Scan Blindness Research Articles

A Millimeter-Wave Wideband Dual-Polarized Magnetoelectric Dipole Phased Array With Scan Blindness Mitigation

A Millimeter-Wave Wideband Dual-Polarized Magnetoelectric Dipole Phased Array With Scan Blindness Mitigation

High efficiency and circular polarization in SATCOM phased arrays using tri-ridge apertures

A new antenna array architecture is proposed here to overcome a current bottleneck in phased arrays concerning the enhancement of radiation efficiency and avoidance of scan blindness. In contrast to the conventional approach of using patches with circular or square geometries that exploit 90∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^\\circ$$\\end{document} or 180∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^\\circ$$\\end{document} rotational symmetry, this work proposes to use waveguide radiating elements based on 120∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^\\circ$$\\end{document} symmetry. To implement such symmetry, the tri-ridge aperture is proposed, and its capability to scan widely within a broad frequency bandwidth is demonstrated. A modal analysis is performed to explain the physical phenomena underlying such superior performance. A successful experimental validation is provided by means of a monolithic prototype built in metal additive manufacturing. The measured results show, for the first time, that it is possible to achieve high radiation efficiency and circular polarization when scanning widely in a broad bandwidth. Such an accomplishment constitutes a major achievement in the field of active electronically steered phased arrays, and impacts significantly the capabilities and potential of modern radar and communication systems.

Low-Profile Differentially-Fed Tightly-Coupled Dipole Array

Introduction. Tightly coupled dipoles currently belong to one of the most popular types of antenna arrays. Their main advantages include an electrically low-profile height, the ability to scan the beam across a wide sector of angles without the onset of scan blindness, and a low level of cross-polarization. In recent years, the number of publications on the topic of antenna arrays of this type has increased significantly. The authors have paid sufficient attention to baluns included in the antenna array elements. However, the possibility of implementing a differentially-fed scheme in antenna arrays of this type remains poorly studied. This makes the study of this subject especially relevant in the development of radio devices where such feed technique is preferable.Aim. Differentially-fed tightly-coupled dipole array design and study.Materials and methods. The following materials were used to create the prototype: copper sheet, ceramic glass substrate ST-50-1, dielectric RO3003. A numerical study of the characteristics was carried out in the ANSYS HFSS environment; an experimental study of the prototype was carried out in an anechoic chamber using an automated measuring complex and a vector network analyzer.Results. The results of designing a planar antenna array of tightly-coupled dipoles for the X-band are presented. In the antenna array, each of the dipole arms is fed using a separate coaxial cable, while the two arms of one dipole are fed out-of-phase. The results of a numerical study of the characteristics of an 8 × 8 antenna array made from the developed elements are presented. Across the range from 6.5 to 12.25 GHz, the average active VSWR does not exceed 3, while the gain varies from 21.5 to 25.7 dBi. The possibility of beam scanning in a sector of angles up to ±45° is shown. The results of an experimental study of the radiation characteristics and matching of the prototype of a single element are presented.Conclusion. The importance of taking into account the effects that arise at the edges of finite antenna arrays during simulations is shown. The feasibility of manufacturing and measuring antenna array prototypes with a large number of elements is experimentally confirmed. The proposed element design demonstrates the possibility of implementing the differentially-fed scheme in tightly coupled antenna arrays.

A Planar SIW-Based Mm-Wave Frequency-Scanning Slot Antenna Array With No Scan Blindness at Normal

Planar antenna reflectors are the modern design trend of both multibeam and frequency-scanning antenna arrays. The planar implementation of reflectors is typically performed using substrate-integrated waveguide (SIW) technology. A reflector’s profile can be different from the canonical one (parabolic, elliptic, hyperbolic, etc.) because of the effect of spatial dispersion of the reflection coefficient of the SIW-based surface. It should be synthesized considering the magnitude and argument of the field reflected from such a surface to maximize the efficiency of the reflection. In this article, we present a planar millimeter-wave (mm-wave) slot antenna array with SIW-based horn–reflector feeding. We analytically formulate the optimization of the SIW surface dimensions while accounting for the spatial dispersion of the reflection coefficient. We minimize the dimensions of the planar horn–reflector feeding. Finally, we demonstrate that using a dual-slot radiating element, and we can avoid the effects of scan blindness along the normal direction. A prototype has been built and a good agreement has been achieved between the measured results and the predicted results based on calculations. The prototype achieved ±17° beam scanning within 16% of the operational frequency range, with no scan blindness along the normal direction.

