A fluid switch is proposed for a frequency-agile Vivaldi antenna whose operating frequency band can be switched between two selected bands. A study of various ionized solutions of different concentrations is performed. A 2 mol KCl solution is selected as the fluid for the switch because of its relatively good properties in conductivity, relative permittivity, and loss tangent. The fluid-switched reconfigurable Vivaldi antenna can function well between two user-defined operating bands: 3.2 and 4.5 GHz with stable measured gain of 11 dBi in both bands and an isolation of 15 dB. This reconfigurable antenna demonstrates that a lowcost fluid switch may be an alternative device for reconfigurable antenna designs providing more flexibility.Index Terms-Ionized solutions, reconfigurable antennas.
A low-cost 3D-printed frequency agile fluidic monopole antenna system is demonstrated to respond to the increasing demand for reconfigurable antennas, which can operate in a dynamic environment, in this paper. Antennas that can be reconfigured for different operating frequencies, polarizations, or radiation patterns are attracting attention. Traditional reconfigurable antennas using a metallic radiating element with electronic switches are limited by their pre-defined physical geometries. As conductive fluid, either liquid metal or ionized fluid has no defined shape, so it is possible to create the desired shape of a fluidic antenna to support different wireless environments. The fabrication of the leakage-free containers for fluidic antennas needs special consideration, and stereo-lithography-based 3D-printing technology is a possible option to support the fabrication. Moreover, researchers will have higher design freedom and accuracy to create new container shapes for fluidic antennas. The fluidic monopole antenna proposed is coupling-fed by a ring geometry for separating the electrical and mechanical structures; such an approach enables individual optimization and minimizes mutual disturbances in the system. A parametric study of the proposed coupling-feed geometry and the experimental verification of the antenna prototypes have been performed. Reasonable frequency agility from 3.2 to 5 GHz has been demonstrated, and the peak efficiency is about 80%. A maximum gain of 3.8 dBi is obtained. The radiation patterns of the antenna are stable across the operating bandwidth. The proposed antenna could be useful for the applications in the recent 5G mid-bands operations.INDEX TERMS 3D-printing, antennas, closed loop system, fluidic antennas, fluid control methods, monopole antennas, multifrequency antennas, omnidirectional antennas, reconfigurable antennas.
A frequency agile Vivaldi antenna whose operating frequency band can be switched between two selected bands is proposed in this study for spectrum monitoring and cognitive radio applications. A radiofrequency (RF) switch is introduced into the back-slot of a Vivaldi antenna to allow switching of the operational band. The realised gains of the antenna are 10.5 dBi in the low band around 3.1 GHz, and 12 dBi in high band around 4.1 GHz. The radiation pattern is stable and its direction is consistent across the two bands. This design can be applied to multiple reconfigurable bands by using more RF switches to tune the desired operating frequency. A set of reliable design equations has been provided as well. This reconfigurable antenna offers improved gain and isolation over multiple, wideband and multiband antennas without increasing the cost and size when compared with those designs reported.
Continuous exposure to urban noise has been found to be one of the major threats to citizens’ health. In this regard, several organizations are devoting huge efforts to designing new in-field systems to identify the acoustic sources of these threats to protect those citizens at risk. Typically, these prototype systems are composed of expensive components that limit their large-scale deployment and thus reduce the scope of their measurements. This paper aims to present a highly scalable low-cost distributed infrastructure that features a ubiquitous acoustic sensor network to monitor urban sounds. It takes advantage of (1) low-cost microphones deployed in a redundant topology to improve their individual performance when identifying the sound source, (2) a deep-learning algorithm for sound recognition, (3) a distributed data-processing middleware to reach consensus on the sound identification, and (4) a custom planar antenna with an almost isotropic radiation pattern for the proper node communication. This enables practitioners to acoustically populate urban spaces and provide a reliable view of noises occurring in real time. The city of Barcelona (Spain) and the UrbanSound8K dataset have been selected to analytically validate the proposed approach. Results obtained in laboratory tests endorse the feasibility of this proposal.
A frequency agile Vivaldi antenna whose operating frequency band can be switched is proposed. High-performance radio-frequency microelectromechanical system (RF-MEMS) switches allow tuning of the operational band between 2.0 GHz, 3.7 GHz and 5.2 GHz. The average gains of the antenna for the low, mid and high bands are 8.5 dBi, 12.5 dBi and 13.7 dBi, respectively. This reconfigurable antenna offers improved performance over multiple, wideband and multiband antennas without increases in cost and size.
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