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Programmable metasurfaces provide emerging platforms for real‐time electromagnetic (EM) manipulations, showing enormous potential in various information applications. Achieving multiplexed manipulations of EM parameters such as polarization multiplexing and frequency multiplexing on a shared metasurface aperture is very important to improve the control ability and efficiency. In the usual implementation scheme, however, the multiplexed structures and tunable components are laid on the same surface of dielectric substrate, which tends to cause undesired crosstalk due to the physical connections. Here, a method is proposed to design a unique meta‐atom by embedding two varactors into the stacked layers to control orthogonally polarized waves without crosstalk. By arranging the demountable meta‐atoms on a baseboard, a scalable and high‐isolation dual‐channel programmable metasurface is further realized, which can be used to control dual‐polarized waves independently, even under the oblique incidence with 60°. As experimental validation, simultaneous and independent transmissions of different videos in space‐ and polarization‐division channels are carried out using the scalable dual‐channel programmable metasurface. The approach opens up avenues to develop low‐crosstalk multiplexed programmable metasurface, which may promote performance and stability of metasurface‐assisted information systems. [ABSTRACT FROM AUTHOR]

In this study, we propose the wide field of view (FoV) radar module for autonomous vehicles. The proposed wide FoV radar (WFR) module was constructed using of an RF module comprising wide beamwidth microstrip patch antennas, an AWR1642 radar sensor chip, and a control module. To achieve a wide FoV of 150° using the fabricated radar module, the 3-dB beamwidth characteristic of the applied microstrip patch antenna had to wider than 150°. The patch antenna was designed using a comb-line structure along 10-by-1 array structure, each radiator characterized by a shorted patch structure, such as a planar inverted-F antenna. The designed antenna was then fabricated on the same board surface as the sensor chip. To identify the characteristics of the implemented radar module, a trihedral corner reflector with a radar-cross-section of 180 m2 was used as the reflector target, and the CA-CFAR (cell averaging constant false alarm rate) target detection algorithm was applied. The measurement results, showed good detection performance of the radar in the view angle of 150°, from −75° to +75°, and a broad bandwidth of 4 GHz in the 77–81 GHz millimeter band. Therefore, the proposed WFR is applicable for used in blind spot detection sensors in autonomous vehicles.

In this paper, a broadband reconfigurable active frequency selective rasorber is proposed, which can be used as a radome for antenna radar cross section (RCS) reduction. By tuning the active components, the radome can achieve in‐band RCS reduction and reconfigurable absorptive/transmissive states. In the absorptive state, the max bandwidth with an absorption rate greater than 90% spanning from 1.62 to 5.37 GHz; in the absorptive/transmissive state, 2.2 GHz is the transmissive frequency with the insertion loss of 93% while absorbing in 0.94–2.06 GHz and 2.63–6.5 GHz, which demonstrate impressive characteristics of broadband and a high absorption rate. Additionally, the radome can maintain performance at ±35° angular incidence and is insensitive to incident wave polarization. Furthermore, it features a lightweight and low‐profile design, with a cell electrical size of just 0.078λ × 0.078λ × 0.066λ. The prototype test shows a noteworthy correlation with simulation. This study has wider applications in the electromagnetic stealth of communication antennas and aircraft, as well as in the control of electromagnetic pollution signals in space. [ABSTRACT FROM AUTHOR]

The total focusing method (TFM) has been increasingly applied to weld inspection given its high image quality and defect sensitivity. Oblique incidence is widely used to steer the beam effectively, considering the defect orientation and structural complexity of welded structures. However, the conventional TFM based on the delay-and-sum (DAS) principle is time-consuming, especially for oblique incidence. In this paper, a fast full-matrix imaging algorithm in the Fourier domain is proposed to accelerate the TFM under the condition of oblique incidence. The algorithm adopts the Chebyshev polynomials of the second kind to directly expand the Fourier extrapolator with lateral sound velocity variation. The direct expansion maintains image accuracy and resolution in wide-angle situations, covering both small and large angles, making it highly suitable for weld inspection. Simulations prove that the third-order Chebyshev expansion is required to achieve image accuracy equivalent to the TFM with wide-angle incidence. Experiments verify the algorithm's performance for weld flaws using the proposed method with the transverse wave and the full-skip mode. The depth deviation is within 0.53 mm, and the sizing error is below 15%. The imaging efficiency is improved by a factor of up to 8 compared to conventional TFM. We conclude that the proposed method is applicable to high-speed weld inspection with various oblique incidence angles. [ABSTRACT FROM AUTHOR]

