Antenna Size Research Articles

Structural insights into the assembly and energy transfer of the Lhcb9-dependent photosystem I from moss Physcomitrium patens.

In plants and green algae, light-harvesting complexes I and II (LHCI and LHCII) constitute the antennae of photosystem I (PSI), thus effectively increasing the cross-section of the PSI core. The moss Physcomitrium patens (P. patens) represents a well-studied primary land-dwelling photosynthetic autotroph branching from the common ancestor of green algae and land plants at the early stage of evolution. P. patens possesses at least three types of PSI with different antenna sizes. The largest PSI form (PpPSI-L) exhibits a unique organization found neither in flowering plants nor in algae. Its formation is mediated by the P. patens-specific LHC protein, Lhcb9. While previous studies have revealed the overall architecture of PpPSI-L, its assembly details and the relationship between different PpPSI types remain unclear. Here we report the high-resolution structure of PpPSI-L. We identified 14 PSI core subunits, one Lhcb9, one phosphorylated LHCII trimer and eight LHCI monomers arranged as two belts. Our structural analysis established the essential role of Lhcb9 and the phosphorylated LHCII in stabilizing the complex. In addition, our results suggest that PpPSI switches between different types, which share identical modules. This feature may contribute to the dynamic adjustment of the light-harvesting capability of PSI under different light conditions.

Excess manganese increases photosynthetic activity via enhanced reducing center and antenna plasticity in Chlorella vulgaris

Photosynthesis relies on many easily oxidizable/reducible transition metals found in the metalloenzymes that make up much of the photosynthetic electron transport chain (ETC). One of these is manganese, an essential cofactor of photosystem II (PSII) and a component of the oxygen-evolving complex, the only biological entity capable of oxidizing water. Additionally, manganese is a cofactor in enzymatic antioxidants, notably the superoxide dismutases—which are localized to the chloroplastic membrane. However, unlike other metals found in the photosynthetic ETC, previous research has shown exposure to excess manganese enhances photosynthetic activity rather than diminishing it. In this study, the impact of PSII heterogeneity on overall performance was investigated using chlorophyll fluorescence, a rapid, non-invasive technique that probed for overall photosynthetic efficiency, reducing site activity, and antenna size and distribution. These measurements unveiled an enhanced plasticity of PSII following excess manganese exposure, in which overall performance and reducing center activity increased while antenna size and proportion of PSIIβ centers decreased. This enhanced activity suggests manganese may hold the key to improving photosynthetic efficiency beyond that which is observed in nature.

A compact printed hybrid‐mode antenna for dual‐band dual‐sense circular polarisation

AbstractA compact printed hybrid‐mode antenna for dual‐band dual‐sense circular polarisation (CP) has been proposed. To achieve dual‐band dual‐sense CP, a hybrid mode produced by an L‐shaped element and a loop element is used. In the lower frequency band, the left‐handed CP is radiated by a vertical electric field from the L‐shaped element and a horizontal electric field from the loop element. In the higher frequency band, the right‐handed CP is radiated by a horizontal electric field from the L‐shaped element and a vertical electric field from the loop element. Both the L‐shaped and the loop elements produce resonances in the lower and higher frequency bands. The operational principle for dual‐band dual‐sense CP is clarified using the simulated orthogonal components of the electric fields and the simulated electric current distributions. Parametric studies are discussed in the design procedure. The simulated and measured input reflection coefficient, axial ratio, absolute gain, and radiation pattern are presented. The measured bandwidths of −10dB‐input reflection coefficient with a 3dB‐axial ratio are 2.37–2.55 GHz (7.32%) in the lower frequency band and 3.38–3.70 GHz (9.04%) in the higher frequency band. The antenna size is 0.0741λ2.452 and 0.151λ3.52 (λ f is a wavelength at f GHz).

