Asymmetric Patch Research Articles

An effective technique based on off‐set fed patch to enhance the bandwidth of microstrip planar antenna

ABSTRACTIn this article a microstrip planar antenna with new bandwidth enhancement technique is proposed for broadband wireless communication. The antenna consists of a rectangular radiating patch, a fed line, and a conducting ground plane. To increase the operating band of a conventional microstrip patch antenna, the radiating patch is shifted from the center of the substrate (asymmetric) while the feed line is made as off‐set. It is observed that this asymmetric patch and off‐set feed line improve the impedance matching resulting in a bandwidth enhancement of more than 115% without changing of the overall antenna size. It is observed from the measurement that the proposed planar design with this technique can achieve an operating band ranging from 2.96 to 19GHz (146%) which makes it very suitable for a number of wireless communication applications such as WiMAX, WLAN, UWB, C‐band, X‐band, Ku‐band etc. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1221–1226, 2016

Circularly polarized frequency reconfigurable Koch antenna for GSM/Wi‐Fi applications

ABSTRACTA novel circularly polarized frequency reconfigurable Koch fractal boundary antenna is proposed. Initially, a Koch slot is etched on the Koch fractal boundary patch of larger dimension (48 × 48 mm2). Within the etched slot, an asymmetrical Koch fractal patch of smaller dimension (36 × 36 mm2) is embedded and switches are introduced along x and y‐directions to connect these inner and outer patch structures. By making ON/OFF switching of the diodes frequency reconfiguration is achieved. Measured results are in close agreement with the simulation results which demonstrates that the proposed antenna is well suited for GSM/Wi‐Fi wireless applications. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2895–2898, 2015

Polarization Tunable Terahertz Metamaterial Absorber

Metamaterial-based perfect absorbers have attracted considerable attention due to their potential for practical applications. The existing absorbers, however, are mostly polarization insensitive or only sensitive to one direction, which is inapplicable in some areas. Polarization tunable or high absorption in two orthogonal directions is very useful and necessary. Herein, we present a polarization tunable absorber formed by an asymmetric patch and a dielectric layer on top of a metallic board. With this structure, the frequency of the absorber can be tuned by merely changing the polarization of the incident. The tunable mechanism originates from the different length of the patch along the two orthogonal directions. The concept is rather general and applicable to various absorbers, as long as the asymmetric design is valid. The absorber can find practical applications in manipulation of the polarization of the light and detecting waves with specific polarization.

Ultra-broadband and strongly enhanced diffraction with metasurfaces.

Enhanced high-order diffractions which are spatially dispersive are desirable in such as spectroscopy studies, thin-film solar cells, etc. Conventionally, the dielectric gratings can be used to realize the enhanced diffraction, but the facets are usually rugged and optically thick (~μm). Plasmonic materials may exhibit unprecedented ability for manipulating light. Nonetheless, much interest has been focused on the subwavelength metasurfaces working in the zero-order regime. Here, we show that ultra-broadband and strongly enhanced diffraction can be achieved with the super-wavelength metasurfaces. For the purpose, we employ symmetric or asymmetric metal patches on a ground metal plane, which support the localized oscillation of free electrons and enhanced scattering of light. The zero-order reflection is suppressed, giving rise to an enhancement of first-order diffraction (50 ~ 95%) in an ultra-wide bandwidth (600 ~ 1500 nm). The proposed plasmonic structure is planar and ultra-thin (with an etching depth of only 80 nm), showing new potential for constructing compact and efficient dispersive elements.

A Survey and Study of Planar Antennas for Pico-Satellites

Works on pico-satellites have gained momentum recently, especially those that consider pico-satellites as part of a much larger constellation or swarm. This feature allows pico-satellites to provide high temporal resolution of observational data and redundancy. In particular, it reduces the need for satellite-to-ground communications and, hence, helps save energy and allows the execution of distributed processing algorithms on the satellites themselves. Consequently, satellite-to-satellite or cross-link communication is critical. To realize these advantages, the cross-link antenna employed on pico-satellites must meet many criteria, namely, small size, lightweight, low-power consumption, high gain, wide bandwidth, circular polarization, and beam steerability. To date, no works have examined the suitability of existing planar antenna designs for the use on pico-satellites. To this end, this paper contributes to the literature by focusing on microstrip patch and slot antennas that have the ability to achieve high gain, beam steering, and wide bandwidth. This paper reviews 66 planar antenna designs, which includes 38-patch and 28-slot antennas. In addition, we provide an extensive qualitative comparison of these antennas in terms of their mass, size, gain, beam steerability, type of polarization, operating frequency band, and return loss. In addition, we have evaluated three antenna designs that best address the pico-satellite challenges on a common platform. We find that the asymmetric E-shaped patch antenna design is the most suitable for the use on 2U CubeSats. This is because of its small size (34 × 13 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) and high gain (7.3 dB). In addition, the E-shaped patch antenna yields a wide -10-dB bandwidth of 2300 MHz and a small return loss of -15.2 dB.