Glass windows are an important part of indoor‐to‐outdoor wireless communication channels, but the transmission loss of the normal glass limits the quality of the radio frequency (RF) signals, especially for the transverse‐electric (TE) polarized waves incident at large angles due to the impendence mismatch. Although some design methods for wide‐angle high RF transmission (WHRT) have been proposed recently, they can only work in a single frequency band. Here, an optically transparent metasurface is presented to realize high RF transmissions for dual polarizations in dual bands (2.2–3.2 and 4.4–5.2 GHz) and wide incidence angles (0–80°). The central frequencies of the two bands can be tuned independently by changing the structural parameters. A theory based on the transmission line (TL) model is proposed to explain the mechanism of the design, and a prototype is fabricated by using flexible printed circuit technology. The measured results of the prototype have good agreement with numerical calculations and full‐wave simulations. The design is expected to be beneficial to improve the quality of wireless signals in 5G systems. [ABSTRACT FROM AUTHOR]

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In the near-field meta-steering method, the near electric-field phase distribution is dynamically altered by rotating a pair of phase-gradient metasurfaces that are typically made out of dielectric lattices or metal patterns printed on bonded dielectric substrates. As a lightweight alternate, a new class of fully metallic metasurfaces (MMs) is proposed in this article. The lack of dielectrics not only substantially reduces the cost and weight but also increases its potential in space and high-power applications. More importantly, the new MMs are designed such that they can be made by cutting narrow slots in fully planar thin metal sheets, retaining structural rigidity while reducing the complexity, cost, and weight. The same MM works for any polarization. Each cell in the new MMs has close to ideal phase shift and transmission magnitude greater than −0.9 dB. A prototype was designed and fabricated to validate this MM-based beam-steering concept in the Ku-band. The maximum measured steering range in zenith is ±42°, with a full 360° steering in the azimuth. The measured 3 dB gain bandwidth is 700–800 MHz (5.6%–6.4%), and the measured gain variation (scan loss) when steering over the whole range is 2.2–4.5 dB. The weight density and thickness of each MM are 0.88 g/cm2 and $0.8\lambda _{0}$ , respectively. Including the feed, the total antenna height is $4.9\lambda _{0}$. [ABSTRACT FROM AUTHOR]

In the characteristic basis function method (CBFM) for the wide-angle electromagnetic scattering problems of electrically large objects, the low generation efficiency, and many characteristic basis functions exist due to the dependence on external excitation. This paper proposes a characteristic mode basis function method (CMBFM) with novel basis function construction to address this issue. In CMBFM, characteristic modes of each extended block obtained by dividing objects are calculated separately, and then the effective modes are selected as basis functions according to the modal significance. Compared with CBFM, the time performance of constructing basis functions is improved significantly. Furthermore, fewer basis functions are generated without a loss of accuracy. The corresponding numerical results demonstrate that significant efficiency and accuracy can be achieved by the proposed approach. [ABSTRACT FROM AUTHOR]

Structural colorations with artificially engineered nanostructures provide a dye‐free mechanism for subdiffraction color generation with enhanced stability and environment friendliness. However, it remains elusive to create universally deep subwavelength pixels for arbitrary coloration at the single pixel level. The main obstacles are the unavoidable near‐field coupling between neighboring pixels and the angular dependent hues associated with the scattering process. Here, a generic principle is proposed and developed to create deep subwavelength bright‐field structural colors at the single pixel level by using alumina disk‐on‐film nanocavities. As a result of the gap‐plasmon‐induced perfect absorption, wide‐angle complementary colors are achieved across the full visible spectrum where both the near‐field coupling and angular dispersion are strongly suppressed. Deep subwavelength pixels down to 160 nm × 160 nm and green colors produced by composite pixels are experimentally demonstrated. The strategy represents a significant step toward practical application of structural colors at the single pixel level for nanoscale optical and optoelectronic devices. [ABSTRACT FROM AUTHOR]

This report outlines a proposed method of packaging wide-angle (WA) mini-light-emitting diode (mini-LED) devices without optical lenses to create a highly efficient, ultrathin, flexible planar backlight for portable quantum dot light-emitting diode (QLED) displays. Since the luminous intensity curve for mini-LEDs generally recommends a beam angle of 120°, numerous LEDs are necessary to achieve a uniform surface light source for a QLED backlight. The light-guide layer and diffusion layer were packaged together on a chip surface to create WA mini-LEDs with a viewing angle of 180°. These chips were then combined with a quantum dot (QD) film and an optical film to create a high-efficiency, ultrathin, flexible planar light source with excellent color purity that can be used as a QLED display backlight. A 6 in (14.4 cm) light source was used as an experimental sample. When 1.44 W was supplied to the sample, the 3200-piece WA mini-LED with a flexible planar QLED display had a beam angle of 180° on the luminous intensity curve, a planar backlight thickness of 0.98 mm, a luminance of 10,322 nits, and a luminance uniformity of 92%. [ABSTRACT FROM AUTHOR]

