95 research outputs found

    Metamaterials

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    Editorial

    Compact Folded Bandpass Filter in Empty Substrate Integrated Coaxial Line at S-Band

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    © 2019 IEEE. Personal use of this material is permitted. Permissíon from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertisíng or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.[EN] This letter presents a novel compact folded bandpass filter in empty substrate integrated coaxial line (ESICL) technology. To obtain these compact filters, the inverters are modified to provide a 180 degrees bend when inserted in an ESICL. As a result, the proposed filter has a more compact topology based on parallel resonators. A sixth-order Chebyshev bandpass filter operating at 3 GHz has been designed, manufactured, and measured to experimentally validate this new folded configuration. The length of the novel compact filter has been reduced by 82.2% with respect to an equivalent in-line filter, obtaining very similar results in terms of electrical response.This work was supported in part by the Ministerio de Economia y Competitividad, Spanish Government through Research Projects under Grant TEC2016-75934-C4-3-R and Grant TEC2016-75934-C4-1-R and in part by the Ministerio de Ciencia, Innovacion y Universidades through the Fellowship Program for Training University Professors.Martinez, L.; Belenguer, A.; Boria Esbert, VE.; Borja, AL. (2019). Compact Folded Bandpass Filter in Empty Substrate Integrated Coaxial Line at S-Band. IEEE Microwave and Wireless Components Letters. 29(5):315-317. https://doi.org/10.1109/LMWC.2019.2909178S31531729

    Reconfigurable Liquid Metal-Based SIW Phase Shifter

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    This article presents the first substrate integrated waveguide (SIW) phase shifter that can be reconfigured using liquid metal (LM). This digital phase shifter exhibits low insertion loss and is reciprocal and bidirectional. It incorporates a series of holes which can be filled or emptied of liquid metal, enabling us to add or remove via connections dynamically, on-the-fly. Using a collection of such holes, it is possible to create a wall along the E-plane or H-plane of the waveguide. When the wall is in place, it blocks the passage of energy. When the wall is absent, energy is able to flow. In this way, it is possible to guide the electromagnetic (EM) waves through one of three paths, having different electrical lengths. The result is a digital switched-line phase shifter that achieves coarse steps of phase change, from 0° up to 180°, in steps of 60°. By filling or emptying individual holes, it is possible to introduce reactive loading into each path. In this way, it is possible to achieve fine phase control in steps of 10°. Using both forms of reconfiguration in unison, the proposed phase shifter is able to deliver a phase shift of up to 180°, in steps of 10°. The proposed phase shifter operates at 10 GHz and exhibits an insertion loss of less than 2.3 dB over its entire operating band. Furthermore, the underlying concept of the proposed phase shifter can be readily scaled for operation in the millimeter-wave (mm-wave) band. The existing phase shifters operating in that band exhibit significant insertion losses. MM-wave phase shifters are expected to find application in 5G mobile access points

    Highly Efficient and Well-Matched Empty Substrate Integrated Waveguide H-plane Horn Antenna

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    In this letter, an empty substrate integrated waveguide H-plane sectorial horn antenna is presented. The antenna is integrated within a planar substrate and is fed by means of a microstrip transmission line. It is composed of a partially empty substrate layer stacked between two cover metallic plates. Results obtained for a prototipe designed and fabricated at Ku-band show a measured efficiency close to 90% and matched responses. No extra loading elements are needed in order to reduce reflection at the end of the aperture conversely to previous designs. Moreover, the structure is quite simple, cheap and does not depend on substrate characteristics i.e. dielectric permitivity or loss tangent. This new methodology for manufacturing substrate integrated antennas without dielectric considerably improves the performance of conventional substrate integrated horn antennas

    Highly Efficient Heterogeneous Modal Superposition Method for the Full-Wave Analysis of Arbitrarily Shaped H-Plane Structures Fed through Rectangular Waveguides

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    A new fully modal characterisation procedure is proposed to reduce the number of unknowns needed to characterise the ports of an arbitrary H-plane device in rectangular waveguide, so that no equivalent currents will be involved in the characterisation of the ports. Moreover, since no currents are needed to characterise the ports, the weights of the scattered modes can be unknowns of the resulting system of equations. This is an important fact, since, to find the wanted modal weights, a subsequent projection step is not necessary anymore. The new method is then advantageous when compared to other hybrid alternatives in the literature, not only because the ports are solved using fewer unknowns, which is the main advantage of the proposal, but also because the scattering parameters can be computed directly, once the system of equations is posed

    Krylov’s Solver Based Technique for the Cascade Connection of Multiple N-Port Multimodal Scattering Matrices

