Search

In this paper, a design and radiation characteristics of an electrodynamics model of a capacitive feed printed dipole array element are presented. The array element is for operation in a millimeter wave range (25-26 GHz) of the fifth-generation communication systems for the wireless local network. It has a linear polarization. On the level of the VSWR less than 3, its operating frequency band is in the range from 23.325 to 28.201 GHz. In the needed frequency range, the value of the VSWR is no more than 1.3. Based on this array element was made the antenna array model with size 4 × 4. On the level of the VSWR less than 3, its operating frequency band is less than array elements and is located in the range from 23.778 to 27.865 GHz. In the needed frequency range, the value of the VSWR of its corner elements is no more than 1.6 and no more than 1.5 for all other elements. The value of the realized gain is in the range from 16.8 to 17.1 dB. [ABSTRACT FROM AUTHOR]

This study presents a substrate integrated waveguide (SIW) broadband circularly polarized (CP) high‐gain low‐profile magneto‐electric dipole antenna array. The antenna array is characterized by wide impedance bandwidth (IBW), novel CP operating principle, small form factor, and good radiation performance. First, the antenna element consists of a two‐layer dielectric substrate, two pairs of magneto‐electric dipoles, and a SIW cavity coupled and fed through a cross‐shaped rectangular slit. To achieve a wide CP bandwidth (BW), a pair of magneto‐electric dipoles is rectangularly chamfered and then an "L" type parasitic patch is introduced. The simulation results show that the antenna element has an axial ratio (AR) BW of 14.2% in the 31.48–36.16 GHz range, the IBW in the 29.08–35.98 GHz range is 21.2%, and the gain is greater than 8 dBic in all bands. The antenna exhibits stable patterns and wide overlap IBW (31.48–35.98 GHz). Then, a planar 2 × 2 antenna array fed by a one‐part‐four SIW power divider was designed, fabricated, and measured. The measured results show that the array has an ARBW of 14% in the range of 31.29−35.83 GHz, an IBW of 21.8% in the range of 29.28–35.83 GHz, and a peak gain of 14.1 dBic. [ABSTRACT FROM AUTHOR]

This paper presents a broadband magneto-electric dipole (MED) circularly polarized (CP) microstrip antenna array with continuous rotating feed (SRF). The antenna element consists of a quarter-circle ring with irregular cross slits and a rectangular patch. The energy is combined with four metallized perforations and then transmitted to the radiating block to better excite the magnetic dipole-electric dipole energy and expand the bandwidth. Then, a 2 × 2 subarray was designed to further increase the axial ratio(AR) bandwidth. Finally, a 4 × 4 circularly polarized array arranged in a diamond shape is designed to utilize sequential rotating feeds to further improve the gain for millimeter-wave applications. Simulation results show that the impedance bandwidth (IBW) of the proposed array is 54.5% (20–35 GHz), and AR bandwidth of 3 dB is 27.2% (22.2–29.2 GHz), and the maximum gain is 16 dBic. [ABSTRACT FROM AUTHOR]

Ultra‐wideband (UWB) systems utilise a broad frequency spectrum to achieve high data transmission rates and enhanced precision, creating a demand for specialised UWB antennas. Circularly Polarised (CP) antennas are considered essential for maintaining robust performance under varied environmental conditions. Among them, the crossed dipole is effective for UWB CP applications, but its relatively large size could limit its use in various systems. A miniaturised crossed dipole design employing the Koch fractal structure is proposed and the measurement results are presented. The prototype antenna achieved an effective bandwidth covering 88% of the frequency range from 1.4 to 3.6 GHz. Additionally, a 4 × 4 array using this design was tested in the same frequency band, demonstrating beam‐steering capabilities up to 30°. The proposed antenna has demonstrated effective deployment in diverse communication systems and phased array applications within ultra‐wideband (UWB) CP environments. [ABSTRACT FROM AUTHOR]

An antenna array design method of trade‐off between high gain and low profile is proposed. A high‐gain circularly polarised (CP) substrate integrated waveguide (SIW)‐fed magnetoelectric dipole (ME‐dipole) antenna array with metallic radiating structures is presented for millimetre‐wave (MMW) applications. The CP antenna element comprises a set of horizontally and vertically metal plates and a metallic cavity that is excited by an X‐shaped coupling slot etched on the broader side of SIW. The metallic cavity is designed to improve the gain and axial ratio (AR) performances. Utilising this antenna element, a proof‐of‐concept is established through the design of a 2 × 2 subarray and a 4 × 4 array. The fabricated 4 × 4 CP antenna array has a measured impedance bandwidth of 6.1% (36.4–38.7 GHz), with |S11| ≤ −10dB. The measured 3dB AR bandwidth is 5.4% (36.0–38.0 GHz). The measured maximum gain achieved is 19.1 dBic. The height of the proposed array is 0.74λ0 which is larger than the heights of typical SIW‐based microstrip arrays (0.1–0.4λ0) and lower than the heights of metallic arrays (larger than 2λ0). [ABSTRACT FROM AUTHOR]

Summary: A broadband ±45° dual‐polarized omnidirectional array with small size is presented. A crossed‐arranged dipole element is proposed to generate a wide unidirectional radiation beam. A crossed‐arranged parasitic strip is used to dramatically widen the impedance bandwidth of the dipole element. Based on the dipole element, a rotational two‐unit subarray, which comprises a small number of dipole elements and occupies a small space, is originally proposed to generate excellent omnidirectional radiation performance. Then a four‐unit array with a simple feed network is designed based on the rotational subarray. The array obtains a wide bandwidth of 59.4% (1.55–2.86 GHz) for reflection coefficient <−10 dB and an isolation beyond 21 dB between the two polarizations. Meanwhile, a very low gain variation of below 3 dB, as well as a stable and high realized gain of 5.1 ± 0.5 dBi are achieved over the operating band. [ABSTRACT FROM AUTHOR]

