Array Factor Research Articles

Phase and amplitude simultaneously coding metasurface with multi-frequency and multifunctional electromagnetic modulations

The integration of multiple functionalities into a single, planar, ultra-compact metasurface has presented significant opportunities for enhancing capacity and performance within compact 5G/6G communication systems. Recent advances in multifunctional metasurfaces have unveiled comprehensive wavefront manipulations utilizing phase, polarization transmission/reflection, and coding apertures. Despite these developments, there remains a critical need for multifunctional metasurfaces with expanded channel capabilities, including multiple operational frequencies, minimal crosstalk, and high-efficiency computable array factors. This study introduces a multifunctional metasurface that integrates phase- and amplitude simultaneous coding meta-atoms at dual frequencies. By altering the polarization of electromagnetic (EM) waves, it is possible to reshape the wave-fronts of reflected waves at these frequencies. The coding metasurface proficiently manipulates both x and y linearly polarized waves through phase and amplitude coding at dual frequencies, thereby enabling distinct functionalities such as anomalous reflection, reflection imaging, and vortex wave beam generation. Both theoretical analysis and full-wave simulation confirm the anticipated functionalities of the designed devices, paving the way for advancements in integrated communication systems with diverse functionalities.

A Generalized Array Factor for Time-Modulated Hexagonal Based Antenna Array Geometry with Novel Trapezoidal Switching

A Generalized Array Factor for Time-Modulated Hexagonal Based Antenna Array Geometry with Novel Trapezoidal Switching

Antenna Array Diagnosis in the Presence of Unknown Mutual Coupling using Optimization Technique

Antenna array diagnosis is an important operation in communication systems, whenever element (s) failure in the array that worsening the projected radiation pattern occur. There are various diagnostic techniques found in literature that employ compressive sensing. Conversely, the techniques are based on easy formulation of array factor with no incorporation of mutual coupling existing between the radiators. This article shows how this deficiency lead to defective and bad diagnosis when there is presence of mutual coupling using port-level coupling matrix and average embedded antenna pattern. Furthermore, the element excitations are optimized to reduce the effect of mutual coherence of system measurement matrix, causing reduced measurements required for effective fault detection. Numerical simulation and experimental results demonstrate how the incorporation of mutual coupling generates an adequate and reliable array diagnosis, which are not found in literature. For instance, when fault number is set at 5, and SNR equals 10 dB, the smallest measurements needed for the diagnosis, which is the most effective diagnosis, are achieved when the optimized excitations are used. In conclusion, the implementation of the developed framework using measurement probe in space, shows enough results towards the practical deployment for antenna systems in wireless communication system.

Radio Frequency Interference Mitigation in Data and Image Bi-Domains for an Aperture Synthesis Radiometer

For synthetic aperture microwave radiometers, the problem of Radio Frequency Interference (RFI) is becoming more and more serious, which affects both the scientific retrieval of remote sensing data and the imaging quality of brightness temperature (BT) images. In the visibility data domain, the array factor synthesis algorithm is commonly employed to mitigate RFI sources and their Gibbs trailing. In the BT image domain, the CLEAN algorithm is typical applied to mitigate RFI sources and their Gibbs trailing. However, the array factor synthesis algorithm can result in anomalous BT points near the “zero trap” region, and the CLEAN algorithm will miss some BT points below a certain threshold. In this paper, a Bi-domain combined mitigation algorithm is proposed to mitigate RFI sources and their Gibbs trailing. Following initial mitigation in the visibility data domain, dual thresholds are applied to normalize anomalous BT points near the “zero trap” region, thereby enhancing imaging quality. The effectiveness of the Bi-domain combined mitigation algorithm is verified by using both measured data from SMOS L1A and simulated data. The experimental results demonstrate that the Bi-domain combined mitigation algorithm is superior to the array factor synthesis algorithm and the CLEAN algorithm in mitigating RFI sources and their Gibbs trailing.

