARBWs in a wide frequency range. The peak total radiation efficiency and aperture efficiency are about 97% and 91%, respectively. [ABSTRACT FROM AUTHOR]

In this paper, a new transversal configuration is presented for waveguide bandpass filters (BPFs) on stacked rectangular $ H$ -plane waveguide cavities. Different from the conventional ladder BPFs, cavities constituting the proposed transversal BPFs are arrayed in a stacked manner. Odd- and even-mode resonators of transversal BPF are realized by TE101 and TE102 modes of rectangular $ H$ -plane waveguides, respectively. Using the configuration proposed herein, the realization of an $N$ th-order filter could be decomposed into realizations of $N$ first-order subfilters, and each subfilter could be realized independently, which is guaranteed by the unique array of resonators of transversal filters. Therefore, the complexity of realizing BPFs could be reduced, especially for filters with multiple transmission zeros (TZs). A class of transversal filters, including BPFs and dual-band filter, are synthesized, fabricated, and measured to verify the approach. [ABSTRACT FROM AUTHOR]

This paper presents the proposal and design of multistate diplexer on uniform- and 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. [ABSTRACT FROM AUTHOR]