A metamaterial-based non-uniform dipole array antenna is presented for high gain 5G millimeter-wave applications with a wideband characteristic. Initially, a non-uniform dipole array is designed on a 0.202 mm thick Rogers RO4003C substrate, offering a wide operating bandwidth ranging from 23.1 GHz to 44.8 GHz. The dipole array antenna emits unidirectional end-fire radiation with a maximum gain of 8.1 dBi and an average gain of 6.7 dBi. Subsequently, to achieve high gain performance, a 5 × 7 metamaterial structure is designed in the direction of the antenna radiation. The implemented metamaterial structure is optimized for the operating frequency, enhancing the directivity of the antenna radiation and resulting in a gain increment of more than 3 dBi compared to the dipole array alone. The developed metamaterial-integrated dipole array antenna offers an operating bandwidth (S11 < −10 dB) of more than 21 GHz (63.92%), ranging from 23.1 GHz to 44.8 GHz, covering the most commonly used 5G millimeter-wave frequency bands (n257, n258, n259, n260, and n261). Furthermore, the presented antenna yields a stable high gain with a peak gain of 11.21 dBi and a good radiation efficiency of more than 64%. The proposed antenna is an excellent option for millimeter-wave 5G systems due to its overall properties, particularly its high gain and end-fire radiation characteristics, combined with a wide operating bandwidth. [ABSTRACT FROM AUTHOR]

The use of electromagnetism and the design of antennas in the field of medical imaging have played important roles in clinical practice. Specifically, magnetic resonance imaging (MRI) utilizes transmission and reception antennas, or coils, that are tuned to specific frequencies depending on the strength of the main magnet. Clinical scanners operating at 3 Teslas (T) function at a frequency of 127 MHz, while research scanners at 7 T operate at 300 MHz. An 11.74 T scanner for human imaging, which is currently under development, will operate at a frequency of 500 MHz. MRI allows for the high‐definition scanning of biological tissues, making it a valuable tool for enhancing images acquired with positron emission tomography (PET). PET is an imaging modality used to evaluate the metabolism of organs or cancers. With recent advancements in the development of portable PET systems that can be integrated into any MRI scanner, we propose the design based on electromagnetic simulations of a triple‐tuned array of dipole antennas to operate at 127, 300, and 500 MHz. This array can be attached to the PET inset and used in 3, 7, or 11.74 T scanners. [ABSTRACT FROM AUTHOR]

This paper presents an antenna-in-package (AiP) design realised with the conventional multi-layer printed circuit board manufacturing method. The design consists of a wideband 2 × 2 magneto-electric dipole array antenna operating from 24.25 − 29.5 GHz and a wideband transition from the analogue beamformer integrated into the proposed MED array antenna (IMED). The IMED array antenna has been fabricated with two distinct NXP analogue beamformer chips, i.e., MMW 9004 KC and MMW 9002 KC covering the N257 and the N258 band, respectively. The measured effective isotropic radiated power at P1dB was 35.3 dBm and 35.1 dBm for the IMED with the MMW 9004 KC and the MMW 9002 KC analogue beamformer chip, respectively. Our proposed antenna demonstrates the feasibility of designing a single wideband AiP that can be integrated with different analogue beamformers operating within the frequency band of the proposed antenna. This is true, provided the RFIC used for integration has the same footprint for RF ports, serial peripheral interface control ports, and DC power supply ports. The primary benefit of the proposed technique is the design antenna can adapt the operating frequency to different frequency standards by incorporating additional analogue chips without increasing the design complexity. This feature enables the antenna manufacturer to tailor the antenna products to different frequency standardisations depending on where the antenna will be employed. The AiP operates at 5G millimeter-wave (mmWave) frequencies, with the potential for Internet of Things applications. Furthermore, from our simulation results, the proposed IMED can potentially be extended as a phased array antenna with 2D scanning. [ABSTRACT FROM AUTHOR]

In this letter, a beam downtilt reconfigurable linear antenna array is presented for the demand of the electrical downtilt of 5G/6G macro base station antennas. The antenna is capable of fine‐angle beam direction reconfiguration, allowing for improved adaptability in various environmental conditions. A hierarchical network design is employed, which incorporates essential elements such as phase shifter modules, power dividers, and couplers. These fundamental components are used to construct a five‐element reconfigurable feeding network for the antenna array. The designed network ensures stable phase shifts and excellent impedance matching performance. By integrating the feeding network with the antenna elements, the system achieves electronic beam tilt adjustment across four states, enabling the linear array to tilt downward within a range of 6–12° around 3.5 GHz. This design provides enhanced beam control, making it suitable for next‐generation macro base station applications in 5G and 6G networks. [ABSTRACT FROM AUTHOR]

A broadband printed thin-layer radio absorbing structure based on an array of coupled dipole antennas has been developed and created. The resulting material can be used to solve the problems of shielding electromagnetic waves and reduce the level of electromagnetic emission from various devices in the 4–7 GHz frequency range, as well as to create building radio shielding materials. [ABSTRACT FROM AUTHOR]