Miniaturization of ultra‐wideband Vivaldi antenna by utilizing double‐layer structure with slots

AbstractIn a Vivaldi antenna, a symmetrical double‐sided structure is introduced to reduce the lower‐side frequency. Multiple transverse and longitudinal slots loaded into the redundant conductor layer of the Vivaldi structure can stimulate resonant modes at the higher frequency end, further broadening the antenna bandwidth towards high frequencies. Meanwhile, impedance matching slots are introduced into the conductor layer on the feed side to achieve ultra‐wideband (UWB) antenna. The overall size of the final antenna is 23.5 mm × 30.0 mm × 2.4 mm, while the relative bandwidth (S11 < –10 dB) reaches 142% (2.49–14.78 GHz). This miniaturized UWB antenna has similar directional patterns in the operating band, with an average gain of 4.82 dB.

Generation and characterization of reduced PSII antenna size mutants of Chlorella sorokiniana for improved biomass

Generation and characterization of reduced PSII antenna size mutants of Chlorella sorokiniana for improved biomass

Design and optimization of a graphene-enhanced tunable wire-grid-like polarizer operating in the 0.5–0.75 THz band

Wireless networks are experiencing a surge in demand for data bandwidth, necessitating higher performance and faster data rates. However, conventional signal processing techniques are inadequate for potential future developments that require the use of higher carrier frequencies. The terahertz region of the spectrum has become an increasingly prominent area of research for wireless communication applications. However, components commonly utilized for lower frequency ranges exhibit inefficiencies and significant losses when operating at terahertz frequencies. Furthermore, the miniaturization of antenna sizes to the micrometer scale has made the concept of perfect electric conductor ineffective in the terahertz range. Therefore, it is imperative to establish a reference system of electromagnetic devices. Due to the essential role of polarization in wireless communication and the convenient and widely used properties of wire-grid polarizers, this article establishes a reference for the polarization effect of wire grid polarizers and obtains their optimal parameters. The optimal parameters are 61.58 μm distance, 20 μm thickness and 20 μm width within the frequency band from 0.5 THz to 0.75 THz. We proposed a three-layer structure consisting of copper wire-grids, monolayer graphene, and silicon dioxide substrate to combine the remarkable electromagnetic properties of graphene with wire-grids polarizer. The resulting graphene-enhanced polarizer achieved excellent polarization improvement, with a strongly reduced S21 transmission magnitude up to −55 dB compared to the case without graphene, representing an approximately 20 dB decrease.

Modified Babinet Principle for Complementary Antennas in a Dielectric Half-Space

In this letter, the modified Babinet principle is applied to complementary antennas on the substrate interface. First, it is verified that the existing Babinet principle only holds for complementary metallic elements in the homogenized substrate. Then, the effective relative permittivity is introduced into the substrate interface through the zero-thickness effective substrate, which can keep the electromagnetic behavior (such as total electrical field and surface current density) of metallic element unchanged. Thereby, the modified Babinet principle can be established for arbitrary complementary metallic elements on the substrate interface. Finally, the proposed theory is applied to input impedances of complementary antennas on the substrate interface. The simulation strongly supports the proposed theory, regardless of the substrates and antenna sizes. The study not only establishes the modified Babinet principle for complementary metallic elements on the substrate interface, but also clarifies the electromagnetic influence of effective relative permittivity for the metallic element at the substrate interface.

Self-decoupled tri band MIMO antenna operating over ISM, WLAN and C-band for 5G applications

