Coupling Window Research Articles

A ridged waveguide filter design with ultra-wideband and harmonic suppression

In this paper, a new structure for wide-band rectangular waveguide bandpass filters with distinguished harmonic suppression is presented. The filter is realized by using ridged waveguides in both resonant cavities and coupling windows and a metal plate, which performs like a low-pass filter and makes it arduous to form parasitic passbands. According to the field analysis and out-of-band response, the ridge structure can expand pass bandwidth and obtain a wide stopband by harmonic suppression. The filter is designed to perform a passband of 67% fractional bandwidth at center frequency at 75 GHz. The harmonic suppression of the design is increased from 1.5 times to 3.6 times the center frequency of the filter with 20 dB suppression levels. Finally, the measurement results validate the proposed design.

Miniaturized filter with harmonic suppression characteristics by embedding microstrip resonators in half‐mode substrate‐integrated waveguide resonant cavities

AbstractA novel filter design is proposed that employs harmonic rejection characteristics based on half‐mode substrate‐integrated waveguide resonance cavities and microstrip resonators. The objective is to expand the filter's blocking bandwidth and reduce the filter's size. The filter employs two half‐mode substrate‐integrated waveguide resonant cavities, which serve to effectively reduce the size of the filter. Moreover, the higher‐order modes TE201 and TE202 are unable to propagate within the resonant cavities. The suppression of the TE102 mode is achieved by setting the coupling window between the resonant cavities at the weakest field strength of this mode. Concurrently, two microstrip resonators are integrated into the coupling window, thereby enabling the realization of a fourth‐order filter response with only two resonant cavities. The filter was processed and measured, and the results were found to be in good agreement with the simulation. It is proved that the design method proposed in this paper is feasible.

Experimental and numerical studies on the seismic performance of fully cast‐in‐situ concrete exterior walls

AbstractTo investigate differences in the seismic performance of the main structure between a window sill wall and a coupling beam under two different flexible connections, two coupled shear wall specimens with concrete window sill walls and one counterpart specimen without infill walls (S‐1) were designed for quasistatic tests. The test results indicated the following: In specimen S‐2, fully disconnected by polyvinyl chloride (PVC) tubes, the coupling beam and window sill wall formed a double coupling beam working mode. The failure mode of the main structure of specimens S‐1 and S‐2 was the beam‐hinge mechanism. In specimen S‐3, which was partially disconnected by extruded polystyrene board strips, the coupling beam and the window sill wall worked together as an integral beam and underwent shear failure, revealing significant differences in failure mode compared to S‐1. In addition, the relative deformation between the first‐floor window wall and the main structure of specimen S‐2 could occur, and the interaction between the two was relatively small compared with that of specimen S‐3. Similarly, compared with those of specimen S‐1, the peak loads of specimens S‐2 and S‐3 were approximately 52.37% and 79.99% greater, respectively. The ductility coefficient of S‐2 was equivalent to that of S‐1, while the displacement ductility coefficient of S‐3 decreased by approximately 41.95% compared to that of S‐1. The connection between the main structure and the concrete infill wall with PVC effectively reduced the interaction between the two components and reduced the damage. Finally, MSC. Marc software was used to establish a solid model and simplified model of the equivalent compression bars of all the specimens, and the results were compared with the test results.

A U-band cascaded quadruplet quartz glass SIW filter based on double row vias coupling window

A U-band Substrate Integrated Waveguide (SIW) Cascaded Quadruplet (CQ) filter is designed based on low-cost quartz glass planar integrated circuits process with limited depth-to-diameter ratio and via spacing, which challenge the control accuracy of coupling coefficients. To address this issue, a double-row vias coupling structure control strategy is proposed to enhance the precision of coupling coefficient control. Cascaded quadruplet topology based on the proposed coupling structure with asymmetric coupling window is designed to improve the passband selectivity and harmonic suppression. The filter exhibits −3dB relative bandwidth of 4.6 % (1.94 GHz) at a central frequency of 42.2 GHz, insertion loss of 4.2 dB and rectangular coefficient (−20 dB BW/−3dB BW) of 1.47.

