Spherical Antenna Research Articles

A simple way to achieve planar excitation of arc-shaped array feeds in two-dimensional beam-steerable spherical lens antenna

In this article, a simple technique for achieving planar excitation positions of arc-shaped array feeds in a two-dimensional (2D) beam-steerable spherical lens antenna (SLA) is proposed. Specifically, a cuboid solder model is introduced to connect the feedlines of the feeds with the coaxial probe. An equivalent circuit model of the bowtie feed unit with solder is proposed to illustrate the impact of the introduced solder on the port matching. Additionally, the excitation position is altered by extending the microstrip feedline, which does not change the radiation structure of the feed nor affect its phase center. Subsequently, a homogeneous dielectric SLA with a 139-element bowtie-shaped dipole feed array is constructed to verify the planar excitation position scheme for the arc-shaped array feeds, which facilitates system integration. The theoretical calculation formulas for the beam pointing angles of numerous beams are also proposed. In the fabricated prototype, all feeds exhibit an overlapping bandwidth of 31–36.7 GHz for reflection coefficients, with the coupling less than -20 dB. The 139 switched beams cover a 2D continuous beam space of [−33°, 33°], with adjacent beam crossover levels around -4 dB. The measured peak gain is 28.7 dBi at 34.5 GHz, with an aperture efficiency of 57%.

Two Types of Bandwidth Evaluation of Crossed Spherical Helix Antennas Using Numerical Simulation

Two Types of Bandwidth Evaluation of Crossed Spherical Helix Antennas Using Numerical Simulation

Streamlined Millimeter-Wave and Subterahertz Spherical Far-Field Measurement System Supporting Various Antenna Types and Feed Interfaces: Use cases of antenna measurement system

Streamlined Millimeter-Wave and Subterahertz Spherical Far-Field Measurement System Supporting Various Antenna Types and Feed Interfaces: Use cases of antenna measurement system

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.

Dynamic control of spontaneous emission using magnetized InSb higher-order-mode antennas

We exploit InSb’s magnetic-induced optical properties to design THz sub-wavelength antennas that actively tune the radiative decay rates of dipole emitters at their proximity. The proposed designs include a spherical InSb antenna and a cylindrical Si-InSb hybrid antenna demonstrating distinct behaviors. The former dramatically enhances both radiative and non-radiative decay rates in the epsilon-near-zero region due to the dominant contribution of the Zeeman-splitting electric octupole mode. The latter realizes significant radiative decay rate enhancement via magnetic octupole mode, mitigating the quenching process and accelerating the photon production rate. A deep-learning-based optimization of emitter positioning further enhances the quantum efficiency of the proposed hybrid system. These novel mechanisms are promising for tunable THz single-photon sources in integrated quantum networks.

Multi-Frequency Spherical Near-Field Antenna Measurements Using Compressive Sensing

Multi-Frequency Spherical Near-Field Antenna Measurements Using Compressive Sensing

Review of Luneburg Lens Antenna Designs Manufactured Using 3D Printing

Introduction. The interest in multibeam dielectric lens antenna arrays has been growing in recent years due to the development of millimeter-wave telecommunication and radar systems. Progress in the development of mobile communication systems based on adaptive beamforming technology is increasingly associated with multibeam systems based on lens antenna structures, providing an alternative to hard-to-implement and energy-consuming phased antenna arrays. In recent years, spherical and cylindrical Luneburg lens antennas implemented using additive manufacturing technology have attracted research attention. Despite their complexity of execution, these design exhibit excellent electromagnetic characteristics. This paper provides a review of Luneburg lens antennas manufactured using 3D printing, which can find application in 5G and 6G communication systems.Aim. To review achievements in the design of lens antenna structures manufactured using additive manufacturing.Materials and methods. Materials for analysis, comparison, and systematization were derived from various sources, including research articles, publications in proceedings of Russian and international conferences, and websites of manufacturers of lens antennas over the past 20 years. The material selection mechanism was based on the originality of the presented designs of printed Luneburg lens antennas.Results. A review of Luneburg lens antennas manufactured using 3D printing, which differ from each other in terms of mechanical strength, complexity of execution, and electrodynamic characteristics, was carried out. The results of a comparative analysis of the key characteristics of these antennas are presented, along with examples of their practical implementation.Conclusion. The disadvantage of Luneburg lens antennas has always been the complexity of their manufacture; however, additive manufacturing technologies open up new opportunities for their fast, high-quality, and automated production. Various 3D printing technologies can be used to create dielectric lens antennas, which differ in the resolution of printers, printing speed, and cost. Additive manufacturing methods are constantly developing, having reached the technological possibility of printing Luneburg lens for the sub-THz range with a high level of resolution and accuracy. In addition, 3D printers capable of printing multiple lenses simultaneously have also appeared.