Reactive Impedance Surface-Loaded Wideband Wide-Scanning Phased Array in Triangular Lattice

A phased array loaded with a reactive impedance surface (RIS) is proposed for wideband wide-scanning performance. The mushroom-like RIS structure, etched on the same printed circuit board (PCB) of the antenna, is introduced as a superstrate over the antenna aperture. The reactance of the RIS structure compensates for the scan impedance variation of the antenna during the beam scanning, explained by the equivalent transmission-line model. A superior scanning performance in all azimuth planes is achieved, and the scan blindness in the H-plane is alleviated, especially. The total compact design is capable of operating over a 2.3:1 (6 –14 GHz) bandwidth in broadside and over a 1.8:1 bandwidth in ±60° E-plane, ±70° D-plane, and ±65° H-plane scanning. The array is implemented in a triangular lattice, and edge elements in the E-plane are connected to metal walls for edge effect elimination. A 45-element ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5\times 9$ </tex-math></inline-formula> ) array prototype is fabricated and measured. Active reflection coefficients are calculated, and scanning patterns are synthesized.

Design and Analysis of a Novel Wide-Angle Scanning Stub-Loaded Cavity Array Element

A novel design methodology is presented to mitigate scan blindness in cavity antenna arrays without the need for any changes on the radiating structure itself. For a first proof-of-concept demonstration, a fully PCB-compliant dual-polarized cavity element is loaded by vertical stubs to manipulate the dispersion characteristics in the aperture plane. In contrast with its conventional cavity antenna counterpart, the proposed stub-loaded unit cell element shows through scattering and eigenmode analysis that the vertical stubs may effectively enhance the antennafs wide-angle scan performance by preventing the onset of surface and leaky wave resonances. Owing to this additional design freedom, an element gain improvement of at least 1 dB is achieved, due to a truly TE and TM mode-free characteristic along the lateral directions. A dual-polarized 11&#x00D7;11 array prototype was implemented. The measurement results are in very good agreement with those obtained by full-wave simulations. The realized stub-loaded cavity element exhibits reflection coefficients lower than -10 dB with a very low inter-port coupling &#x003C;-40 dB across the frequency range from 26.8 GHz to 32.7 GHz. Moreover, the co-polarized embedded elements are close to the ideal cos(&#x03D1;)-pattern for 60&#x2218; E-and H-plane scans from 28 GHz to 31.5 GHz without oversampling the aperture.

Design of an Active Beam-Steering Array With a Perforated Wide-Angle Impedance Matching Layer

In this communication, a tapered slot antenna array with a perforated wide-angle impedance matching (WAIM) layer is studied for active beam steering. To achieve the wide-angle beam scanning characteristic, a tapered slot antenna is used in the array antenna design. For active impedance matching in a wide beam-steering angle, a thin dielectric type of WAIM is introduced, and an optimal WAIM characteristic is realized by changing the effective dielectric constant by adding an air hole to the WAIM. To verify the characteristics of the designed antenna, a 16×16 array is fabricated and measured. The fabricated array shows active S-parameter characteristics of less than -9.13 dB during E-plane scanning and -9.31 dB during H-plane scanning when the beam is steered up to 70° on both planes. It was also confirmed that when the beam is steered to 70°, no scan blindness or grating lobes occur within the operating frequency.

Wideband Wide-Scanning Planar Triangular-Lattice Phased Array With Substrate-Integrated Cavity-Backed U-Slot Patches

A compact wideband and wide-scanning planar triangular-lattice phased array is proposed. The proposed element is a U-slot microstrip antenna surrounded by a substrate-integrated cavity (SIC) structure fed by a 50 Ω coaxial cable. The scan blindness is effectively shifted out of the operation band as the SIC structure obstructs the surface wave and mutual coupling. The proposed array is arranged in a triangular lattice with fewer elements than a rectangular one. A 4×8 planar array prototype is fabricated and measured over X-band. The antenna provides a bandwidth of over 30% frequency range under ±60° scanning in all azimuth planes.