For ISM, WLAN, and C-band applications, a multiple-stub loaded CPW feed tri-band antenna is presented in this study. The suggested antenna uses Rogers RT/Duroid 5880 substrate material with a 0.79 mm thickness. The antenna has a straightforward design, measures just 33 mm × 20 mm, and provides broad performance with excellent gain. A 4-port MIMO arrangement is subsequently used to fulfill the demands of upcoming 5G and 6G devices. The MIMO antenna contains little space between elements and offers a good value of < –30 dB isolation. The overall size of a 4-port MIMO antenna is MW × ML × H = 60 mm × 60 mm × 0.79 mm and offers a minimum value of ECC <0.0001. Besides ECC, the MIMO antenna also offers good results in terms of DG, CCL, and MEG. To validate the findings of the simulation, a hardware prototype of the suggested antenna is created. It is clear that the results from simulations and measurements coincide well. The proposed antenna was created with the aid of the software tool Ansoft HFSSv9. Also, the proposed work is evaluated against previously published material. The suggested antenna has a small size, a simple geometry, a wideband, high gain, and a good value for the MIMO parameters, according to the results and comparisons of the proposed work (in terms of ECC, DG, CCL, and MEG), and low spacing between elements, which makes it a promising candidate for future 5G devices operating over ISM, WLAN, and C–band applications.

A truncated antenna mutant of the unicellular green alga Coccomyxa sp. strain Obi shows better biomass productivity than the wild-type strain under higher irradiance, at higher cell density, and in greater depth of culture

Mutants with reduced chlorophyll contents were isolated from the industrial green alga Coccomyxa sp. strain Obi after chemical mutagenesis. The growth of most of the isolates was slower than that of the parental strain with one exception, which was named strain 5P. Chlorophyll a (Chl a) content in rapidly growing cells of strain 5P was >30 % lower than the wild-type level, while its chlorophyll b (Chl b) content was below 20 %. Strain 5P did not have trimeric light-harvesting antenna complexes (LHCs) for photosystem (PS) II, but its reaction centers for PSI and PSII were intact. Whole-genome resequencing of strain 5P identified many mutations, including a nonsynonymous mutation in the gene encoding chlorophyllide a oxygenase (CAO) involved in the biosynthesis of Chl b. Chl b is present only in LHCs, and the reduction of Chl b confers the reduction of LHCs that accompanies the reduction of Chl a. Genetic complementation of strain 5P with the genomic CAO gene (CAO) resulted in the full recovery of Chl a and Chl b contents. Thus, the low-chlorophyll phenotype of strain 5P was caused by the CAO mutation. The growth yields of strain 5P were superior to those of the wild-type strain in deeper cultures, and in nutrient-rich culture medium that supported cell growth to higher densities. The growth advantage over the wild-type strain was not observed in the CAO-complemented strains. We concluded that the mutant possessing a smaller antenna size exhibits a growth advantage under limited growth conditions.

Formulas for Beam Shift and Beam Narrowing in 1-D Leaky-Wave Antennas Due to Element Pattern

The radiation pattern of one-dimensional (1-D) unidirectional leaky-wave antennas (LWAs) is typically derived from the analysis of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">space factor</i> (SF) only. However, when the antenna aperture is characterized by a longitudinal radiating current, a cosine-type <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">element pattern</i> term has to be included: this factor may considerably affect the beam properties. Specifically, the beam peak is shifted and the beamwidth is narrowed when the element pattern is included. These effects are more prominent as the antenna size decreases and the beam angle increases. Approximate but accurate analytical formulas are here provided and numerically validated to predict the beam angle and the half-power beamwidth for these kinds of 1-D unidirectional LWAs when the element pattern is included.

A sub 1 GHz ultra miniaturized folded dipole patch antenna for biomedical applications

A miniaturized folded dipole patch antenna (FDPA) design for biomedical applications operating at sub 1 GHz (434 MHz) band is presented. Antenna is fabricated on FR-4 substrate material having dimensions of 16.40 mm times 8.60 mm times 1.52 mm (0.023lambdatimes 0.012lambdatimes 0.002lambda). Indirect feed coupling is applied through two parallel strips at bottom layer of the substrate. The antenna size is reduced by 83% through lumped inductor placed at the center path of the radiating FDPA, suitable for biomedical (implantable) applications and hyperthermia. Moreover, Impedance matching is achieved without using any Balun transformer or any other complex matching network. The proposed antenna provides an impedance bandwidth of 6 MHz (431–437 MHz) below − 10 dB and a gain of − 31 dB at 434 MHz. The designed antenna is also placed on a human body model to evaluate its performance for hyperthermia through Specific Absorption Rate (SAR), Effective Field Size (EFS), and penetration depth (PD).

