Antenna Efficiency Research Articles

Broadband Antenna Design for Terahertz Communication Systems

This paper provides an overview of broadband terahertz antenna elements and arrays for integrated communication systems. The fundamental challenges of integrated on-chip and off-chip antenna design, the trade-offs between performance metrics, and the impact of interface between the chip and off-chip antennas are studied in detail. The limitations and benefits of various interface technologies are discussed. The deployment of printed circuit boards (PCB) and flexible printed circuits (FPC) technologies for implementation of efficient broadband antennas is compared against on-chip counterparts. As a proof of concept, an off-chip antenna for the 91–134 GHz is presented.

An efficient hierarchical self-assembly approach to construct structurally diverse two-step sequential energy-transfer artificial light-harvesting systems

This research provides an efficient hierarchical self-assembly approach to construct artificial LHSs featuring excellent energy transfer efficiency and high antenna effects with diverse architectures.

Bandwidth Maintenance and Decoupling for Two Planar Inverted-F Antennas Using Bridge Line

In this paper, a simple method is proposed that allows two planar inverted-F antennas (PIFAs) maintain their bandwidth while simultaneously reducing the mutual coupling between them. By creating a slit on each PIFA patch and then connecting the two PIFAs by a bridge line (BL), the bandwidth can be maintained and the mutual coupling between them can be simultaneously reduced to less than －10 dB. Therefore, total antenna efficiency can be significantly improved over a wide band. The proposed model is fabricated and measured, and the simulation results are validated by the measurement results.

Modeling analysis of patch antenna efficiency considering impedance matching characteristics of cable feed end

The small size of patch antenna makes its application scenarios diverse, and its research is quite extensive. However, the calculation of the influence of the applied excitation source and operating band on the overall operation of the antenna is very complicated, and the related modeling is less. Therefore, a patch antenna model with dual input feed is constructed by COMSOL based on the finite element analysis method. After considering the reasonableness of the coaxial cable insulation medium setting, the geometry structure of the patch antenna with dual input end feeding is constructed. The balanced antenna uses two input feeds, so in the balanced system, the operational performance of the antenna is changed by adjusting the two input signal excitation, so the spatial electric field distribution of the patch antenna under different operating frequencies is explored by applying different external applied excitation sources. Finally, the electric field change law of patch antenna under different operating working conditions is compared and analyzed, and the way to analyze the antenna operating performance is summarized.

On-Glass Grid Structure and Its Application in Highly-Transparent Antenna for Internet of Vehicles

In this paper, a low-cost printed-circuit-board (PCB) technology-based on-glass grid structure and its application in highly-transparent antenna for the internet of vehicles are presented. Firstly, a diamond-shaped grid structure on a glass substrate for high optical transparency (OT) is studied. To show the feasibility, two equal-length co-planar waveguide (CPW) transmission lines (TMLs) with conventional solid and the proposed grid structure are compared. It is found that identical electrical length and comparable performance of the two TMLs are obtained. The relationship between OT and electrical performance is also derived. In the next place, the application of the on-glass grid structure in the highly-transparent antenna design is explored, and the detailed fabrication process is presented. Finally, for demonstration, a CPW-fed wideband end-fire on-glass highly-transparent antenna covering the 5.8-GHz vehicle-to-vehicle band is designed, fabricated, and measured. Ultra-broad impedance bandwidth of 64.6% (3.08–6.02 GHz), wide H-plane beamwidths of over 146°, high antenna efficiencies of over 71.9%, and high OT of 69.8% are achieved. Easily fabricated with mature PCB technology and integrated on the vehicle windows, the proposed structure provides a low-cost highly-transparent solution for the internet of vehicles.

