Radial Transmission Line Research Articles

Network Analysis of Millimeter-Wave Omnidirectional Periodic Dielectric Rod Antenna with Arbitrary Grating Profile

The radiation characteristics of the omnidirectional periodic circular dielectric rod leaky-wave antenna with arbitrary grating profile are investigated by the network method combining with staircase approximation. In the analysis, the arbitrary grating profiles are transformed to a multilayer rectangular periodic structure, which is represented by a radial transmission line with a series current source. As a result, the calculations are greatly simplified and the effects of grating profile on the performance of the grating antenna are systematically studied in a very efficient way. Some useftil guidelines for the design and fabrication of the omnidirectional dielectric grating antenna are thereby suggested.

The Analysis of Radial Transmission-Line in W-Band Circular Groove Guide

In this paper, finite-difference time-domain (FDTD) method is used to calculate the driving-point impedance of radial transmission-line in circular groove guide. A simple way is used to approximate the curvilinear metal boundary of circular groove guide. And perfectly matched layer (PML) is applied on the open boundary of circular groove guide. Fine-grid is used to calculate the EM fields in the radial transmission-line in which we are interest. Discretized wave equation is used to update the tangential electric field on the boundary of coarse- and fine-grid. At last, the driving-point impedances related to different diameter of the radial transmission-line are obtained from the ratio of the Fourier transform of the voltage to the Fourier transform of the current.

System and method to enhance reproduction of sub-bass frequencies

A bass reflex loudspeaker system capable of an optimized sub-bass (<100 Hz) response. The loudspeaker system incorporates a closed cabinet (10), an electromechanical driver (22), an acoustic radial transmission line (12), a reactive alternate density transmission medium (18) load, and a radial right angle wave guide (16). The acoustic radial transmission line (VARTL) is disposed around and in front of the cone of the driver. The alternate density transmission medium (ADTM) slows the speed of the wave, thereby causing delay and intentional attenuation of the initial waveform. The radial right angle wave guide (RRAWG) acts as a port and is disposed within the VARTL to introduce a signal into the throat of the VARTL. In addition, the loudspeaker system effectively reduces mechanical vibrations that are normally transferred to the speaker cabinet by effecting a lack of unbalanced pressures.

Analytical calculation of the impedance of lossy power/ground planes

Power and ground planes are required to have low impedance over a wide range of frequencies. Parallel ground and power planes in multilayer printed-circuit boards exhibit multiple resonances, which increase the impedance. Dissipative loading of the radial transmission line structure of the planes reduces the resonance peaks. The dissipative loads can be realized by resistors distributed on the surface or the edges of plain pairs and lossy dielectric material can be applied for distributed loading, and the characterization of the impedance by simulation is very important during the design phase. Measurement results are compared with analytical solutions and simulation results. Furthermore, in this paper, a new algorithm is given for the more efficient calculation of the impedance of power distribution structures.

Exploiting voltage support of voltage-source HVDC

The inherent voltage support in voltage-source converters (VSCs) which form a back-to-back VSC–HVDC asynchronous link can increase the power transmissibility by a factor of 1.68 if the installation is sited at the midpoint of the radial AC transmission line. The figure of 1.68 is the limit set by the ‘transient stability’ which is reached by simulations using HYPERSIM, a real-time digital simulator. The transmission line is modelled by the telegraph equations. The hydraulic turbine, speed governor, generator, field-excitation system, power-system stabiliser (PSS) and transformers are modelled in detail.

An Improved Perturbation Analysis of a New Omnidirectional Circular Rod Antenna with Double Dielectric Gratings for Millimeterwave Application

The leakage characteristics of a new millimeter-wave omnidirectional circular rod antenna with double dielectric gratings are analyzed by an improved perturbation method. The electromagnetic fields are described in terms of a radial transmission-line network, which brings considerable physical insight into the overall behaviour of the leaky wave antenna. The analysis yields expression for the leakage constant in a closed form so that the design procedure of the antenna becomes very convenient. It is found that under the condition of the same radiation intensity, the double dielectric-grating antenna has relatively smaller dimension than that of the single one. The results obtained by the present analysis are compared with the exact solution based on the mode matching method; it is found that the improved perturbation analysis yields as accurate results as the rigorous method with extreme simplicity of the analysis and calculations.