Scan Blindness Free Design of Wideband Wide-Scanning Open-Ended Waveguide Phased Array

A wideband wide-scanning open-ended rectangular waveguide phased array in a triangular lattice is presented. Dielectric or metamaterial wide-angle impedance matching superstrates have been widely used in phased arrays to improve the scanning performance. However these dielectric-containing covers cannot solve the problem of scan blindness caused by the surface waves, or even further aggravate the surface wave effect. The modulated surface structures, which consist of the impedance-gradient structures and the surface wave bandgap structures are designed to maximize the wideband wide-scanning performance of the array. The proposed array achieves 40% bandwidth (8–12 GHz), while covering a scanning range of ±65° in the E-plane (VSWR < 2.3) and H-plane (VSWR < 2). The practical working frequency band occupies the whole potential operating frequency band between the waveguide TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> cutoff frequency and the onset frequency of the first grating lobe. An <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$11\times11$ </tex-math></inline-formula> prototype is fabricated and measured. Good agreement is achieved between the simulated and measured results.

Removal of scan blindness of phased array antenna using fourth-order Hilbert curved EBG structure

ABSTRACT It has been shown that the Hilbert curved electromagnetic band gap (HC-EBG) structure effectively reduces the surface wave excitation in the substrate. This paper investigates the performance of HC-EBG structure for probe-fed microstrip patch phased array antenna. The results show that not only the mutual coupling between two elements is reduced about 20 dB, but also the blind angle is removed. Based on the proposed method, a probe-fed microstrip patch antenna phased array 9 × 7 elements are designed and simulated that shows the blind angle has been eliminated without increasing the dimensions of the antenna. Simulation results show improvement in the active reflection coefficient of center element and gain of the array.

Dual-Polarized Metal-Flare Sliced Notch Antenna Array

This article presents a dual-polarized metal-flare sliced notch antenna (SNA) array comprising metallic Vivaldi flares “sliced” by air gaps. Aside from the slice gaps in the flares (supported with foam sheets in the array build), the SNA is an exact duplicate of a conventional all-metal Vivaldi array, against which the SNA is presented directly in a one-to-one comparison to isolate the effect of slicing on dual-polarized radiator performance. The SNA has very similar capabilities as the Vivaldi in all metrics (match, gain, port isolation, and bandwidth), except that the SNA demonstrates lower cross-polarization (cross-pol) across all scan angles and frequencies. Both arrays are optimally sampled and have excellent matching from 2.6 to 21.2 GHz with zero scan blindness out to wide angles. For this demonstration, uniform slices are introduced in the flares to satisfy a single design criterion of −10 dB cross-pol (relative to copolarized fields) for a 45° scan cone at all frequencies, culminating in a peak SNA cross-pol improvement of 35 dB (relative to the reference Vivaldi array). Infinite array predictions are followed up by measurements on a 256-port prototype aperture. This work demonstrates that the slicing technique can be applied to effectively mitigate high cross-pol in dual-polarized Vivaldi arrays without inhibiting other performance metrics.

Experimental Validation of a Correcting Coupling Mechanism to Extend the Scanning Range of Narrowband Phased Array Antennas

This article presents a technique designed to extend the scanning range of a probe-fed patch array whose performances are limited by scan blindness, due to a strong surface wave coupling. The current framework relates to the context of radar applications requiring a large scanning range (up to 60°) and where no inter-element spacing modification is possible as a result of strong T/R modules integration constraints. The proposed solution is based on the introduction of an additional correcting coupling within the array, by means of microstrip lines connecting the sources two by two. A thorough step-by-step description of the design methodology is introduced. It is then implemented in the case of a single-polarized ten-element patch array operating in $X$ -band. Simulation results as well as an experimental validation of the concept are presented. They assess the effective improvement of the active impedance matching and realized gain resulting from the use of connecting lines.