Abstract The clutch is an important component of the vehicle driveline system. One of its major functions is to attenuate or eliminate the torsional vibration and noise of the driveline system caused by the engine. Based on experiments of vibration damping under different vehicle conditions, the structure and functional principle of a clutch-driven disc assembly for a wide-angle, large-hysteresis, multistage damper is investigated in this study using an innovative combined approach. Furthermore, a systematic integration of key technologies, including wide-angle low-stiffness damping technology, large-hysteresis clutch technology, a novel split pre-damping structure technology, damping structure technology for component cushioning, and multistage damping structure technology, is proposed. The results show that the total torsional angle of the wide-angle large-hysteresis, multistage damper is more than twice that of the traditional clutch damper. The multistage damping design allows a better consideration of various damping requirements under different vehicle conditions, which can effectively address problems of severe idle vibrations and torsional resonance that occur under idled and accelerated conditions. Meanwhile, the use of a large-hysteresis structure and wear-resistant materials not only improves the vibration damping performance, but also prolongs the product service life, consequently resulting in multi-faceted optimization and innovative products.

Metasurface (MS) absorbers with polarization-insensitivity and wide-angle reception features have attracted much attention due to their unique absorption property. A polarization-insensitive broadband MS absorber structure, having wide-angle reception based on square split-ring resonators (SSRRs) and loaded with lumped resistors, is proposed in this paper. The proposed MS unit cell consists of a fixed-thickness FR4 dielectric substrate and a variable air-thickness substrate. The simulation results show that the proposed MS absorber is stable across a wide angular range for both normal and oblique incidences. Furthermore, the simulated results show that some parameters, such as unit-cell geometry and lumped resistors, can be varied to improve the performance of the MS absorber. The experimental results indicate that the proposed MS absorber can be achieved an absorption higher than 90% across the frequency range from 1.89 GHz to 6.85 GHz with a relative bandwidth of 113%, which is in agreement with simulation results. Thus, the proposed MS absorber can be more suitable in RF energy harvesting or wireless power transfer applications. [ABSTRACT FROM AUTHOR]

A dual-band miniaturized linear-to-circular polarization converter (LCPC) metasurface with wideband and wide-angle axial ratio (AR) is proposed and demonstrated. The metasurface is formed with periodic arrays of unit cells. The unit cells consist of three metallic layers separated by two substrates. The top and bottom metallic layers contain the identical cells with two metal strips and an “I”-type strip with four stubs for $y$ -polarization each. The middle metallic layer comprises an infinitely long metal strip and two “I”-type strips for $x$ -polarization. The LCPC performs a wideband response in both operating bands with the wide passbands generated by the orthogonal “I”-type strips. Prototyped $K$ -/ Ka-band design shows that the simulated/measured AR remains below 3 dB over the lower bandwidth of 15–21.2 GHz (34.3%)/16.3–21.1 GHz (25.7%) and higher bandwidth of 27–30.3 GHz (11.5%)/27–29.8 GHz (9.9%) under normal incidence in $y-{z}$ plane, respectively. For a 45° incidence, the measured AR still achieved the 3 dB bandwidth of 33.7%/9.4% in both the bands. The study shows that by virtue of orthogonal structures placed at different layers, the element size and the cross-polarization level are suppressed by 65% and 10 dB, respectively, compared to the previous work. Furthermore, the LCPC with the miniaturized elements shows wide-angle response in both the bands. [ABSTRACT FROM AUTHOR]

Abstract Background Inherited retinal degeneration (IRD) refers to a heterogenous group of progressive diseases that cause death of photoreceptor cells and subsequent vision loss. These diseases often affect the peripheral retina, objective evaluation of which has been difficult until recently. Fundus autofluorescence (FAF) is a non-invasive retinal imaging technique that depicts the distribution of intrinsic fluorophores in the retina. The primary source of retinal autofluorescence is lipofuscin, which is contained in the retinal pigment epithelium (RPE). Excessive accumulation of lipofuscin and a window defect attributable to loss of photoreceptor pigment result in increased FAF whereas loss of the RPE results in decreased FAF. These changes can be seen during the course of IRD. Mainbody While conventional modalities are limited in their angle of view, recent technologic advances, known as wide-field and ultra-widefield FAF imaging, have enabled visualization of the far peripheral retina. Although clinical application of this technique in patients with IRD is still in its infancy, some studies have already indicated its usefulness. For example, an area with decreased FAF correlates well with a visual field defect in an eye with retinitis pigmentosa (RP) or cone-rod dystrophy. An abnormal FAF pattern may help in the diagnosis of IRD and associated diseases. In addition, female carriers of X-linked RP and female choroideremia show characteristic appearance. Conversely, absence of abnormal FAF despite severe retinal degeneration helps differentiation of cancer-associated retinopathy. Conclusion This paper reviews the principles of FAF, wide-field imaging, and findings in specific diseases. Wide-field imaging, particularly wide-field FAF, will provide further information for the characteristics, prognosis, and pathogenesis of IRD.

