Small Antenna Research Articles

Performance of antenna-based and Rydberg quantum RF sensors in the electrically small regime

Rydberg atom electric field sensors are tunable quantum sensors that can perform sensitive radio frequency measurements. Their qualities have piqued interest at longer wavelengths where their small size compares favorably to impedance-matched antennas. Here, we compare the signal detection sensitivity of cm-scale Rydberg sensors to similarly sized room-temperature electrically small antennas with active and passive receiver backends. We present and analyze effective circuit models for each sensor type, facilitating a fair sensitivity comparison for cm-scale sensors. We calculate that contemporary Rydberg sensor implementations are less sensitive than unmatched antennas with active amplification. However, we find that idealized Rydberg sensors operating with a maximized atom number and at the standard quantum limit may perform well beyond the capabilities of antenna-based sensors at room temperature, the sensitivities of both lying below typical atmospheric background noise.

Optimizing photosynthetic light-harvesting under stars: simple and general antenna models

In the next 10–20 years, several observatories will aim to detect the signatures of oxygenic photosynthesis on exoplanets, though targets must be carefully selected. Most known potentially habitable exo-planets orbit cool M-dwarf stars, which have limited emission in the photosynthetically active region of the spectrum (PAR, 400<λ<700\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$400< \\lambda < 700$$\\end{document} nm) used by Earth’s oxygenic photoautotrophs. Still, recent experiments have shown that model cyanobacteria, algae, and non-vascular plants grow comfortably under simulated M-dwarf light, though vascular plants struggle. Here, we hypothesize that this is partly due to the different ways they harvest light, reflecting some general rule that determines how photosynthetic antenna structures may evolve under different stars. We construct a simple thermodynamic model of an oxygenic antenna-reaction centre supercomplex and determine the optimum structure, size and absorption spectrum under light from several star types. For the hotter G (e.g. the Sun) and K-stars, a small modular antenna is optimal and qualitatively resembles the PSII-LHCII supercomplex of higher plants. For the cooler M-dwarfs, a very large antenna with a steep ’energy funnel’ is required, resembling the cyanobacterial phycobilisome. For the coolest M-dwarfs an upper limit is reached, where increasing antenna size further is subject to steep diminishing returns in photosynthetic output. We conclude that G- and K-stars could support a range of niches for oxygenic photo-autotrophs, including high-light adapted canopy vegetation that may generate detectable bio-signatures. M-dwarfs may only be able to support low light-adapted organisms that have to invest considerable resources in maintaining a large antenna. This may negatively impact global coverage and therefore detectability.

Performance Analysis and Optimization of Switch Device for VLF Communication Synchronous Tuning System Based on Coupled Inductors

The very low frequency (VLF) communication system is characterized by a limited transmit bandwidth. Due to the low operating frequency, the dimensions of VLF antennas are significantly smaller than the corresponding wavelength. Therefore, VLF antennas are considered electrically small antennas (ESAs) with high Q values and narrow bandwidth. To achieve broadband VLF communication, synchronous tuning technology is commonly employed. In this study, we focus on analyzing the performance of the switching device in the synchronous tuning system using coupled inductors and IGBT as core components. By considering the equivalent circuit of the controlled source associated with coupled inductors, we propose an adaptive input impedance optimization algorithm based on the variable capacitor (hereinafter referred to as VC-ADIO) to address issues arising from coupling coefficient variations and internal parameters within IGBTs that affect primary loop input impedance. The radiated power of the VLF antenna is improved effectively.

Miniaturized Antenna Design for Wireless and Powerless Surface Acoustic Wave Temperature Sensors.

This paper presents the introduction, design, and experimental validation of two small helical antennae. These antennae are a component of the surface acoustic wave (SAW) sensor interrogation system, which has been miniaturized to operate at 915 MHz and aims to improve the performance of wireless passive SAW temperature-sensing applications. The proposed antenna designs are the normal-mode cylindrical helical antenna (CHA) and the hemispherical helical antenna (HSHA); both designed structures are developed for the ISM band, which ranges from 902 MHz to 928 MHz. The antennae exhibit resonance at 915 MHz with an operational bandwidth of 30 MHz for the CHA and 22 MHz for the HSHA. A notch occurs in the operating band, caused by the characteristics of the SAW sensor. The presence of this notch is crucial for the temperature measurement by aiding in calculating the frequency shifting of that notch. The decrement in the resonance frequency of the SAW sensor is about 66.67 kHz for every 10 °C, which is obtained by conducting the temperature measurement of the system model across temperature environments ranging from 30 °C to 90 °C to validate the variation in system performance.