Antenna Modification in a Fast-Growing Cyanobacterium Synechococcus elongatus UTEX 2973 Leads to Improved Efficiency and Carbon-Neutral Productivity.

Our planet is sustained by sunlight, the primary energy source made accessible to all life forms by photoautotrophs. Photoautotrophs are equipped with light-harvesting complexes (LHCs) that enable efficient capture of solar energy, particularly when light is limiting. However, under high light, LHCs can harvest photons in excess of the utilization capacity of cells, causing photodamage. This damaging effect is most evident when there is a disparity between the amount of light harvested and carbon available. Cells strive to circumvent this problem by dynamically adjusting the antenna structure in response to the changing light signals, a process known to be energetically expensive. Much emphasis has been laid on elucidating the relationship between antenna size and photosynthetic efficiency and identifying strategies to synthetically modify antennae for optimal light capture. Our study is an effort in this direction and investigates the possibility of modifying phycobilisomes, the LHCs present in cyanobacteria, the simplest of photoautotrophs. We systematically truncate the phycobilisomes of Synechococcus elongatus UTEX 2973, a widely studied, fast-growing model cyanobacterium and demonstrate that partial truncation of its antenna can lead to a growth advantage of up to 36% compared to the wild type and an increase in sucrose titer of up to 22%. In contrast, targeted deletion of the linker protein which connects the first phycocyanin rod to the core proved detrimental, indicating that the core alone is not enough, and it is essential to maintain a minimal rod-core structure for efficient light harvest and strain fitness. IMPORTANCE Light energy is essential for the existence of life on this planet, and only photosynthetic organisms, equipped with light-harvesting antenna protein complexes, can capture this energy, making it readily accessible to all other life forms. However, these light-harvesting antennae are not designed to function optimally under extreme high light, a condition which can cause photodamage and significantly reduce photosynthetic productivity. In this study, we attempt to assess the optimal antenna structure for a fast-growing, high-light tolerant photosynthetic microbe with the goal of improving its productivity. Our findings provide concrete evidence that although the antenna complex is essential, antenna modification is a viable strategy to maximize strain performance under controlled growth conditions. This understanding can also be translated into identifying avenues to improve light harvesting efficiency in higher photoautotrophs.

Compact highly isolated dual-band 4-port MIMO antenna for sub-6 GHz applications

In this work, a compact 4-element multiple-input multiple-output (MIMO) antenna system is presented for sub-6 GHz applications. A modified M-shaped strip is used to form each antenna element in the MIMO system. To improve performance, a rectangular-shaped area is etched on the opposite side of each element in the ground plane. The antenna size is 100 × 60 mm2. Most interestingly, the port isolation is improved by rotating the etched areas and the corresponding radiating elements. This one-of-a-kind approach aided in the development of a highly isolated MIMO antenna with a small footprint. The theory of characteristic modes (TCM) is used to analyze the behavior of rotating the etched areas in the ground of the antenna. The antenna provides significant port isolation above 20 dB, stable radiation patterns, and an outstanding ECC less than 0.01. The design is simple and compact, making it suitable for MIMO operation in handheld devices.