An all‐metal wideband circularly polarized single‐patch antenna based on TM11 mode

AbstractThis paper proposes an all‐metal wideband circularly polarized (CP) single‐patch antenna based on TM11 mode. The conventional square patch is divided into four small square patch units by loading metal shorting walls under the two vertical centerlines. The shorting walls are windowed to facilitate coupling between the adjacent units. When the TM11 mode is excited, the coupling windows not only distribute energy but also provide the 90° phase difference required for CP radiation. An additional feeding network is not required, and its profile is less than 0.05λ0 (λ0 is the free space wavelength at the center frequency). Three minima in the axial ratio (AR) response are present. The results show that right‐hand circularly polarized (RHCP) radiation is achieved. The measured 3 dB AR bandwidth is 6.9%, ranging from 1.52 to 1.62 GHz, and the RHCP realized peak gain is 7.72 dBic. An all‐metal construction suitable for satellite communication systems is designed that has superior performance in harsh space environments.

Realization of a Wide Stopband Filter Using the Weakest Electric Field Method and Electromagnetic Hybrid Coupling Method

To enhance filter performance in terms of stopband, we propose a wide-stopband substrate-integrated waveguide filter based on the rejection of higher-order modes. The filter establishes the inner and outer coupling windows at the mode’s weakest electric field to achieve mode suppression. Simultaneously, we employ the electromagnetic hybrid coupling theory to analyze the electromagnetic distribution of the particular modes and determine the dimensions of the coupling circular apertures and slits based on the extracted coupling coefficients to attain suppression of the specific modes. The filter successfully suppresses all higher-order modes having resonant frequencies below that of the TE150 mode, as demonstrated by simulation results. We conducted measurements and found that the filter has a center frequency of 4.78 GHz, a bandwidth of 100 MHz with a -3 dB attenuation, and a stopband of -25 dB that extends up to 16.62 GHz (i.e., 3.48 times the center frequency). Simulation and measurement results demonstrate a good correlation. This method, compared to other SIW filters, is easy to design, has a wider stopband range, can be readily applied to practical microwave communication systems, and has potential applications.

Two‐dimensional multichannel bandpass filter bank with improved fractional bandwidth and selectivity

AbstractThis letter presents a six‐channel bandpass filter bank created on substrate integrated waveguide (SIW) with improved bandwidth and frequency selectivity on the lower band. Through SIW square cavities and slant slots, a two‐dimensional multichannel bandpass filter bank with a transmission zero constructed with the SIW orthogonal resonant modes is produced. The substrate integrated square cavity approach is used to achieve the propagation of the two orthogonal‐oriented transverse electric modes, TE102 and TE201, which resonate on the same frequency and bandwidth, depending on the location of the feed ports. The bandwidth could be altered by the coupling matrix synthesis and coupling windows. Better transmission and bandpass responses are produced in each channel when the feed ports and coupling gaps are positioned and appropriately adjusted. However, a pair of slot lines are imprinted along each cavity's designated diagonal to guarantee better isolation while attaining an increased fractional bandwidth. A 3 × 3 array of six bandpass filters with a center frequency of 8.65 GHz has been built, simulated, and measured to establish the suggested technique. Low insertion loss, high return loss, high isolation, an improved fractional bandwidth, and a compact device were the proposal's advantages.

Interface flux recovery framework for constructing partitioned heterogeneous time‐integration methods

AbstractA common approach for the development of partitioned schemes employing different time integrators on different subdomains is to lag the coupling terms in time. This can lead to accuracy issues, especially in multistage methods. In this article, we present a novel framework for partitioned heterogeneous time‐integration methods, which allows the coupling of arbitrary multistage and multistep methods without reducing their order of accuracy. At the core of our approach are accurate estimates of the interface flux obtained from the Schur complement of an auxiliary monolithic system. We use these estimates to construct a polynomial‐in‐time approximation of the interface flux over the current time coupling window. This approximation provides the interface boundary conditions necessary to decouple the subdomain problems at any point within the coupling window. In so doing our framework enables a flexible choice of time‐integrators for the individual subproblems without compromising the time‐accuracy at the coupled problem level. This feature is the main distinction between our framework and other approaches. To demonstrate the framework, we construct a family of partitioned heterogeneous time‐integration methods, combining multistage and multistep methods, for a simplified tracer transport component of the coupled air‐sea system in Earth system models. We report numerical tests evaluating accuracy and flux conservation for different pairs of time‐integrators from the explicit Runge‐Kutta and Adams‐Moulton families.