Scalability of MIMO Antennas: Assessing Gain and HPBW for Different Antenna Element Configurations

The design of Massive MIMO Antennas presents challenges due to their large size, which can impede the design process. Additionally, the arrangement of multiple antenna elements in Massive MIMO Antennas poses a challenge, as it surpasses the capabilities of simulation software and involves complex procedures. Therefore, to address these issues, a scalability technique utilizing array factor theory is employed to determine the relationship between the configuration of MIMO antennas and the corresponding values of gain and half-power beamwidth (HPBW). By utilizing a simpler MIMO Antenna array with incremental configurations, such as 2x2, 4x4, 8x8, and 16x16 MIMO element schemes, the array factor theory allows for the prediction of the gain and HPBW values for a Massive MIMO Antenna array with a specific configuration. This research aims to explore the scalability process and derive equations that relate the gain and HPBW values to the different MIMO configurations. The designed MIMO antenna arrangement is based on rectangular antennas with truncated corners and circular antennas with X slots, allowing for the investigation of various configurations operating at a frequency of 3.5 GHz.

Design of Linear and Planar Arrays With Low Sidelobe Levels and High Directivity Using Two-Way Array Factor

Design of Linear and Planar Arrays With Low Sidelobe Levels and High Directivity Using Two-Way Array Factor

Design of a Circular Micro-strip Patch Antenna for Improved Directivity and Gain of Mobile Communication Base Station

This study presents the design of Circular Micro-strip Patch Antenna (CMPA) for improved directivity and gain of mobile communication base station. The design incorporates a Rogger/5880 substrate material with a permittivity of 2.2, tangent angle of 0.00009 and a substrate height (thickness) of 0.98μm at a frequency of 1.65THz. Diversity Antenna Array Processing (DAAP) and Chebyshev Antenna Array (CAA) methods were used in the design. AutoCAD software and 2D data plotter were used for the diagrams and charts while Maple software was used for simulation. For angles of 0o, 30o, 60o, 90o, 120o, 150o and 180o, the array factors are 7.84dB, 7.85dB, 7.87dB, 7.88dB, 7.87dB, 7.85dB and 7.84db respectively. The results from the design demonstrated a remarkably low side lobe level of 0.01dB, indicating excellent suppression of unwanted radiation in undesired directions. Additionally, the antenna exhibits a Voltage Standing Wave Ratio (VSWR) of unity, ensuring maximum power transfer efficiency from the source to the load. Furthermore, the antenna shows a high directivity and gain of approximately 9dB, which enhances the signal strength and coverage range. The Half Power Beam-width (HPBW) and First Null Beam-width (FNBW) was measured as 300 and 600 respectively. These parameters depict the angular width of the main radiation beam and the sharpness of the beam pattern’s nulls. In all, the designed CMPA with its CAA based antenna array holds great potential for communication networks and for mobile communication base station, offering enhanced performance in terms of radiation characteristics and signal quality.

Far-field mapping and efficient beaming of second harmonic by a plasmonic metagrating

Abstract We study numerically and experimentally the second-harmonic generation (SHG) from rectangular metagratings of V-shaped gold nanoantennas. We show that by carefully engineering the array pitch to steer the diffraction orders toward the single antenna emission, the extracted signal is maximized. This enhancement is attributed to the angular overlap between the radiation pattern and array factor and is comparable to the improvement yielded by the coupling of surface lattice resonances (SLRs) with local modes. Moreover, we demonstrate a simple technique to experimentally reconstruct the emission diagram of an antenna from measurements of the collective grating response as a function of the excitation angle. Excellent agreement is obtained with simulations when the sample is immersed either in air or in water, which is crucial in view of future sensing application. Thanks to the high signal-to-noise ratio and low dependence on the statistical particle dispersity, this method constitutes an effective alternative to back-focal plane imaging when very weak signals such as SHG are involved.

Synthesis of antenna arrays with main lobe and sidelobes of arbitrary levels and widths

ABSTRACT An analytic method is proposed to synthesise linear antenna arrays in order to have a main lobe and a specified number of sidelobes whose levels and widths are to arbitrary. This method is based on synthesising the array factor as the Summation of Contiguous Independent Lobes (SCIL). These independent lobes are similar to each other except that their levels and widths are individually specified. Then, an explicit relation is obtained for excitation currents through Fourier’s series theorem. Some examples are brought to verify the effectiveness of the proposed method.

