Circular ring shaped ultra-wideband metamaterial absorber with polarization insensitivity for energy harvesting

<span>A circular ring-shaped metamaterial (CRM) absorber was designed to harvest radio frequency (RF) energy in the ultra-wideband (UWB) frequency band applications. The proposed metamaterial unit cell features a circular shaped structure, with rectangular strip lines connected in the form of a cross leaving a square shaped slot at center. The unit cell dimensions are 15×15×1.6 mm. The absorber was etched on a low cost FR4 substrate having a dielectric constant of 4.4. Ansys high frequency structure simulator (HFSS) software was used for simulation and the analysis were carried out for unit cell, 2×2, 3×3, and 4×4 array structures. The absorber parameters plotted are absorption characteristics and reflection characteristics. Also, the metamaterial parameters (μeff) and (εeff) are also retrieved from the absorber parameters and analyzed. From the analysis, the values (μeff) and (εeff) were found to be negative, leaving refractive index also negative (n&lt;0), which proved the metamaterial property. The proposed CRM absorber showed good absorption characteristics of more than 80% and also metamaterial property in the entire UWB band (4-13 GHz). Hence the absorber proves to be a good candidate in powering low power sensors/microcontrollers for internet of things (IoT) applications.</span>

Transparent 2-Element 5G MIMO Antenna for Sub-6 GHz Applications

A dual-port transparent multiple-input multiple-output (MIMO) antenna resonating at sub-6 GHz 5G band is proposed by using patch/ground material as transparent conductive oxide (AgHT-8) and a transparent Plexiglas substrate. Two identical circular-shaped radiating elements fed by using a microstrip feedline are designed using the finite element method (FEM) based high-frequency structure simulator (HFSS) software. The effect of the isolation mechanism is discussed using two cases. In case 1, the two horizontally positioned elements are oriented in a similar direction with a separate ground plane, whereas in case 2, the elements are vertically placed facing opposite to each other with an allied ground. In both cases, the transparent antennas span over a −10 dB band of 4.65 to 4.97 GHz (300 MHz) with isolation greater than 15 dB among two elements. The diversity parameters are also analyzed for both the cases covering the correlation coefficient (ECC), mean effective gain (MEG), diversity gain (DG), and channel capacity loss (CCL). The average gain and efficiency above 1 dBi and 45%, respectively with satisfactory MIMO diversity performance, makes the transparent MIMO antenna an appropriate choice for smart IoT devices working in the sub-6 GHz 5G band by mitigating the co-site location and visual clutter issues.

A Novel Wideband Coplanar Waveguide (CPW) Fed Antenna for Energy Harvesting at 2.45 GHz

Conversion of electric power from a high voltage to a low voltage causes power losses that also require efficient circuit design techniques to be implemented for durability of a system. Energy harvesting techniques have been implemented to cater to the power demand of low power electronic devices using electromagnetic, electrostatic, and other related technologies. This paper represents the compact design of an antenna system tuned at 2.45 GHz for radio frequency energy harvesting applications. The simulation results achieve a better gain of 5.4 dB along with enhanced radiation patterns. Impedance matching for 50 Ohm is implemented using a high frequency structure simulator (HFSS). The results of the antenna gain, VSWR, and radiation efficiency are compared with the literature. Furthermore, the size of the antenna system has great significance in medical and military related applications; this aspect is also considered in this design and overall, a 20 mm × 37 mm compact antenna is achieved by using mm wave considerations. This antenna design can be embedded in the wireless sensor network (WSN), RFID, and IoT related application to generate the required power required. Mostly, WSN nodes currently use traditional batteries that need to be replaced after some time. As in most cases, WSN nodes are scattered in wide geographical areas, so maintaining the power to these systems becomes challenging. RF energy harvesting provides a solution in these cases where wind, vibration, and solar sources are scarce. The simulated impedance bandwidth is found to range from 1.1 GHz to 5.2 GHz within the acceptable VSWR values.

Optimization of the Coupling Coefficient of the Inductive Link for Wireless Power Transfer to Biomedical Implants

This work focuses on the optimization of coupling coefficient (k) of the inductive link for the wireless power transfer (WPT) system to be used in implantable medical devices (IMDs) of centimeter size. The analytic expression of k is presented. Simulations are conducted by using the high-frequency structure simulator (HFSS). Analytic results are verified with simulations. The receiving (Rx) coil is implanted in the body and set as a circular coil with a radius of 5 millimeters for reducing the risk of tissue inflammation. The inductive link under misalignment scenarios is optimized to improve k. When the distance between the transmitting (Tx) and Rx coils is fixed at 20 mm, it is found that, to maximize k, the Tx coil in a planar spiral configuration with an average radius of 20 mm is preferred, and the Rx coil in a solenoid configuration with a wire pitch of 0.7 mm is recommended. Based on these optimization results, an inductive link WPT system is proposed; the coupling coefficient k, the power transfer efficiency (PTE), and the maximum power delivered to the load (MPDL) of the system are obtained with both simulation and experiment. Different media of air, muscle, and bone separating the Tx and Rx coils are tested. For the muscle (bone) medium, PTE is 44.14% (43.07%) and MPDL is 145.38 mW (128.13 mW), respectively.

Effects of the Feedline Position on Microstrip Patch Antenna Performance

In this study, it is aimed to demonstrate the effects of the feed line position on the operating frequency, return loss and bandwidth of the rectangular patch microstrip antenna. For this purpose, a compact-sized antenna that can operate at 2.4-2.45 GHz frequencies is designed in High Frequency Structure Simulator (HFSS) program. Then, the position of the feedline is changed horizontally and vertically, and its effects are observed. The results obtained after the modificaions are given and discussed. It is stated that the feed line position is a very important parameter that affects the basic characteristics of the antenna.