Excitation of a rectangular resonator through communication windows in the conveyor installation of microwave heating

Abstract Based on the excitation theory of L.A. Vainstein obtained simple and convenient iterative relations for excitation of a resonator in the form of a rectangular parallelepiped with a dielectric layer through several coupling windows in its walls. Theexpansion of the field in terms of the complete system of solenoidal functions of a rectangular resonator is used. Solenoidality is due to the fact that the electric fields of excitation in the openings of rectangular waveguides on the resonator walls, fed through coaxial-waveguide transitions, are tangent to the boundaries of the heated dielectric layer. Simple formulas for expansion coefficients and calculation of fields are obtained. It is convenient to solve the obtained implicit formulas iteratively; in this case, it is possible to take into account both a linear dielectric and a nonlinear dielectric, the permittivity of which depends on the square of the electric field. The algorithm is implemented to simulate a conveyor installation of microwave heating. It is possible to modify the algorithm by introducing potential basic subsystems of functions for the case of modeling complex dielectric inclusions. The results are suitable for modeling other nonlinear inclusions, as well as in problems when using volumetric given sources instead of surface ones. For given electric fields in the coupling windows, the power entering the resonator is calculated on the basis of the Poynting vector.

The parameters of radio frequency quadrupole linear accelerator for DARIA project

The new proton linear accelerator (linac) with output energy 13 MeV and 100 mA current is under development at NRC “Kurchatov Institute” - ITEP for DARIA project. The linac consists of Radio-Frequency Quadrupole (RFQ) and Drift Tube Linac (DTL) with operating frequency 162.5 MHz. The RFQ is based on 4-vanes structure with shifted coupling windows. DTL has a modular structure and consists of separated individually phased cavities with focusing magnetic quadrupoles located between the cavities. The DTL is based on interdigital H-mode (IHDTL) 5-gaps cavities. The 6D beam matching between RFQ and DTL is provided by magnetic quadrupole lenses and RF-bunchers. The paper presents results of the radio-frequency (RF) design, thermal analyses and RF tuning of RFQ linac accelerating structure.

A simple SIW balanced directional coupler with high common‐mode suppression

AbstractIn this letter, a simple balanced directional coupler with high common‐mode (CM) suppression is designed by using a single‐layer substrate‐integrated waveguide (SIW). The SIW can be considered a naturally balanced structure. The CM noises are able to be intrinsically suppressed when differentially excited along the symmetric H‐plane of SIW. The coupling window with tapered transition is designed for broadening the bandwidth of 3‐dB coupling. The microstrip differential feeding structure with inductive vias and inductive matching section enables planar integration and better impedance matching. Finally, a SIW balanced directional coupler operating at 14–16 GHz is designed and fabricated. Measured results are in good agreement with simulated ones.

A Multirate Discontinuous-Galerkin-in-Time Framework for Interface-Coupled Problems

A framework is presented to design multirate time stepping algorithms for two dissipative models with coupling across a physical interface. The coupling takes the form of boundary conditions imposed on the interface, relating the solution variables for both models to each other. The multirate aspect arises when numerical time integration is performed with different time step sizes for the component models. In this paper, we seek to identify a unified approach to develop multirate algorithms for these coupled problems. This effort is pursued though the use of discontinuous-Galerkin time stepping methods, acting as a general unified framework, with different time step sizes. The subproblems are coupled across user-defined intervals of time, called coupling windows, using polynomials that are continuous on the window. The coupling method is shown to reproduce the correct interfacial energy dissipation, discrete conservation of fluxes, and asymptotic accuracy. In principle, methods of arbitrary order are possible. As a first step, herein we focus on the presentation and analysis of monolithic methods for advection-diffusion models coupled via generalized Robin-type conditions. The monolithic methods could be computed using a Schur-complement approach. The framework and analysis herein accommodate multirate coupling for a wide variety of single-step, multistep, and multistage methods. A concrete example of Crank--Nicolson integrators coupled in a multirate fashion is also included to illustrate the ideas. We conclude with some discussion of future developments, such as different interface conditions and partitioned methods.