We present the optical characterization of two-scale hierarchical phased-array antenna kinetic inductance detectors (KIDs) for millimeter/submillimeter wavelengths. Our KIDs have a lumped-element architecture with parallel plate capacitors and aluminum inductors. The incoming light is received with a hierarchical phased array of slot dipole antennas, split into 4 frequency bands (between 125 GHz and 365 GHz) with on-chip lumped-element band-pass filters, and routed to different KIDs using microstriplines. Individual pixels detect light for the 3 higher-frequency bands (190–365 GHz), and the signals from four individual pixels are coherently summed to create a larger pixel detecting light for the lowest frequency band (125–175 GHz). The spectral response of the band-pass filters was measured using Fourier transform spectroscopy (FTS), the far-field beam pattern of the phased-array antennas was obtained using an infrared source mounted on a 2-axis translating stage, and the optical efficiency of the KIDs was characterized by observing loads at 294 K and 77 K. We report on the results of these three measurements. [ABSTRACT FROM AUTHOR]

FarView is an early-stage concept for a large, low-frequency radio observatory, manufactured in-situ on the lunar far side using metals extracted from the lunar regolith. It consists of 100,000 dipole antennas in compact subarrays distributed over a large area but with empty space between subarrays in a core-halo structure. FarView covers a total area of ∼200 km2, has a dense core within the inner ∼36 km2, and a ∼power-law falloff of antenna density out to ∼14 km from the center. With this design, it is relatively easy to identify multiple viable build sites on the lunar far side. The science case for FarView emphasizes the unique capabilities to probe the unexplored Cosmic Dark Ages – identified by the 2020 Astrophysics Decadal Survey as the discovery area for cosmology. FarView will deliver power spectra and tomographic maps tracing the evolution of the Universe from before the birth of the first stars to the beginning of Cosmic Dawn, and potentially provide unique insights into dark matter, early dark energy, neutrino masses, and the physics of inflation. What makes FarView feasible and affordable in the timeframe of the 2030s is that it is manufactured in-situ, utilizing space industrial technologies. This in-situ manufacturing architecture utilizes Earth-built equipment that is transported to the lunar surface to extract metals from the regolith and will use those metals to manufacture most of the array components: dipole antennas, power lines, and silicon solar cell power systems. This approach also enables a long functional lifetime, by permitting servicing and repair of the observatory. The full 100,000 dipole FarView observatory will take 4–8 years to build, depending on the realized performance of the manufacturing elements and the lunar delivery scenario. [ABSTRACT FROM AUTHOR]

In this research, the effectiveness of six element uniform circular uniform dipole array is designed. To determine the most productive design for the ISM Band, numerous array antenna topologies are tested in this work. The proposed antenna is appropriate for the ISM, IEEE 802.11, Bluetooth, as well as Zigbee, WiMAX, and WiFi applications. We first set up a 6-element dipole linear array for this, after which we switched to a rectangular array using a combination of triangular and rectangular lattice arrangements. The identical 6-element dipole antenna was then configured in a circular fashion, and the results appear to be excessively good when compared to all previous configurations. The symmetrical arrangement of a uniform circular array design allows the phasing of array antennas to operate azimuthally with little variation in its wavelength and side lobe intensities. There are 6 isotropic components in this uniform circular array design. To adjust the antenna to shifting surroundings, complicated values of the antennas array components are calculated. The correlation effect between various elements were analysed. In this work a return loss of – 35 dB was obtained as a maximum value for circular array configuration at 2.45 GHz. The goal of employing array antennas is to provide increased efficiency and broad band capabilities, allowing for usage in a variety of everyday applications. [ABSTRACT FROM AUTHOR]

Spatially controllable focal fields play a pivotal role in light manipulation and provide significant opportunities for precisely manipulating light–matter interactions in a wide range of applications. In particular, the double-helix focal field—characterized by a distinctive helical structure—exhibits exceptional optical properties, thus differentiating it apart from conventional focal fields. However, the rapid construction of a double-helix focal field with controllable characteristics and a uniform intensity remains a challenging task. Based on the theory of pattern synthesis of an antenna array, we propose and realize the generation of three-dimensional doughnut-spot arrays and double-helix focal fields with specified characteristics in a 4 π system by reverse-solving the radiation field of the virtual antenna. Numerical examples indicate that the desired novel focal fields, including features such as shape, orientation, length, and period, could be rapidly, conveniently, and flexibly customized by selecting appropriate parameters for the magnetic dipole array antennas. This method could reveal an avenue for enhanced light manipulation for applications in materials processing, optical lithography, and optical communications. [ABSTRACT FROM AUTHOR]

This article presents a planar, non-angular, series-fed, dual-element dipole array MIMO antenna operating at 28 GHz with the metasurface-based isolation improvement technique. The initial design is a single-element antenna with a dual dipole array which is series-fed. These dipole elements are non-uniform in shape and distance. This dipole antenna results in end-fire radiation. The dipole antenna excites the J 1 mode for its operation. Further, with the view to improve channel capacity, the dipole array expands the antenna to a three-element MIMO antenna. In the MIMO antenna structure, the sum of the J 1 , J 2 , and J 3 modes is excited, causing resonance at 28 GHz. This article also proposes a metasurface structure with wide stopband characteristics at 28 GHz for isolation improvement. The metasurface is composed of rectangle-shaped structures. The defected ground and metasurface structure combination suppresses the surface wave coupling among the MIMO elements. The proposed antenna results in a bandwidth ranging from 26.7 to 29.6 GHz with isolation improvement greater than 21 dB and a gain of 6.3 dBi. The antenna is validated with the diversity parameters of envelope correlation coefficient, diversity gain, and channel capacity loss. [ABSTRACT FROM AUTHOR]