Improved perturbation analysis for a new omnidirectional periodic dielectric rod leaky‐wave antenna for millimeter‐wave application

AbstractThe leakage characteristics of a new millimeter wave omnidirectional periodic circular dielectric rod leaky‐wave antenna are analyzed by an improved perturbation method. The electromagnetic fields are described in terms of a radial transmission‐line network, which brings considerable physical insight into the overall behavior of the leaky‐wave antenna. The analysis yields expression for the leakage constant in a closed form so that the design procedure of the antenna becomes very convenient. It was found that the circular dielectric shell layer greatly affects the leaky characteristics of the antenna. The results obtained by the present analysis are compared with the exact solution based on the mode‐matching method. It is justified that the improved perturbation procedure yields as accurate results as the rigorous method, with extreme simplicity of the analysis and calculations. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 344–346, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10316

Correction to "Nonlinear analysis of disk resonators. application to material characterization and filter design"

A procedure for the numerical prediction of the microwave nonlinear behavior (intermodulation products, degradation of quality factors, etc.) of TM010 disk resonators has been developed. The procedure is based on relating a very general description of HTS nonlinearities with the circuit elements of a nonlinear radial transmission line. This radial transmission line is then analyzed using the harmonic balance algorithm. Successful cross-checks are performed by comparing simulations with theoretical results obtained for a specific model of HTS nonlinearity. The application of this procedure to the determination of nonlinear material parameters from disk resonator measurements is illustrated as well as its use for simulating filters with several inter-coupled disks. Correction: J. Mateu, IEEE Trans. Appl. Superconduct., vol. 11, pp. 135–138, Mar. 2001. On p. 137 of the above paper, the first sentence of the paragraph immediately following equation (14) should read as follows.

Basis for optimization of in vitro exposure apparatus for health hazard evaluations of mobile communications

The main objective of this paper is to carefully study the fields induced in flasks exposed to RF electromagnetic fields. The study focuses on the widely used 60 mm Petri dishes and rectangular T-75 flasks for the two following cases: 1) cells in homogeneous suspension and 2) cell monolayers. The dependence of the coupling and the homogeneity of the SAR distribution on frequency (0.7 GHz to 2.5 GHz), polarization (E, H and k polarizations) and the amount of medium (1.9 mm to 4.7 mm medium height) is studied. In addition, the effects of the environment, meniscus and field impedance as well as the distortion of the incident field are discussed. Based on these results, advantages and disadvantages of different fundamental designs of apparatus used in the past are compared. These are TEM cells, HF chambers, radial transmission lines (RTL), waveguides and wire patch cells. Furthermore, the major optimization parameters are identified for the development of highly optimized exposure systems, enabling the conduct of high quality experiments.

Chromosome damage and micronucleus formation in human blood lymphocytes exposed in vitro to radiofrequency radiation at a cellular telephone frequency (847.74 MHz, CDMA).

Peripheral blood samples collected from four healthy nonsmoking human volunteers were diluted with tissue culture medium and exposed in vitro for 24 h to 847.74 MHz radiofrequency (RF) radiation (continuous wave), a frequency employed for cellular telephone communications. A code division multiple access (CDMA) technology was used with a nominal net forward power of 75 W and a nominal power density of 950 W/m(2) (95 mW/cm(2)). The mean specific absorption rate (SAR) was 4.9 or 5.5 W/kg. Blood aliquots that were sham-exposed or exposed in vitro to an acute dose of 1.5 Gy of gamma radiation were included in the study as controls. The temperatures of the medium during RF-radiation and sham exposures in the Radial Transmission Line facility were controlled at 37 +/- 0.3 degrees C. Immediately after the exposures, lymphocytes were cultured at 37 +/- 1 degrees C for 48 or 72 h. The extent of genetic damage was assessed from the incidence of chromosome aberrations and micronuclei. The kinetics of cell proliferation was determined from the mitotic indices in 48-h cultures and from the incidence of binucleate cells in 72-h cultures. The data indicated no significant differences between RF-radiation-exposed and sham-exposed lymphocytes with respect to mitotic indices, frequencies of exchange aberrations, excess fragments, binucleate cells, and micronuclei. The response of gamma-irradiated lymphocytes was significantly different from that of both RF-radiation-exposed and sham-exposed cells for all of these indices. Thus there was no evidence for induction of chromosome aberrations and micronuclei in human blood lymphocytes exposed in vitro for 24 h to 847.74 MHz RF radiation (CDMA) at SARs of 4.9 or 5.5 W/kg.

