Pattern Synthesis Research Articles

Printed Metasurface Leaky Wave Antennas Based on Penetrable Aperture Field Synthesis

A design methodology for 1-D modulated printed metasurface leaky-wave antennas (LWAs) with a pattern synthesis capability in 2-D TE polarization is presented. For a desired radiation pattern, complete tangential fields on the surface of a grounded dielectric substrate are constructed and optimized to find a pointwise passive surface impedance distribution. Dielectric and conductor losses are taken into account in the field synthesis process via a design curve obtained using analysis of a physical unit cell with lossy constituents. It enables accurate prediction of the aperture field distribution when practical lossy materials are used. A spatially modulated impedance can be realized using an array of printed copper strips. Three 10-wavelength-long LWA designs are demonstrated numerically for broadside, two-beam, and sector patterns. The LWA for broadside radiation is fabricated and measured, showing a good agreement with the simulation results.

Circularly Polarized Dual-Frequency MIMO Antenna With Cosecant-Squared Radiation Pattern for Ku-Band Applications

In this paper, the realization of a circularly polarized multiple-input, multiple-output (MIMO) array antenna with a cosecant squared pattern, is presented. The proposed antenna structure consists of microstrip patches with rectangular slots etched from the top. The desired radiation pattern is generated using amplitude tapering obtained by modifying patch widths and slot lengths, based upon the amplitude coefficients of the Woodward-Lawson method for pattern synthesis. A MIMO arrangement with circular polarization is formed by connecting two such arrays excited by two ports. A <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Z</i> -shaped slot is used to minimize the mutual coupling. Using two shorting pins, the isolation is enhanced and kept above 30 dB. This arrangement offers a small size (52 mm ×24 mm × 0.8 mm), wide bandwidth, and high gain antenna operating at 13.2 and 16.6 GHz. The antenna operates in a wide bandwidth, from 12.6 GHz to 14.25 GHz, and from 16 to 17.61 GHz, with admirable directional characteristics. The achieved gain is 16.9 dB and 16.6 dB with a cosecant pattern and low side lobe level. The analysis of the, VSWR, gain, axial ratio, group delay, efficiency, and MIMO performance metrics are also investigated, both in simulation and in experiment.

Hierarchical Codebook-Based Beam Training for RIS-Assisted mmWave Communication Systems

Reconfigurable intelligent surface (RIS) has emerged as a competitive solution to the blocking problem in millimeter wave (mmWave) communications. However, due to the passive nature of the RIS, obtaining channel state information (CSI) for RIS-assisted mmWave communication systems is rather difficult. Considering that the currently available RIS hardware cannot arbitrarily switch between the active (reflection with configurable phase response) and deactivate (absorption) modes, we suggest a new beam training method for RIS-assisted mmWave communication systems in this study. First, a predefined hierarchical codebook is created using the pattern synthesis method. Then, we provide a novel hierarchical beam training method using two multi-mainlobe codewords in each layer of the hierarchical codebook for beam sweeping. Combining the results of the beam identification in all the layers will yield the ultimate ideal beam direction. Theoretical analyses demonstrate that the suggested approach can effectively reduce training overhead while ensuring successful beam alignment. Simulation results show that the practical codebook can be created successfully, and the suggested method can achieve accurate beam alignment with reduced training overhead.

Laser-synthesis of conductive carbon-based materials from two flexible commercial substrates: A comparison

One of the key challenges in the field of flexible electronics relies on finding conductive materials that can withstand bending and stretching stresses while maintaining their performance. In this context, this work presents a comparative study of laser-induced conductive materials from the direct laser-scribing of two commercial flexible films: the benchmark Kapton® HN polyimide (PI) precursor and the UltemTM 1000 polyetherimide (PEI) alternative contender. The synthesis process on both materials is optimized in terms of electrical conductivity using a high-performance galvanometric laser with a wavelength of 532 nm for the fabrication of multiple samples at different laser powers and speeds. The samples are structurally characterized using Scanning Electron Microscopy (SEM), Raman spectroscopy, X-ray Photoelectron Spectroscopy (XPS), and Fourier-Transform Infrared Spectroscopy (FTIR) aiming at understanding the chemical and physical changes of the ablated material. The results demonstrate that the proposed setup is feasible for the synthesis of uniform and reliable conductive patterns on the surface of both substrates with high reproducibility. In particular, it is proved that PEI is more suitable precursor for flexible electronics applications which demand high electrical conductivity, leading to a sheet resistance of 3.62 ± 0.35 Ω/sq at 0.8 W and 5 mm/s once the laser-synthesis process is optimized (against the 6.04 ± 0.63 Ω/sq at 0.6 W and 5 mm/s offered by the LIG on PI). The performance of both laser-induced patterns as electrodes for the fabrication of electrochemical capacitors is also studied and compared in terms of areal specific capacitance.