This paper presents a theoretical method to estimate the pulse radiation characteristics of Vivaldi antennas. Based on the surface current distribution and the ultra-wideband radiation principle, Vivaldi antenna is equivalently modeled as a dipole array, and the pulse radiation characteristics of a single Vivaldi antenna are brought out utilizing the spatial superposition approach. Then, the influences and results of the Vivaldi antenna pulse characteristics prediction with different construction ways of the dipole array and element numbers are furthermore investigated. Next, a quadratic spatial superposition technique is employed to complete the theoretical prediction for time-domain radiation characteristics of Vivaldi antenna arrays. Experiments and simulations are conducted separately to verify the proposed method for both single Vivaldi antenna and array. The validated results demonstrate that the dipole array-based theoretical prediction method can effectively capture the pulse radiation characteristics for both individual Vivaldi antenna and array operating in different modes, thereby addressing challenges associated with estimating radiation characteristics in ultra-wideband pulse applications. [ABSTRACT FROM AUTHOR]

This paper presents a four-port multiple-input multiple-output (MIMO) magneto-electric dipole antenna array with high gain and high isolation for 5G millimeter-wave communications. Each antenna contains an eight-way power divider, an eight-element magneto-electric dipole antenna array, a metal rectangular ring, and a dielectric slab. The proposed magneto-electric dipole antenna array has high radiation gain. The metal rectangular ring is applied to not only support the dielectric slab but suppress the surface wave propagation and thus the mutual coupling can be reduced. A further increase in the isolation performance can be realized based on the polarization diversity. The simulated and measured impedance bandwidths at 10 dB return losses are 24–31.86 GHz (28.1%) and 24.12–32 GHz (28.1%), respectively. The simulated and measured isolation levels are larger than 25 and 20 dB, respectively. The simulated and measured realized peak gains at 30 GHz are 20.5 and 19.2 dBi, respectively. [ABSTRACT FROM AUTHOR]

This paper investigates various array beam shapes for high-power electronic warfare applications using an actual broadband array antenna. For use in a limited mounting space, a compact printed log periodic dipole array (LPDA) operating over a wide bandwidth is designed. The LPDA is then extended to an 8 × 1 array, with active element patterns (AEPs) obtained through simulation and measurement. Beam synthesis is performed by the superposition of several array patterns, which involves adjusting the weight of each AEP. To derive a synthesized array beam shape that is similar to the guided mask, the Taylor window weighting method is applied to each array pattern. Finally, beam synthesis for the flat-top beam, cosecant-squared beam, and iso-flux beam is performed using Taylor window-weighted AEPs, and the results are compared with those of beam shapes using ideal isotropic patterns. The results demonstrate that various beam shapes can be achieved for high-power electronic warfare applications using the AEPs of an actual array antenna. [ABSTRACT FROM AUTHOR]

This document is a correction notice for an article titled "Wideband miniaturized circularly polarized magnetoelectric dipole antenna array for millimeter-wave applications" published in the journal Microwave & Optical Technology Letters. The correction notice addresses errors in several figures in the original article, including the geometry of the proposed CP ME-dipole antenna, the design procedure, the comparison of |S11| for different antennas, and the geometry of the proposed CP ME-dipole antenna array. The corrected figures are provided in the correction notice. The authors apologize for these errors. [Extracted from the article]

In this paper, the first in a series of four articles, the scientific goals of the Metron project are highlighted, and the characteristics of the cosmic objects available for study within its framework are provided. The Metron interferometer radio telescope should include arrays of meter-range dipole antennas placed on Earth, in outer space, or on the far side of the Moon (or a combination of these options). Working in the meter range will enable the study of the so-called cosmological epoch of the "Dark Ages", which is challenging to observe but highly interesting for understanding the origin of the first stars, galaxies, and black holes, as well as for the search for new cosmological objects and processes. One possibility is to search for absorption in the 21-cm line within the extended halos around early protogalaxies and supermassive primordial black holes, whose existence is predicted in a number of models. Another goal of Metron may be to clarify the anomalous absorption in the 21-cm line previously detected by the EDGES telescopes and to observe radio emissions from the magnetospheres of stars and exoplanets. The Metron project aims to achieve unprecedented resolution in the meter range, which is expected to yield new world-class scientific results. Meter-range antennas and receivers are relatively simple and inexpensive, and the construction of interferometric arrays from them can be accomplished in a relatively short period of time. [ABSTRACT FROM AUTHOR]

This work presents a printed Ka-band dipole array antenna with wide bandwidth for millimeter-wave communication applications. The operating band of the proposed antenna ranges from 27.8–38.2 GHz exhibiting a wide bandwidth of 10.4 GHz. A balun structure is designed with interlaced U-shaped bending lines on the upper and lower metal layers to feed the dipole differentially. Parasitic trapezoidal patches are exquisitely placed adjacent to the driven dipoles for coupling, which can enhance bandwidth significantly through multiple resonances. The low-frequency radiation is mainly contributed by the resonance of the dipole, while the high-frequency radiation is affected by both the dipole and the parasitic trapezoidal patch. Due to the trapezoidal patch, the equivalent path length of the resonant current becomes shorter, thus supporting high-frequency resonance. A prototype of the proposed 1 × 2 dipole array antenna was fabricated for validation. The measured –10-dB impedance bandwidth is up to 27.8∼38.2 GHz (or 31.5%) and the realized gain is as high as 8 dBi, which is suitable for advanced millimeter-wave communication applications. [ABSTRACT FROM AUTHOR]