An effective method to suppress high-order modes of SIW filters with compact size

In this paper, an effective method for substrate integrated waveguide (SIW) filter with improved stop band performance is proposed. By configuring the position and the direction of the coupling window, the transmission of the parasitic mode such as TE102 and TE201 can be effectively suppressed without adding any extra structure and element. Under the above theory, a Ka-band SIW filter centered at 35.71 GHz based on quartz glass substrate with compact size and simple structure is designed and tested. The stop rejection of the design is increased from 1.03 times to 1.95 times the center frequency within −35 dB of the filter with the insertion loss of −2.5 dB and the return loss of −20 dB. Finally, the measurement results validated the proposed design.

Peak Power Handling Capability in Groove Gap Waveguide Filters Based on Horizontally Polarized Resonators and Enhancement Solutions

This letter studies the peak power handling capability (PPHC) in groove gap waveguide filters based on horizontally polarized resonators. Moreover, a modification of the resonant cavity is proposed, where the central pins of the original structure are replaced by a rounded metal block. As a result of this change, the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">101</sub> -like mode can still be excited, but the maximum electric field strength is shifted to the center of the cavity, which leads to a higher PPHC. The main advantages of the original structure are maintained, and greater robustness in the manufacturing process is achieved. Next, some guidelines for the design of the coupling windows and the dimensions of the blocks are shown to minimize the electric field strength and, consequently, maximize the PPHC. Finally, two third-order bandpass filters (with pins and with blocks) centered at 16 GHz have been manufactured and tested in a measurement campaign, where a PPHC enhancement of 8.7 dB at high pressures is achieved for the novel solution presented in this work.

Wide‐stopband substrate‐integrated waveguide diplexers and dual‐band bandpass filter with large frequency ratios

Compact substrate-integrated waveguide (SIW) diplexers and dual-band bandpass filter (BPF) with widely separated passbands and wide-stopband are proposed for the first time based on half-mode substrate-integrated rectangular cavity (HMSIRC). Thanks to the dual-mode cavities and two respective channels, the frequencies and couplings of the two passbands can be flexibly controlled. To conquer the limitation of conventional full-mode cavity, the use of HMSIRC could intrinsically reject TE201 mode and many higher-order even modes, simultaneously realizing wide-stopband and widely separated passbands based on TE101 and TE102 modes. Moreover, the properly arranged internal coupling windows, which could intrinsically suppress the specific unwanted modes by sufficiently employing the existing design degrees of freedom, help further separate the two passbands and extend the stopband. The passband and stopband responses are systematically analyzed for different frequency ratios with the realizable frequency ratio and stopband bandwidth up to 1.91 and 2.65f1, respectively, which supplies the design guideline for SIW diplexers and dual-band BPFs with widely separated passbands and wide-stopband. Two SIW diplexers and an SIW dual-band BPF with frequency ratios of 1.72, 1.85, and 1.72 are synthesized and designed for demonstration, realizing the rejection levels and stopband bandwidths of 20 dB/2.34f1, 35 dB/2.36f1, and 20 dB/2.6f1, respectively.

A Fourth-order Dielectric Narrow-band Bandpass Filter Using Coaxial Resonator

In this paper, a compact fourth-order dielectric bandpass filter is proposed. The filter adopts the mode of linear coupling and is composed of four coaxial resonators and two coupling slots, which are fed by two probes, and the four coaxial resonators are resonated to form a passband. The resonant frequency can be controlled by the radius and height of the resonators, and the inter-cavity coupling is controlled by the width of the coupling windows formed by the coupling slots. At last, the simulation results of the filter show that the filter has narrow bandwidth and good in-band matching performance and out-of-band suppression.

