Coaxial Source Research Articles

Clover-shaped antenna for ultra-wideband communications

In this paper, a clover-shaped microstrip patch antenna for application under an Ultra-Wide Band (3.1–10.6 GHz) is designed and fabricated. To obtain sufficient bandwidth when the Return Loss is < −10 dB, a partial ground plane and coaxial probe source is used. The measured bandwidth of the fabricated antenna is 8.25 GHz when VSWR <2. Referenced to the center frequency, the gain is 3.20–4.00 dBi. The experimental 3-dB beam width (HPBW) in the azimuth and elevation are 55.35° and 62.27°, respectively. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2111–2113, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21869

A comparison of different analytical methods of determining the solid angle of a circular coaxial source–detector system

In this work, seven different analytical expressions for the solid angle subtended by a circular detector for a coaxial circular source are compared. These expressions—which have been published by different investigators over the course of the last half century—are compared for previously published geometries, and for geometries planned in future experimental work. As compared to benchmark Monte Carlo calculations, the expressions published by Segre, Knoll, and Ruby, were the most accurate and exhibited the highest degree of self-correlation.

Static Ocular Counterroll: Video-based Analysis After Minimizing the False-Torsion Factors

To determine the validity and usefulness of a newly developed measurement method of static ocular counterrolling (s-OCR) that eliminates false-torsion factors and to test the Jampel hypothesis that s-OCR does not exist. A lightweight measurement device, consisting of a video camera, a coaxial light source, and a laser pointer projecting a fixation target on the wall, was fixed to a subject's head by means of a mouthpiece. In 11 healthy adults (mean age: 30 +/- 15 years), digital images of the right eye were captured while the subject kept his head tilted at a randomly selected angle ranging from 0 degrees to 50 degrees . By a frame-by-frame analysis of movements of the corneal light reflex and the iris patterns, OCR was evaluated. Torsional eye movement in the opposite direction to head tilt was found in all subjects. The amount of torsion continuously increased until the head-tilt angle reached 40 degrees. The average (+/- SD) amplitude of a fitted sine curve was 7.6 +/- 3.2 degrees (range: 4.3 degrees-10.3 degrees), and the individual amplitude was significantly larger than the test-retest repeatability of the measurement (+/-1.7 degrees). The measurement method used in this study provided good test-retest repeatability and ease of application. The characteristics of torsional eye movements that we observed after minimizing the false-torsion factors agree with previous reports supporting the existence of s-OCR.

Plasma and ion beam injection into an FRC

Experiments on the transverse injection of intense (5–20 A/cm2), wide cross-section (10-cm), neutralized, ∼100-eV H+ plasma and 100-keV H+ ion beams into a preformed B-field reversed configuration (FRC) are described. The FRC background plasma temperature was ∼5 eV with densities of ∼1013 cm−3. In contrast to earlier experiments, the background plasma was generated by separate plasma gun arrays. For the startup of the FRC, a betatron-type “slow” coaxial source was used. Injection of the plasma beam into the preformed FRC resulted in a 30–40% increase of the FRC lifetime and the amplitude of the reversed magnetic field. As for the ion beam injection experiment into the preformed FRC, there was evidence of beam capture within the configuration.

Large area microwave coating technology

Microwave plasma enhanced chemical vapour deposition (PECVD) of thin films is the preferred technology when highest deposition rates are desirable. However, large area applications have always suffered from poor film thickness uniformity and unacceptable variations of thin film properties. Coaxial plasma line sources in various arrangements have recently proven their ability to overcome most limitations, which prevented microwave PECVD of becoming a mainstream technology in the field of large area coatings. In this article, the advantages and the potential of the coaxial plasma line sources and suitable vacuum processes are discussed in detail.

Microwave PECVD for large area coating

Microwave Plasma Enhanced Chemical Vapour Deposition (PECVD) of thin films is the method of choice when highest deposition rates and/or high fragmentation of precursor material is desirable. However, large area applications have always suffered from poor film thickness uniformity and unacceptable variations of thin film properties. Coaxial plasma line sources in various arrangements have proven their ability to generally overcome all former technological limitations inherent in many other types of microwave plasma sources, which prevented microwave PECVD from becoming a mainstream technology in the field of large area coatings. In this article, the advantages and the potential of the coaxial plasma line sources and suitable vacuum processes are described. Improvements of the coaxial plasma lines are introduced which are indispensable for large area plasma applications and which have been investigated in several laboratory and production prototype vacuum process systems. A variety of thin films have been deposited, ranging from organic and ceramic silicon dioxide to nanocrystalline diamond and microcrystalline silicon for photovoltaic applications.