A wideband and miniaturized circularly polarized (CP) magnetoelectric (ME) dipole antenna is proposed. Two pairs of rotationally symmetric patch structures replace the rectangular structure of the original linearly polarized ME dipole, generating a rotating electric field that results in CP‐radiated waves. And the magnetic dipole is modified to broaden the impedance bandwidth (IBW) and the axial ratio bandwidth (ARBW). Meanwhile，the simple l‐shaped feed structure makes the antenna more compact. To improve the antenna gain, a 2 × 2 CP ME‐dipole antenna array was designed, completed, and measured. The measured results show that the IBW of the antenna array is 41.5% (from 29.2 to 44.5 GHz), and 3 dB ARBW of 26.7% (from 34.7 to 45.4 GHz) has a peak gain of 13.7 dBic. [ABSTRACT FROM AUTHOR]

A 1 x 4 magneto-electric dipole (ME dipole) antenna array for 77 GHz automotive radar is proposed. The ME dipole is fed by a fork-shaped microstrip line coupling through a dog-bone slot. To meet the requirements aimed at automotive radar applications, the beamwidths of the proposed antenna are well-designed. Specially, a method of adding passive elements on both sides of the array is proposed to increase the 3 dB beamwidth from ±34° to ±52° in azimuth. Additionally, in elevation, a 3 dB beamwidth of ±10° is achieved by designing the spacing between array elements. Moreover, based on low-loss printed circuit board substrates, radiation efficiency of the proposed array can reach approximately 90% at 77 GHz. Furthermore, a 4 x 4 array is established by arranging four 1 x 4 subarrays spacing 1.95 mm (half a free-space wavelength at 77 GHz) to study the interactions between subarrays for multiple input multiple output scenarios. A 1 x 4 and a 4 x 4 antenna prototypes are fabricated and measured to validate the correctness of this design. The results show that the proposed antenna is an eligible candidate for the medium- and short-range automotive radars. [ABSTRACT FROM AUTHOR]

To improve radio access capability, sky connections relying on satellites or unmanned aerial vehicles (UAV), as well as high-altitude platforms (HAP) will be exploited in 6G wireless communication systems, complementing terrestrial networks. For long-distance communication, a large smart antenna will be used that is characterized by high amounts of power consumed by digital beamformers. This paper focuses on reducing power consumption by relying on a thinned smart antenna (TSA). The performance of TSA is investigated in the sub-6 GHz band. The differential evolution (DE) algorithm is used to optimize excitation weights of the individual dipoles in the antenna array and these excitation weights are then used in TSA for beamforming, with signal processing algorithms deployed. The DE technique is used with the least mean square, recursive least square and sample matrix inversion algorithms. The proposed method offers almost the same directivity, simultaneously ensuring lower side lobes (SLL) and reduced power consumption. For a TSA of 20, 31, and 64 dipoles, the power savings are 20%, 19.4%, and 17.2%, respectively. SLL reductions achieved, in turn, vary from 5.2 dB to 8.1 dB. [ABSTRACT FROM AUTHOR]

After years of preparation, the Indonesia National Observatory, located in Mount Timau, Kupang Regency, is currently in the completion stage of research in astronomy and astrophysics and related subjects. An optic telescope with a 3.8 m diameter is expected to receive its first light in mid-2024. A feasibility study for Indonesia's radio telescopes and networks is in progress. A single-dish parabolic radio antenna with a diameter of 20 m is proposed to work in a frequency range of 1–50 GHz. An array dipole antenna with an area of 100 m × 100 m will also be installed at a 70–350 MHz frequency. A feasibility study about system design is in progress, and a radio frequency interference (RFI) survey has been underway since 2014. In this paper, we described the design of radio telescopes such as parabolic reflectors, horn antenna, and the radio frequency interference (RFI) in the surrounding area of the National Observatory, covering the frequency band from 45 MHz to 18 GHz. The frequencies in 45–85 MHz and 120–360 MHz intervals are still relatively quiet and suitable for developing radio telescopes. The selected higher frequency of 1.4 GHz for a neutral hydrogen (HI) spectral line, 6.6 GHz for a methanol (CH3OH) spectral line, and 8.6 GHz for a helium (3 He+) spectral line is still relatively quiet and suitable for the development of radio telescopes. [ABSTRACT FROM AUTHOR]

Tightly coupled dipole arrays, including connected arrays, and capacitively coupled arrays, are one of the best solutions for wideband phased array antenna designs. However, to increase bandwidth and maximum scan angle, we can use a metasurface superstrate. We propose an analytical model to compute the scan impedance of a tightly coupled dipole array loaded with a metasurface. This analytical model helps us to simplify the calculation of the scan impedance of the array and speeds up the design process of these array antennas. It is shown that the metasurface superstrate improves the bandwidth and beam scanning angles of the array. Using the proposed general transmission line model, the computation of the scan impedance of tightly coupled dipole arrays is done very fast with minimum error. The semi-analytical model is about 7 times faster than a full-wave simulation. [ABSTRACT FROM AUTHOR]

This paper presents an investigation of a microwave near-field power focusing (NFPF) analytical approach utilizing a cylindrical array of electric line sources along the z-axis, applicable to any arbitrary homogeneous linear medium. A novel parameter, termed the "focus ability" (FA), is introduced to quantitatively assess a method's capabilities in achieving power focusing. In the following, the phases and amplitudes of the excitation signals of the array elements are obtained with optimization to maximize FA over a certain studied area. Each stage of the theoretical analysis is supported through COMSOL full-wave simulations, ensuring the validity of the results. Theoretical results relevant to focused power are then compared to outcomes obtained from CST full-wave simulations with the same array configuration while employing half-wave dipole antenna elements with excitations obtained via optimization. These comparisons indicate that the excitation signals obtained by theoretical analysis can be used for power focusing when the array of half-wave dipole antenna sources is utilized. Furthermore, the proposed method leads to a significant reduction in the optimization time. Also, in the provided examples, the FA parameter and NFPF are investigated for the different conditions consisting of the type of the homogeneous medium and the number of antennas. [ABSTRACT FROM AUTHOR]