Design of an electrically small printed square loop antenna for closely spaced Tx/Rx systems

AbstractA highly miniaturised electrically small square loop antenna has been designed for operation at 2.5 GHz. The antenna is loaded using a simple series combination of two lumped inductors and two interdigitated capacitors in order to realise inherent impedance matching at a given miniaturisation level with respect to a specified source impedance, without using any external matching network. The designed antenna has an overall size of 0.061λ0 × 0.061λ0, which is approximately 75.6% miniaturised in terms of total loop length and 94% miniaturised in terms of overall footprint. The designed antenna is fabricated and the corresponding impedance matching and radiation patterns are measured, which are found to be in reasonable agreement with their simulated counterparts. Moreover, an investigation with two closely spaced electrically small SLAs, one for transmitting and the other for receiving, is carried out in this work in pursuit of maximising the isolation, which plays a crucial role in the Tx/Rx systems.

Development and analysis of small Multi Input Multi Output antenna with better isolation for Frequency Range‐2 5th Generation band applications

SummaryA simple planar wideband four‐port MIMO antenna of size 2.75𝜆l × 2.75𝜆l × 0.04𝜆l (𝜆l is the wavelength when fl is 24.26 GHz) with high isolation that offers the 24.26 to 30.2 GHz bandwidth covering the 5G FR‐2 spectrums is proposed in this work. Total fractional bandwidth of 21.8% has been achieved that covers the n257 (26.5 to 29.5 GHz), n258 (24.25 to 27.5 GHz), and n261 (27.5 to 28.35 GHz) 5G spectrums. Popular rectangular radiator‐based 4‐port MIMO antenna with symmetric stubs loaded parallel to feed line and tapered semi‐circular cut in the lower corners of patch is incorporated that exhibits an excellent isolation that is below −27 dB through the entire spectrum and the extreme realized separation is −40 dB. The projected MIMO radiator is premeditated on RT/duroid 5880 of 0.508 mm depth and permittivity (εr) of 2.2. The maximum radiation efficiency and gain of the proposed antenna are 93.07% and 6.48 dBi, respectively. The MIMO antenna parameters such as envelope correlation coefficient (ECC) were achieved lesser than 0.003, diversity gain (DG) was achieved around 10 dB, channel capacity loss (CCL) was achieved lower than 0.15 bits/s/Hz, and mean effective gain (MEG) was achieved between −3.6 dB and −3 dB throughout the impedance band, which exhibit the excellent MIMO properties, and thus, the projected antenna is appropriate for 5G/beyond 5G wireless technologies.

Design of Electrically Small Intraocular Antenna for Retinal Prosthesis System and Its Validation.

This paper presents an ultra-miniaturized circular-shaped triple band microstrip antenna as an intraocular unit applicable for retinal prosthesis. The reported antenna is developed by modifying a conventional circular-shaped patch with a pair of open-ended circular annular rings and a semicircular ring-loaded rectangular stub. Additionally, a shorting pin is used at the periphery of the patch to achieve the frequency bands of interest. Further, to make the structure electrically small and accommodate highly dense electrodes, the circular ground plane is modified by making symmetrical slots over the four quadrants and edges. Specific absorption rate distribution for 1g and 10g of different tissue layers over three operating frequencies has been studied by placing electromagnetic sources at different locations. With these arrangements, the proposed strip antenna offers multiband operation within the frequency band of 1.25 GHz (1.13-1.46 GHz), 2.45 GHz (2.24-2.66 GHz), and 3.32 GHz (3.09-3.50 GHz). Besides, circularly polarized radiation has also been achieved at 1.25 GHz with a 3-dB axial ratio bandwidth of 10 MHz. Finally, the proposed antenna structure is fabricated, and its measured performance metrics are in close aggreement with the simulated parameters. The proposed antenna's performance inside a customized canonical eye model (DMCM) and anthropomorphic Zubal head model is studied and compared with the prior studies.