This report outlines a proposed method of packaging wide-angle (WA) mini-light-emitting diode (mini-LED) devices without optical lenses to create a highly efficient, ultrathin, flexible planar backlight for portable quantum dot light-emitting diode (QLED) displays. Since the luminous intensity curve for mini-LEDs generally recommends a beam angle of 120°, numerous LEDs are necessary to achieve a uniform surface light source for a QLED backlight. The light-guide layer and diffusion layer were packaged together on a chip surface to create WA mini-LEDs with a viewing angle of 180°. These chips were then combined with a quantum dot (QD) film and an optical film to create a high-efficiency, ultrathin, flexible planar light source with excellent color purity that can be used as a QLED display backlight. A 6 in (14.4 cm) light source was used as an experimental sample. When 1.44 W was supplied to the sample, the 3200-piece WA mini-LED with a flexible planar QLED display had a beam angle of 180° on the luminous intensity curve, a planar backlight thickness of 0.98 mm, a luminance of 10,322 nits, and a luminance uniformity of 92%.

Camera traps are widely used to collect data for wildlife management, but species-specific testing is crucial. We conducted three trials to optimise camera traps for detecting numbats (Myrmecobius fasciatus), a 500–700-g mammal. We compared detection rates from (1) Reconyx PC900 camera traps installed at heights ranging from 10–45 cm, and (2) Reconyx PC900, Swift 3C standard and wide-angle camera traps with differing detection zone widths. Finally, we compared elevated, downward-angled time-lapse cameras installed at heights ranging from 1–2 m to obtain dorsal images for individual numbat identification. Camera traps set at 25 cm had the highest detection rates but missed 40% of known events. During model comparison, Swift 3C wide-angle camera traps recorded 89%, Swift 3C standard 51%, and Reconyx PC900 37% of known events. The number of suitable images from elevated, downward-angled cameras, depicting dorsal fur patterns, increased with increasing camera height. The use of well regarded camera trap brands and generic recommendations for set-up techniques cannot replace rigorous, species-specific testing. For numbat detection, we recommend the Swift 3C wide-angle model installed at 25-cm height. For individual numbat identification, elevated, downward-angled time-lapse cameras were useful; however, more research is needed to optimise this technique. Species-specific camera optimisation trials are critical for camera trap studies that inform wildlife management. We compared detection rates between camera trap heights and models, and explored elevated, angled cameras for the identification of individual numbats (Myrmecobius fasciatus). We found that Swift 3C wide-angle camera traps positioned at 25 cm above ground can increase detection rates by 140% compared to Reconyx PC900 models, and that elevated, angled cameras are suitable for the identification of individual animals. Photograph by Anke Seidlitz. [ABSTRACT FROM AUTHOR]

Acoustic metasurfaces can reshape a reflected wavefront rather arbitrarily, despite being much thinner than the wavelength, thus allowing on-demand wavefront modulation in a variety of applications. Recent passive metasurfaces, however, have suffered from bandwidth limitations, thus restricting their range of operation. In this work, we propose the systematic design of ultra-broadband passive metasurfaces by combining the broadband local reflection rule with an optimization method. The validation of the technique is demonstrated by fabrication and measurement of an ultra-broadband carpet cloak. Numerical and experimental results show that the relative bandwidth of the optimized carpet cloak, thinner than one fifth of the maximum wavelength, can exceed 93.33%, a value that is much larger than that of previous passive metasurfaces. Furthermore, multi-frequency pulse incidence tests reveal the excellent time-domain broadband characteristics of the metasurface over a wide range of angles of incidence. The proposed strategy opens a new route for the design of advanced passive metasurfaces for ultra-broadband wave manipulation and thus promotes practical applications of broadband acoustical devices.

Digital breast tomosynthesis (DBT) is a pseudo 3D mammography imaging technique that has become widespread since gaining Food and Drug Administration approval in 2011. With this technology, a variable number of tomosynthesis projection images are obtained over an angular range between 15° and 50° for currently available clinical DBT systems. The angular range impacts various aspects of clinical imaging, such as radiation dose, scan time, and image quality, including visualization of calcifications, masses, and architectural distortion. This review presents an overview of the differences between narrow- and wide-angle DBT systems, with an emphasis on their applications in clinical practice. Comparison examples of patients imaged on both narrow- and wide-angle DBT systems illustrate these differences. Understanding the potential variable appearance of imaging findings with narrowand wide-angle DBT systems is important for radiologists, particularly when comparison images have been obtained on a different DBT system. Furthermore, knowledge about the comparative strengths and limitations of DBT systems is needed for appropriate equipment selection. [ABSTRACT FROM AUTHOR]

