Coaxial Array Research Articles

Fabrication of TiO2−Pt Coaxial Nanotube Array Schottky Structures for Enhanced Photocatalytic Degradation of Phenol in Aqueous Solution

Well-aligned TiO2−Pt coaxial nanotube array schottky structures on Ti substrate (TiO2−Pt/Ti) were successfully fabricated by direct current (DC) electrodeposition using anodic aluminum oxide (AAO) templates and the subsequent atmospheric pressure chemical vapor deposition (APCVD) technique. Environmental scanning electron microscopy (ESEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), energy-dispersive X-ray spectra (EDX), and X-ray diffraction patterns (XRD) indicated that the as-prepared samples were a vertically well-aligned TiO2−Pt coaxial nanotube array, and the outer TiO2 nanotube was anatase with the preferential orientation of (101) plane. The asymmetry of the current−voltage (I–V) curve revealed that a schottky barrier had been formed between TiO2 and Pt. The enhanced separation of photogenerated holes and electrons was demonstrated by surface photovoltage (SPV) and photocurrent measurement. For the degradation of phenol under UV light irradiation, the TiO2−Pt coaxial nano...

Dual resonance mechanisms facilitating enhanced optical transmission in coaxial waveguide arrays

We experimentally and computationally demonstrate high transmission through arrays of coaxial apertures with different geometries and arrangements in silver films. By studying both periodic and random arrangements of apertures, we were able to isolate transmission enhancement phenomena owing to surface plasmon effects from those owing to the excitation of cylindrical surface plasmons within the apertures themselves.

Investigation of hybrid elliptical antenna arrays

Novel types of antenna arrays constructed from combination of linear and elliptical antenna arrays are presented. These types are called elliptical, concentric elliptical, elliptical cylindrical and elliptical coaxial cylindrical arrays where only the array factors are considered. The effect of the element factor can be considered separately and combined to the array factor. The expression for the array factor of elliptical array has been obtained. Then, array factors of other three types are derived by the combination of linear and elliptical array properties. Their directivities and sidelobe levels are simulated in various current distributions. The effect of ellipse eccentricity, element spacing and number of elements are calculated and compared with those parameters.

Investigation of a power divider using a coaxial probe array in a coaxial waveguide

A novel coaxial-waveguide power divider using coaxial probe array that achieved low-loss probe-to-waveguide transitions is presented. The small reflection theory of transverse electomagnetic (TEM) lines is extended to synthesise the gradual waveguide taper, and the equivalent-circuit approach is applied to analyse the coaxial probe array. The design and simulation of a single probe-to-waveguide transition have been developed. The detailed design, simulation, fabrication and measurements of a four-way coaxial power divider are discussed. The measured results agree well with the simulated results. The measured 15 dB return loss bandwidth of this waveguide power divider is demonstrated to be 8.2 GHz (fL = 7.8 GHz, fH = 16 GHz) and its 0.5 dB insertion loss bandwidth 11 GHz.

Second Harmonic Generation from a Nanopatterned Isotropic Nonlinear Material

Second harmonic generation (SHG) from a nanopatterned isotropic nonlinear material (GaAs) located inside the subwavelength gaps of a metallic coaxial array is demonstrated. The SHG results from the strong electromagnetic fields in the vicinity of the coaxial gaps; the signal strength is comparable to that from z-cut LiNbO3 even though the path length is much shorter (∼100 nm compared to 14 μm). Numerical simulations are in good agreement with the experimental data. The observation of a peak-wavelength blue shift between the SH spectrum and the linear transmission spectrum is explained.

Large-area, infrared nanophotonic materials fabricated using interferometric lithography

In this paper, we discuss the characterization and fabrication of two nanophotonic materials for the infrared region by using IL—realizing a negative refractive index material and enhancing transmission through annular metallic coaxial aperture arrays.

Analysis of coupling between array of open-ended coaxial lines in an infinite ground plane

The problem of coupling through an open-ended coaxial line array in a conducting plane is solved using the integral transform, superposition principle, and eigenfunction expansions. Computation is performed to illustrate the coupling behavior of coaxial line array. Our theory agrees well with other simulation results.

Mechanism of the superenhanced light transmission through 2D subwavelength coaxial hole arrays

By using FDTD numerical simulations, we show that mechanism that is different from surface plasmon polaritons set up by the periodicity at the in-plane metal surfaces may account for the superenhanced light transmission through coaxial hole arrays. We propose that resonant cavity-enhanced light transmission is responsible for it. When an axis is introduced into a hole, slits of definite length are formed. We suppose that a coaxial hole will support the standing waves of Fabry–Pérot-like modes with frequency higher than its cutoff frequency if its gap is small enough in comparison to the wavelength of the incident light and if the metal film is thick enough.

Enhanced mid-infrared transmission through nanoscale metallic coaxial-aperture arrays

Using a single interferometric lithography patterning step along with self-aligned pattern-definition techniques, uniform, large-area metallic coaxial arrays with ~ 100-nm toroidal gaps are fabricated. Enhanced (5x) mid-infrared (4 mum) transmission through these sub-wavelength coaxial arrays is observed as compared with that through the same fractional opening area hole arrays as a result of the complex coaxial unit cell. Varying the coaxial dimensions shifts the resonance wavelength and impacts the maximum transmission; design rules are derived. The ability to control the transmission wavelength combined with dramatically enhanced transmission represent a promising path toward nanophotonic applications.