This study explores the application of LMS and RLS algorithms in adaptive beamforming for a linear array of half wavelength dipole (HWD) antennas with known mutual coupling. The research initiates by deriving analytical expressions for the covariance matrix of signal impinging on an HWD antenna array, accounting for mutual coupling effects. Leveraging these expressions, we calculate the weights for both LMS and RLS algorithms, enabling the evaluation of the overall far-field radiation patterns of the HWD antenna array. The results demonstrate that these algorithms effectively steer the main lobe of the radiation pattern towards the desired user while creating nulls in the direction of undesired users. Notably, simulations indicate that the proposed compensation method enhances the performance of beamforming algorithms, particularly when considering mutual coupling effects. Specifically, the LMS algorithm outperforms the RLS algorithm in reducing interference, resulting in lower side lobe levels (SLL) in the radiation pattern. [ABSTRACT FROM AUTHOR]

The December 2024 issue of Microwave Review journal (Vol. 30, No. 2) features twenty research papers from various universities and countries. Topics covered include compressed sensing image communication, antenna designs for broadband applications, and optimization techniques for antenna structures. Authors from India, Algeria, Russia, and other countries contribute to the diverse range of research presented in this issue. The journal highlights innovative advancements in microwave technology and antenna design, showcasing global collaboration and expertise in the field. [Extracted from the article]

The article discusses the importance of antenna integration and miniaturisation techniques in meeting the demands of wireless communications. It presents recent advancements in theory, design, and application of antennas, showcasing innovative designs for various applications. The Special Issue includes six high-quality papers that address challenges in design, fabrication, and performance enhancement for miniaturised and integrated antennas. The authors express gratitude to contributors and reviewers for their valuable input in enhancing the quality of the publication. [Extracted from the article]

A low profile four‐element multiple‐input multiple‐output (MIMO) array of printed dipole antenna (PDA) backed by second iteration of Giuseppe Peano fractal artificial magnetic conductor (AMC) is introduced for broadband wireless communications. First, a suggested PDA with a pair of microstrip E‐shaped dipoles excited by an E‐shaped microstrip feedline is used to expand the bandwidth in the range of 5.47–6.92 GHz (S11 ≤ −10 dB). Then, the suggested 4 × 4 Giuseppe Peano fractal AMC reflector is loaded into the PDA to exhibit −10 dB measured impedance bandwidth from 4.21 to 7.06 GHz (50.61%) for wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications. The proposed four‐element MIMO array loaded by 6 × 6 AMC reflector with diverse polarizations of elements introduces a low profile wideband structure. The measured results of four elements include the broad bandwidths from 4.3 to 7.05 GHz with enhanced gains (more than 8 dBi) and high efficiencies. The high isolations between the four elements with diverse polarizations are obtained larger than 26.5 dB and they reach 66 dB over the operating bandwidth for MIMO systems. The suggested PDA with AMC compared to the PDA without AMC exhibits a size reduction of 51.33%, enhanced radiation efficiency up to 94%, and excellent impedance matching with uni‐directional radiation patterns. [ABSTRACT FROM AUTHOR]

The newly installed CALLISTO spectrometer, hosted by the Department of Space Environment, Institute of Basic and Applied Sciences- EJUST, commenced operation on August 14, 2021. The system contains a cross dipole long-wavelength array antenna with high sensitivity to monitor solar radio transients. Its antenna was strategically positioned and appeared to be in the center of the CALLISTO network of spectrometers. Moreover, in the northern section of Africa, the Egypt-Alexandria CALLISTO and ALGERIA-CRAAG stations are the only ones operating. There are no stations in the West African region, while stations in the eastern part of Africa are not working. Thus, Egypt- Alexandria station serves as a reference for other stations within the e-CALLISTO network. Despite the low solar activity, the instrument detected several solar radio bursts not limited to type II, type III, and type V. A vigorous case study was conducted on two selected radio burst events to validate the authenticity of the recorded events. Other solar radio stations at different geographical locations recorded all the radio bursts detected by the spectrometer. The case study included brief analyses that indicated a type II radio burst observed on October 09, 2021, between 06:30 and 07:00 UT, was associated with an M1.6 solar flare located at N18E08 within NOAA-AR 2882 and a CME with a shock front speed of ∼ 978 km/s. However, the type III radio burst is neither CME nor solar flare associated. These analyses examine the instrument's capacity to provide real-time solar radio transient data 24 h a day to mitigate the challenges of data gaps faced in the African continent. Hence, the instrument has become an integral part of space weather monitoring and forecasting over the region and other parts of the globe. [ABSTRACT FROM AUTHOR]