Measurement of DNA damage in mammalian cells exposed in vitro to radiofrequency fields at SARs of 3-5 W/kg.

In the present study, we determined whether exposure of mammalian cells to 3.2-5.1 W/kg specific absorption rate (SAR) radiofrequency fields could induce DNA damage in murine C3H 10T(1/2) fibroblasts. Cell cultures were exposed to 847.74 MHz code-division multiple access (CDMA) and 835.62 frequency-division multiple access (FDMA) modulated radiations in radial transmission line (RTL) irradiators in which the temperature was regulated to 37.0 +/- 0.3 degrees C. Using the alkaline comet assay to measure DNA damage, we found no statistically significant differences in either comet moment or comet length between sham-exposed cells and those exposed for 2, 4 or 24 h to CDMA or FDMA radiations in either exponentially growing or plateau-phase cells. Further, a 4-h incubation after the 2-h exposure resulted in no significant changes in comet moment or comet length. Our results show that exposure of cultured C3H 10T(1/2) cells at 37 degrees C CDMA or FDMA at SAR values of up to 5.1 W/kg did not induce measurable DNA damage.

Nonlinear analysis of disk resonators. Application to material characterization and filter design

A procedure for the numerical prediction of the microwave nonlinear behavior (intermodulation products, degradation of quality factors, etc.) of TM/sub 010/ disk resonators has been developed. The procedure is based on relating a very general description of HTS nonlinearities with the circuit elements of a nonlinear radial transmission line. This radial transmission line is then analyzed using the harmonic balance algorithm. Successful cross-checks are performed by comparing simulations with theoretical results obtained for a specific model of HTS nonlinearity. The application of this procedure to the determination of nonlinear material parameters from disk resonator measurements is illustrated as well as its use for simulating filters with several inter-coupled disks.

Complex gyrator circuit of three-port circulators using gyromagnetic resonators with six-fold symmetry

An important planar resonator for use in the design of commercial three-port circulators consists of a radial gyromagnetic region symmetrically loaded by six uniform or radial transmission lines. One possible model for this sort of junction is, in general, a six-port network with three-fold symmetry with three coupled ports and three short- or open-circuited ones. The development of the open-circuited parameters and the complex gyrator circuit of this arrangement is made particularly simple by taking advantage of the symmetry of the problem region. Its tracking solution is given special attention.

Physics-based CAD models for the analysis of vias in parallel-plate environments

In this paper, physics-based computer-aided-design (CAD) models for through and buried vias in parallel-plate environments are presented based on radial transmission-line theory. The crosstalk power transferred by the TEM parallel-plate mode between vias is characterized, and extended to the treatment of vias in finite substrates by means of image theory. The presented CAD models can be combined with lumped and distributed circuit elements, as well as linear and nonlinear devices, providing an accurate and fast procedure for the global modeling of high-speed electronic circuits. The corresponding simulation time for representative single or multiple via configurations has been drastically reduced compared to full-wave simulations while maintaining comparable accuracy.

Reducing the effects of lightning in cogeneration plants

Georgia Transmission Corporation (GTC) serves the Weyerbaeuser Flint River Mill in Oglethorpe, GA, with a new, nondedicated 115 kV radial-transmission line connecting from the North Americus substation with a tap to the South Oglethorpe substation. The Flint River mill is a cogenerator with a single 46.6 MVA steam-turbine generator fueled by biomass. The line suffered from repeated outages, primarily due to lightning strikes, since the day it was commissioned. As a result, increased attention and concern has been given to the problems associated with resultant voltage fluctuations and momentary outages in the mill. More effort has been placed on service reliability and tracking these fluctuations and outages. Several lightning engineering programs have been studied. In particular, the Windows-based Lightning-Protection Design Workstation, developed by EPRI, was investigated. The program was used to provide a comparison of pole-line configuration, arrester usage, and static protection as would relate to power outages. It calculates the lightning performances of overhead transmission lines and indicates what, if any, flashover design improvements are required to reduce iightning-caused outages. A further investigation involved the use of a computer-based scope with the ability to see storms over 483 km (300 mi) away. Early detection of storms with the potential to produce strikes on the mill site or the transmission line will allow the mill to take the necessary steps to operate independently from the electric utility company until the thunderstorm subsides.