Dual-Band Shared-Aperture Variable Inclination Continuous Transverse Stub Antenna

This article presents a dual-band shared-aperture variable inclination continuous transverse stub (VICTS) antenna with large beam coverage for both frequency bands. A novel hybrid radiating structure is introduced to enable approximately consistent initial beam direction at the boresight for both bands and therefore large beam coverage, by exciting different sets of the radiation elements at each of the two bands. The hybrid structure is formed of interlaced conventional CTS elements and those backed by double-ridge waveguide slots. The latter suppresses the lower band while allowing the high band to radiate. This configuration allows maximum aperture reuse. A parallel-plate waveguide (PPW) diplexer combines the generated plane waves from the two bands to enable one-side excitation. Combined with the nonuniform slow wave structure (SWS), optimized amplitude distribution is achieved across the two frequency bands, thereby improving the antenna efficiency. A prototype is designed, fabricated, and measured for 12.25–12.75 GHz (Ku-band) and 19.6–21.2 GHz (K-band). The measured reflection coefficients are kept less than −11.5 dB during the beam steering. At the center frequencies of 12.5 and 20.4 GHz, the measured beam coverage of over ±49° and ±59° in elevation plane is demonstrated from a relative rotation angle of 40°. During the beam steering, the measured peak gain varies in the range of 26.1–21.1 dBi/30.4–25.2 dBi at these two frequencies.

Design of Compact Antenna Array for MIMO Implementation Using Characteristic Mode Analysis for 5G NR and Wi-Fi 6 Applications

In this paper, we present a compact antenna for 5G new radio (NR) and Wi-Fi 6 applications. Using characteristic mode analysis (CMA), two orthogonal modes have been separated and then a gapcoupled shaped feed-line has been used to excite the radiator. An open stub is added to achieve the wide operating bandwidth of the antenna. The size of a single antenna element and the 1×2 array-unit (AU) are 20×21.5 mm2 and 40×21.5 mm2, respectively. The operating and fractional bandwidths (FBW) of the AU are 5.18-7.71GHz and 39.25%, respectively. The proposed AU is used to develop a number of radiating element-independent multiple-input-multiple-output (MIMO) antennas comprising of 2AUs, 4AUs, and 8AUs with identical electrical characteristics and good isolation (I).18.8 dB. All the AUs have realized gain 3.0 dBi, and the total antenna efficiency 70% making it suitable for the single-user MIMO (SU-MIMO) and multiple users MIMO (MU-MIMO) needed for Wi-Fi 6 applications. To show the application of these antennas, the deployment scenario of a 16AUs MIMO antenna on a large size ground plane which mimics the smart TV panel and router chassis, etc., is also presented. These AUs may find potential applications in radiator-number independent MIMO systems.

Low-Profile Laptop Antenna Design for Wi-Fi 6E Band

In this letter, a low-profile (3.5 mm) dual-band operation laptop antenna designed for wireless fidelity 6E (2.4/5/6 GHz) bands is proposed. The proposed antenna is a double-slit loaded modified inverted-L antenna (ILA) structure that can excite multifrequency mode, allowing it to fully cover the desired 5 and 6 GHz bands (5150–7125 MHz). To further cover the 2.4 GHz band (2400–2485 MHz), a C-shaped coupling strip is further printed behind the modified ILA. Besides exhibiting a small planar size of only 22.3 mm × 3.5 mm that allows it to be applied in a narrow screen bezel laptop, the proposed antenna can still yield desirable measured 10 dB bandwidths of 2.4–2.485 and 4.74–7.26 GHz, with good antenna efficiency of more than 40% and 61%, respectively.

THE INFLUENCE OF MISMATCHES ON THE RESULTS OF MEASURING THE NOISE TEMPERATURE AND THE EFFECTIVE APERTURE OF ANTENNAS BY RADIO ASTRONOMY METHODS