The results of the fabrication of active electronically scanned array (AESA) antennas with low-profile, low-weight, wide-scan, and thermal stability characteristics for aircraft-mounted radar are described. To reduce the size and weight of the antenna, a transmit– receive block is constructed in a quasi-tile structure in which the radio-frequency circuit-related transmit–receive module is a brick type, which is a flat structure, and the control board is a tile type, which is a stacked structure, to reduce the depth of the front of the antenna. In addition, the depth of the rear part of the antenna was reduced by manufacturing power and plate-shaped control-related modules at the rear of the antenna. The reduced antenna depth maximizes the effective isotropic radiated power (EIRP) and gain to noise temperature (G/T) by enlarging the antenna aperture. The manufactured antenna can scan a wide angle of ±70°. The cooling efficiency is improved by using a dual cooling structure that allows the cooling water to pass through the front cooling plate and then through the rear cooling plate. The EIRP of the manufactured AESA antenna is 104.04 dBmi, and G/T is 7.46 dB/K in Taylor weighting. [ABSTRACT FROM AUTHOR]

In this article, a compact ultrathin polarization‐insensitive wide‐angle metamaterial‐based microwave absorber with quad‐band characteristics is presented. The designed microwave absorber provides simulated peak absorption of 99.16%, 98.21%, 98.32%, and 99.76% at 3.7 GHz, 6.4 GHz, 10.7 GHz, and 14.3 GHz, respectively. The absorption frequency lies in microwave frequency bands of S, C, X, and Ku. The unit cell of the proposed microwave absorber consists of two diagonally connected closed ring resonator (CRR) along with one metallic patch enclosed by the inner CRR. Each side of the enclosed patch is connected with inner CRR at the center of length. The unit cell of the proposed 0.0197λlowest (wavelength at lowest frequency) thick multiband absorber fits in a volume of 8 × 8 × 1.6 mm3. The proposed metamaterial‐based microwave absorber exhibits identical absorption characteristics for both transverse‐electric and transverse‐magnetic polarized radiations and also provides well peak absorption for an oblique incidence up to 75°. Finally, the absorber is fabricated and experimental result validates simulated one. [ABSTRACT FROM AUTHOR]

Terahertz perfect metamaterial absorbers (PMA) based on higher order resonances have exhibited important applications in detecting, sensing, and imaging. However, most of them suffer from polarization and incident-angle dependence due to their asymmetrical structure. Here, we numerically investigate a kind of ultrathin triple-band PMA with polarization stability and wide angle of incidence. Numerical results reveal that three resonance peaks with nearly 100% absorptivity are obtained at 1.605, 4.425, and 4.946 THz under different polarization angles. It is interestingly found that the absorptance of two higher order resonances is inversely increased when the size of the middle dielectric spacer is smaller. The three resonance peaks in transverse electric and transverse magnetic modes nearly maintain fixed for oblique incidence up to 60°. Importantly, another four-band and dual-band perfect absorptions are easily achieved by a complementary method without doing iterative numerical simulation. The complementary metamaterial based absorber reaches more than 98% absorptance at four resonance frequencies. The metamaterial absorber based on complementary resonator also obtains two absorption peaks at 2.65 and 5.84 THz.

In this paper, a C/X dual-band wide-angle re¬flective polarization rotation metasurface (PRMS) with high rotation efficiency is proposed and realized. Aiming to miniaturize the size of the unit cell, a metallic flower-like shape ring is selected to extend the current path and the 45 degree slanting stitch along diagonal direction is used to form the asymmetric structure. The simulated results show that the proposed PRMS achieves polarization rotation at 4.61 GHz and 8.67 GHz with high efficiency, at which the linear polarization incident wave is converted into its orthogonal polarization after reflection. Furthermore, the high polarization rotation efficiency of the proposed PRMS is maintained under an oblique incident direction from 0° to 60°. To verify the simulated results, the proposed PRMS is fabricated and measured. The measured results are in good accordance with the simulated ones.

A novel multiband metamaterial absorber (MTMA) is proposed which is capable of well presenting a polarization-insensitive and wide incident angle stability in the microwave frequency range. The proposed MTMA comprising two vertically stacked asterisk-based copper resonators separated by dielectric layer of flame retardant type four and backed with a thin copper film. High-frequency structure simulator was used to simulate the absorber and to depict surface current distribution. The results showed that the absorber is operated at three narrow bands with high absorptivity of about 92, 100 and 100% at frequencies of 2.75, 4.3 and 9.5 GHz, respectively. The position of the resonant peaks can be effectively tuned by adjusting the geometry parameters of the structure, thereby achieving a multiband, polarization-independent and wide-angle absorber. The designed structure is important for the application of sensors, thermal images and in constructing broad multiband signals for electromagnetic compatibility/interference. [ABSTRACT FROM AUTHOR]

