In this paper, An Equiangular Spiral Slot Patch Antenna has been designed and simulated at operating frequency range between 4 GHz to 10 GHz. This antenna is modeled on a thin single sided Rogers RO4003C substrate with dielectric constant of 3.38. The proposed design is achieved by cutting a equiangular spiral slot on the circular patch. The modeling and simulation of the proposed Antenna has been done with Finite Element Method (FEM) based software COMSOL Multiphysics. A parametric analysis has been done with variation in geometry of Spiral slot. The results of the proposed Equiangular Spiral Slot Antenna acclaim its use for C-band applications and also demonstrate its wideband operation in the range 4 GHz to 10 GHz.
Abstract—An improved directional equiangular spiral antenna with wide CP band and high gain is proposed, in which the impedance bandwidth is 2 ∼ 12 GHz, CP bandwidth, 4.5 ∼ 7 GHz, and gain 6 ∼ 9.5 dBi. The antenna includes 4 layers. The top layer is equiangular spiral antenna, and the bottom layer is the ground. The middle two layers are parasitic metal films with irregular rectangular holes, which are introduced to improve the performance of equiangular spiral antenna and reduce the profile. The measured results are in good agreement with the simulated ones.
Abstract: In this study, the accurate and numerically efficient Finite Element (FE) based Beam Propagation Method (BPM) has been employed to investigate Second Harmonic Generation (SHG) in highly nonlinear soft glass (SF57) Equiangular Spiral Photonic Crystal Fibers (ES-PCF) for the first time. It is shown here that the SHG output power in highly nonlinear SF57 soft glass PCF exploiting the ES design is significantly higher compared to that of Silica PCF with hexagonal air-hole arrangements. The effects of fabrication tolerances on the coherence length and the modal properties of ES-PCF are also illustrated. Moreover, phase matching between the fundamental and the second harmonic modes is discussed through the use of the quasi-phase matching technique. Furthermore, the ultra low bending loss in the SF57 ES-PCF design has been successfully analyzed.
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In the ES – PCF, air holes of each ring are rotated with respect to the previous ring. This effectively stops the field from spreading into regions between air holes and confines the mode tightly in the core area. The ES – PCF parameters used in this paper are: 3 ring, 6 arm structure with spiral radius,r 0 = 0.75 µm, spiral angle, θ = 30 o and hole radius r 1 , r 2 and r 3
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Abstract—In practical applications, the low-profile spiral antennas suffer from the lack of proper planar feeding ways. The vertical balun always has a significantly long length, inconsistent with the requirements of the low profile spiral antenna geometry. A spiral antenna with integrated parallel- plane feeding structure is proposed in this paper. The antenna used has obviously improved axial ratio compared to the equiangular spiral antenna at low frequencies. And the traditional balun in the third dimension is moved to the planar plane. The antenna and the Dyson-style balun have been integrated into a multi-layer structure. The resulting structure maintains the typical radiation behavior and the broadband operation of the spiral antennas, but the vertical balun is integrated at the same plane with the antenna. The overall size of the spiral antenna is largely reduced.
In many occasions, short arm length is necessary. In recent studies, spiral antennas with planar feeding structure have attracted more attraction. The traditional balun usually has a significantly long length and extends to the third dimension. Feeding the equiangular spiral with a transmission line that follows the metal layer beneath the spiral to the center point is proposed . The vertical balun is replaced by parallel-plane feeding structure, and the overall size of the antenna is largely reduced. But it is impossible to feed Archimedean spiral antenna the same way because of the long and thin arm. However, Archimedean spiral antenna has a noticeable advantage at axial ratio bandwidth over its equiangular counterpart. Under this condition, improving radiation characteristics as well as reducing the arm length is necessary.