COSECANT-SQUARED BEAM PATTERN SYNTHESIS OF CONCENTRIC CIRCULAR ANTENNA ARRAY IN A RANGE OF AZIMUTH PLANE USING EVOLUTIONARY ALGORITHM

This paper presents, a pattern synthesis method based on Differential Evolutionary Algorithm. A cosec2 beam pattern has been generated from different concentric circular ring arrays of isotropic elements by finding the optimum set of elements amplitude and phase using the Differential Evolution algorithm. The shaped beam pattern (cosec2) is generated in three predefined azimuth planes (φ=0°, 5° and 10°) from a Concentric Circular Antenna Array (CCAA) having two rings, three rings, and four rings. The total number or isotropic elements are equal for array geometries. The optimum excitation for array geometries is also verified for a range of arbitrarily chosen azimuth planes. The obtained main beam is similar to the desired pattern with some minor variations in peak Side Lobe Level (peak SLL) and ripple. Dynamic range ratio (DRR) is improved by using 4-bit discrete Amplitudes and 5-bit discrete Phases. These discrete excitations also simplify the design complexity of the feed networks.

Floral volatiles evoke partially similar responses in both florivores and pollinators and are correlated with non-volatile reward chemicals.

Plants often use floral displays to attract mutualists and prevent antagonist attacks. Chemical displays detectable from a distance include attractive or repellent floral volatile organic compounds (FVOCs). Locally, visitors perceive contact chemicals including nutrients but also deterrent or toxic constituents of pollen and nectar. The FVOC and pollen chemical composition can vary intra- and interspecifically. For certain pollinator and florivore species, responses to these compounds are studied in specific plant systems, yet we lack a synthesis of general patterns comparing these two groups and insights into potential correlations between FVOC and pollen chemodiversity. We reviewed how FVOCs and non-volatile floral chemical displays, i.e. pollen nutrients and toxins, vary in composition and affect the detection by and behaviour of insect visitors. Moreover, we used meta-analyses to evaluate the detection of and responses to FVOCs by pollinators vs. florivores within the same plant genera. We also tested whether the chemodiversity of FVOCs, pollen nutrients and toxins is correlated, hence mutually informative. According to available data, florivores could detect more FVOCs than pollinators. Frequently tested FVOCs were often reported as pollinator-attractive and florivore-repellent. Among FVOCs tested on both visitor groups, there was a higher number of attractive than repellent compounds. FVOC and pollen toxin richness were negatively correlated, indicating trade-offs, whereas a marginal positive correlation between the amount of pollen protein and toxin richness was observed. Plants face critical trade-offs, because floral chemicals mediate similar information to both mutualists and antagonists, particularly through attractive FVOCs, with fewer repellent FVOCs. Furthermore, florivores might detect more FVOCs, whose richness is correlated with the chemical richness of rewards. Chemodiversity of FVOCs is potentially informative of reward traits. To gain a better understanding of the ecological processes shaping floral chemical displays, more research is needed on floral antagonists of diverse plant species and on the role of floral chemodiversity in visitor responses.

Low Sidelobe Level Pattern Synthesis of 2-D Slot Array Antenna Based on Ridged Waveguide

Slotted waveguide antennas have received much attention due to features such as low loss, high efficiency, and high power capacity. In this article, a 2-D slot array antenna based on a ridged waveguide with a low level of side lobe is synthesized. The antenna consists of four slotted ridged waveguides, each of which consists of eight slots as the radiating elements. A fast and easy way is proposed to synthesize the aperture distribution in the H-plane. Further, a corporate feed network based on ridged waveguide is designed to feed the antenna. The feed network is designed such that the desired aperture distribution in the E-plane is achieved. A prototype of the antenna is fabricated and measured. The measured sidelobe levels in the H- and E-planes are, respectively, -24.5 dB and -23.9 dB, and the reflection coefficient of the antenna is -19 dB at the design frequency, indicating the accuracy of the design procedure. The measured antenna gain is approximately 20.4 dBi at the entire frequency band. The stable radiation pattern of the antenna makes the antenna suitable for radar applications.