Photosystems under high light stress: throwing light on mechanism and adaptation

High light stress decreases the photosynthetic rate in plants due to photooxidative damage to photosynthetic apparatus, photoinhibition of PSII, and/or damage to PSI. The dissipation of excess energy by nonphotochemical quenching and degradation of the D1 protein of PSII and its repair cycle help against photooxidative damage. Light stress also activates stress-responsive nuclear genes through the accumulation of phosphonucleotide-3'-phosphoadenosine- 5'-phosphate, methylerythritol cyclodiphosphate, and reactive oxygen species which comprise the chloroplast retrograde signaling pathway. Additionally, hormones, such as abscisic acid, cytokinin, brassinosteroids, and gibberellins, play a role in acclimation to light fluctuations. Several alternate electron flow mechanisms, which offset the excess of electrons, include activation of plastid or plastoquinol terminal oxidase, cytochrome b6/f complex, cyclic electron flow through PSI, Mehler ascorbate peroxidase pathway or water-water cycle, mitochondrial alternative oxidase pathway, and photorespiration. In this review, we provided insights into high light stress-mediated damage to photosynthetic apparatus and strategies to mitigate the damage by decreasing antennae size, enhancing NPQ through the introduction of mutants, expression of algal proteins to improve photosynthetic rates and engineering ATP synthase.

Performance analysis of pixelated antennas employing shifted cross‐shaped elements

AbstractThis article presents a detailed analysis of pixelated antennas employing shifted cross‐shaped elements optimised by evolutionary algorithms. Although, the size and number of the involved pixels, as well as the overall antenna size strongly influence performance of such antennas, detailed investigations on the interplay of geometrical considerations and their influence on parameters such as gain are missing from literature. Thus, the influence of various geometrical parameters on the performance of pixelated antennas for the first time, resulting in valuable design considerations is presented in this study. A maximum cross size could be found, for which an optimisation is viable. Based on this, a dataset consisting of 400 pixelated antennas was created, for different pixel‐ and antenna sizes and investigated certain parameters such as bandwidth and antenna gain. Most notably, a directly proportional dependence from the pixel‐on the antenna size for the optimisation of electrically large antennas was found. For small antennas, this dependency begins to deviate, leading to the fact that smaller pixels are needed to successfully optimise an antenna. Furthermore, the authors find that multi‐objective optimisation is a necessity to optimise matched antennas with a defined bandwidth and gain. The antenna gain shows a dependency on the cross size for electrically small antennas. From these results, design considerations for pixelated antennas can be derived. In addition to the extensive simulations, the dataset was verified in laboratory measurements.

An Ultra-Miniaturized High Efficiency Implanted Spiral Antenna for Leadless Cardiac Pacemakers.

This paper presents an ultra-miniaturized implant antenna with a volume of 22.22mm3 in the Medical Implant Communication Service (MICS) frequency band 402-405MHz to be integrated with a leadless cardiac pacemaker. The proposed antenna has a planar spiral geometry with a defective ground plane exhibiting a radiation efficiency of 3.3% in the lossy medium with more than 20dB of improved forward transmission, while the coupling can be further enhanced by adjusting the thickness of the antenna insulation and the antenna size according to the application area. The implanted antenna demonstrates a measured bandwidth of 28MHz, covering beyond the MICS band needs. The proposed circuit model of the antenna describes the different behaviors of the implanted antenna over a wide bandwidth. The antenna interaction within human tissues and the improved behavior of the electrically small antenna are explained in terms of radiation resistance, inductance, and capacitance that are obtained from the circuit model. The results are demonstrated using electromagnetic computations and are validated by the measurement using liquid phantom and animal experiments.

Miniaturized Dual Antiphase Patch Antenna Radiating into the Human Body at 2.4 GHz.

An on-body antenna, comprised of two closely-spaced antiphase patch elements, for microwave imaging may provide enhanced signal penetration into the tissue. By further integrating a 180-degree on-chip power combiner with the dual antiphase patch antenna element, a low-profile miniaturized antenna, integrated into a single 18.5 mm x 10 mm x 1.6 mm circuit board assembly, is designed and evaluated both numerically and experimentally. This is the smallest on-body antenna known to the authors for the given frequency band. This linearly polarized antenna may potentially serve as a building block of a dense antenna array for prospective high-resolution microwave imaging. A 2.4 GHz band was chosen as the design target. The final antenna size was a compromise between the miniaturization, the SNR (Signal-to-Noise Ratio), and the targeted antenna bandwidth (2.3-2.5 GHz). The effect of surface waves (the secondary radiating components) was also factored in the design consideration, while maximizing the detected signals' SNR.