Galactic disk simulations have investigated gravity driven turbulence (Wada et al., 2002), stellar feedback (Wada & Norman, 2001; de Avillez & Breitschwerdt, 2005; Dib et al., 2006) and the influence of spiral density waves on ISM dynamics (Chapter 4). Analytical results also indicate that vorticity is generated in centrally condensed clouds subject to galactic shocks (Kornreich & Scalo, 2000), and the induced velocities follow the observed velocity size-scale relation. Previous numerical work on colliding flows showed that density and velocity perturbations occur even in uniform flows subject to cooling instabilities (Heitsch et al., 2005), although a velocity length scale correlation was not investigated. Simulations of clumpy flows have also indicated that a Salpeter type clump mass spectrum can be reproduced (Clark & Bonnell, 2006). Spiral shocks have also been proposed to explain the dynamics of molecular clouds (Bonnell et al., 2006; Zhang et al., 2001). Bonnell et al. (2006) model giant molecular cloud formation as gas passes through a clumpy spiral shock. The dynamics of the molecular clouds are determined on all scales simultaneously as the clouds form and the induced velocity dispersion size scale relation is consistent with observations. This can account for the observed velocity dispersions that are found even in regions devoid of massive stars. Furthermore, there is no need for a continuous driving mechanism as the time for the decay of these velocities is proposed to be of similar magnitude to the cloud lifetime.
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wireless communication. Microstrip patch may have many conventional shapes example rectangular, circular, spiral . Rectangular spiral structure consist thin spiral pattern printed on substrate and fed from the center. It has advantages like reduced size, low profile and high efficiency. These structures show characteristics of circularly polarization with moderate gain. It can have any number of turns. Spiral structures are broadly classified into two categories- Archimedean spiral and rectangular spiral. Spiral antennas are basically frequency independent antenna. Frequency independent antennas are antennas whose radiation pattern, impedance and polarization remain unchanged over wide bandwidth. Frequency pattern of such antennas depends only on physical dimensions. Spiral antenna’s radiation pattern direction is perpendicular to plane of spiral.
According to the particle motion in the space forming the curve and the movement of the curve forming the surface, characteristics of particle movement determine the attribute features of space surface. In Euclidean space, particle can be described as P (x, y, z, t), where t is the time parameter, and x, y, z are coordinate parameters with respect to time t. The construction of the parametric models of spiral surface is created in the following section. Initially we discuss the spiral surface with straight line segment and circle arc on cross-section.
E.M Turner has introduced the spiral antennas in 1954.The spiral antenna is class of frequency independent antenna under angular concept. The spiral is a planar structure that is fabricated by photo etching a two-arm spiral on copper clad substrate. When the spiral arms are fed in anti phase at the centre, the spiral radiates circularly polarized energy in bidirectional beam perpendicular to the plane. Only the physical dimensions of the spiral limit the frequency band of radiation. To obtain unidirectional beam, the spiral is mounted at the open end of a closed back metallic cavity ,which, when in the region of /4 deep, redirects this half of the energy constructively to for a single beam .However the energy within the cavity is absorbed to achieve a broadband radiation. The spiral radiator, being a balanced device, needs to be fed from a balanced transmission line. This necessitates the incorporation of a balun transformer. Thus the spiral antenna consists of three main components
Bolometer sensor is a good candidate for THz imaging due to its compact system, low cost, and wideband operation. Based on infrared microbolometer structures, two kinds of antenna-coupled microbridge structures are proposed with different spiral antennas: spiral antenna on support layer and spiral antenna with extended legs. Aiming at applications in detection and imaging, simulations are carried out mainly for optimized absorption at 2.52 THz, which is the radiation frequency of far-infrared CO 2 lasers. The effects of rotation angle, line width, and spacing of the spiral antenna
This paper described the design of square spiral shaped patch antennas operable over a wide frequency range or at multi-frequencies by incorporating suitable tuning elements. Ansoft HFSS software is used for analytical modelling and simulation. A good impedance matching is observed near the frequencies 1.6 GHz, 2 GHz, and 2.4 GHz using two symmetrical tuning elements as shown in Fig. 3 for the multifrequency operation of mobile hand set. The same antenna with four symmetrical tuning elements (Fig.5) can be used for broad band communication over a band width of 25.6%.
We proposed fractal type of EBG structure. The important property of fractal type of structure is that a long electrical length can be incorporated in a small area. The self similarity of fractal geometry generats multiple notch band and thus the wide band response is created. The second one is fork shaped EBG structure. This type of structure is very simple to design also the band gap is very large. The third structure is spiral shaped EBG structure. The design and band gap properties of all three structures are compared in the next sections.
ar-vestibule ganglion (CVG), and then part of the neurons from the CVG divide and segregate along Rosenthal’s canal to form spiral gangli- ons [24, 25]. In the current study, we selected three key time points during the cochlear devel- opment of postnatal rats to measure the FGF8 protein expression. P7 is when the SGN soma undergoes myelination, P14 is when mature IHC is formed, and P28 represents rat matura- tion (rats older than P28 are considered as adult rats) . Thus, according to the evidenc- es described above, our results showing differ- ential patterns of FGF8 protein expression in the spiral ganglion during postnatal develop- ment, suggesting the involvement of FGF8 in spiral ganglionneural development.