Background: Inherited retinal degeneration (IRD) refers to a heterogenous group of progressive diseases that cause death of photoreceptor cells and subsequent vision loss. These diseases often affect the peripheral retina, objective evaluation of which has been difficult until recently. Fundus autofluorescence (FAF) is a non-invasive retinal imaging technique that depicts the distribution of intrinsic fluorophores in the retina. The primary source of retinal autofluorescence is lipofuscin, which is contained in the retinal pigment epithelium (RPE). Excessive accumulation of lipofuscin and a window defect attributable to loss of photoreceptor pigment result in increased FAF whereas loss of the RPE results in decreased FAF. These changes can be seen during the course of IRD. Mainbody: While conventional modalities are limited in their angle of view, recent technologic advances, known as wide-field and ultra-widefield FAF imaging, have enabled visualization of the far peripheral retina. Although clinical application of this technique in patients with IRD is still in its infancy, some studies have already indicated its usefulness. For example, an area with decreased FAF correlates well with a visual field defect in an eye with retinitis pigmentosa (RP) or cone-rod dystrophy. An abnormal FAF pattern may help in the diagnosis of IRD and associated diseases. In addition, female carriers of X-linked RP and female choroideremia show characteristic appearance. Conversely, absence of abnormal FAF despite severe retinal degeneration helps differentiation of cancer-associated retinopathy. Conclusion: This paper reviews the principles of FAF, wide-field imaging, and findings in specific diseases. Wide-field imaging, particularly wide-field FAF, will provide further information for the characteristics, prognosis, and pathogenesis of IRD. [ABSTRACT FROM AUTHOR]

A wide-angle broadband converter from odd-mode spoof surface plasmon polaritons (SPPs) to spatial waves is proposed using spatially gradient Vivaldi-shaped flaring structure. We first show the dispersion, Eigen mode, and effective circuit topology of the designed SPP structure and show that it can support a propagating odd mode. A conversion structure between odd-mode spoof SPPs and spatial mode has been designed to realize smooth impedance and wavenumber transition. Through the full-wave simulation method, we obtained the optimized geometric parameters, from which we fabricate the converter using the print circuit board technology. The measured results from both far field and near field show that the proposed structure has successfully excited odd-mode spoof SPPs coming from an extremely wide-angle spatial radiation. The allowed azimuthal and pitched angle ranges are larger than 72°. [ABSTRACT FROM AUTHOR]

Graphene aerogel has been a promising microwave absorber due to ultralow density and strong dielectric loss ability. However, its intrinsic brittleness, and poor absorbing properties because of impedance mismatch severely hinders practical engineering applications. Herein, flexible silica fibers with excellent impedance matching properties were introduced into graphene honeycomb structures to co-construct a dual-structure aerogel (GS) by eco-friendly and low-cost technology. The unique dual-structure significantly enhances its resilience, enabling it to rebound after 1000 cycles of 75% compression. In addition, it can withstand 450 times of 180° folding and 360° rotation without damage, featuring remarkable flexibility and reliability. Furthermore, the simulation and experimental results indicate that GS has excellent wave absorbing performance. When the thickness is 6 mm, the effective absorption bandwidth is 32.55 GHz; when the thickness increases to 10 mm, the reflection loss is less than −8 dB in the range of 2.79–40 GHz. Moreover, the reflection loss remains almost constant when the oblique incidence angle ranges from 5° to 45°, which further demonstrates the critical role of impedance matching in enhancing the microwave absorption performance. These superior characteristics make GS an ideal candidate for many microwave absorption applications such as flexible electronics and aerospace. [Display omitted] • The ultralight graphene-based aerogels prepared by an eco-friendly method. • It possesses an ultra-broad effective absorption band of 32.55 GHz at only 6 mm. • Its reflection loss is insensitive to the incident angle. • Remarkable elasticity, flexibility and reliability endowed by dual structure. • It may be promising for various applications. [ABSTRACT FROM AUTHOR]

A novel metamaterial sensor with ultrahigh Q-factor of 665.85 and 1883.3 at 5.46 GHz and 11.3 GHz is presented in this paper, which consists of a metal pattern with cross structure and ring (CSR), a dielectric slab FR4 and a metal backplate. Based on the principle of the absorber, the Q-factor of the two resonance frequency points is improved by optimizing the ring and cross structure to strengthen the resonance. It is because of its wide angle incidence, insensitive polarization, and narrow-band absorptivity greater than 90 %, which is very conducive to the design of material refractive index sensor. Equivalent circuit method is used to analyze the characteristic of the metamaterial structure and the experimental results are in good agreement with the simulations. By loading three giving materials, the sensing function is analyzed and verified in experiments. The design has the advantages of ultrahigh Q-factor, angle and polarization insensitivity, and has potential application prospects in metamaterial sensing. [Display omitted] • Strong coupling and ultrahigh Q-factor. • Wide angle and polarization insensitivity. • High sensitivity. [ABSTRACT FROM AUTHOR]