Theoretical and Experimental Investigation of N-Bit Reconfigurable Retrodirective Metasurface

The PIN diode-based N-bit reconfigurable retrodirective metasurface (N-bit RRDM) is a next-generation retro-reflector that offers the advantages of effective electronical control of the retro-reflection angle, low loss, and thin planar structure. However, since the unit cell of an N-bit RRDM is controlled by a quantized N-bit phase (360°/2<sup>N</sup>), it encounters operational errors, such as beam gain reduction and spurious beams. This can be a fatal disadvantage in military radar or satellite communication, which requires accurate beam tracking. This paper theoretically analyzes the operation of the N-bit RRDM by utilizing generalized Snell’s law and array factor theory. The analysis results present the design criteria for an N-bit RRDM that eliminates issues related to beam gain reduction and spurious beam errors. Furthermore, to verify the theoretical analysis results, High-Frequency Structure Simulator (HFSS) full-wave simulation and experimentation are conducted using the 1-bit RRDM.

An Analytical Investigation on the Performance of 1D and 2D Antenna Arrays for mm-Wave Modern Communication Systems

Millimeter wave (mm-Wave) wireless technology has invaded every aspect of modern life because of its ability to transmit data quickly and securely. This paper presented a square patch antenna at a resonance frequency of 26.2GHz for millimeter wave wireless communication. The proposed antenna consists of single square radiating element. The suggested antenna was designed using CST Microwave Studio’s version 2020 on a Rogers RO 3003 lossy substrate with a relative permittivity of 3 . The result of this paper shows a minimum S11 of 19.34 dB, a gain of 6.97dBi, with bandwidth of 2GHz at the resonant frequency of 26.2GHz. The gain was enhanced to 16dBi and 25.8dBi with a high radiation efficiency by converting the single element patch antenna to a uniform linear array of 8 elements and uniform planar array of 8 × 8 elements respectively. The simulation results show that despite the simple design of the patch (without holes and cracks), which facilitates manufacturing in a small size; However, it achieves higher gain than the more complex designs found in the previous literature to suit mm wave communication requirements. Also, we used CST Microwave Studio for simulation which provides two methods for implementing arrays: the array factor method, which builds virtual arrays (the direct method), or building arrays by repeating the elements depending on the required size of the array, A comparison has been conducted between the numerical analysis of both methods, and the results show that even though the numerical analysis of the second method gives more accurate results that can be close to a manufactured antenna array, it needs high processing ability and time. Creating arrays with array factor may save time and processing ability but the results may not be accurate. Therefore, a relation was driven to show the error that can be added to give precise results.

A Theoretical Design of Angular-Phased Broadband Antenna Array for Submillimeter Wave Applications

In this article, a broadband semicircular antenna array geometry was examined, along with its design and configuration in the submillimeter wave range (9.35-42.89 GHz). The work has been divided into two prime phases; in the first phase of work, an innovative angular-phased 1 : 4 broadband power divider has been presented in which its isolation, insertion, and return losses are investigated. In the next phase, the proposed power divider was used to configure a 4-element antenna array, and its theoretical analysis was carried out. The angular path difference in the array was used to introduce phase difference in between the antenna elements to minimize the mutual coupling and to optimize the narrow beamwidth. Using geometry and fundamental array theory, the array factor of a novel broadband array configuration has been derived and analytically investigated.

Synthesis of Large Ultra-wideband Sparse Circular Planar Arrays Based on Rotationally Symmetric Structure

This article aims to improve the synthesis efficiency and radiation performance of large ultra-wideband (UWB) rotationally symmetric sparse circular planar arrays by using a modified differential evolution algorithm (MDEA). In the proposed MDEA, we adopt a new encoding mechanism in which an individual represents an element position expressed in polar coordinates. Importantly, such an encoding mechanism can facilitate the multiplication calculation for the array factor in the individual being updated while making it easier to meet the given minimum element spacing constraint. Moreover, to cater to the new encoding mechanism, some low-dimensional evolution operators are introduced to avoid the prematurity. In particular, the UWB rotationally symmetric sparse planar array synthesis problem is transformed into the sidelobe suppression problem of the array pattern at the highest frequency under the given array aperture, and the minimum spacing constraints is used to guarantee enough space to place physical UWB antenna elements. Two synthesis examples of UWB sparse planar arrays based on rotationally symmetric structures are presented. The results show that the peak sidelobe level (PSL) obtained by the proposed MDEA is significantly lower than the results obtained by some existing algorithms in an acceptable CPU time, which proves the effectiveness and superiority of the proposed MDEA.