The topology of the artificial magnetic unit cell based on fractal spiral geometry is presented in Figure 4. The resonator is basically designed by connecting two fractal ring resonators in a spiral form. Both outer and inner rings are the mirrored image of the first order Hilbert fractal to form the ring shape. Upper half of the inner and outer rings is the replica of the lower half. These two concentric rings are then joined at one end to achieve the spiral form. The marked inner section is the extension of the inner curve. It is imperative in order to decrease the resonance frequency through inductive and capacitive coupling amid the different sections.
Abstract—In this paper we describe a tessellation of the unit sphere in the 3 -dimensional space realized using a spiral joining the north and the south poles. This tiling yields to a one dimensional labeling of the tiles covering the whole sphere and to a 1 -dimensional natural ordering on the set of tiles of the tessellation. The correspondence between a point on the sphere and the tile containing it is derived as an analytical function, allowing the direct computation of the tile. This tessellation exhibits some intrinsic features useful for general applications: absence of singular points and efficient tiles computation. Moreover, this tessellation can be parametrized to obtain additional features especially useful for spherical coordinate indexing: tiles with equal area and good shape uniformity of tiles. An application to spherical indexing of a database is presented, it shows an assessment of our spiral tiling for practical uses.
One of the key factors that determine the heat transfer per- formance is the cross-sectional tube geometry. This study examines four different square cross section tubes geome- tries: straight, conical spiral, in-plane spiral, and helical spiral with water as the base working fluid. Since the con- vective heat transfer inside the tube is directly linked to flow behavior, it is of interest to investigate the flow pat- terns inside the tubes. In our previous studies [1-3], albeit using air as working fluid, showed that the presence of cen- trifugal force due to curvature leads to significant radial pressure gradients in flow core region. In the proximity the inner and outer walls of the coils, however, the axial velo- city and the centrifugal force will approach zero. Hence, to balance the momentum transport, secondary flow should develop along the outer wall. This is indeed the case, as can be seen in Figure 4, where the secondary flow with higher velocities is generated in the outer wall region of
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both video – a sixty-minute video composition – and live 3D graphics were projected. Set three comprised a table on which was placed a 1930s typewriter; there was a bucket suspended above the table out of which a long bolt of paper descended to the typewriter. A contact microphone placed inside the typewriter was used for the live processing of the acoustic sound it produced. Four loudspeakers were positioned around the space across which both live and pre-recorded audio was mixed. An eighty-minute (including sile- nces) electroacoustic soundtrack functioned as both an underscore for live audio events, a full-blown com- positional feature and a timeline that provided the performers with a constant structure to work within. In addition, a video projector positioned front-of-house projected large-scale real-time 3D computer graphics (manipulated via the Bodycoder System) across the entire smoke-filled performance space. Lighting was tight and minimal. Two radio microphones were used to amplify and selectively process the speech of the two performers. In Spiral Fiction the Bodycoder was used to sample and affect the live voice of the actor and the voice of the Bodycoder performer herself, thus creating ‘virtual’ dialogues, subversions, fracturing meaning and generating pure electroacoustic landscapes. The bodycoder was also used to generate and manipulate the large 3D computer graphics that spun in and out of the main smoke-filled performance arena.
q = − , in structures of spiral waves for different C , each pattern is based on the same initial spatial values. C is (a): −0.50; (b): −0.40; (c): −0.33; (d): Phase diagram revealing regions of different wave forms; I and IV: Medium cannot support spiral waves; II: Medium can support stepped spiral waves; III: Medium can support sim- ple spiral waves. Simulations were carried out on a disk-shaped domain of radius 600.
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On my right, a faded, red couch sits against the far wall. A long glass coffee table with white birch trunks for legs rests in front of the sofa. A few armchairs sit with small tables in a little circle around the couch. The left side of the room has the exact same furniture in the exact same alignment. Two displays of Golden Spiral ground beans in bright, metallic packages stand like suits of armor guarding the front of the store. If you had a picture of the inside of the shop and you folded it right down the middle, along the blue and red carpet, the two halves would be identical.