The Two-Port Transmission Method With Applications to Microstrip Phased Arrays

A novel method is presented to investigate substrate leaky and/or surface wave mode effects within microstrip antenna arrays. The proposed methodology provides accurate modal analysis for the array elements, while including all metallic and different material inclusions, regardless of geometrical shape. Furthermore, the proposed methodology is very general because it accounts for all phenomena and design requirements including arbitrary excitation of the antenna elements in amplitude and phase, the effect of the substrate modes, mutual coupling, and scan blindness. Substrate waves can be studied directly from the same setup with an operating microstrip phased array. One additional significant advantage of this approach is that interelement antenna array spacing can be larger than half a wavelength in the design of phased arrays, thus, overcoming heretofore limitations in the study of scan blindness.

Mechanism and Elimination of Scan Blindness in a T-Printed Dipole Array

In this article, the scan blindness in a T-printed dipole is analyzed, and an elimination strategy is proposed. First, the main cause of scan blindness is analyzed. The scan characteristics are obtained using an active element pattern (AEP) with an infinite rectangular lattice arrangement. Based on the propagation of a guided wave along the antenna row and the electric-field ( $E$ -field) distribution observed during simulations, an equivalent circuit model for a unit cell of the T-printed dipole is obtained. A quasi-transverse electromagnetic (TEM) guided wave is predicted using the dispersion relation curve obtained from the equivalent circuit, and it is proven that the calculated curve is in good agreement with the eigen mode simulations and measured trajectory of the scan blind angle, for different frequencies. Next, slits and stubs are introduced as parasitic structures to eliminate the scan blindness and improve the antenna scan range. To confirm the effects of these parasitic elements, a linear array simulation is performed, which confirms the suppression of a quasi-TEM guided wave. Analysis of the active reflection coefficient and dispersion diagram indicates that the scan characteristics have been improved by the addition of parasitics. Four types of array prototypes are fabricated and their measurements validate the scan blindness prediction and confirm the proposed mechanism of scan blindness and its improvements.

Wideband mutual coupling reduction and scan blindness elimination in a microstrip patch phased array antenna with truncated soft surface structures

This article introduces a new type of soft surface as truncated soft surface (TSS) for the mutual coupling reduction in stacked aperture-coupled microstrip patch phased array antennas. Also, a meandered TSS (MTSS) is introduced with a reduced size compared to the TSS. Conventional soft surfaces not only prevent the propagation of waves in the soft longitudinal direction but also guide the waves in the transversal direction. So, the mutual coupling decreases in the soft longitudinal direction and increases in the transversal direction. Truncation in the transversal direction prevents the waves from guidance on TSSs. Simulation results show that using this technique helps to decrease the mutual coupling in the E-plane of a phased array antenna without any noticeable increase in the H-plane coupling. Also, there is no blind spot in the desired scan range and the embedded element pattern will not have any null in the scan range. Using this technique, the acceptable scan range for an antenna substrate with a low relative permittivity of 2.33, can be increased up to 45°. Finally, measurement results show that using TSS leads to an 8-dB decrement in the E-plane mutual coupling.

일차원과 이차원 Ka-대역 프린티드 다이폴 배열 안테나의 스캔 블라인드니스 분석

In this study, an active element pattern (AEP) of a printed dipole was analyzed in 1D and 2D arrays. First, an AEP of the printed dipole was obtained using the simulation in the 2D infinite array. The scan blindness in the 2D array occurred in the E-plane direction at around ±36°; however, it was barely observed in the 1D array. To analyze the cause of the scan blindness in the 2D array, the dispersion properties of a unit cell was obtained and compared with the scan blindness by frequency change. The difference between the scan blindness of the 1D and 2D arrays was clarified using the comparison of the Q value in the unit cell in the 1D and 2D arrays. Then, the coupling of the electric field in the E-plane direction was observed when nine elements were separated between the two ports in a linearly arranged dipole structure. Finally, the printed dipole array was fabricated, and an AEP was measured for the 11×1 and 11×3 sub arrays. The proposed theory was verified using these observations and by comparison with the simulation results.