The radio astronomy methods for measuring antenna properties allow to measure noise temperature and effective antennas aperture with high accuracy when the antenna and the standard load are ideally matched in the input of the radiometer. Due to appear-ance of high-efficiency antennas, the requirements to high-precision measurements of noise temperature and the effective aperture of antennas have increased. The earth meth-ods for measuring those antenna parameters turns out to be insufficient and, in some cas-es, impossible. In practice, antenna parameters measuring and radioastronomy research with high efficiency convincingly proved that the difficulties in measuring by earth meth-ods are relatively easy to overcome. As high efficiency antennas and low noise receivers have appeared the require-ments to measuring antenna properties with high accuracy have increased. For measuring the parameters of large antennas more than 10 cosmic standard sources are chosen. Among them standard sources Cassiopeia - A, Cygnus - A, Taurus - A, and Virgo – A meet the requirements, that have an aperture of up to 80 m of mirrors. In real systems antenna – radiometer, standard load – radiometer always exist a whole reason leading to power re-reflection. At that, the measure and values are characterized by errors (mismatch errors). The goal of the work is consideration of errors which are conditioned by mismatch and giving methods to decrease them, which allows to eliminate the influence of mis-matches in the measurement results. The influence of mismatch are studied when we measure noise temperature and effective antenna aperture in a system which consists of a noisy signal source plus radiometer. Methods which decrease and fully eliminate the influ-ence of those mismatches in measurement results are proposed.

Flexible Antenna Sensor in Thumb Spica Splint for Noninvasive Monitoring of Fluctuating Blood Glucose Levels

Antenna is used as a sensor in wearable technology because of its small size. Reduced flexible antenna size avoids mounting problems and crumbling effects on the human skin region during signal acquisition. Moreover, continuous diabetes monitoring needs an efficient antenna sensor design. In this article, we develop a continuous glucose monitoring device using a flexible antenna sensor planted inside the thumb spica splint glove. The flexible antenna sensor comprises polyimide substrate with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\xi _{r}$ </tex-math></inline-formula> = 3.5, tan <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\delta $ </tex-math></inline-formula> = 0.0027, and a thickness of 0.1 mm. The proposed flexible antenna sensor senses dielectric radiations from glucose in the blood and improves the accuracy of glucose-level prediction. Traditional antenna sensor methods use skin layers and muscles as sources of permittivity, resulting in errors in diabetic value measurement. The acquired antenna sensor signal from the designed thumb spica splint glove is processed using the tunable <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}$ </tex-math></inline-formula> -factor wavelet transform (TQWT) algorithm. It differentiates the dielectric properties of glucose in the blood, skin, and muscle through subband energy levels. The subband energy level of glucose from the proposed antenna sensor and the quadratic regression algorithm is used to predict the human glucose level. The predicted glucose levels using the proposed flexible antenna are validated through Accu-Chek Active Glucometer. From experimental results, the proposed method-based glucose prediction-level accuracy achieved about 96.8% compared to traditional methods.

Design of a Miniature Rectangular Patch Antenna for KU Band Applications

A significant portion of communication devices employs microstrip antennas because of their compact size, low profile, and ability to conform to both planar and non-planar surfaces. To achieve this, we present a miniature inset-fed rectangular patch antenna using partial ground plane for Ku band applications. The proposed antenna design used an operating frequency of 15.5 GHz, a FR4 substrate with a dielectric constant of 4.3, and a thickness of 1.4 mm. It is fed by a 50 Ω inset feedline. Computer simulation technology (CST) software is used to design, simulate, and analyze. The simulation yields the antenna performance parameters, including return loss (S11), bandwidth, VSWR, gain, directivity, and radiation efficiency. The simulation findings revealed that the proposed antenna resonated at 15.5 GHz, with a return loss of -22.312 dB, a bandwidth of 2.73 GHz (2730 MHz), VSWR of 1.17, a gain of 3.843 dBi, a directivity of 5.926 dBi, and an antenna efficiency of -2.083 dB (61.901%).