A Rare Colocalization of Lichen Planus and Vitiligo.

We report an unusual manifestation of vitiligo colocalizing with lichen planus (LP). A 76-year-old Greek male presented with a history of a red, scaly, itchy, asymmetrical patch located at the umbilicus within a well-demarcated depigmented macule of vitiligo. Histology showed features of a lichenoid interface dermatitis, favouring a diagnosis of LP. Colocalization of LP and vitiligo has rarely been reported in the literature. After reviewing the literature, we believe that at present there is insufficient evidence to resolve the uncertainties in the aetiology of this colocalization. It seems to us that the association between LP and vitiligo is more than coincidental, but none of the theories discussed in this paper can sufficiently account for it. Rather, the association is likely to be multifactorial in its pathogenesis.

Recognizing the benefits and pitfalls of reflectance confocal microscopy in melanoma diagnosis.

Recognizing the benefits and pitfalls of reflectance confocal microscopy in melanoma diagnosis.

Performance and radiation patterns of aesthetic and asymmetric logo-based patch antennas

This paper investigates microstrip patch antennas designed using aesthetic and asymmetrical logo-based shapes. A range of shapes have been considered and analyzed using electromagnetic simulations and measurements. Particular attention has been given to the radiation patterns of these asymmetric antennas.

Template-Assisted GLAD: Approach to Single and Multipatch Patchy Particles with Controlled Patch Shape

Template-assisted glancing angle deposition (GLAD) is explored for the fabrication of single and multipatch patchy particles with one or more patches of controlled but asymmetric shape. The template is used to ensure the formation of uniform patchy particles, whereas rotation of the template gives access to a large number of asymmetric patch shapes caused by the shadowing effect of the templating groove and/or the neighboring particle. Careful analysis with a straightforward geometric model reveals the effect of the angle of incidence, rotational angle, groove size, and particle size on the patch shape. Initial magnetic field assembly results are presented to illustrate the removal of patchy particles from their template and accessibility to a large number of patchy particles. Two-patch particles with overlapping patches are also accessible by means of secondary metal vapor deposition. The connectivity of these two patches on each particle and the predictable size of the overlapping section provide access to functional patchy particles. The combination of the template-assisted GLAD method with rotation of the template and secondary evaporation is demonstrated to be a good method for fabricating patchy particles with a variety of asymmetric patch shapes, sizes, and multipatches where every particle of a batch carries exactly the same patch pattern and thereby provides valuable input on experimentally accessible patch shapes for future experimental and computational studies of patchy particles.

A wideband circularly polarized stacked slotted microstrip patch antenna

A wideband, single-feed, circularly polarized, stacked, square, slotted microstrip patch antenna is proposed for radio-frequency-identification-reader applications. The proposed antenna consists of an upper square asymmetric slotted patch, stacked over a lower square asymmetric slotted radiating patch and a microstrip stub, along with a coaxial feed. The wideband circularly polarized radiation of the antenna is achieved using a microstrip stub in the lower patch and a stacked slotted square patch. The proposed antenna is designed using a combination of low-cost FR4 substrate and foam. The measured 10 dB return-loss bandwidth of the antenna was around 21% (833 MHz to 1033 MHz), and the 3 dB axial-ratio bandwidth of the antenna was around 13.4% (835 MHz to 955 MHz). The gain was around 7.0 dBic over the 3 dB axial-ratio bandwidth. The overall antenna volume was 0.601?0 × 0.601?0 × 0.895?0 (where ?0 is the free-space wavelength at 900 MHz).