Multiband Pattern Synthesis of Time-Modulated Conformal Array with Quadratic Convex Optimization Algorithm

Aiming at the multiband pattern synthesis problem of time-modulated conformal array antenna, a quadratic convex optimization algorithm is proposed for sum and difference beamforming with low sidelobe levels. This articles method synthesizes a difference beam with a low sidelobe level by generating nulls at the center frequency band and optimizing the switch-on duration time of array elements. And the sum beamforming and sidelobe suppression of the first-order sideband are realized by optimizing the switch-on instant time of the array elements. The proposed algorithm has excellent properties of sidelobe suppression and angular sweep. The simulation results of circular and satellite array antenna verify the effectiveness of the algorithm.

Beam Stabilization of Deformed Conformal Array Antenna Based on Physical- Method -Driven Deep Learning

The array antenna will be inevitably deformed affected by the motion of the communication system or other special requirements, which will reduce the original good radiation performance, such as the gain dropping, the side lobes increasing, and even the beam splitting. In order to cope with the beam deterioration caused by the array antenna’s deformation, it is necessary to quickly manipulate the amplitude and phase distribution according to the current conformal array shape to stabilize the beam. This paper proposes a physical-method-driven deep-learning-based (PMDL-based) fast beam stabilization algorithm for the antenna array deformation. Firstly, we theoretically analyze the radiation pattern synthesis of the conformal array with the arbitrary surface to design the corresponding physical method, and we verify the accuracy of the method by the calculated and simulated results. Then, the deep neural network driven by the physical method is designed integrated with the aforementioned radiation pattern synthesis, whose training process is given. Finally, a 1×16 array antenna is taken as an example to verify the validity of the beam stabilization algorithm when the designed array is deformed. The simulated and measured results both indicate that the gain dropping and the sidelobe level rising are respectively less than 1.5 dB and 2 dB by applying the proposed PMDL-based fast beam stabilization when the array antenna is deformed within the range of 100° of the normal vector of each array element, while the beam stabilization time is less than 1.0 ms (testing time).

Flat-Topped Radiation Pattern Synthesis of a Conformal Leaky-Wave Holographic Antenna

A novel method to synthesize a flat-topped pattern in single-curvature conformal leaky-wave antennas (CLWAs) is presented. When synthesizing the antenna, aperture field estimation (AFE), the holographic principle, the transformation optic (TO) approach, and the effects of the geometrical parameters of a curved structure on the far-field radiation pattern are considered. In the design process, three software packages (HFSS, MATLAB, and CST) are used to achieve the desired far-field radiation pattern at the design frequency. The shaped beam is in the broadside direction at 10 GHz. This CLWA is composed of unit cells with square patches that are printed on a double-layer grounded substrate which consists of PLA (Polylactic Acid) and Rogers RO4003 having thicknesses of 4 mm and 0.127 mm, respectively. An edge-fed 1:8 power divider excitation with a substrate integrated waveguide (SIW) structure is designed to illuminate the hologram. The proposed CLWA is fabricated and tested. The maximum realized gain of the novel antenna at the design frequency is about 13 dBi, and the weighted aperture efficiency of the proposed CLWA is about 0.86. There are also good agreements between the simulation and the measurement results of the proposed antenna frequency responses.

A synthesis of priorities, patterns, and gaps in large carnivore corridor research

IntroductionConservation research plays an integral role in the effort to conserve biodiversity globally. However, research gaps can limit conservation research’s potential contribution to addressing global biodiversity problems such as habitat fragmentation. While a synthesis of the research literature does not attain effective conservation action by itself, it can inform future research and corridor conservation planning and practices.MethodsWe used a systematic search of peer-reviewed research articles in Scopus, Web of Science, and grey literature in the Connectivity Conservation Specialist Group library published before December 2020. Our review assessed research on the identification and use of corridors, a primary instrument used to address the threats of habitat fragmentation, for large carnivores to identify patterns, priorities, and gaps in the literature. We focused on large carnivores because they are frequently used for connectivity planning owing to their higher sensitivity to habitat fragmentation and their importance as conservation flagship species.Results and discussionWe found that peer-reviewed studies primarily focused on single-species corridors with a strong preference toward apex predators, whereas grey literature focused on multi-species corridors. More than 80% of studies included one of the following five species, the mountain lion (n=46 studies), American black bear (n=31 studies), jaguar (n=25 studies), tiger (n=25 studies), and brown bear (n=18 studies). Although research on the identification of corridors was relatively more common in the past, we found an increasing trend in the publication of studies assessing the use of corridors by large carnivores in recent years. The published research is predominantly from North America (47%) and Asia (30%), with comparatively fewer studies from Africa (4%), despite having several large carnivore species. While climate change and human-wildlife conflict are considered major concerns for large carnivore conservation, these were seldomly considered in corridor research. Corridor research collaborations exist between academia, government, and non-government institutions, but the involvement of the private sector is lacking.ConclusionsOur review shows that there is scope for future corridor research to (i) focus on areas where geographical gaps exist, (ii) target multi-species corridors, (iii) include climate change and human-wildlife conflict scenarios, and iv) increase collaboration with the private sector to better inform connectivity solutions.