Investigations on Three-Pole Microstrip Low-Pass Filters Incorporated with DGS and Fractals for Selectivity Improvement

In this paper, an investigation on compact microstrip low-pass filters (MLPFs) with extremely perfect low-pass characteristics and improved out-band suppression has been carried out for the improvement of the selectivity parameter ([Formula: see text]). For this purpose, two different defected ground structures (DGSs) based on Moore fractals and Meander line have been designed and experimentally validated. The proposed third-order low-pass filter (LPF) configurations are designed and simulated using the High-Frequency Structure Simulator (HFSS). To validate the simulation models, the prototypes of the suggested low-pass filters are fabricated using Teflon (TM) substrate having a relative permittivity of 2.65 and a loss tangent of 0.001, and measured using the Vector Network Analyzer. The simulation and measurement results are in good agreement. The proposed filters occupy a compact size of [Formula: see text]. The selectivity parameter values for the proposed Moore fractals- and Meander line-modeled DGS-based LPFs are 425[Formula: see text]dB/GHz and 850[Formula: see text]dB/GHz, respectively. The proposed microstrip low-pass filters offer a significant improvement in the selectivity parameter, offering a maximum value of 850[Formula: see text]dB/GHz. The proposed filters exhibit a very high figure of merit (FOM), reporting 71,335 for Moore fractals-based LPF and 118,354 for the Meander line-based LPF. These proposed filters are suitable for advanced mobile phone services, [Formula: see text]-band radar, Global Positioning System, mobile, paging services, Wi-Fi, Bluetooth and wireless LAN.

Design of frequency reconfigurable planar antenna using artificial neural network

In this paper, the design of frequency reconfigurable planar antenna by incorporation of metasurface superstrate (FRPA-MSS) is presented using an artificial neural network. The dual-layer radiating structure is created on a 1.524 mm thick Rogers RO4350B substrate board (εr = 3.48, tan δ = 0.0037). The candidate antenna is designed and analyzed using a high-frequency structure simulator (HFSS) tool. The transfer matrix method is employed for the successful retrieval of electromagnetic properties of the metamaterial. Frequency reconfiguration is achieved by placing the metasurface superstrate onto the rectangular patch antenna. A simplified ANN approach has been employed for the design of metasurface incorporated proposed antenna. Presented prototypes are characterized through experimental measurements. It is found from the practical observations that the proposed antenna effectively reconfigures the tuning range from 5.03 to 6.13 GHz. Moreover, the presented antenna operates efficiently with agreeable gain, good impedance matching, and stable pattern characteristics across the entire operational bandwidth. The experimental results obtained validate the simulated performance.

Performance evaluation and design of 5G communication-based millimeter wave antenna

Multiple categories of electronic devices have been introduced recently in response to the demands and developments in the industry. Around 5.19 billion telecom services subscribers today have a significant effect on the allocation and utilization of bandwidth, and hence, there is extensive need to use higher-frequency bands, e.g., mm band to achieve the required quality of service since there is extensive need to shift the paradigm to the next generation. For 5G networks, antenna structuring and designing is an integral part of the communication system. In antenna theory, improving antenna gain is important to attain isotropic antenna, antenna gain can be improved by the controlled behavior of frequencies, beam forming and choosing the right antenna fabric. Through antenna design using different substrates thickness, the propagation losses are examined in order to determine the variation with radiation characteristics. In this way, the examination of the 5G mm-wave spectrum with comparative analysis of input impedance, gain and radiation efficiency is shown through mathematical modeling. Using this approach, the antenna efficiency is improved by up to 20% with increase in substrate thickness. Different antenna arrays have been designed for effective improvement in reflection coefficients. The results are obtained using simulation of antenna in CST and high-frequency structure simulator.

THE EFFECTS OF STRUCTURAL-INDUCED DEFORMATION ON THE RESONANCE OF PATCH ANTENNAS

Conformal Loadbearing Antenna Structures (CLAS) take advantage of a combination of structural and electromagnetic functions. CLAS have been developed as an advanced replacement for conventional antennas (such as blades, wires and dishes) to improve the structural efficiency, as well as the electromagnetic and aerodynamic performance of a platform. The CLAS concept permits the direct integration of microwave radiating elements in the structural skin of a platform. Therefore, the antenna will be subjected to structural loading and will deform accordingly. The effects of these structural-induced deformations on the resonant frequency of the antenna will be reported in this paper. This paper will investigate the performance of a carbon veil patch antenna when it is subject to static in-plane. The work presented will include the effects of in-plane loading on the resonant behavior of the patch antenna when the carbon veil is fully bonded and when it is disbonded by the parent structure. This paper will also discuss the effects of substrate delamination on the RF response of the patch antenna. The RF characteristics of the antenna will be modelled using ANSYS High Frequency Structure Simulator (HFSS).

Enhancing the resonance characteristics of circular patch antenna for SHF applications

Microstrip patch antenna is attractive for various applications due to its easy fabrication, low cost and small size. It simply comprises of a radiating patch and ground plane that are separated by a dielectric substrate. However, the resonance bandwidth of the microstrip antenna is still an issue that needs to be considered in research. This paper aims to enhance the bandwidth of a microstrip antenna or introduce more resonant frequencies within the Super High Frequency (SHF) band. The paper demonstrates empirical results for circular-shaped patch antenna using the High Frequency Structure Simulator (HFSS). It begins by investigating different patch sizes and substrate materials, so that an optimal preliminary design is introduced. Then, different slot shapes are inserted into the patch for significant enhancement of the resonance characteristics. As a result, new ultra-wideband (UWB) antenna designs are presented with bandwidth results reaching 15.5 GHz within the C, X, Ku and K bands. Also, new multiband antenna designs are presented with improved reflection valleys in the Ku, K and Ka bands.