Mutual Coupling in Arrays of Coaxial Waveguides and Horns

A solution is presented for the mutual coupling between the modes of different-sized circular coaxial aperture arrays, which are used as direct radiators and feed antennas. This solution is expressed in terms of integral transforms and the mutual admittances for the cross coupling between all three mode types, TE, TM, and TEM, are obtained. The accuracy of this new integral formulation is demonstrated by comparing computed results with measured data for a three-element test array. Excellent agreement is obtained between theory and experiment for both coupling coefficients and radiation patterns. Results are also presented for a coaxial feed array for the Lovell radio telescope.

Light transmission by subwavelength square coaxial aperture arrays in metallic films

Using the Fourier modal method, we study the enhanced transmission exhibited by arrays of square coaxial apertures in a metallic film. The calculated transmission spectrum is in good agreement with FDTD calculations. We show that the enhanced transmission can be explained when we consider a few guided modes of a coaxial waveguide.

Radiation pattern of a planar electromagnetically coupled coaxial dipole array mounted over a finite metallic reflected plate

An efficient numerical method is proposed to analyze the far-field of electromagnetically coupled coaxial dipole (ECCD) element, and then uniform physical theory of diffraction (PTD) together with the above method is applied to investigate the radiation pattern of a novel planar ECCD array mounted over a finite metallic plate. Finally, as an application to the above ECCD array, lower troposphere radar (LTR) is briefly introduced. The analysis procedure in this paper can also be expected for optimum design in the systems involving the ECCD array antenna.

Coupling through a flanged coaxial line array

AbstractCoupling through a flanged coaxial line array is investigated. The Hankel transform and superposition principle are used to obtain the coupling parameters. The mutual coupling expression is shown to be identical with other results based on the Green's‐function approach. Computation and experiment are performed to illustrate the coupling behavior. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 467–470, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10353

The enhanced photoluminescence of zinc oxide and polyaniline coaxial nanowire arrays in anodic oxide aluminium membranes

Z. X. Zheng, Y. Y. Xi, P. Dong, H. G. Huang, J. Z. Zhou, L. L. Wu and Z. H. Lin, PhysChemComm, 2002, 5, 63 DOI: 10.1039/B201201D

Microwave cardiac ablation: A comparison of lesions created with a novel coaxial slot array to lesions with a helical coil antenna

Microwave cardiac ablation: A comparison of lesions created with a novel coaxial slot array to lesions with a helical coil antenna

A compact three-dimensional packaging technique using super-fine-pitch coaxial connector arrays for on-board satellite equipment

A compact three-dimensional (3-D) inter-module microwave packaging technique has been developed that drastically reduces the volume of on-board satellite equipment of phased-array beam control (PBC). A super-fine-pitch coaxial connector (SCC) array has been successfully implemented with this 3-D structure along with very flat, superior-performance ceramic MMIC packages and combiner packages. Two types of SCC have been developed-a lead-to-jack array and a plug-to-plug array-both of which have a 2-mm pin pitch. Through application of this 3-D packaging technique to S-band 61-beam 32-radiator PBC equipment, an ultra-small packaging unit was developed that houses a 32/spl times/64 interconnection in a 2600-cc chassis. This technique promises to make possible compact, light-weight on-board PBC equipment that is especially suitable for use in satellite transponders.

Electromagnetically coupled coaxial dipole array antenna

A new type of collinear antenna called electromagnetically coupled coaxial dipole array antenna is proposed. The antenna has an advantage of structural simplicity due to a novel use of an electromagnetically coupled feed structure for the radiating element. An analysis of the radiating element is presented and compared with experimental results. Fabrication and measurement of a prototype array antenna are also presented.

Analysis of mutual coupling in a cavity-backed coaxial array of annular-slot antennas

The problem of mutual coupling in a coaxial array of annular-slot antennas is formulated in terms of a magnetic-field integral equation (MFIE). The MFIE is solved numerically, under the assumption of narrow slot width, using a moment method with a Fourier basis and point matching. The operation of the array under multiport excitation is analysed, and an impedance matrix representation of the multiport antenna is calculated. Results predicted by the theory are shown to be in good agreement with experimental measurements on a two-port, two-element coaxial annular-slot array.

Implementation of a large-scale optical neural network by use of a coaxial lenslet array for interconnection

Optical implementation of a large-scale neural network with 32 x 32 neurons is reported. The experimental setup is described, error caused by limited precision of hardware is analyzed, and experimental results are presented.

A solid-state Compton camera for three-dimensional imaging

A Compton camera was constructed using four individual high-purity germanium (HPGe) coaxial detectors in the front plane and four elements of a 15 element HPGe coaxial array in the back plane. 60Co, 133Ba, and 137Cs sources were used in configurations that included single sources in positions covering the intended field-of-view and multiple sources of both identical isotopes and different isotopes. Experiments were also conducted with sources in waste-container sized attenuating media. This proof-of-concept experiment was designed to demonstrate non-tomographic three-dimensional imaging for the characterization of mixed waste containers. The present analysis demonstrates three-dimensional imaging of multiple sources at multiple energies and the imaging of sources within a waste-container sized attenuating medium.