A low‐profile 16‐element printed dipole antenna (PDA) array backed by a planar artificial magnetic conductor (AMC) is introduced for multiple‐input multiple‐output (MIMO) wireless communications. The proposed 16‐element MIMO array loaded by a 13 × 13 AMC reflector with various polarized directions exhibits a low‐profile wideband structure, which includes the broad measured bandwidths from 4.25 to 7.25 GHz with increased gains (>8 dBi) and high efficiency. The high isolation between the 16 elements with diverse polarizations is larger than 27 dB and reaches 67 dB over the operating band for MIMO systems. The suggested PDA with a microstrip V‐shaped dipole excited by a V‐shaped microstrip feedline is used to expand the broad simulated band spanning 5.34–6.70 GHz (S11 ≤ −10 dB). Moreover, the suggested 13 × 13 planar fractal AMC reflector is loaded into the PDA array to exhibit a reflection coefficient, S11, of less than −10 dB across the band of 4.26–6.90 GHz for wireless local area network and worldwide interoperability for microwave access applications. The proposed design with AMC compared to the design without AMC exhibits a size reduction of 50.3%, increased gain up to 8.2 dBi, and excellent impedance matching with unidirectional radiation patterns. The novel AMC unit cell is realized based on the planar patch with inserted slots to operate at 6.10 GHz with an AMC band spanning 5.15–7.10 GHz (32%). Plain Language Summary: A low profile sixteen‐element multiple‐input multiple‐output (MIMO) array of printed dipole antenna backed by planar artificial magnetic conductor is introduced for broadband wireless communications. It shows an enhanced features such as high stable gains, efficiencies, bandwidth, reduced size and high isolation for diverse elements of MIMO array. Key Points: Wiced gain and isolationLow‐profile multiple‐input multiple‐output array with enhanced isolation between elements can be used for wireless systemsArtificial magnetic conductors as periodic structures have been applied in microstrip antennas to improve their radiation performance [ABSTRACT FROM AUTHOR]

In microwave hyperthermia tumor therapy, electromagnetic waves focus energy on the tumor to elevate the temperature above its normal levels with minimal injury to the surrounding healthy tissue. Microwave hyperthermia applicator design is important for the effectiveness of the therapy and the feasibility of real-time application. In this study, the potential of using fractal octagonal ring antenna elements as a dipole antenna array and as a connected array at 2.45 GHz for breast tumor hyperthermia application was investigated. Microwave hyperthermia treatment models consisting of different fractal octagonal ring antenna array designs and a breast phantom are simulated in COMSOL Multiphysics to obtain the field distributions. The antenna excitation phases and magnitudes are optimized using the global particle swarm algorithm to selectively increase the specific absorption rate at the target region while minimizing hot spots in other regions within the breast. Specific absorption rate distributions, obtained inside the phantom, are analyzed for each proposed microwave hyperthermia applicator design. The dipole fractal octagonal ring antenna arrays are comparatively assessed for three different designs: circular, linear, and Cross—array. The 16-antenna dipole array performance was superior for all three 1-layer applicator designs, and no distinct difference was found between 16-antenna circular, linear, or cross arrays. Two-layer dipole arrays have better performance in the deep-tissue targets than one-layer arrays. The performance of the connected array with a higher number of layers exceeds the performance of the dipole arrays in the superficial regions, while they are comparable for deep regions of the breast. The 1-layer 12-antenna circular FORA dipole array feasibility as a microwave hyperthermia applicator was experimentally shown. [ABSTRACT FROM AUTHOR]

A broadband dual‐polarized antenna array with excellent impedance matching and stable radiation performance is proposed. The array comprises four folded‐dipole antenna elements. Two trapezoidal baluns are used to excite the folded‐dipole antenna to obtain good impedance matching and generate a ±45°‐polarized radiation pattern. To improve the impedance matching and achieve steady radiation performance, a square parasitic director is used and placed above the folded dipoles. The antenna element realizes a broad bandwidth of 76.9% (voltage standing wave ratio [VSWR] < 1.5 from 1.69 to 3.8 GHz) and high isolation of 28 dB. Then an antenna array comprised of four elements is designed. It is fed by two miniaturized 1‐to‐4 power divides. Several metal baffles are added between adjacent elements to reduce the mutual coupling. The array achieves a broad bandwidth of 78.4% (VSWR < 1.5 from 1.66 to 3.8 GHz), high isolation of 25 dB, stable half power beamwidth in the E‐plane within 65° ± 5°, and high gain within 12–15 dBi. [ABSTRACT FROM AUTHOR]

In this paper, a miniaturized high gain magnetoelectric dipole (MED) antenna array is proposed, which is composed of a one‐to‐two‐way substrate‐integrated waveguide E‐plane T‐type waveguide power divider as the feeding network. The MED antenna consists of a pair of mirror‐symmetrical E‐patches and a pair of vertical metallized vias. The size of the antenna array is 1.2λ0× 1.6λ0× 0.17λ0. A bandwidth of 29.3% (25.6–34.4 GHz) for S11 < −10 dB can be achieved and has unidirectional radiation performance in the operating frequency band. The peak gain of the antenna reaches 11 dBi, and the average gain can reach more than 10 dBi. [ABSTRACT FROM AUTHOR]

This publication proposes a fabricated multiple input multiple output (MIMO) antenna geometry of multiple dipole arrays and its numerical findings through simulations. The role that antenna resonators have in antenna performance is explored. The antenna's characteristics have been studied, such as its return loss, peak gain, bandwidth, polar plot, and electric field distribution. The proposed antennas described in the study can produce three to seven resonance bands, making them suitable for multiband, wideband, and short-band settings. With the radiator placed in a mirror image, a gain of ~ 27 dBi is seen in the design. This layout is successful at achieving a bandwidth of 0.98 GHz. The maximum bandwidth of 7.44 GHz was achieved in antenna design when the antenna was inverted and mounted vertically. We measure a peak gain of ~ 4.1 dBi for this antenna configuration. In addition, the suggested antenna may provide a multi-beam antenna radiation pattern, capable of producing both a narrow beam of 10° and a wide beam of 250°. The proposed antenna has numerous potential uses; the study's findings can be applied to various wireless networking and telecommunications technologies, including Zigbee, WiFi, WiMAX, satellite, and 5G. [ABSTRACT FROM AUTHOR]