3D‐structure coupled monopole designs with lower frequency resonance

AbstractIn this study, we investigated three‐dimensional configurations involving a monopole‐coupled wired ring, a hollow metallic cylinder, and wired helix spring to achieve resonance lower than quarter‐wave resonance. The resonance frequency of a quarter‐wave monopole, originally 2.05 GHz, was significantly lowered by 54.53% through effective coupling with a wired ring, and a quarter‐wave monopole properly coupled with a hollow metallic cylinder experienced a large decrease of 64.34%. The primary incentive for connecting a wired ring to a hollow metallic cylinder is to significantly reduce resonance frequency. Efforts were also made to lower resonance frequency in a wired helix spring with a length close to that of the wired ring, resulting in a substantial 78.83% reduction in resonance frequency. The −10 dB bandwidth was 14.63% for the quarter‐wave monopole, 27.21% for the monopole‐coupled wired ring, 33.71% for the monopole‐coupled hollow metallic cylinder, and 4.69% for the monopole‐coupled helix spring. The ka values for the monopole‐coupled wired ring, hollow metallic cylinder, and helix spring were 0.35, 0.27, and 0.16, respectively. Hence, these antennas can be classified as electrically small antennas. The achieved resonant frequencies have applications in various wireless communication scenarios. The experimental results from the fabricated prototype agree well with the simulation results.

Polarization conversion metasurface enabled broadband circularly polarized patch antenna

AbstractAssembling polarization conversion metasurface (PCM) and a simple patch antenna to realize a circularly polarized (CP) antenna with over 10% fractional bandwidth (BW) is a challenging task. A kind of PCM composed of S‐ring and grating structure that converts linearly polarized (LP) wave into CP wave in a broadband frequency from 8.74 to 12 GHz can address the challenge. The universality of the PCM in realizing antenna polarization conversion is verified by using a standard LP horn antenna. Then, we design a broadband LP rectangular patch antenna to demonstrate that the present PCM can be integrated with small antenna devices to achieve CP antenna. A broadband CP patch antenna with a 12.4% −10 dB BW and 11.3% 3 dB axial ratioBW is obtained. The antenna gain reaches 8.1 dB with the enhancement gain of 4.1 dB. The findings are very attractive for wireless communication, radar monitoring, and satellite systems because the proposed antenna has excellent broadband CP performances, simple structure, and easy fabrication.

Integrative implementation of scattering reduction and radiation enhancement for an electrically small antenna by subwavelength plasmas

The integrative design of scattering and radiation characteristics of antennas is of great practical significance for modern wireless communication. In this work, from the perspective of separate and cooperative modes, we comprehensively discussed the possibility of simultaneously and harmoniously implementing scattering suppression and radiation enhancement for an electrically small antenna by subwavelength plasmas. For the separate mode where the two functions are decoupled based on a two-layer structure, it is shown that an overdense–underdense core–shell density profile is preferred to achieve the optimal synergism between radiation enhancement and plasmonic-cloaking-induced invisibility, where the angular frequency of detecting waves (ωd) is supposed to be lower than that of communication signals (ωc). For the cooperative mode where the two functions are coupled within one plasma shell, the collaborative strategies between plasmonic-cloaking/Fano-resonance-induced invisibility and radiation enhancement are analyzed. The results show that the plasmonic-cloaking type requires ωd &amp;gt; ωc, while for the Fano-resonance type, ωd is larger/less than ωc when radiation enhancement is dominated by the symmetrically/asymmetrically coupled plasmon modes. Also, we provided clearer perspectives to distinguish the physical differences between plasmonic-cloaking and Fano-resonance-induced invisibility and between radiation enhancement underlying the two modes. Our results provide promising solutions for designing next-generation plasma-based tunable and intelligent stealth antennas.

Microwave ablation on ex vivo porcine pancreas: The influence of ablation parameters on ablation results and fat liquefaction.

The pancreas is adjacent to critical organs; excessive microwave ablation (MWA) can result in serious complications. The purpose of this paper is to provide the reference data of pancreas MWA for clinicians, analyze the ablation outcomes under different ablation parameters, and determine the critical temperature of pancreatic surface fat liquefaction outflow. Combinations of two power levels (30 W and 55 W), three antenna diameters (1.3 mm, 1.6 mm, and 1.9 mm), and three ablation times (1 min, 1.5 min, and 2 min) were applied to an ex vivo pig pancreas. Temperature measurements were taken at four thermocouple points. The center point is located 5 mm horizontally from the antenna slot, with a temperature measurement point located 5 mm above, below, and to the right of the center point. Main effect analysis and variance analysis were used to quantify the influences of each factor on the ablation outcomes. At 30 W, the antenna diameter contributing the most at 48.5%. At 30 W-1.3 mm-1 min, the spherical index (1.41) is closest to 1. At 55 W, the coagulation zone size was almost only affected by the ablation time, with a contribution rate of 28.7%, the temperature at point C exceeds point B. On the surface of the ex vivo porcine pancreas, the fat outflow temperature was 54ã. Ablation combinations with low power, short duration, and small antenna diameter results in a more nearly spherical coagulation zone. When performing MWA on the pancreas, it is advisable to avoid areas with higher fat content, while keeping the pancreatic surface temperature below 54°C.