In this paper, we report a prism with two liquid–liquid interfaces based on electrowetting effect. The prism is filled with two immiscible liquids which form two liquid–liquid interfaces. In the device, the filling liquids from the top to the bottom are conductive liquid, oil and conductive liquid. The shape of the two liquid–liquid interfaces will be changed when different voltages are applied to the opposite sidewalls. Our device is capable of wide-angle beam steering and the function of light beam translational. Our results show that the light beam can be deflected by ∼ 22 . 3 ° ( − 11 . 5 ° to + 10 . 8 ° ) and the translational distance is 3.1 mm (−1.5 mm to +1.6 mm). The proposed prism has a wide application in light detection, telecommunications, light alignment and other industrial applications. [ABSTRACT FROM AUTHOR]

This contribution presents the results of a dual-polarized radiating element designed to achieve low cross-polarization (lower than −40 dB measured for the E-and H-plane, at least −30 dB in the D-plane based on simulations) and large fractional bandwidth (18%) over wide scanning angles (±60°). The proposed design includes multiple features that enable high isolation between ports, reduction of spurious radiation, highly symmetrical radiated fields, and suppression of diffracted fields between contiguous subarray gaps. To verify the polarimetric requirements for a weather radar, simulated and measured results, including electronic scanning of the array and embedded element patterns of the antenna, are shown. [ABSTRACT FROM AUTHOR]

In this communication, an aperiodic dual-band phased array with wide-angle scanning performance is presented. A substrate integrated waveguide cavity-backed antenna, which has wide beamwidths at 4.8 and 5.8 GHz, is used as the basic array element. The phased array contains eight subarrays with an equally spaced arrangement, and each subarray is arranged in a symmetric structure. Theoretical and optimization methods, in which the main beams of the subarray and the full array are coincident and the maximum sidelobe of the full array points to the null of the subarray, are proposed for sidelobe reduction. Based on the optimized results, the main beam of the phased array can scan from −75° to +75° at both the frequency bands, and the array supports the 3 dB beam coverage from −86° to +86° at the low-frequency band and from −82° to +82° at the high band, respectively. The phased array is simulated, fabricated, and measured. The measured results validate its wide-angle scanning performance. [ABSTRACT FROM PUBLISHER]

The simultaneous detection of energy, momentum and temporal information in electron spectroscopy is the key aspect to enhance the detection efficiency in order to broaden the range of scientific applications. Employing a novel 60° wide angle acceptance lens system, based on an additional accelerating electron optical element, leads to a significant enhancement in transmission over the previously employed 30° electron lenses. Due to the performance gain, optimized capabilities for time resolved electron spectroscopy and other high transmission applications with pulsed ionizing radiation have been obtained. The energy resolution and transmission have been determined experimentally utilizing BESSY II as a photon source. Four different and complementary lens modes have been characterized. [ABSTRACT FROM AUTHOR]

The wide-angle Claerbout scheme of threedimensional time domain parabolic equation (Claerbout-TDPE) is derived in this paper, which can provide accurate results at angles within 25° of the paraxial direction. At first, the Crank-Nicolson (CN) type is introduced to discretize the Claerbout-TDPE. In this way, a three-dimensional EM scattering problem can be divided into a series of two-dimensional ones. Moreover, the alternating direction implicit (ADI) type is utilized to the Claerbout-TDPE. In this way, a three-dimensional EM scattering problem can be further reduced to a series of one-dimensional ones. Furthermore, the alternating group explicit (AGE) type is introduced to the Claerbout-TDPE for higher computational efficiency. Comparisons are made among the CN, ADI and AGE types in the numerical results. [ABSTRACT FROM AUTHOR]

This paper presents the Greene second-order parabolic equation (PE) solution to model radio propagation over irregular terrain. This solution is implemented by finite-difference and shift-map technique. The second-order finite-difference approach performs well for slopes up to about 15°, and discontinuous slope changes up to about 30°, which is better than can be achieved using the split-step/Fourier approach. The results prove that the Greene PE solution has greater propagation angles than does the Claerbout PE solution. Thus, the Greene second-order solution can certainly give better results for large angle propagation over complicated terrain boundaries. Besides, we treat the important problem of accuracy of the different approximations of the PE-based propagation models, and derive the general PE solutions with respect to the terrain slope for the different approximations. It is useful to have collected in one paper, the most important PE approximations for radio propagation. [ABSTRACT FROM AUTHOR]