This work proposes a new circularly polarized (CP) 4 × 4 magneto-electric (ME) dipole antenna array using metallic walls for 28 GHz band applications. The ME dipole element is surrounded by eight metallic walls and is excited fed by microstrip line. By introducing metallic walls, the 3-dB axial ratio (AR) bandwidth of the element is increased from 23% to 36.5%. The 4 × 4 array is fed by a simple 1-to-16 microstrip power divider. In contrast to the conventional substrate integrated waveguide (SIW) power divider using two layers, the proposed microstrip divider only needs one substrate layer. The experimental 3-dB AR bandwidth of the array achieves 30.1%, ranging from 22.5 to 30.5 GHz, which falls inside the −10 dB impendence bandwidth. The measured maximum gain is 19.2 dBic. [ABSTRACT FROM AUTHOR]

This document is a guest editorial from the journal "Electronics Letters" that discusses the importance of wideband/multiband millimeter-wave antennas for 5G/6G and radar applications. It highlights the increasing demand for higher data rates and system capacity in wireless systems. The editorial presents 16 research papers accepted for publication in a special issue, covering topics such as millimeter-wave antennas for 5G/6G and radar applications, microwave antennas for 5G/6G and radar applications, measurement methods for millimeter-wave antennas, and decoupling methods and other millimeter-wave components. The papers explore innovative designs and technologies to meet the requirements of these applications. The authors of the papers are researchers and professors from various universities and research institutions. [Extracted from the article]

We proposed and fabricated large-scale arrays of resonant tunneling diode (RTD) oscillators for high-output-power terahertz (THz) sources. The array element is composed of an RTD, a slot resonator, and a dipole array antenna on a dielectric layer stacked on the RTD. In this structure, the output power is radiated in the upward direction of the substrate without a hemispherical silicon lens. The dipole array antenna was designed so that the average output power determined by the variation in the size of the RTD in the array was maximized. The experimental output power was proportional to the element number, and its value was 0.73 mW for an 89-element array at ∼1 THz in a pulsed mode with a repetition rate of 300 Hz and a duty ratio of 10%. Multiple peaks were observed in the oscillation spectra, because the elements were not intentionally coupled with each other. The average output power per element was 9 μW in the array, which was lower than that of the separated single oscillators (21 μW). Possible causes of this difference are discussed. [ABSTRACT FROM AUTHOR]

This paper presents a high-gain wideband circularly polarized antenna composed of an end-fire dipole array antenna integrated with a metasurface. The antenna consists of a two-layer cascaded non-uniform metasurface made up of 4 × 4 circular patches with cross-slots of unequal lengths placed above an end-fire dipole array antenna with an air gap between the structures. The end-fire dipole array antenna comprises four equally spaced dipole elements, and each dipole is connected to a parallel stripline printed on the front and back sides of the substrate. The metasurface, which is made up of a circular patch with 2 × 2 center patches that have a different radius than the outer patches, and the cross-slots of unequal lengths are used for the polarization conversion of a linearly polarized wave to a circularly polarized wave. The measured reflection coefficients for |S11| < -10 dB yielded an impedance bandwidth of 25.6-31.8 GHz (21.5%), a 3-dB axial ratio (AR) bandwidth of 26.1-30.5 GHz (15.5%), a 3-dB gain bandwidth of 26.0-31.1 GHz (17.4%) with a peak gain of 11.0 dBic, and a radiation efficiency of more than 80% in the axial ratio bandwidth. [ABSTRACT FROM AUTHOR]

A high-gain and wideband interconnected magneto-electric (ME) dipole on a single-layer PCB substrate is designed for 5G communication applications. Microstrip lines and coplanar striplines (CPSs) serve as transmission lines to connect the ME dipole elements along the E-plane and the H-plane directions, respectively. Impedance matching and sidelobe-level suppression are the key challenges to design a large-scale interconnected ME dipole antenna array. It is shown that impedance matching can be improved by introducing slots and adjusting the width of microstrip lines. Sidelobe level can be enhanced by properly choosing the length of the microstrip lines. A 5 × 5 interconnected ME dipole array is fabricated on a single layer of the RT/duroid 5880 substrate. The proposed antenna exhibits a measured −10 dB impedance bandwidth of 14.5 GHz (52% at 28 GHz) and a maximal peak realized gain of 20.44 dBi at 27.5 GHz with a 3 dB gain bandwidth of 3.5 GHz (12.5% at 28 GHz). The proposed antenna array is a good candidate for 5G communication applications due to its advantages of simple feeding structure, wide bandwidth, high gain, and low profile. [ABSTRACT FROM AUTHOR]

A dual‐band printed dipole array antenna for a wireless local area network (WLAN) application is presented. A radiation element consists of four pairs of printed dipoles, and two radiation elements are collinearly arrayed. A broadside coupling microstrip line‐based two‐sectional impedance transformer is used to feed the radiation elements in parallel. The proposed dual‐band antenna is designed to cover the dual‐frequency bands (2.4–2.48 and 5.15–5.825 GHz) which are the lower‐ and upper‐frequency bands for WLAN operation. The experimental results support the proposed design theory and also exhibit the gain values of 3.89–4.88 and 5.79–7.18 dBi at the lower‐ and upper‐bands, respectively, maintaining the omnidirectional radiation pattern. The measured radiation efficiencies at each frequency points, 2.4, 5.2, and 5.5 GHz are 87.39%, 75.43%, 69.96%, and 73.07% $ \% $, respectively. In addition, for mass production, the effect from a low‐cost flexible coaxial cable, and polyethylene housing on the antenna performance is also investigated in this letter. [ABSTRACT FROM AUTHOR]