Investigating the Impact of Diverging Spacing Factors on Array Antennas

This paper analyzed the antenna patterns for dipole array antennas of diverging spacing factor. In order to minimize the complexity of the task required in the computation, we assumed a negligible width for the dipole elements. Thus, the current flowing through the wire is assumedly constant. The Array Factor for dipole array antennas of diverging spacing factor was derived via Magnetic Vector Potential model. The required radiation patterns for the antennas were generated using the MatLab simulation tools. The generated results showed a trade-off between directivity and power loss as expected. While the diverging spacing factor results to a swift increase in the directivity of the radiation pattern, it produces many ripples for an increase in the array antenna element. Keywords: dipole, array antennas, array factor, electromagnetic fields, diverging spacing factor, Magnetic Vector Potential.

Embedded Patterns and Extended Array Admittance Matrix

Sparse arrays of antennas can sometimes be modelled without accounting for the mutual coupling. In that case, the array radiation pattern can be expressed as the product of two factors: the isolated antenna radiation pattern and the array factor. Using the array impedance matrix, this formalism can be extended to account for the mutual coupling when the array is made of single-mode antennas. In this paper, we propose an extension of that formalism to the case of multi-mode antennas. We show that, contrary to the single-mode case, the array impedance matrix and isolated element patterns are not sufficient to rigorously account for mutual coupling. Building on these concepts, we propose a new quantity, the extended array admittance matrix. Combined with a modal decomposition of the currents on the antennas, it can be used to rigorously account for mutual coupling between multi-mode antennas in an array. The proposed formalism is illustrated by numerical examples.

Different 2D and 3D mask constraints synthesis for large array pattern shaping

Abstract In this article, different 2D and 3D mask styles for synthesizing large array pattern shaping to meet the requirements of modern applications are realized. The composition of the different beam pattern shaping is achieved by comparing the array factor with the proposed masks whose details (upper and lower borders) are predefined according to the designer. The generated pattern shapes are as follows: unscanned 2D single-pencil beam, scanned 2D pencil beam, 2D multi-beam scanning, 2D wide flat beam with little ripple, unscanned 3D single-pencil beam, 3D multi-beam scanning, and footprint (or contour) pattern for linear and planar arrays. The process of constructing these patterns is followed by predicting the amplitude-only weights (i.e., the phase weighting is considered zero in all computations) of the elements using the particle swarm optimization algorithm. In all proposed masks, different sidelobe levels are controlled, ranging from −20 to −100 dB. Also, the radiated beamwidth is controlled, ranging from 0.1334 rad (7.6 deg.) to 0.4 rad (23 deg.). The analysis and construction of linear and planar array arrangements depend on the formulation of antenna array theory through the implementation of the proposed (estimated) equations using MATLAB code. The simulation results showed the effectiveness of the proposed methods in controlling the pattern shape according to the required modern trends.

A Gain-Enhanced Differential-Fed Stacked Circular Patch Antenna With Simultaneously Controllable E-Plane and H-Plane Radiation Nulls

In this work, a differential-fed three-layer stacked circular patch antenna with enhanced gain performance is theoretically investigated for the simultaneous control of radiation nulls over both <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</i> -plane and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> -plane patterns. First, the bottom layer patch is meticulously designed based on a modified TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode to meet the matching conditions. Then, the structures of the parasitic layer patches are contrived to form similar peripheral radiative current distributions compared with the bottom one, aiming to simplify the analysis process. After that, the three-layer patches are stacked in a capacitively coupled fashion, which guarantees the out-of-phase scheme between the middle layer patch and the other two-layer patches. By means of the cavity-model theorem, further investigations on the multilayer distributions of the equivalent magnetic currents for the three radiators have successfully demonstrated that the destructive interference among the currents will result in the emergence of radiation nulls for both <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</i> -plane and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> -plane patterns. As a result, the beamwidth of the antenna in the two principal planes can be narrowed, which contributes to a significant improvement in the overall gain performance. Furthermore, a thorough array factor analysis on the flexible control of the radiation nulls is highlighted with both theoretical predictions and full-wave quantitative verifications. Finally, an experimental prototype is fabricated and measured to prove its validity. Compared with other stacked antennas with approximately the same longitudinal profiles, this design features the highest measured peak gain of 13.9 dBi, with an attractive increment of 8.0 dB pronounced.