Cost-Effective Broadband and Compact Patch Antenna Based on Ball Grid Array Packaging for 5G NR FR2 Band Applications

This brief introduces a compact, cost-effective broadband patch antenna based on ball grid array (BGA) packaging technology for 5G millimeter wave new radio (NR) FR2 band application. Based on the low-cost FR-4 substrate and single-layer configuration, the patch antenna achieves an ultra-low cost, which is attractive for large-scale 5G millimeter-wave array applications. Parasitic patches are added to the antenna to obtain broadband impedance bandwidth. To further reduce the antenna size and eliminate bulky connectors, solder balls are added to form a BGA package with connectorless interconnects. Consequently, the proposed antenna element achieves a compact size of 5.2 mm × 3.2 mm × 1.4 mm. Antenna elements and 1 × 8 array prototypes have been fabricated and verified. The measurement results show that the proposed antenna element has a -10 dB bandwidth of 56.1% (20-35.6 GHz), fully covering the 5G millimeter wave n257 (26.5-29.5 GHz), n258 (24.25-27.5 GHz), and n261 (27.5-28.35 GHz) bands. The maximum realized gains of the antenna elements and the 1 × 8 array prototype are 7.2 dBi and 13.9 dBi, respectively.

Ultrawide-Angle and Compact Leaky-Wave Antenna Based on Complex Periodic Structure

A compact antenna with the characteristic of wide-angle frequency beam scanning based on complex periodic structure is proposed. A double gradient spoof surface plasmon polaritons (SSPPs) structure is added to the standard microstrip line for reducing the antenna size. The miniaturization of the proposed antenna is analyzed with the method of dispersion curves and electric field distribution. Periodic changes of the groove depth and trapezoidal gradient structure increase the beam scanning angle from backward to forward and suppress the open stopband effect. The proposed structure is printed on the FR-4 substrate with a compact size of 0.23λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 3.71λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the wavelength of the lowest operating frequency), and has a working frequency band from 12.5 to 42.5 GHz for |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> |< –10 dB. Meanwhile, a wide beam-scanning angle of 142° (–52° to +90°) and an average gain of 7.9 dBi are obtained by simulation and measurement. The proposed leaky-wave antenna has a potential application in wireless communication system due to its small size, broad frequency band, wide beam scanning angle and low cost.

Miniaturized Pattern-Reconfigurable Multimode Antennas With Continuous Beam-Steering Capability

In this paper, two miniaturized multi-mode pattern steering antennas for Internet of Things (IoTs) applications are proposed. A compact multi-mode cavity functions both the hybrid and radiator. A continuous 360° pattern scanning in the azimuth plane is controlled by the amplitude and phase of three excitation ports. The first design achieves the smallest size with TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">02</sub> and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> modes. In contrast, the second design has improved impedance bandwidth and mode isolation by introducing TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">02</sub> and high-order TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> modes. Eight dipole chokes are attached to the cavity for surface current suppression. This approach eliminates the unwanted patch mode radiation. The antennas support multibeam applications with digital beamforming and analog beamforming with the 0°/180° phase switch and variable gain amplifier (VGA). The direction of arrival (DOA) can be estimated by directly measuring the amplitude and phase of the receiving signal. No full phase shifter and signal classification algorithm are required. The prototypes are fabricated and measured at 2.4 GHz. The diameters of the two antennas are 0.4 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> and 0.9 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> . The achieved antenna size is very miniature as shown by the literature comparison. The radiation and DOA performance is evaluated. The peak system efficiency is better than 60% after calibration and a good DOA estimation result is obtained.