Erratum: Design of a multi-band asymmetric patch antenna for wireless applications

Originally published Microwave Opt Technol Lett 55:730–734, 2013. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1703, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27669 (Original article DOI 10.1002/mop.27449)

Design of a multi-band asymmetric patch antennal for wireless applications

A novel design for probe-fed compact multiband microstrip patch antenna for wireless applications is presented in this article. The antenna is achieved by cutting the different slots' length on the patch and using unequal resonance arms. By adjusting unequal arms, various resonant frequencies are obtained. Also, this antenna presents resonance tuning ability within impedance bands by varying the length of the slots. The proposed antenna is designed and fabricated for operating at 3.66 GHz, 5.3 GHz, 5.8 GHz, and 7.03 GHz. The size of patch is 0.314λL × 0.342λL at its lower operating frequency. In addition, parametric studies are performed by investigating the effects of some key parameters on obtaining an optimal design of the proposed antenna. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:730–734, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27449

DESIGN OF A NOVEL SUPER WIDE BAND CIRCULAR-HEXAGONAL FRACTAL ANTENNA

In this paper, a novel circular-hexagonal Fractal antenna is investigated for super wide band applications. The proposed antenna is made of iterations of a hexagonal slot inside a circular metallic patch with a transmission line. A partial ground plane and asymmetrical patch toward the substrate are used for designing the antenna to achieve a super wide bandwidth ranging from 2.18GHz to 44.5GHz with a bandwidth ratio of 20:4 : 1. The impedance bandwidth and gain of the proposed antenna are much better than the recently reported super wideband antennas which make it appropriate for many wireless communications systems such as ISM, Wi-Fi, GPS, Bluetooth, WLAN and UWB. Details of the proposed antenna design are presented and discussed.

Miniaturised asymmetric E‐shaped microstrip patch antenna with folded‐patch feed

A design of probe-fed compact wideband microstrip patch antenna which is configured of an asymmetric E-shaped patch, a folded-patch feed and shorting pins, is presented in this study. In this design, unequal resonance arms fed by a folded patch produce three resonances to broaden the impedance bandwidth. Shorting pins are applied to miniaturise the size of the patch. The performance of broadening the impedance bandwidth is explored by investigating the behaviour of the surface currents on the patch. The antenna presents resonance tuning ability within the impedance bandwidth by varying the length of unequal arms. The measured -10 dB impedance bandwidth of the fabricated antenna is 76.18% from 3.34 to 7.45 GHz for ultra-wideband applications. The size of this antenna is 0.379 λ L × 0.145 λ L × 0.078 λ L , where λ L is wavelength at the lower frequency of the measured operating bandwidth in the free space. Fabrication of this antenna is less complex than similar wideband antennas with folded-patch feed. In addition, parametric studies are performed by investigating the effects of different key parameters on obtaining an optimal design of the proposed antenna design.

Thermonuclear Burst Oscillations

Burst oscillations, a phenomenon observed in a significant fraction of Type I (thermonuclear) X-ray bursts, involve the development of highly asymmetric brightness patches in the burning surface layers of accreting neutron stars. Intrinsically interesting as nuclear phenomena, they are also important as probes of dense matter physics and the strong gravity, high magnetic field environment of the neutron star surface. Burst oscillation frequency is also used to measure stellar spin, and doubles the sample of rapidly rotating (above 10 Hz) accreting neutron stars with known spins. Although the mechanism remains mysterious, burst oscillation models must take into account thermonuclear flame spread, nuclear processes, rapid rotation, and the dynamical role of the magnetic field. This review provides a comprehensive summary of the observational properties of burst oscillations, an assessment of the status of the theoretical models that are being developed to explain them, and an overview of how they can be used to constrain neutron star properties such as spin, mass, and radius.

Ternary Asymmetric Particles with Controllable Patchiness

This work demonstrated a facile approach to the fabrication of the ternary asymmetric silica particles that consisted of different components on the opposite poles, such as metal or fluorescent quantum dots, with the aid of the mask-unmask method and double-sided etching and modifying. By controlling the thickness of the polymer mask, the surface of the particle was precisely further controlled for functional modification. At the same time, as-prepared ternary particles could self-assemble into dimers and trimers. Asymmetric patch could be clearly distinguished by SEM, EDS mapping, TEM, and fluorescence microscopy. The asymmetric particles are stable and show the potential applications in supraparticle assembly and catalysis, etc.