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    In this paper a novel technique for cascading generalized scattering matrices based on a Krylov’s iterative solver is presented. This new technique is fully general, since it can be applied to solve the connection of an arbitrary number of networks, each one with an arbitrary number of ports, and it is easy to implement. This technique is able to compute, not only the modal spectra at the free ports of the global network, but also the modal spectra at the connected ports, so that the field inside the full network can be computed for an arbitrary incidence. In addition, this technique can also be used to evaluate the scattering parameters of the global network

    Systematic Procedure to Avoid Unintended Polarity Mismatch in the Cascade Connection of Multiport Devices with Symmetric Feeding Lines

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    This paper is a postprint of a paper submitted to and accepted for publication in [journal] and is subject to Institution of Engineering and Technology Copyright. The copy of record is available at IET Digital LibraryThe traditional cascading of generalised scattering matrices (GSMs) assumes that the modal sets at the connected ports of a cascaded network are strictly equal. This implies a careful selection of the modal polarities, or the reference systems, of every port. Usually, the connection scheme of every device is known a priori. Then, the individual GSMs are pre-processed, or auxiliary devices, which correct possible modal mismatches at the ports, are included in appropriate positions among the cascade, so that the traditional cascading-by-pairs approach can be directly applied. This scheme clearly complicates the reutilisation of previously calculated GSMs, and mixes the cascading with the solution of the individual building blocks. In this study, a systematic procedure is proposed to define the polarity of the modes at the ports of a device fed with transmission lines or waveguides showing a single or double symmetry. The modified expressions to calculate the scattering parameters of the cascade of two multiport devices, incorporating the regular modal corrections to apply when this criterion is used to define the modal polarity at the ports, is also presented in this study. This strategy is more convenient from the point of view of programming, less error-prone and easier to implement.This work was supported by the Ministry of Science and Innovation, Spanish Government, under Research Projects TEC2013-47037-C05-3-R and TEC2013-47037-C05-1-R.Belenguer Martínez, Á.; Borja, A.; Díaz Caballero, E.; Esteban González, H.; Boria Esbert, VE. (2015). Systematic Procedure to Avoid Unintended Polarity Mismatch in the Cascade Connection of Multiport Devices with Symmetric Feeding Lines. IET Microwaves Antennas and Propagation. 9(11):1128-1135. https://doi.org/10.1049/iet-map.2014.0167S1128113591

    Effects of physical exercise on physical function in older adults in residential care: a systematic review and network meta-analysis of randomised controlled trials

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    Background: Physical exercise is effective at attenuating ageing-related physical decline in general, but evidence of its benefits for older adults in residential care, who often have functional dependency, multimorbidity, and polypharmacy, is inconclusive. We aimed to establish the effects of exercise interventions on the physical function of this population. Methods: For this systematic review and network meta-analysis, we searched PubMed, Web of Science, Cochrane Library, Rehabilitation & Sports Medicine Source, and SPORTDiscus to identify randomised controlled trials assessing the effects of exercise interventions (vs usual care) on physical function (ie, functional independence, physical performance, and other related measures, such as muscle strength, balance, or flexibility) in adults aged 60 years or older living in residential care. Relevant studies published in English or Spanish up to Jan 12, 2023, were included in the systematic review. The quality of studies was assessed using the Tool for the Assessment of Study Quality and Reporting in Exercise (TESTEX) score. A network meta-analysis was performed for physical function-related outcomes reported in at least ten studies, with subanalyses for specific intervention (ie, exercise type, training volume, and study duration) and participant (eg, having cognitive impairment or dementia, pre-frail or frail status, and being functionally dependent) characteristics. The study protocol was registered on PROSPERO (CRD42021247809). Findings: 147 studies (11 609 participants, with mean ages ranging from 67 years [SD 9] to 92 years [2]) were included in the systematic review, and were rated as having overall good quality (median TESTEX score 9 [range 3–14]). In the meta-analysis (including 105 studies, n=7759 participants), exercise interventions were associated with significantly improved overall physical function, with a standardised mean difference [SMD] of 0·13 (95% credible interval [CrI] 0·04–0·21), which was confirmed in all analysed subpopulations. The strongest association was observed with 110–225 min per week of exercise, and the greatest improvements were observed with 170 min per week (SMD 0·36 [95% CrI 0·20–0·52]). No significant differences were found between exercise types. Subanalyses showed significant improvements for almost all analysed physical function-related outcomes (Barthel index, five-times sit-to-stand test, 30-s sit-to-stand test, knee extension, hand grip strength, bicep curl strength, Short Physical Performance Battery, 6-min walking test, walking speed, Berg balance scale, and sit-and-reach test). Large heterogeneity was found between and within studies in terms of population and intervention characteristics. Interpretation: Exercise interventions are associated with improved physical function in older adults in residential care, and should, therefore, be routinely promoted in long-term care facilities. Funding: None. Translation: For the Spanish translation of the abstract see Supplementary Materials section.10 página
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