Древесно-композитные плиты с низким коэффициентом линейного теплового расширения

A number of industries require materials with a low coefficient of linear thermal expansion (CLTE), in particular, in the production of satellite spherical antennas. The latter are formed from composites containing carbon fibers and synthetic resins. The composition is cured by heating up to 180 °C. This leads to a thermal expansion of the mold and a change in the geometric characteristics of the product. Therefore, specific requirements are imposed on the materials for making molds. The high cost of special materials used for molds determines the need to search for other materials with a low CLTE. Wood is a possible solution to this problem. Its CLTE along the fibers is less than that of the vast majority of materials, and is approximately 3 ‧ 10-6 K–1, which is comparable to special materials. However, the expansion of wood across the fibers is much higher than the longitudinal one, which excludes the use of solid wood. Anisotropy can be reduced by creating a composite in which the fibers are uniformly oriented in all structural directions, bringing the value of wood expansion across the fibers closer to the value of expansion along the fibers. The traditional approach to producing wood composites, based on the use of synthetic adhesives, fails to achieve a noticeable reduction in thermal expansion due to the high CLTE of adhesives The use of boards made of hydrodynamically activated wood particles without binders is promising. Three series of experiments have been carried out: with varying the density of the boards, preliminary thermal modification of the original wood and the use of alkali during hydrodynamic processing. The thermal expansion study has been carried out using the NETZSCH DIL-402 C induction dilatometer in dynamic mode with a heating rate of 2 K/min. It has been established that thermal expansion increases with increasing density.The average CLTE at a density of 950 kg/m3 is 12 ‧10–6 K–1 and at a density of 1,100 kg/m3 it is 17‧10–6 K–1. At a comparable density, the thermal expansion of boards without binders is significantly lower than that of fiberboards (MDF). Preliminary thermal modification of wood does not significantly affect the CLTE of the boards. The use of alkali in the hydrodynamic treatment also has no effect.

Phaseless Probe-Corrected Spherical Near-Field Antenna Measurements Using Two Scan Spheres

Phaseless Probe-Corrected Spherical Near-Field Antenna Measurements Using Two Scan Spheres

A Tiling Method for Sub-Arrayed Spherical Conformal Phased Array Antennas Based on Maximum 3-D Space Entropy Model

A Tiling Method for Sub-Arrayed Spherical Conformal Phased Array Antennas Based on Maximum 3-D Space Entropy Model

Analytical Expressions for Spherical Wire Antenna Quality Factor Demonstrating Exact Agreement Between Circuit-Based and Field Integration Techniques

Analytical Expressions for Spherical Wire Antenna Quality Factor Demonstrating Exact Agreement Between Circuit-Based and Field Integration Techniques

A Multiclass Support Vector Machine Based Direction-of-Arrival Estimation Technique using Spherical Antenna Array with Undefined Mutual Coupling

A Multiclass Support Vector Machine Based Direction-of-Arrival Estimation Technique using Spherical Antenna Array with Undefined Mutual Coupling

A Compact Spherical Rectifier Antenna Array for Directionally Insensitive Wireless Energy Harvesting Systems

A Compact Spherical Rectifier Antenna Array for Directionally Insensitive Wireless Energy Harvesting Systems

SOLVING FIRST SCIENTIFIC PROBLEMS ON PRELIMINARY ADJUSTMENT OF THE ANTENNA OF THE ROT-54/2.6 RADIO-OPTICAL TELESCOPE

The ROT-54/2.6 radio-optical telescope was built in the Aragats Scientific Center by the institution headed by Professor Paris Herouni in 1980-1987 and still has the world's largest double-reflector spherical antenna. After working for more than three decades, it was mothballed in 2012, since there was a physical impact on various structures of the radio-optical telescope due to natural and artificial phenomena. In connection with the fact that the ROT-54/2.6 radio-optical telescope has remained in the mentioned state for a long time, some antenna parameters may have changed compared to the initial parameters. In particular, in 2015, one of the support brackets of the East-West axis of the antenna structure failed and its axis was welded by the decision of the autorities of the National Institute of Metrology without carrying out research and repairs at that time, just to keep the axis stationary. For this reason, at present, the small reflector of the telescope can move only due to rotating around one axis. Therefore, in order to reactivate and reboot the radio optical telescope, it is necessary to know with high accuracy the shift of the physical, ge-ometric and radio engineering parameters of the antenna, and thus estimate the amount of work on the reboot.

Radiation Pattern Synthesis Using Constraint Convex Optimization Algorithm for Conformal Antenna Array

In this paper, a model based on constraint convex optimization is proposed for the radiation pattern synthesis in cylindrical and spherical microstrip conformal array antennas. The optimization algorithm is modeled to decrease the Euclidean distance between the obtained radiation pattern of the deformed array and the desired radiation pattern of the planar array by calculating the suitable amplitude and phase values for the individual array patches. Four prototypes of 2×2, 3×3, 4×4, and 5×5 microstrip patch array antenna are used as the radiating elements which are deformed from planar arrangement and placed on the faces of prescribed spherical and cylindrical shapes with various radii of curvatures. The results reveal that the performance of optimization algorithm performs better in 5×5 array, followed by 4×4 array, 3×3 array, and 2×2 array. However, 5×5 array provides more degrees of freedom for tuning the radiation pattern in desired form. The 5×5 array computes suitable amplitude and phase values for the radiating elements of the array, which restore the radiation pattern in terms of mainlobe reconstruction, null locations, sidelobe levels, up to the deformation of 20 cm in both spherical and cylindrical configurations of conformal array. The proposed optimization technique when applied to conformal antenna array offers fast computational speed and good convergence accuracy for radiation pattern synthesis, which can be useful for various engineering applications.

