Metallic Antenna Research Articles

The Design and Manufacturing Process of an Electrolyte-Free Liquid Metal Frequency-Reconfigurable Antenna.

This communication provides an integrated process route of smelting gallium-based liquid metal (GBLM) in a high vacuum, and injecting GBLM into the antenna channel in high-pressure protective gas, which avoids the oxidation of GBLM during smelting and filling. Then, a frequency-reconfigurable antenna, utilizing the thermal expansion characteristic of GBLM, is proposed. To drive GBLM into an air-proof space, the thermal expansion characteristics of GBLM are required. The dimensions of the radiating element of the liquid metal antenna can be adjusted at different temperatures, resulting in the reconfigurability of the operating frequency. To validate the proposed concept, an L-band antenna prototype was fabricated and measured. Experimental results demonstrate that the GBLM in the antenna was well filled, and the GBLM was not oxidized. Due to the GBLM being in an air-proof channel, the designed liquid metal antenna without electrolytes could be used in an air environment for a long time. The antenna is able to achieve an effective bandwidth of over 1.25–2.00 GHz between 25 °C and 100 °C. The maximum radiation efficiency and gain in the tunable range are 94% and 2.9 dBi, respectively. The designed antenna also provides a new approach to the fabrication of a temperature sensor that detects temperature in some situations that are challenging for conventional temperature sensing technology.

3D Metallic Plate Lens Antenna based Beamspace Channel Estimation Technique for 5G Mmwave Massive MIMO Systems

Beamspace channel estimation mechanism for massive MIMO (multiple input multiple output) antenna system presents a major process to compensate the 5G spectrum challenges caused by the proliferation of information from mobile devices. However, this estimation is required to ensure the perfect channel state information (CSI) for lower amount of Radio Frequency (RF) chains for each beam. In addition, phase shifter (PS) components used in this estimation need high power to select the beam in the desired direction. To overcome these limitations, in this work, we propose Regular Scanning Support Detection (RSSD) based channel estimation mechanism. Moreover, we utilise a 3D lens antenna array having metallic plate and a switch in our model which compensates the limitation of phase shifters. Simulation results show that the proposed RSSD based channel estimation surpasses traditional technique and SD based channel estimation even in lower SNR area which is highly desirable in the millimeter wave (mmWave) massive MIMO systems.

3D Metallic Plate Lens Antenna based Beamspace Channel Estimation Technique for 5G Mmwave Massive MIMO Systems

3D Metallic Plate Lens Antenna based Beamspace Channel Estimation Technique for 5G Mmwave Massive MIMO Systems

Conceptual design, manufacturing and investigation of dipole plasma ‎antenna with the capability of frequency variation in the VHF band

In this article, we simulate and manufacture a dipole plasma antenna whose frequency is variable in the VHF band. The conductive medium of antenna is the plasma created by the DC discharge in a glass tube. To excite the antenna, we use a cylindrical aluminum coupler installed at the middle of the antenna. By varying values of gas pressure, input impedance of circuit and the voltage deference between two ends of the plasma medium, one can change the working area of antenna at a few hundred gigahertz frequency interval. Simulation and numerical calculations are carried out for an antenna with 78cm length and 2cm radius at 0.8 bar pressure exerted under 15KV voltage difference. At constant pressure, by using some parallel resistors in the antenna circuit, the impedance of discharge circuit is changed and consequently the plasma density is varied. For plasma frequencies and , using semi-experimental formulae, analysis shows resonances at frequencies 250MHz and 311MHz, respectively, which are in good agreement with the experimental results which take place at frequencies 217MHz and 272MHz. Additionally, simulation is accomplished for a metal antenna with corresponding geometry whose working frequency detected at 184MHz.

Broadband Spin-Dependent Directional Coupler via Single Optimized Metallic Catenary Antenna.