An Electrically Small Antenna With Wide Tuning Capability for UHF Applications

An Electrically Small Antenna With Wide Tuning Capability for UHF Applications

Class-E, active electrically small antenna with enhanced bandwidth-efficiency product and high radiated power at the high-frequency (HF) band

Antennas operating at the high-frequency (HF) band (3–30 MHz) are frequently electrically small due to the large wavelength of electromagnetic waves (10–100 m). However, the bandwidth-efficiency products of passively matched electrically small antennas (ESAs) are fundamentally limited. Wideband HF waveforms using bandwidths of 24 kHz or more have recently received significant attention in military communications applications. Efficiently radiating such signals from conventional passive ESAs is very challenging due to fundamental physical limits on bandwidth-efficiency products of ESAs. However, active antennas are not subject to the same constraints. In this work, we present the design and experimental characterization of a high-power, class-E active ESA with enhanced bandwidth-efficiency product compared to that of passively matched ESAs. Specifically, the proposed class-E active ESA can radiate wideband HF signals with bandwidths of 24 kHz or more at 3 MHz (fractional bandwidths of ≈1%–4%), with total efficiencies ranging from 40% up to 80% depending on the modulation type and radiated power levels approaching 100 W. Our approach uses a highly efficient, integrated class-E switching circuit specifically designed to drive an electrically small, high-Q HF antenna over a bandwidth exceeding 24 kHz at 3 MHz. Using a high-Q RLC antenna model, we have successfully demonstrated wideband binary ASK, PSK, and FSK modulations with the proposed class-E active ESA. Experimental results indicate that the bandwidth-efficiency product of this class-E active ESA is 5.4–9.8 dB higher than that of an equivalent passive design with the same data rate and bit-error-rate.

Rapid construction of electrically small spherical and cylindrical antennas

Using three-dimensional (3D) printing technologies, two of the folded electrically small antennas (FESAs) are simulated, fabricated, and evaluated. A folded spherical helix and a cylindrical helix are chosen as a part of the verification of this fabrication process. FESAs are constructed on the polylactic acid (PLA) material-based 3D printed support and the effect of this extra support on antenna performances are discussed. The similarity index between measured and simulated performance parameters of both spherical helix and cylindrical helix shaped FESAs is high. The fabrication process is faster, dependable and provides the design flexibility of any complex-shaped spiral antenna.

An Ultra-Wideband Dual Polarization Antenna Array for the Detection and Localization of Bright Fast Radio Transients in the Milky Way

Fast radio bursts (FRBs) are extraordinary astrophysical phenomena characterized by short radio pulses that last only a few milliseconds, yet their power can surpass that of 500 million suns. To date, most detected FRBs originate from beyond our galaxy. However, if an FRB were to originate within the Milky Way, it could be detected using small antennas. In this paper, we propose a compact and ad-hoc antenna array designed for the efficient detection and localization of FRBs within the Milky Way. The antenna operates within the 1200–1800[Formula: see text]MHz range and consists of three sub-arrays placed in an L-shape for source localization, occupying a total volume of [Formula: see text]. Each sub-array consists of 4 miniaturized, dual-polarized, half-space radiation antenna elements, forming a one-dimensional array that allows shaping the radiation pattern to match the form of the Milky Way without exhibiting grating lobes. A prototype was constructed and characterized to validate the design. The measured results exhibit good agreement with the simulations. In addition to having a custom elongated radiation pattern, the array has attractive merits, such as low reflections at the input ports, high radiation efficiency, and a distribution that inhibits the existence of phase ambiguities, thus facilitating source localization.

Electrically Small Antenna for Sensing Application: A Review

Abstract: This study focuses on the electrically small antennas (ESAs) tailored for sensing applications. Recognizing the critical role of antenna size and performance in modern sensing systems, the research employs advanced simulation and optimization techniques to explore various configurations. Additionally, discussions on potential enhancements, such as meta material, Dielectric resonating antenna, meander line antenna, etc. integration and reconfigurable structures, provide insights for future developments in compact antenna technology for wireless sensing systems. Thus, in In this paper, a comprehensive overview of various types of electrically small antennas (ESAs) is presented, along with their significance in enhancing performance and their application in 5G and 6G communication systems.