Wideband Wide-Scanning Phased Array in Triangular Lattice With Electromagnetic Bandgap Structures

A phased array in a triangular lattice, with a large element spacing, wide band, and wide scan angle, is investigated in this letter. The array is designed based on a connected backed-cavity antenna element. Scan blindness is observed for this triangular lattice array when the beam scans in the E-plane due to large element spacing, which provides a suitable propagation condition for the leaky surface waves in the array aperture. Therefore, compact electromagnetic bandgap (EBG) structures are loaded in the array element to suppress the leaky surface waves and then remove the E-plane scan blindness for the largest impedance bandwidth. The bandwidths close to the theoretical values are achieved as the beam is scanned in the E- and H-planes, for the given element spacing. The validity of design is verified by fabricating a 13 × 5 prototype, the measured results are in good agreement with the full-wave simulations.

A Dual-Band Shared Aperture Antenna Array in Ku/Ka-Bands for Beam Scanning Applications

A dual-band shared aperture antenna array for phased array system operated in Ku/Ka-bands is proposed in this paper. By judiciously designing the geometrical structure and parameters, compact and integrated antenna elements are proposed to achieve the maximum scanning angle without the grating lobes phenomenon. The patch-dipole antenna elements operating in Ku-band and microstrip patch antenna elements operating in Ka-band are designed and fabricated utilizing a four-layer lamination substrate. Metal shielding vias are introduced to suppress the coupling between the antenna elements operating in different bands, meanwhile, defected ground structure is introduced to eliminate the scan blindness effect and improve the beam scanning range effectively. The proposed antenna array has 208 Ku-band elements and 832 Ka-band elements distributed in the shared aperture with a diameter of 200 mm. Measured results show that the proposed antenna array has a broad impedance bandwidth of 10.7% in Ku-band and 9.1% in Ka-band, meanwhile it has a relatively wide scanning angle ranging from -45° to +45° with low gain decrease and side lobe level. The proposed phased array antenna has potential application in a radar system, mobile communication system, and so on.

Phased Array Antenna Handbook (Third Edition) [Book Review

The third edition of the Array Antenna Handbook is a very welcome addition to the antenna field. It brings together many ideas and techniques that one would normally have to search through the literature to find. The book is a comprehensive treatment of phased array antennas written by a single author, and it is thus an integrated text that flows smoothly from one topic to another. The publication does not contain homework problems, but the material is presented in such a sufficiently explanatory manner that it could be used as a textbook for a course on phased or antenna arrays, in general, or as a supplement to a course on antennas. The book contains nine chapters, and it has a total length of 530 pages. The text focuses on the antenna aspects of phased arrays and, thus, focuses on aspects related to the radiation patterns of a phased array, along with the antenna elements that are used in phased arrays, and other antenna-related concepts such as mutual coupling in antenna arrays (and their associated effects on scan behavior such as scan blindness). Phased arrays are steadily gaining in relevance with applications in 5G and many other systems, both military and commercial. Better affordability and a wider variety of applications ensures this positive trend. Subsequently, this third edition is a most welcome addition to the antennas and propagation community. This latest edition has been updated to include new contributions to scanning antennas based on reflectors and lenses, as well as thinned arrays, and a more contemporary presentation of numerical methods for pattern synthesis has also been provided. The book provides a comprehensive coverage of all aspects of phased arrays from an antenna point of view, and it also provides an excellent overview of systemlevel aspects of phased arrays in the first chapter. It is very well written by a leading expert in the field, and it is one of the few texts written entirely on phased arrays. As such, it is a must-have publication for every antenna engineer, system engineer, scientist, or practitioner who works with or is interested in phased arrays. This book will also make a great supplement for instructors who teach a course in antenna engineering and who wish to cover phased arrays as part of their course topics.

Realization of Scan Blindness Free Finite Microstrip Phased Arrays Based on Mode-Free Radiating Electromagnetic Bandgap Materials

This paper demonstrates finite-sized microstrip phased arrays based on a novel electromagnetic bandgap material, which is mode-free along the lateral directions while radiating to the broadside direction as an antenna element; it improves array radiation along all scan directions compared to uniform substrate arrays. Scan characteristics of the array are obtained by using the active element pattern and active reflection coefficient of the center element, instead of using phase shifters and power dividers. Comparison of the fabricated bandgap and uniform substrate array prototypes validate the bandgap array’s performance; i.e., it eliminates the scan blindness problem.