With the rapid development of on-chip optics, integrated optical devices with better performance are desirable. Waveguide couplers are the typical integrated optical devices, allowing for the fast transmission and conversion of optical signals in a broad working band. However, traditional waveguide couplers are limited by the narrow operation band to couple the spatial light into the chip and the fixed unidirectional transmission of light flow. Furthermore, most of the couplers only realize unidirectional transmission under the illumination of the linear polarized light. In this work, a broadband polarization directional coupler based on a metallic catenary antenna integrated on a silicon-on-insulator (SOI) waveguide has been designed and demonstrated under the illumination of the circularly polarized light. By applying the genetic algorithm to optimize the multiple widths of the metallic catenary antenna, the numerical simulation results show that the extinction ratio of the coupler can be maintained larger than 18 dB in a wide operation band of 300 nm (from 1400 to 1700 nm). Moreover, the coupler can couple the spatial beam into the plane and transmit in the opposite direction by modulating the rotation direction of the incident light. The broadband polarization directional coupler might have great potential in integrated optoelectronic devices and on-chip optical devices.

One-dimensional terahertz dielectric gradient metasurface for broadband spoof surface plasmon polaritons couplers.

At present, most of the gradient metasurfaces used to construct surface plasmon polaritons (SPPs)/spoof SPPs (SSPs) couplers are usually compact metal antennas working under reflection and transmission. In reflection mode, meta-couplers link propagating waves and surface waves (SWs), and SWs will undergo significant scattering before coupling to an Eigen SPP in the target system. In transmission mode, metal meta-couplers will encounter complex multilayer designing at the microwave/terahertz region and metal absorption loss at optical frequencies. In this Letter, to the best of our knowledge, a novel design using dielectric gradient metasurfaces instead of metal metasurface couplers is proposed to excite broadband SSPs on the metal groove array. We demonstrate that the well-designed phase dielectric gradient metasurface converts the normal incident terahertz wave to the predetermined angle in the dielectric substrate and then excites the broadband SSPs with the transmission coupling between the dielectric meta-coupler and SSPs surface. This research may open up new avenues in simple and broadband plane dielectric meta-couplers for SSPs in ultra-thin and compact functional devices for versatile applications.

Liquid Antennas: Past, Present and Future

The liquid antenna, as a new member of the antenna family, has drawn significant and increasing attention from both academia and industry due to its unique features. In this paper, a comprehensive review on this technology is presented which covers both metallic and non-metallic liquid antennas. Non-metallic liquid antennas are further divided into water-based and non-water-based liquid antennas. We first review and compare different liquid antennas and highlight the major developments in the past. Detailed discussions on state-of-the-art designs and current technical challenges are then presented, and finally the ways forward for the future are suggested. As a special feature, an in-depth review and discussion on materials for liquid antennas are provided which was not well covered in the literature in the past, important properties of selected materials are given in three comparison tables which can serve as antenna material selection references. It is shown that Galinstan is probably the best choice for metallic liquid antennas while ionic liquid materials are the preferred choice for dielectric liquid antennas. The challenges of making the liquid antenna for real-world applications are identified and discussed. It is believed that a liquid antenna implemented in radio systems is probably just around the corner.

Study of Solar Radiation Effect on Radio Signal Using Plasma Antenna

Plasma antenna can be formed by energizing glass tubes which are filled with neutral gases. It works similarly as metal antenna where it can transmit and receive wireless signal. This study aims to investigate the effect of weather focused on solar radiation towards the performance of plasma antenna represented by signal strength. Fluorescent lamp was set as plasma because it used ionized gas as its conducting element instead of metal. Execution of electrical properties measurements need to be done first, in order to obtain discharge current and voltage values, that need to be used into Glomac programming for the generation of electron temperature and electron density. Next, calculations of the plasma properties was performed to derive the value of plasma and collision frequencies. The plasma properties are important parameters to design and simulate plasma antenna using Computer Simulation Technology (CST). Antenna parameters in terms of return loss, gain, directivity and radiation pattern can be simulated using CST. Signal strength experiment was conducted to evaluate plasma antenna performance in terms of its capability to capture the signals and analyse the effect of solar radiation on that particular moment through the rate of power level over time versus solar radiation data. It was observed at the highest solar radiation rate which is 920 V/m, the power level recorded is the lowest value at-172.93 dBm. Therefore, the signal strength received by the plasma antenna shows remarkable changes under the influence of solar radiation.