Efficient Phase-Only Dual- and Multi-Beam Pattern Synthesis With Accurate Beam Direction and Power Control Employing Partitioned Iterative FFT

In this communication, a novel phase-only method based on a partitioned iterative Fourier transform (PIFT) is presented to efficiently synthesize dual- and multibeam patterns for uniformly spaced linear and planar arrays. To achieve accurate mainlobe peak directions, the PIFT integrates a partitioned beam calibration strategy into the IFT to successively calibrate the beams by partitioning the multibeam pattern into single-beam patterns and calibrating them individually. Besides, the peak powers of the multiple beams are precisely controlled through proper mainlobe corrections. Several numerical examples of synthesizing dual- and multibeam patterns with accurately controlled peak directions and beam powers as well as reduced sidelobe levels (SLLs) are presented to demonstrate the effectiveness and efficiency of the proposed method. Synthesized results are validated with full-wave simulation. Comparisons with other phase-only methods are also presented to show the superiority of the proposed method.

Efficient and Accurate Pattern Synthesis for Radome‐Enclosed Planar Arrays Using Iterative FFT via Two‐Dimensional Least‐Square Active Element Pattern Expansion

AbstractThis work generalizes the iterative fast Fourier transform (FFT) via least‐square active element pattern expansion method to efficiently synthesize two‐dimensional (2D) patterns with accurate sidelobe and mainlobe shape control for planar arrays with radomes. The 2D active element patterns (2D‐AEPs) of a planar array‐radome structure are utilized to include the mutual coupling and radome effect. The 2D‐LSAEPE method is presented to approximate each 2D‐AEP as the pattern by exciting a virtual rectangular subarray with identical element patterns, and the weighting coefficients of the virtual subarray are found by minimizing the least‐square error of the 2D‐AEP approximation. With the help of the 2D‐LSAEPE, the pattern of a planar array with a radome can be efficiently calculated by FFT. To apply the FFT via 2D‐LSAEPE for planar array pattern computation, a blocked accumulating matrix is introduced which relates the virtual and physical excitation vectors. In addition, an interpolation‐based pre‐processing technique is implemented to obtain the virtual element pattern data in uniform grid of the (u, v)‐space so as to meet the requirement of employing the 2D‐FFT. By integrating the FFT with the 2D‐LSAEPE and the interpolation technique, an efficient iterative method is developed to implement accurate pattern synthesis for planar arrays with radomes. Three examples of synthesizing different planar array‐radome systems are conducted. Synthesis results show that the proposed method achieves much more accurate synthesis result than the traditional FFT‐based technique, while taking much less computation time than some other methods. This verifies the effectiveness of the proposed method.

Array Design Using Genetic Algorithm for the Generation of Sum and Difference Patterns

In the field of pattern synthesis, the design of arrays to synthesis optimized sum and difference patterns in a successive manner is an important problem in most of the radars. Although several researchers published many papers in the open literature, investigations are made by the authors to design arrays of discrete radiators using a well-formulated Genetic Algorithm (GA). The practical constraints are taken into account to design an amplitude distribution to produce the sum pattern with desired side lobe levels without broadening the main beam. Such sum patterns are found to be very useful in high-resolution radars where the EMI problems are also addressed. In IFF radars, both sum and difference patterns are extremely useful to distinguish between friendly aircraft and enemy aircraft. Such patterns are conventionally produced involving two antennas. One is a directional antenna and another is an omnidirectional antenna. However, in the present work, they are generated using only one directional antenna. The patterns with a deep null in the boresight direction and difference lobes with a high slope are produced with an antiphase excitation to one-half of the array.

Pattern synthesis of nonuniform linear antenna array based on FFDM

To optimize the number, spacing and excitation of nonuniform linear array at the same time, a Fourier basis filter diagonalization method (FFDM) is proposed in this paper. By constructing a set of Hamiltonian operator functions that can be decomposed by orthogonal eigenvectors, the synthesis of nonuniform linear arrays is transformed into a generalized eigenvalue decomposition under Fourier basis. The introduction of Fourier basis can improve the computational rate. The least square method (LSM) is used to solve the array element excitation, which improves the matching accuracy. A number of numerical simulations shown that the proposed algorithm can improve the accuracy of the array factor (AF) pattern of many types of practical arrays reconstruction.