The design strain sensitivity of the schenberg spherical resonant antenna for gravitational waves

The main purpose of this study is to review the Schenberg resonant antenna transfer function and to recalculate the antenna design strain sensitivity for gravitational waves. We consider the spherical antenna with six transducers in the semi dodecahedral configuration. When coupled to the antenna, the transducer-sphere system will work as a mass-spring system with three masses. The first one is the antenna effective mass for each quadrupole mode, the second one is the mass of the mechanical structure of the transducer first mechanical mode and the third one is the effective mass of the transducer membrane that makes one of the transducer microwave cavity walls. All the calculations are done for the degenerate (all the sphere quadrupole mode frequencies equal) and non-degenerate sphere cases. We have come to the conclusion that the “ultimate” sensitivity of an advanced version of Schenberg antenna (aSchenberg) is around the standard quantum limit (although the parametric transducers used could, in principle, surpass this limit). However, this sensitivity, in the frequency range where Schenberg operates, has already been achieved by the two aLIGOs in the O3 run, therefore, the only reasonable justification for remounting the Schenberg antenna and trying to place it in the sensitivity of the standard quantum limit would be to detect gravitational waves with another physical principle, different from the one used by laser interferometers. This other physical principle would be the absorption of the gravitational wave energy by a resonant mass like Schenberg.

Phaseless Spherical Near-Field Antenna Measurements With Reduced Samplings

Phaseless Spherical Near-Field Antenna Measurements With Reduced Samplings

Wrap-like transfer printing for three-dimensional curvy electronics.

Three-dimensional (3D) curvy electronics has wide-ranging application in biomedical health care, soft machine, and high-density curved imager. Limited by material properties, complex procedures, and coverage ability of existing fabrication techniques, the development of high-performance 3D curvy electronics remains challenging. Here, we propose an automated wrap-like transfer printing prototype for fabricating 3D curvy electronics. Assisted by a gentle and uniform pressure field, the prefabricated planar circuits on the petal-like stamp are integrated onto the target surface intactly with full coverage. The driving pressure for the wrapping is provided by the strain recovery of a prestrained elastic film triggered by the air pressure control. The wrapping configuration and strain distribution of the stamp are simulated by finite element analysis, and the pattern and thickness of the stamps are optimized. Demonstration of this strategy including spherical meander antenna, spherical light-emitting diode array, and spherical solar cell array illustrates its feasibility in the development of complex 3D curvy electronics.

Combined Application of Partition Clustering Classification and Gerchberg-Papoulis Optimization Algorithm for Spherical Near Field Antenna Measurements

An adaptive sampling and optimized extrapolation scheme for spherical near-field antenna testing is proposed. The method relies on the partition clustering classification algorithm and Voronoi classification to divide a small amount of initial data into subclasses and cells. The sampling density and rates of variation between adjacent sampling points are used as an overall metric function to evaluate the sampling dynamics at each location. Appropriate interpolation is performed in the highly dynamic region to increase the effective data in the near-field samples. The Gerchberg-Papoulis algorithm extrapolates the unnecessary interpolation region to improve the near-field sampling accuracy. This method uses a small amount of initial near-field sampled data for near-far field conversion to achieve the same precision as uniform oversampling. The feasibility and stability of the algorithm are proved from the actual measurement results.

Closed-Form Expression of Radiation Characteristics for Electrically Small Spherical Helix Antennas

To understand the radiation mechanism of an electrically small spherical helix antenna, we develop a theory on the radiation characteristics of the antenna. An analytical model of the antenna presuming a current on the wire to be sinusoidally distributed is proposed and analyzed with the spherical wave expansion. The radiation efficiency, radiation resistance, and radiation patterns are obtained in closed-form expression. The radiation efficiency evidently varies with the surface area of the wire and the radiation resistance depends on the square of the length of the wire. The obtained result for the radiation pattern illustrates the tilt of the pattern caused by the modes asymmetric to the z-axis. The radiation efficiency formula indicates a good agreement between the simulation and measurement result. In addition, the radiation resistance of the theoretical and simulation results exhibits good agreement. Considering the effect of the feeding structure of the fabricated antenna, the radiation resistance of the analytical model can be treated as a reasonable result. The result of radiation pattern also shows good agreement between the simulation and measurement results excluding a small contribution from the feeding cable acting as a scatterer.