Case of mucosal lentiginous melanoma in situ on the upper lip with a long radial growth phase

Dear Editor, Melanoma of the oral mucosa is a rare condition and lip melanoma is even rarer. Lip melanoma has been reported to behave aggressively and to be usually encountered at an advanced stage at diagnosis. However, in-depth understanding of lip melanoma is limited due to extreme rarity. Therefore, the disease is commonly misdiagnosed and patients with an initial misdiagnosis are more likely to die. Herein, we report a case of mucosal lentiginous melanoma of the upper lip over the long term. A 72-year-old Korean male presented with a pigmented patch on the upper lip in July 2009. He recalled that the 1-cm pigmented macule had been on his upper lip for 10 years and had gradually increased in size. He received renal transplantation and subsequent immunosuppression in 2006 and the lesion had abruptly grown in size. Physical examination revealed a 5.2 cm · 4.7 cm asymmetrical pigmented patch with an irregular border and color variegation located on the inner labial mucosa, the cutaneous side of the upper lip, and perioral skin (Fig. 1). The gingiva and maxilla were spared. No lymph node enlargement was detected. He was taking medica-

ULTRA-WIDEBAND SHORTED PATCH ANTENNAS FED BY FOLDED-PATCH WITH MULTI RESONANCES

Novel designs of probe-fed broadband shorted patch antennas for ultra-wideband (UWB) applications are presented in this paper. In these designs, unequal resonance arms fed by a folded patch produce multi resonances to broaden the impedance bandwidth. In the flrst design, the antenna consists of an asymmetric E-shaped patch, a folded-patch feed and shorting pins. This antenna is achieved by four adjacent resonances with the measured i10dB impedance bandwidth of 76.18%. The pins are utilized to miniaturize the size of the patch. By introducing a folded ramp-shaped feed in the similar structure with the flrst design, a wider bandwidth with the flve resonances is obtained. This improved design introduces an antenna with an impedance bandwidth of more than 110% and a considerable size reduction compared to the flrst antenna. The antennas present resonance tuning ability within the impedance bandwidth by varying the length of unequal arms. In addition, parametric studies are performed by investigating the efiects of difierent key parameters on obtaining optimal designs of the proposed antennas.

Radiation Efficiency of Longitudinally Symmetric and Asymmetric Periodic Leaky-Wave Antennas

This letter derives efficiency formulas and establishes fundamental limitations for longitudinally symmetric periodic leaky-wave antennas (LWAs). The proposed approach is based on an equivalent transmission-line model for periodic structures, which is derived from a lattice topology providing a perfect decoupling between the series and shunt immittances and their respective radiation contributions. A central result of this letter is that a 2-D array composed of uniformly excited 1-D LWAs cannot exceed a radiation efficiency of 50%. The presented theory is validated by comparing measured and finite-difference time-domain (FDTD) simulated radiation efficiencies with the ones predicted by the lattice model for several symmetrical and asymmetrical series-fed patch (SFP) array antenna and composite right/left-handed (CRLH) antenna configurations.

Evaluation of a Second-Generation Self-Expanding Variable-Porosity Flow Diverter in a Rabbit Elastase Aneurysm Model

The self-expanding V-POD is a second-generation flow-diverting device with a low-porosity PTFE patch on a self-expanding microstent. The authors evaluated this device for the treatment of elastase-induced aneurysms in rabbits. Three V-POD types (A, circumferential patch closed-cell stent [n = 9]; B, asymmetric patch closed-cell stent [n = 7]; and C, asymmetric patch open-cell stent [n = 4]) were evaluated by using angiography, conebeam micro-CT, histology, and SEM. Aneurysm flow modifications were expressed in terms of immediate poststent/prestent ratios of maximum CA volume entering the aneurysm dome tracked on procedural angiograms. Flow modifications were correlated with 4 weeks' follow-up angiographic, micro-CT, histologic, and SEM results. Mechanical stent-deployment difficulties in 4 aneurysms (1 type A; 3 type B) led to suboptimal results and exclusion from analysis. Of the remaining 16 aneurysms, 4-week post-treatment angiograms showed no aneurysm filling in 10 (63%), 3 (∼19%) had no filling with a small remnant neck, and 3 (∼19%) had <0.25 filling. Successfully treated aneurysms (n = 16) demonstrated an immediate poststent/prestent CA maximum volume ratio of 0.13 ± 0.18% (0.0%-0.5%). Favorable contrast-flow modification on immediate angiography after deployment correlated significantly with aneurysm occlusion on follow-up angiography, micro-CT, and histology. The occlusion percentage derived from micro-CT was 96 ± 6.8%. Histology indicated advanced healing (grade ≥3) in the aneurysm dome in 13 of 16 cases. SEM revealed 15 of 16 stents in an advanced state of endothelialization. This study showed the feasibility and effectiveness of V-POD for aneurysm healing in a rabbit elastase model.