Demonstration of a 220-GHz Continuous Wave Traveling Wave Tube

The 220-GHz continuous wave (CW) folded waveguide (FWG) traveling wave tube (TWT) is presented as the high-power amplifier for the terahertz (THz) communication system in this article. This tube is designed and fabricated including FWG circuit, electron gun, periodical permanent magnet system, coupling window, and thermal management structure. The test results show that with the pencil beam of 20.5 kV and 52.4 mA, the output power is 16 W and the corresponding bandwidth is 7 GHz from 213 to 220 GHz, and the maximum power and the corresponding gain are 30 W and 31.2 dB at the frequency of 217 GHz.

Wide-Stopband Substrate-Integrated Waveguide Filtering Crossovers With Flexibly Allocated Channel Frequencies and Bandwidths

Substrate-integrated waveguide (SIW) filtering crossovers featuring wide-stopband characteristics and flexibly allocated center frequencies (CFs) and bandwidths (BWs) for two intersecting channels are presented and studied. The development is devised upon a scheme of an over-mode dual-mode substrate-integrated rectangular cavity (SIRC) coupled with multiple single-mode cavities. First, by exploiting the orthogonal TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">102</sub> and TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">201</sub> modes in the dual-mode SIRC, cross transmission and acceptable isolation can be obtained and implemented for the dual channels. Furthermore, by controlling the resonant frequencies and mutual couplings of the coupled cavities accordingly, especially the over-mode dual-mode SIRC, both the CFs and BWs of the two channels can be allocated flexibly. In addition, by incorporating three kinds of intrinsic spurious-mode suppression techniques, namely, the harmonic staggered technique, centered coupling windows, and offset centered feeding ports, wide-stopband characteristics can be achieved intrinsically and uniquely. Four practical design examples, including fifth-order direct-coupled and fifth-order cross-coupled SIW filtering crossovers with identical channel CFs and BWs, a third-order crossover with the same channel CFs but different channel BWs and another third-order case with different channel CFs but the same channel BWs are synthesized, designed, fabricated, and tested to demonstrate and validate the proposed collaborative design concepts.

Characterization of Si–Cu–C–Al quaternary interface of SiC/2A14 joint via counterintuitive laser butt welding

SiCp/Al matrix composites (SiCp/AMCs) have be widely used in the aerospace structural components, space station solar cell structural framework. However, the double bottleneck of poor formability and low tensile strength exists in laser welding SiCp/AMCs. Here, the SiCp/2A14Al joints were prepared via counterintuitive laser butt welding. The Si–Cu–C–Al quaternary system nanometer precipitations were characterized. A new concept of ‘Perforating Laser Welding’ (PLW) was proposed, under which 205 MPa welded joint was successfully prepared. TEM results showed that amorphous Si was embedded in the Al matrix. AlCu was attached to Al4C3 for heterogeneous nucleation-growth. Al4C3 has a tightly bonded interface with Al matrix, which enhances the load transfer capability. This provides a two-level coupling window for SiCp/2xxx Al welded joint design: the ‘Perforating Laser Welding’ concept and the tailoring load transfer interface between AlCu/Al4C3 and Al matrix.

A Novel Capacitive Cross-Coupling Structure for Ceramic-Filled Cavity Filters

Since the probe coupling for cavity filters is unsuitable for ceramic-filled cavity filters, a novel capacitive cross-coupling structure is proposed to improve stopband suppression by introducing transmission zeros. This structure is implemented by first etching a coupling window on the silver-plated layer on the ceramic surface between two resonant cavities and then placing an isolated metal strip in the window. This structure enjoys high design freedom. Thus, the coupling coefficient between the two cavities is readily adjusted. Moreover, the structure has the advantages of a compact size and simple fabrication and tuning processes. For validation, a ten-pole ceramic-filled cavity filter for 5G applications is designed and evaluated. The proposed cross-coupling technology is used to introduce a pair of symmetrical transmission zeros at the band skirts to increase the frequency selectivity. The measured results are consistent with the simulated ones.