Electromagnetic torque of a synchronous machine during a single out‐of‐phase reclosing

AbstractThe adoption of single‐pole switching for a radial transmission line which connects large synchronous machines to the power system would submit these machines to repetitive mechanical stress. To evaluate the total mechanical stress, it is first necessary to determine the electromagnetic torque and to evaluate its transient maximum values at reclosing. In this paper, maximum values of the electromagnetic transient torque at single‐pole reclosing are first computed using a simplified analytical approach. The analytical results are then validated by numerical simulations and by an experimental test on a laboratory synchronous machine. It will be shown that single‐pole reclosing would be, in the worst case, as restricting as three out‐of‐phase synchronisation.

Experimental and numerical determination of SAR distributions within culture flasks in a dielectric loaded radial transmission line.

The effect of dielectric loading on the cell layer specific absorption rate (SAR) within a T-75 culture flask being irradiated within a transverse electromagnetic (TEM) cell was studied both experimentally and numerically. Direct thermal measurements of a T-75 containing 40 mL of culture medium and resting upon a 3-mm-thick slab of alumina ceramic (epsilon r = 9.6) revealed that, compared to the same flask resting upon a foam slab (epsilon r = 1.0) of the same thickness, the average SAR at the cell layer was increased roughly fourfold. This fourfold increase is significant experimentally because it allows biologists to perform experiments over a larger range of SAR values needed to determine possible dose-response curves without the costs and difficulties of a fourfold increase in amplifier power. Finite-difference time-domain (FDTD) simulations of the SAR distribution were in good quantitative agreement with the experimental measurements. It is concluded that FDTD modeling can be a cost effective and scientifically acceptable means of obviating the thermal measurement of SAR.

A coaxial-radial line junction with a top loading disk for broadband matchings

A new coaxial)radial transmission-line junction is pro- posed and characterized by a rigorous full-wae modal-expansion method. The proposed structure modifies the conentional coaxial)radial junc- tion by introducing a circular disk on the top plate of the radial transmission line whose parameters can be adjusted for broadband matchings. Two examples are presented to demonstrate the junction's practicality. Q 1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 22: 87)90, 1999.

The radial transmission line as a broad-band shielded exposure system for microwave irradiation of large numbers of culture flasks.

The problem of simultaneously exposing large numbers of culture flasks at nominally equivalent incident power densities and with good thermal control is considered, and the radial transmission line (RTL) is proposed as a solution. The electromagnetic design of this structure is discussed, and an extensively bench-tested realization is described. Referred to 1 W of net forward power, the following specific absorption rate (SAR) data were obtained: at 835.62 MHz, 16.0+/-2.5 mW/kg (mean+/-SD) with range (11-22); at 2450 MHz, 245+/-50 mW/kg with range (130-323). Radio-frequency interference from an RTL driven at roughly 100 W is so low as to be compatible with a cellular base station only 500 m distant. To avoid potential confounding by temperature differences among as many as 144 T-75 flasks distributed over 9 RTLs (six irradiates and three shams), temperature within all flasks was controlled to 37.0+/-0.3 degrees C. Experience with over two years of trouble-free operation suggests that the RTL offers a robust, logistically friendly, and environmentally satisfactory solution to the problem of large-scale in vitro experiments in bioelectromagnetics.

PWM-controlled series compensation on a radial feed power system

A series compensation scheme is described employing two pulse width modulation (PWM) switched reactor modules in parallel with a capacitor. The two-module PWM-switched reactors provide continuously variable reactance by employing simple duty ratio control. The switching instants of the two reactor modules are controlled to have 180° phase shift, but equal duty ratio, to achieve harmonic cancellation. The complete series compensator provides a wide range of capacitive and inductive compensation. The harmonic distortion produced by this series compensation scheme with multiple-controlled reactors is analysed. An experimental model of the proposed compensator has been constructed and tested; this was inserted in a radial feed transmission line, to reduce the level of fluctuation of the receiving power on a nominal load subjected to another large load switching. For the two-module system, the voltage harmonics have been found to be well below the IEEE 519-1992 recommended limit, with a switching frequency of only 300 Hz. At the same time, the influence of the large load switching can be significantly reduced by the application of this compensator. The simplicity of the scheme and the quality of the results indicates its potential as another useful power quality controller.