METHOD OF DESIGNING ANTENNAS BY SYNTHESIS OF A BAND FILTER

A novel antenna design technique is proposed, which offers bandwidth enhancement up to the limits defined by element radiation efficiency. The employed technique is referred as frequency pulling (FP) as it mimics the insertion loss design methodology of bandpass filters. This is essentially a wideband matching approach pushing the antenna efficiency to the limits set up by radiation efficiency. There are three options towards this trend: (1) first to enhance a single element bandwidth (compact element) exploiting its possibly multiple symmetrical feeding points as distinct resonator ports, (2) frequency pulled array as to design a small antenna array (less than about 10 elements) where eachelement acts as a resonator and (3) second order frequency-pulled array as to build a small array using compact elements of category (1). Similar to the band-pass filter design, all antennas or distinct-port circuits resonate at the same resonant frequency when isolated, cascading two or more of them; FP yields to multiple-overlapping successive resonances in their overall response. Although the proposed technique is general within this first effort, it is applied to simple patch antenna elements exhibiting multiple symmetrical feeding points, namely two-for rectangular, four-for square and five-for pentagonal. The third option is applied to an array of three compact 4-feeding point square elements offering triple bandwidth with respect to the already wideband single element. However, this is achieved at the expense of a significant beam squint. Thus, in general, these wideband compact elements should be used within a classical array design. Further bandwidth enhancement using FP to antenna elements with inherent multiple resonances as patches with slots or truncated edges constitutes our next task. Their inherent wider bandwidth in radiation efficiency is expected to allow multiply higher bandwidths when exploited with our FP technique.

Machine learning-based theoretical optimization of antenna design

The changing communication era demands higher precision and more efficient antenna designs, which require more automated processing methods and more powerful data storage techniques. Currently, machine learning can optimize solutions at high speed and has shown powerful performance in various fields, attracting much attention. This paper summarizes the application of machine learning in antenna design, analyzing its basic concepts and relationship with artificial intelligence and neural networks. This paper also compares the methods and effects produced in each application by analyzing the results of electromagnetic characteristic curves. The results show that machine learning reduces computational errors and computation time and is able to predict the next input and correct the antenna behavior with high accuracy. The key outcomes are quickening the antenna design procedure, decreased mistakes, and wasted time, and increased antenna design accuracy. Machine learning algorithms can assist antenna design in the future to improve antenna accuracy and design efficiency.

Terahertz antenna with controllable and tunable filtering characteristics

− A terahertz (THz) wideband antenna is implemented and numerically studied for achieving the controllable and tunable filtering characteristics. A rectangular-shaped metal-based monopole antenna is designed for obtaining the wideband response. A slot is engraved in the radiator to obtain the filtering characteristics. The slot in radiator is filled with graphene material which acts as the controller and tuner of obtained filtering characteristics. The surface conductivity of graphene strip is tuned and hence the field confinement in the covered area is varied which tunes and controls the obtained filtering characteristics. The antenna provides monopole like radiation pattern with a high value of gain and radiation efficiency which decay in the filtered frequency band with a sharp roll-off rate to attain their minimum value. The gain and efficiency of antenna remain approximately unchanged in the passband even after application of graphene in antenna structure. This signifies the effectiveness of the proposed technique for obtaining the filtering characteristics in antenna response. Moreover, the antenna response is validated through an electrical circuit theory approach.

Investigation of Multi-Band Reconfigurable Triangular Microstrip Antenna on Magnetic YIG Substrate

Reconfigurable antennas based on magnetised ferrite substrate and electronic components present a remarkable interest for nowadays antennas. The present research contribution deals to investigate an efficient multiband tuneable triangular microstrip antenna with acceptable characteristics, able to operate from 2.6 GHz to 5.8 GHz requiring frequency and polarization agility by dual reconfigurability using a YIG (Yttrium Iron Garnet) substrate and PIN diode. Different magnetic bias fields were applied to the proposed antenna for ON and OFF states. The obtained results and analysis demonstrate the efficiency of magnetic frequency tuning and a high stability of the radiated field, the antenna bandwidth can reach 1300 MHz for ON state, and a maximum tuning range close to 550 MHz is observed. The proposed antenna design exhibits a linear polarization and stable E and H–plane radiation pattern performance at resonance frequencies over the operating bands. These characteristics make the antenna suitable for multiband wireless communications requiring frequency agility.