On the jets, kinks, and spheromaks formed by a planar magnetized coaxial gun

Measurements of the various plasma configurations produced by a planar magnetized coaxial gun provide insight into the magnetic topology evolution resulting from magnetic helicity injection. Important features of the experiments are a very simple coaxial gun design so that all observed geometrical complexity is due to the intrinsic physical dynamics rather than the source shape and use of a fast multiple-frame digital camera which provides direct imaging of topologically complex shapes and dynamics. Three key experimental findings were obtained: (1) formation of an axial collimated jet [Hsu and Bellan, Mon. Not. R. Astron. Soc. 334, 257 (2002)] that is consistent with a magnetohydrodynamic description of astrophysical jets, (2) identification of the kink instability when this jet satisfies the Kruskal–Shafranov limit, and (3) the nonlinear properties of the kink instability providing a conversion of toroidal to poloidal flux as required for spheromak formation by a coaxial magnetized source [Hsu and Bellan, Phys. Rev. Lett. 90, 215002 (2003)]. An interpretation is proposed for how the n=1 central column instability provides flux amplification during spheromak formation and sustainment, and it is shown that jet collimation can occur within one rotation of the background poloidal field.

Design of Multiple U-Shaped Slot Microstrip Patch Antenna in 5 GHz Band WLAN

In this study, a multiple U-shaped slot microstrip patch antenna for application to the 5 GHz band is designed and fabricated. To obtain sufficient bandwidth in the operating band, foam is inserted between the substrate and ground plane, the type of form is styrofoam, the coaxial probe source is used, and the position of the probe shift is adjusted from the center to the left. The measured result (5.02-5.955 GHz) of the fabricated antenna satisfies the conditions of VSWR < 2.0 in 5 GHz band (5.15-5.35 GHz, 5.47-5.725 GHz, 5.725-5.825 GHz), gain of 3.88-9.28 dBi, and broad radiation pattern.

Fabrication and measurement of an arrow‐shaped microstrip patch antenna in the 5‐GHz band

AbstractIn this paper, an arrow‐shaped microstrip patch antenna is designed, fabricated, and measured for a 5‐GHz band wireless local area network (WLAN) application. The geometry of our proposed antenna is suitable for the wideband antenna in the 5‐GHz band. To obtain sufficient bandwidth in the operating band, a foam layer is inserted between the ground plane and the substrate. A coaxial probe source is used. The measured results for the bandwidth and radiation patterns are obtained, with the result of the fabricated antenna (4.79–5.94 GHz) satisfying the conditions of the VSWR &lt; 2.0 in the 5‐GHz band (5.15–5.35 GHz, 5.470–5.725 GHz, 5.725–5.825 Ghz, 5.725–5.925 GHz), and a gain of 5.02–7.25 dBi and a broad radiation pattern are achieved. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 503–505, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20516

Design of multiple U‐shaped slot microstrip patch antenna for 5‐GHz band WLANs

AbstractIn this study, a multiple U‐shaped slot microstrip patch antenna for application in the 5‐GHz band is designed and fabricated. To obtain sufficient bandwidth in the operating band, foam is inserted between the substrate and ground plane, a coaxial probe source is used, and the position of the probe shift is adjusted from the center to the left. The measured result (5.02–5.955 GHz) of the fabricated antenna satisfies the conditions of VSWR &lt; 2.0 in 5‐GHz band (5.15–5.35 GHz, 5.47–5.725 GHz, and 5.725–5.825 GHz): gain of 3.88–9.28 dBi and broad radiation pattern. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 486–488, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20510

An experiment for verification of the auxiliary transmission-line method to evaluate a microwave thermal noise source

In order to verify the usefulness of the auxiliary transmission-line method, which has been proposed to evaluate the noise temperature of a microwave thermal noise source, a liquid nitrogen-cooled coaxial noise source system has been constructed and a preliminary experiment has been made. This measurement result and a result calibrated with two known references have been compared, and it was confirmed that they were in good agreement.

Wall conditioning and power balance for spheromak plasmas in SSPX

We report here results from power balance measurements for ohmically heated plasmas in the sustained spheromak physics experiment. The plasma is formed inside a close-fitting tungsten-coated copper shell; wall conditioning by baking, glow discharge cleaning (GDC), Ti gettering, and helium shot conditioning produces clean plasmas ( Z eff<2.5) and reduces impurity radiation to a small fraction of the input energy, except when the molybdenum divertor plate has been overheated. We find that most of the input energy is lost by conduction to the walls (the divertor plate and the inner electrode in the coaxial source region). Recently, carborane was added during GDC to boronize the plasma-facing surfaces, but little benefit was obtained.