Enhancing Students' Physical Fitness Through Optimized Training based on Genetic Algorithm

With good physical fitness, people can put more energy into their daily life, study and work. Enhancing people's physical fitness is an important foundation in the modernization of our country's socialism. The physical fitness of students has always been the primary concern of colleges and universities. To improve the basic physical ability of students, students can get a significant improvement in their own physical level to ensure the successful completion of their academic career. The data collection terminal is installed around the campus road, the campus card is carried by the students, and the wireless module with small suction cup antenna is installed on the base station and each collection terminal to form a wireless communication between the base station and the collection terminal and between the collection terminal and the campus card. The base station is connected to the Web server through a wired network. In this paper, from the current realistic needs of students' preparation for physical education tests, the physical fitness training methods and means with more obvious effects in competitive training are introduced into physical education, the methods and means of physical fitness training are preferably selected, and the training load is reasonably arranged, and the experimental results prove that the optimized physical fitness training methods and means of genetic algorithm have novel equipment, practice methods The experimental results proved that the optimized genetic algorithm physical training method and means have novel equipment, diverse and interesting exercises, focus on developing coordination quality and mobilizing more muscle fibers and muscle groups to participate in sports, which can stimulate students' interest and emphasize the reasonable use of technical movements, and enhance students' physical fitness by controlling the training intensity and interval time.

A Low-Profile Electrically Small Serrated Rectangular Patch Antenna for RFID Applications

This paper presents the design and analysis of a global system for mobile communication applications, as well as the design and analysis of a compact, bidirectional Electrically Small Antenna (ESA) at 0.9 GHz for Radio Frequency Identification (RFID) applications. In order to attain results at lower frequencies while keeping a compact size, the proposed design consists of a microstrip patch antenna in which an SRR and a semicircular-shaped SRR were subtracted from the ground plane. The dimensions of the FR4 substrate, on which this ESA was designed, were 20 × 18 × 1.6 mm. Ansys HFSS was used for the design and simulation of the antenna. Chemical etching was implemented to fabricate the ESA and MS2037C Anritsu Combinational Analyzer was applied for testing. The simulated results show that at 0.9 GHz, the ESA achieves a bandwidth of 300 MHz (700 MHz-1000 MHz). At the resonance frequency, a bidirectional radiation pattern with a 80% radiation efficiency is obtained in both H and E planes. A 90% agreement between the simulated and the fabricated results has been achieved.

Design, Fabrication and Performance Analysis of a Portable, Antenna Analyzer Based, Quartz Crystal Microbalance Measuring System with Energy Dissipation

Impedance measurements play a critical role in analyzing the electrical behavior of piezoelectric biosensors in general. Antenna analyzers are engineered to measure the specific case of input impedance for antenna systems. In this study small form factor antenna analyzer is repurposed to work as driving circuit for a Quartz Crystal Microbalance (QCM) biosensor in combination with a single board computer as an indication of how small and portable an impedance measuring system can be made, while allowing monitoring of important parameters of series and parallel resonance frequencies together with dissipation factor. A QCM crystal with a 10 MHz fundamental resonance frequency is employed to determine the limit of detection of the system in Bovine Serum Albumin (BSA) and glycerol solutions. Dissipation factor and phase angle were monitored during the experiments. Limit of detection is 20 µg/ml BSA in phosphate buffer saline (PBS) and 250 µl of glycerol in 100 ml of deionized water.

Small planar antenna array design using length and spacing through Matlab‐HFSS interfacing

SummaryThis study presents a novel method for reducing return loss and achieving lower side lobe levels in small planar antenna arrays (PAAs). Quantum particle swarm optimisation (QPSO) findings are utilised for antenna design modelling and performance assessment utilising the MATLAB‐based moment's code approach and MATLAB‐HFSS interface. The mutual coupling between antenna components is considered and computed using the method of moments (MoM). Changing the array elements' length and spacing will accomplish the abovementioned objectives. The Matlab‐based moments code calculates the antenna components' length and spacing, and the antennas' length and spacing are used to produce the radiation pattern via the Matlab‐HFSS interface. Four examples of small PAA designs are given to illustrate how well the applied methodology works. The method discussed in this paper is generic and can be employed in the future for different sizes of the array elements and the different antenna array structure designs.