Frequency selective reconfigurable microstrip antenna for cognitive radio applications

For the efficient utilization of electromagnetic radio spectrum cognitive radio communication system is employed, which deals with the spectrum scarcity. An efficient antenna is essential for the appropriate selection of the available frequencies. This paper presents the design and implementation of frequency reconfigurable antenna for cognitive radio applications. Reconfigurable inverted U-shape microstrip patch antenna feeding by 50 W microstrip line is designed and implemented. The designed and implemented antenna applied for switching frequency between 3.25 GHz to 4.1 GHz by choosing a specific sub-band from the specified wideband. The frequency reconfiguration was achieved by using twelve PIN diode switches by placing them on the slotted ground plane of the antenna. The PIN diodes were organized in such a way as to alter antenna bandwidth and to shift the operating band. The switching of PIN diodes controlled using the microcontroller to select the appropriate frequency. The performance of the simulated and fabricated antenna is investigated using different parameters.

Design of SIW based Frequency Reconfigurable Antenna for K/Ku band applications

A frequency reconfigurable antenna based on substrate integrated waveguide (SIW) technology is proposed in this paper for K/Ku band applications. In most of the previous reconfigurable structures terminal SIW was used but here in this proposed structure, terminal as well as the blind vias is being implanted to achieve maximum reconfigurability and better efficiency of the miniature antenna. The antenna parameters are analysed thoroughly without diode as well as with diode. According to the measurements, the suggested antenna has an impedance bandwidth of 12 to 12.8 GHz in off condition and in addition to this from 22 to 22.8 GHz in ON condition with a peak gain of 7.5 dB. The radiation efficiency of proposed work is 90%.

A Low-Cost SISL Differentially Fed Dual-Polarized Stacked Patch Antenna With Enhanced Common-Mode Suppression Using Characteristic Mode Analysis

A wideband differentially fed dual-polarized stacked patch antenna with high common-mode (CM) suppression is proposed in this article using the characteristic mode analysis (CMA) and the substrate integrated suspended line (SISL) technology. Based on the CMA, orthogonal slots are loaded within the stacked patch to enhance the directivity of the second-order degenerate modes and reallocate the resonating frequency of the fundamental degenerate modes. A crossed dipole is introduced within the driven patch to ensure polarization uniformity between the two paired degeneracies. The CM suppression level ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{S}_{\mathrm {CC}}11$ </tex-math></inline-formula> ) is enhanced from–10 to–1.30 dB within the frequency range of 4.0–7.0 GHz by embedding circular slots embedded within the stacked patch and controlling the slot radius. Measured results demonstrate a–10 dB differential impedance bandwidth of 28.4% (4.62–6.18 GHz) and high isolation of better than–39.5 dB between the differential ports. The antenna depicts stable measured radiation patterns with low cross-polarization (<–30 dB). The measured average antenna gain and efficiency are 9.55 dBi and 85.5% within the DM passband. In addition, a high <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{S}_{\mathrm {CC}}11$ </tex-math></inline-formula> better than–1.05 dB is measured within the desired DM band.

SAR Reduction With Antenna Cluster Technique

An efficient and straightforward antenna design method is presented that maximizes the ratio of total efficiency and specific absorption rate (SAR). This goal is achieved with a multiport antenna cluster technique where several ports are excited collectively with appropriate feeding weights. These weights are found as an eigenvalue solution formulated in terms of the radiated and near-field power of an antenna. The method relies on both the near-field (SAR) and far-field (radiation) physics of an antenna and it can be applied to various design cases. The importance of the maximization of total-efficiency-SAR ratio and the feasibility of the proposed approach are demonstrated with a simple multiple-dipole antenna example and with a more realistic antenna design where a metal-rimmed antenna is held in the user’s hand.

A Half-Mode Groove Gap Waveguide for Single-Layer Antennas in the Millimeter-Wave Band

This letter presents an alternative to significantly reduce the time and difficulty in designing and fabricating antennas in gap waveguide (GW) technology by using a novel half-mode groove GW. GW is often criticized within the subtractive manufacturing field for the high fabrication time required to mill many pins with the waveguides in the same piece. To demonstrate the possibilities of this new approach, two different antennas have been designed, fabricated, and measured. Both antennas, formed by only two pieces with no contact, operate from 29 to 31 GHz and present reflection coefficients below <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> 10 dB and high antenna efficiency above 90 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> . In addition, both prototypes can reuse the bed of nails, which favors shorter manufacturing times and lower costs in the development phase.