In this paper, a C/X dual-band wide-angle reflective polarization rotation metasurface (PRMS) with high rotation efficiency is proposed and realized. Aiming to miniaturize the size of the unit cell, a metallic flower-like shape ring is selected to extend the current path and the 45 degree slanting stitch along diagonal direction is used to form the asymmetric structure. The simulated results show that the proposed PRMS achieves polarization rotation at 4.61 GHz and 8.67 GHz with high efficiency, at which the linear polarization incident wave is converted into its orthogonal polarization after reflection. Furthermore, the high polarization rotation efficiency of the proposed PRMS is maintained under an oblique incident direction from 0° to 60°. To verify the simulated results, the proposed PRMS is fabricated and measured. The measured results are in good accordance with the simulated ones. [ABSTRACT FROM AUTHOR]

Autonomous unmanned aerial vehicles (UAVs) often carry video cameras as part of their payload. Outdoor video captured by such cameras can be used to estimate the attitude and altitude of the UAV by detecting the location of the horizon in the video frames. This paper presents a video frame processing algorithm for estimating the pitch and roll of a UAV, as well as its altitude. The frames are obtained from a downward pointing video camera equipped with a fisheye lens. These open-loop estimates can serve as redundant data used to implement graceful-degradation in the event that the main closed-loop control sensors fail, or for fault-tolerance purposes to augment inertial sensors for increased accuracy. The estimated values had a mean error of ±0.7 angular degrees for roll and ±0.9 angular degrees for pitch, while the altitude estimation from the video had a mean error of ±0.9 meters. The results are presented and compared to actual attitude and altitude values obtained from a traditional inertial measurement unit and, in the case of altitude comparison, an absolute air pressure sensor. The algorithm was developed on a personal computer to work at 10 frames per second and uses only simple image processing functions that can be deployed using open source libraries on lightweight computing boards capable of image processing. [ABSTRACT FROM AUTHOR]

In this communication, a stub-loaded reconfigurable broadband metamaterial absorber (MMA) based on lumped components is proposed and experimentally verified. An absorption bandwidth of 6.3 GHz is realized with more than 90% absorptivity ranging from 8.3 to 14.6 GHz (the relative bandwidth reaches 55%) by selecting certain values of resistors and inductors. The parameter analysis of the loaded stubs illustrates their vital influence on enlarging the absorbing bandwidth. In addition, the designed absorber has good performances on polarization-insensitiveness and wide angles of incident waves for both TE and TM polarization. The waveguide measurement method is utilized to verify the simulated results of the reconfigurable broadband MMA. [ABSTRACT FROM PUBLISHER]

This paper proposes a new interferometric near-field 3-D imaging approach based on multi-channel joint sparse reconstruction to solve the problems of conventional methods, i.e., the irrespective correlation of different channels in single-channel independent imaging which may lead to deviated positions of scattering points, and the low accuracy of imaging azimuth angle for real anisotropic targets. Firstly, two full-apertures are divided into several sub-apertures by the same standard; secondly, the joint sparse metric function is constructed based on scattering characteristics of the target in multi-channel status, and the improved Orthogonal Matching Pursuit (OMP) method is used for imaging solving, so as to obtain high-precision 3-D image of each sub-aperture; thirdly, comprehensive sub-aperture processing is performed using all sub-aperture 3-D images to obtain the final 3-D images; finally, validity of the proposed approach is verified by using simulation electromagnetic data and data measured in the anechoic chamber. Experimental results show that, compared with traditional interferometric ISAR imaging approaches, the algorithm proposed in this paper is able to provide a higher accuracy in scattering center reconstruction, and can effectively maintain relative phase information of channels.

Foveated sight as observed in some raptor eyes is a motivation for artificial imaging systems requiring both wide fields of view as well as specific embedded regions of higher resolution. These foveated optical imaging systems are applicable to many acquisition and tracking tasks and as such are often required to be relatively portable and operate in real-time. Two approaches to achieve foveation have been explored in the past: optical system design and back-end data processing. In this paper, these previous works are compiled and used to build a framework for analyzing and designing practical foveated imaging systems. While each approach (physical control of optical distortion within the lens design process, and post-processing image re-sampling) has its own pros and cons, it is concluded that a combination of both techniques will further spur the development of more versatile, flexible, and adaptable foveated imaging systems in the future.

An efficient 3-D semivectorial horizontally wide-angle beam-propagation method (WA-BPM) based on the alternating direction implicit (ADI) scheme is proposed, where only the paraxial term in the vertical direction is considered. The present formulation reduces the splitting error to the second order and shows good compatibility with previously developed WA-BPMs. A block matrix decomposition process and a simulation window-cutting scheme are utilized to further improve the efficiency of the WA-BPM. Then, by applying Padé approximation to the resulting operator, an efficient ADI scheme that can be solved by the Thomas algorithm is constructed. Alternatively, the resulting operator can be approximated by the Denman–Beavers iterative scheme, leading to an ADI scheme with faster convergence rate and reasonable efficiency. Results from several numerical examples show the effectiveness of the present WA-BPM. [ABSTRACT FROM PUBLISHER]