Broadband THz Corrugated Bull’s Eye Antennas

A 3-dB gain and input impedance bandwidth enhancement technique for THz periodically corrugated metallic antennas, also known as Bull's Eye antennas, is presented. A novel design that exploits the depth qualities of the corrugations is introduced, by employing two different depth values for two sets of indented rings. While the gain bandwidth of most single-depth planar corrugated antennas is limited, the 3-dB gain bandwidth of the proposed dual-depth design is expanded along with a high maximum gain. The simulated optimum model of 10 rings at around 300 GHz exhibits a 3-dB gain bandwidth of 8.85% with a maximum gain at broadside of 21.3 dBi. A leaky-wave analysis has been performed via a simple transcendental equation at the level of the gap openings in order to explain the antenna principle of operation. A prototype of the optimum antenna design has been fabricated and measured. The typical subwavelength slot feeding of Bull's eye corrugated antennas is substituted with an easy-to-fabricate open waveguide aperture, yielding a broadband matching performance. Measured results demonstrate a good agreement with simulations and validate the proposed antenna design.

Liquid metal motor.

SummaryLiquid metal has demonstrated an enormous potential for developing soft functional devices and machines. However, current liquid metal enabled machines suffer from several issues, such as the requirement of a liquid environment, generation of weak actuating forces, and insufficient maneuverability. To overcome these restrictions, here, a motor is developed based on the electrical actuation of liquid metal droplets without the need for conventional electromagnets. The approach is distinguished by (1) the encapsulation of electrolyte and multiple liquid metal droplets within an enclosed system, and (2) the creation of stable and continuous torque outside a liquid environment. In addition, a liquid metal electrical brush is introduced to operate the motor with low friction and low wear. The unique driving mechanism endows the motor with several advantages, including low friction, no sparking, low noise, versatile working environment, and being built from soft materials that could offer new opportunities for developing soft robotics.

Differential reflectivity spectroscopy on single patch nanoantennas

We present an experimental technique adapted to characterize individual metallic nanostructures in terms of differential reflectivity spectroscopy. We analyze gold patch nanoantennas holding different morphological properties. Our experimental methodology shows steady and reliable results consistent with classical analytical approximations and simulation methods. This technique allows us to identify absorption properties of metallic nanostructures commonly associated with surface plasmon resonances. By contrasting the light absorbed solely by the metallic antenna with respect to a surrounding reference medium, we found that some antennas show absorption of almost 50% of the incident light across the range of the visible spectrum. Plasmonic patch nanoantennas are promising systems in which the confinement of the electromagnetic field inside the dielectric gap strongly modifies the local density of states.

Design of a 3D-printable UHF RFID hybrid liquid antenna for biosensing applications

This paper presents a novel 3D-printable polymer-based liquid antenna for radio frequency identification (RFID) in the ultrahigh-frequency (UHF) band. Fused deposition modelling, the most widespread and inexpensive 3D printing technique, is used for printing a substrate including polypropylene (PP) and acrylonitrile butadiene styrene (ABS). An ALN-9762-WRW type RFID tag containing a meander metal antenna is modified and printed with microfluidic channels in the substrate. As an ionic liquid, a saltwater dilution is injected into the microfluidic channels designed via a computer-aided design program. A fabricated hybrid liquid antenna is tested using a 200mW UHF RFID reader with the ISO 18000-6C EPC Gen2 protocol. The sensitivity to liquid antenna radiation is measured at distances of 20–900 mm by varying saltwater dilution’s salinity and conductivity between 0 and 12000 ppm and 0-20000μS, respectively. Besides saltwater, an essential oil, peppermint oil (C62H108O7), is also used for liquid antenna. The absorption, refraction, reflection, and scattering characteristics of the polymer substratum are explored in the estimation method. The essential oil produces a buffer area in the 3D layers, which can change the polarization of the antenna. The designed and fabricated 3D-printed hybrid liquid antenna can be utilized in embedded systems suitable for chemical or biological sensing within perpetual systems such as blood or oil circuits.