A convex optimization based multistage wideband pattern accurate synthesis method for overlapping subarrays

Due to frequency variation and overlapping architecture, some overlapping subarrays may exhibit significant grating lobe problems in their wideband patterns. Furthermore, accurate synthesis methods for wideband patterns with subarray architecture are lacking in traditional approaches, as they cannot control sidelobe level (SLL) accurately while maintaining a narrow half-power beam width (HPBW). To address these challenges, this paper proposes a multistage control approach for achieving precise wideband pattern synthesis of subarray structures. Firstly, we propose a subarray pattern synthesis method based on multi-frequency null control (MNC) to address the grating lobe issue under specific overlapping architectures. Secondly, building on the MNC method, we introduce an improved approach called single-frequency null control (SNC) to enhance the array degrees of freedom utilization. Thirdly, we propose an array factor synthesis method based on multi-frequency minimum mainlobe width (M3W) to accurately control SLL and minimize HPBW. This method leverages the subarray pattern synthesis outcome and enforces the multi-frequency SLL constraint to minimize the mainlobe width. Finally, we validate our proposed methods by comparing wideband array patterns, integration array patterns, and traditional methods. The simulation results demonstrate that our methods offer superior GLL suppression, accurate SLL control, and HPBW minimization. Furthermore, the proposed techniques can be applied to arbitrary overlapping subarray systems without being affected by grating lobes, thus overcoming a limitation of traditional methods.

Joint frequency space design approach for efficient planar frequency diverse arrays

Antenna arrays offer advantages in terms of spatial diversity, allowing for control over pattern specifications in space. The incorporation of frequency diversity in arrays presents an opportunity to manipulate beams in the Space–Time domain. Unlike conventional arrays, Frequency Diverse Arrays (FDA) with added frequency diversity exhibit time-variant and range-dependent patterns. These time variations impact both steering and auto-scanning applications. The array factor is influenced by the coherent interplay between frequency and spatial distributions of elements, thereby correlating the spatial and temporal behavior of the FDA’s pattern. To address this space-frequency coherency, an adjoint spatial-frequency design algorithm is the most effective approach to controlling the array's spatial and temporal behavior. Given the complexity of the array factor formulations in FDAs, elements' frequency and spatial distribution have traditionally been designed separately. However, this study proposes an algorithm that simultaneously allocates the location and frequency of elements to achieve a desired pattern. Symmetrical FDA is initially designed using a straightforward formulation of the array factor obtained through symmetry, ensuring a stable and periodic scanning beam. Subsequently, two important design parameters and several crucial design criteria for scanning applications are suggested by analyzing the formulations. These parameters form the basis of a designing algorithm that enables the simultaneous design of element location and frequency in the space-frequency plan, thus meeting the temporal and spatial requirements of the pattern. To demonstrate the efficacy of the proposed algorithm, two different planar arrays are designed, and their results are compared with those of other planar configurations. This study lays the foundation for a novel approach to designing Frequency Diverse Arrays (FDAs), opening up new possibilities in array design.

Fully-Metallic Additively Manufactured Monolithic Double-Ridged Waveguide Rotman Lens in the K/Ka-Band.

This paper reports on the design and experimental validation of a fully-metallic double-ridged waveguide 10 × 10 Rotman lens additively manufactured as a single part. The wide band operation of this quasi-optical beamformer enables us to cover the uplink and downlink frequencies allocated to satellite communications in the K/Ka-band, from 17.3 GHz to 30 GHz. The feeding port design was adjusted to enable vertical printing, thus minimizing the use of supporting structures. A prototype was manufactured and tested. The reported results indicate losses in the range of 0.5 dB in the lower-frequency band and 0.8 dB in the upper-frequency band, including the waveguide transitions added for test purposes. The measured reflection and coupling coefficients remain below -11.5 dB over the operating band. The standard deviation of the residual phase error across the array ports is below 5° in simulation and below 10° in measurements. Array factors synthesized using the scattering parameters confirm the good stability of the beamforming functionality over the wide frequency band analyzed. This monolithic design is a promising step toward more integrated antenna systems, such as a compact dual-stack configuration for planar array design.