English

Pattern synthesis is one of the most important problems in all wireless communications and Radar systems. Each application demands the generation of a different type of radiation pattern structure. Pencil beams are generated either from parabolic dish antennas or from array antennas for point-to-point communication. Similarly, sector beams are used in search Radars. On the other hand, csc² beams are used for ground mapping and airport surveillance. However, the difference patterns associated with narrow beams are sequentially used in IFF radars. In the present work, investigations are carried out to optimize such difference patterns from array antennas. The patterns are designed using a genetic algorithm, and the results are compared with those of Taylor's distribution. The patterns are presented in sin⁡θ Domain for different arrays. It is found from the results; the designed patterns are extremely useful in all search applications.

New forms of production organization: pearl companies

Objective : to develop a management system for new types of companies (pearl organizations). Methods : abstract-logical, methods of analysis and synthesis of theories and patterns of development of managerial approaches in economics. Results : the study of the evolution of organizational structures in production management within the concept of spiral dynamics by K. Graves, K. Kovan, and D. Beck, combined with the analysis of current problems of domestic corporate management leads to the formulation of the problem of choosing the forms of company management that best correspond to the current state and prospects of the formation of a new intellectual economy. In this context, G. B. Kleiner proposed the concept of pearl enterprises as organizations that ensure the long-term effectiveness of the activities of each employee, a team of departments and the company as a whole by expanding the range and increasing the flexibility of formal and informal, hierarchical and non-hierarchical management models used in its various segments. Such companies may be built by transforming the socalled turquoise organizations, which represent the most advanced form of democratic system management to date. The article analyzes the key problems of creating pearl companies by transforming the existing classical hierarchies, including the transformation of turquoise organizations into pearl ones. Scientific novelty : the requirements for the work of HR management in pearl companies are formulated, taking into account the increasing importance of creative intellectual work. The expediency of expanding the corpus of pearl organizations in the Russian economy under digitalization is substantiated. Practical significance : the main provisions and conclusions of the article can be used in scientific and pedagogical activities when considering the concept of pearl companies and developing modern approaches to HR management in organizations.

Numerical Synthesis of the Dual Frequency 28/35 GHz Power Monitor in the 160° Circular Miter Bend

A numerical method of the synthesis of the array pattern for the linear holes coupler embedded on the miter bend is proposed in this article. This method allows pattern control with the arbitrary incident angle when the waveguide operates at dual frequency. Combined with the analysis method, an algorithm has been developed for synthesizing the antenna pattern. As an example, a power monitor has been designed for a 28/35 GHz waveguide with an incident angle of 55°. An arrangement of the holes array has been obtained to get the desired array pattern at a given angle, and the directivity of the power monitor is larger than 40 dB at 28/35 GHz.

Pattern Synthesis for Different Sparse Planar Arrays by a Hybrid Unconstrained-Heuristic Approach

A hybrid approach that combines the strategy of partial density tapering (PDT) and the multiobjective particle swarm optimization (MOPSO), called PDT-MOPSO, is proposed to address the synthesis of sparse planar arrays (SPAs) of different shapes. By performing the PDT, not only the strong constraint of element placement in SPAs is eased to nonconstrained issue, but also the element locations are forced to follow the distribution of density tapering somewhat to facilitate the sidelobe suppression. Then, by taking the sidelobe level (SLL) and directivity as the optimization objectives, the traditional MOPSO is used to optimize the element locations so that the SPAs with reduced number of elements, minimized SLL and nondegraded directivity are achieved. Some numerical instances confirmed the effectiveness of the proposed method.

Low-Sidelobe Pattern Synthesis for Spaceborne Array Antenna Based on Improved Whale Optimization Algorithm

For the purpose of fulfilling the low sidelobe level (SLL) requirements for spaceborne phased array antenna pattern synthesis, this paper proposes a new improved whale optimization algorithm (IWOA). As a type of new heuristic algorithm inspired by whale hunting behavior, WOA has the advantages of simple structure, few parameters, fast optimization speed, and high precision. In this paper, improvements are made in three aspects of adaptive weight, spiral coefficient optimization, and optimal neighborhood perturbation, and the proposed algorithm is successfully applied to the intelligent calculation of antenna synthesis. In light of the engineering requirements, the mathematical model of the optimization problem is established, and the desired antenna pattern with high gain and low sidelobe is obtained using IWOA under the constraint that the amplitude variation is within 20 dB. Simulation results demonstrate that IWOA is superior in maximum sidelobe level (MSLL) suppression and convergence. Consequently, EM simulations were conducted on a 64-element planar array, with the results consistent with the theoretical simulation, verifying the feasibility and effectiveness of the proposed algorithm.