A Reconfigurable Graphene Nanoantenna on Quartz Substrate

In the terahertz (THz) band, conventional metallic antennas are virtually infeasible, due to the low mobility of electrons and huge attenuation. The existing metallic THz antennas need a high power to overcome scattering losses, and tend to have a low antenna efficiency. Fortunately, graphene is an excellent choice of miniaturized antenna in millimeter/THz applications, thanks to its unique electronic properties in THz band. Therefore, this paper presents two miniaturized reconfigurable graphene antennas, and characterizes their performance in terms of frequency reconfiguration, omnidirectional radiation pattern, and radiation efficiency. The proposed graphene antennas were printed on a quartz substrate, and simulated on CST Microwave Studio. The results show that the excellence of the proposed antennas in reflection coefficient, dynamic frequency reconfiguration (DFR), and omnidirectional radiation pattern. The operation frequency of the two antennas varies from 0.74 to 1.26 THz and from 0.92 to 1.15 THz, respectively. The proposed antennas have great prospects in wireless communications/sensors.

Characterisation of a thermionic plasma source apparatus for high-density gaseous plasma antenna applications

A thermionic plasma source apparatus has been developed and characterised for high-density gaseous plasma antenna (GPA) applications. The system produces a cylindrical plasma column which is 100 mm long with a diameter of 8 mm and operates with a total plasma power consumption of 70 to 200 W, depending mainly on the DC discharge current. The plasma column electron density and temperature is measured via microwave interferometry and optical emission spectroscopy. The plasma properties are investigated for Ar, Kr and Xe at pressures from 1 to 4 mbar. The system has demonstrated higher electron densities (>1019 m−3) at low pressures (<2 mbar) than has been experimentally achieved before for GPA applications. This could allow for high gain GPA operation comparable to that of conventional metallic antennas. Additionally, the source has demonstrated operation over a wide range of electron densities, from 2 × 1018 to 1 × 1019 m−3, which can allow for frequency hopping. The plasma columns electron temperature remains around 1.5 eV for argon, largely uninfluenced by the pressure or discharge current. These plasma column measurements obtained are used to analyse the plasma properties influence on GPA performance. This analysis indicates that at high density operation, a gain is achieved which is only 22% lower than that of the conventional metallic antenna. Furthermore, the density ranges demonstrated could enable wide-range frequency hopping of over 100 MHz, with a gain greater than 1.3 dBi.

Hyperbolic metamaterial-based metal–dielectric resonator-antenna designs for GHz photon collection rates from wide-range solid-state single-photon sources

Solid-state single-photon sources (SPS) based on quantum dots as well as color centers in diamonds and silicon-carbide have promise for application in emerging quantum technologies. Many of these technologies, however, demand photon rates in the GHz range, thereby hindering the use of these SPS, for which the maximum observed count rates are limited to a few tens of MHz. Here we first study the performance of hyperbolic metamaterial-based 5-layered metal–dielectric resonator antenna structures with metallic as well as hybrid metal–dielectric antennas in the wavelength range of 600 to 1000 nm. The performance of these resonator-antenna structures was analyzed for the Purcell enhancement, quantum efficiency (QE), collection efficiency (CE), and normalized collected photon counts (NCPC). The hybrid metal–dielectric antenna helps in providing the directivity to the dipole emission, thereby significantly improving the collection efficiency. We then present the novel design of a 5-layered metal–dielectric pillar resonator. This resonator structure with a metallic cylindrical antenna over the top showed significantly large fluorescence enhancement values. The Purcell factor was observed to reach close to 1600 at 680 nm corresponding to the central peak of the nitrogen vacancy center spectrum. The NCPC value reached close to 550 at 680 nm. The maximum CE from the structure was observed to be around 60%, with the maximum QE reaching close to 80%. With the above performance, the detected photon count rates for a solid-state SPS is expected to be well into the GHz range. Our designs show a state-of-the-art improvement in the antenna performance for SPS with properties very close to a practical SPS.

Terahertz radiation processes in critically coupled graphene plasmonic nanostructures

Plasmonic excitations in graphene nanostructures provide a particularly effective means to enhance light–matter interactions at THz frequencies. Here, we investigate the use of graphene nanoribbons for narrowband THz light emission based on the excitation of plasmonic oscillations under current injection and their resonant decay into free-space radiation. A detailed theoretical model of the underlying plasmon-enhanced thermal emission mechanism is presented, whose predictions are in good agreement with the recent experimental demonstration of this phenomenon. This model highlights the key role played by the nanostructure absorption efficiency to maximize the output radiation at the plasmonic resonance frequency. Based on this idea, we explore the integration of graphene nanoribbons with nearby metallic antennas in an open cavity configuration in order to promote critical coupling to free-space radiation and correspondingly enhance the absorption (and, therefore, radiation) efficiency by up to two orders of magnitude. The simulation results indicate that this approach is promising for the development of novel THz sources with technologically relevant emission characteristics.