Optical radiation flux incident on a circular disc from a coaxial circular and planar multiple-point source separated by a homogeneous plane-parallel plate

Calculation of the radiation flux incident on a circular disc from a coaxial circular and planar multiple-point source is necessary in many radiometric techniques. Such calculations are required in various problems in physics, chemistry and biology for assembling, optimizing and calibrating radiometric systems measuring optical radiation from a circular–planar multiple-point source. However, in some radiometric systems the source must be separated from the irradiated disc. In a simple case a single transparent homogeneous plane-parallel plate (PPP) can be considered to separate the source from the disc. In this paper a formula is derived to calculate the incoherent optical radiation flux incident on a circular disc from several types of multiple-point sources separated from the disc by the transparent homogeneous PPP. This formula is solved in the cylindrical coordinate system and is expressed as a series of single integrals of some superposed elementary functions. These functions are dependent on the radii of the source and the irradiated disc, on the distances between the source and the PPP and between the PPP and the disc, on the absorption coefficient of the PPP and on the refractive indices of all optical media between the source and the disc. The solution is obtained for transparent homogeneous media. Some examples illustrating practical application of the formula are presented as three-dimensional surface plots.

Green's function for the bimaterial elastic solid containing interface annular crack

Green's function is obtained for the infinite bimaterial elastic solid, containing an external annular interface crack, loaded by a singular tangential co-axial circular source. To this scope, two fundamental solutions were treated firstly. The first solution corresponds to the problem of the bimaterial infinite elastic solid without crack, loaded by a singular torsional source. The second one corresponds to the problem of the bimaterial infinite elastic solid containing an external annular interface crack under torsional crack surface traction. Numerical examples are included.

Boundary-integral equation analysis of twisted internally cracked axisymmetric bimaterial elastic solids

Green's function is obtained for the infinite bimaterial elastic solid, containing an internal circular interface crack, loaded by a unit tangential co-axial circular source. An axisymmetric direct boundary integral equation (BIE) is used for the analysis of a finite bimaterial axisymmetric body containing an internal circular interface crack and a finite homogeneous cracked cylinder, both under torsional loading. Using the proposed technique, no discretization of the crack surface is necessary. Numerical results for both examples as obtained by the proposed method are presented and discussed.

A new approach to depth determination from magnetic anomalies

We have developed a semiautomatic method to determine the depth to shallow and deep‐seated structures from a magnetic anomaly profile. It involves using a relationship between the depths to two coaxial sources obtained by combining observations at symmetric points with respect to the coordinate of the sources center. For five established, fixed data points, the depth to the shallow structure is determined for each preassigned depth of the deep‐seated structure. The computed depths to the shallow structure are plotted against the computed depths to the deep‐seated structure, yielding a continuous, monotonically increasing depth curve. The spacing between the observations is then modified, producing several curves. The accepted estimates for the depths to both structures are read at the common intersection of these curves. The effective intensity and the angle of magnetization of both structures are also estimated. The proposed method was tested both on noisy synthetic and real magnetic data. In the case of synthetic data, the depth curves method determined the correct depths of both coaxial and laterally offset sources. In the case of practical data (vertical component anomaly over a chromite body in the Guleman concession, Turkey), the method suggested the shape of the buried shallow structure resembles a horizontal cylinder model buried at a depth of 31 m and the shape of the buried deep seated structure resembles a dike model buried at a depth of 62 m. The estimated shape and depth of the shallow structure are in very good agreement with the results obtained from drilling and surface geology. The area appears to still hold promise for chromite exploration from the deeper structure.

Admittance correction factor for coaxially excited cylindrical antennas

A long standing problem in antenna theory has been the accurate determination of the input admittance of coaxially excited antennas. While reasonably accurate results have been obtained for a range of problems using the so called TEM for the coaxial aperture electric field, these results nonetheless contain an error of small but unknown extent. By examining the infinite coaxially excited antenna problem this approximation error has been quantified and a simple approximation factor has been deduced. This correction factor is applicable to a range of antenna problems having a coaxial source geometry.

Coaxially-fed tapered slot antenna

An improved design of the longitudinal tapered slot antenna is presented which incorporates a tapered coaxial line balun. This transformer type offers large bandwidth, allows for the direct connection of coaxial sources and reduces the complexity of the printed circuit. Experimental results for an antenna prototype are presented.

Final Summary Report: Noise temperature of coaxial (GPC-7) sources

Final Summary Report: Noise temperature of coaxial (GPC-7) sources

Analytical calculations of gamma scintillators efficiencies — II. Total efficiency for wide coaxial circular disk sources

A statistical integral formulation of the total efficiency for the general wide coaxial circular disk source–cylindrical NaI(Tl) detector arrangement (source radius S>detector radius R) is presented. Simple programming is possible and short computer time is needed.