Excitation of localized graphene plasmons by aperiodic self-assembled arrays of metallic antennas

Infrared (IR) and terahertz plasmons in two-dimensional (2D) materials are commonly excited by metallic or dielectric grating couplers with deep-submicron features fabricated by e-beam lithography. Mass reproduction of such gratings at macroscopic scales is a labor-consuming and expensive technology. Here, we show that localized plasmons in graphene can be generated on macroscopic scales with couplers based on randomly oriented particle-like nanorods (NRs) in close proximity to graphene layer. We monitor the excitation of graphene plasmons indirectly by tracking the changes in reflection/absorption spectra of methylene blue (MB) or polymethyl methacrylate(PMMA) molecules deposited on the structure. Hybridization of spectrally broad graphene plasmon and narrow molecular oscillators results in enhanced oscillator strengths and Fano scattering related lines asymmetry in reflection spectra.

Reducing the Induction Footprint of Ultra-Wideband Antennas for Ground-Penetrating Radar in Dual-Modality Detectors

The combination of metal detection (MD) and ground-penetrating radar (GPR) has been successfully deployed to combat the threat from buried antipersonnel landmines. A number of issues arise from the close integration of these two sensing modalities. One issue is the proximity of the metallic GPR antennas to the MD coils, which affects the performance of the MD due to the eddy currents created within the GPR antenna structure. In this article, the effect of traditional solid bowtie antenna design on an MD is investigated, and avenues for the reduction of the eddy currents are explored. Three modifications to the solid bowtie design are proposed and evaluated. This article presents the measurements of the MD response to all four antenna designs using a magnetic induction spectroscopy sensor. It was found that the MD response to the bowtie antenna can be reduced by 91%–98% across the MD operating frequency band, without significantly altering the RF performance, such as reflection and transmission coefficient and radiation pattern.

Biostable conductive nanocomposite for implantable subdermal antenna

Current antennas used for communication with implantable medical devices are connected directly to the titanium device enclosure, but these enclosures are shrinking as batteries and circuits become smaller. Due to shrinking device size, a new approach is needed that allows the antenna to extend beyond the battery pack, or to be entirely separate from it. Softer properties are needed for antennas in direct contact with body tissues. This must be achieved without compromising the high electrical conductivities and stabilities required for acceptable performance. Here, a nanocomposite based approach was taken to create soft, biocompatible antennas that can be embedded in the fat layer as an alternative to the metallic antennas used today. The nanocomposite films combine the exceptional electrical conductivity, biocompatibility, and biostability of Au nanoparticles with the mechanical compliance, biocompatibility, and low water permeability of polyurethane. Nanocomposite film synthesis utilized flocculation and vacuum assisted filtration methods. The soft antenna films display high conductivities (∼103 S/m–105 S/m), reduced Young’s moduli (∼102 MPa–103 MPa), exceptional biocompatibilities characterized by in vivo and in vitro work, and notable biostabilities characterized by accelerated degradation studies. Consequently, the nanocomposite antennas are promising for chronic in vivo performance when the conductivity is above 103 S/m.

Experimental and Numerical Studies of a Tunable Plasma Antenna Sustained by RF Power

In this work, a custom plasma antenna was created, in which the pressure and gas composition could be varied. The reflection coefficient, deposited power, and the antenna transmission and reception gains were measured for an argon plasma at 0.3 torr sustained by radio frequency power up to 150 W at an excitation frequency of 98 MHz. These measurements were performed through a single RF connector with the help of a directional coupler circuit that isolated the high-power excitation signal from the low-power probing ones. It was found that the resonant frequency of this plasma antenna could be tuned over a span of 80 MHz by varying the applied power in the range of 10–150 W. The antenna gain could also be varied with applied power. At power levels exceeding 40 W, the gain approached, within 3 dB, that of a standard reference antenna. The experimental setup was modeled using ANSYS HFSS software. The simulation and experimental results were found to be in good agreement. This study shows the viability of creating tunable plasma antennas with gain comparable to that of metallic antennas.