Propagation Along a Braided Coaxial Cable in a Circular Tunnel

The modes of propagation along a coaxial structure contained within a circular tunnel are considered. The primary objective is to develop an approximate impedance boundary condition at the outer surface of the shielded cable that can be used in previously developed formalisms for axial conductors in tunnels. It is assumed that the metal braid can be characterized by a surface-transfer impedance. We also account for the possibility that a Iossy film exists on the outer surface of the dielectric jacket of the cable.     

Propagation Along a Coaxial Cable with a Helical Shield

A leaky coaxial cable is modelled by a dielectric coated conductor shielded by a finite number of unidirectional helical wires. A modal equation is derived and soIved numerically for the propagation constants of both the monofilar and bifilar modes. Numerical results are also presented for the effective surface transfer impedance of the shield. This parameter is found to depend, in general, on the propagation constant.     

Propagation Along Transversely Inhomogeneous Coaxial Transmission Lines (Short papers)

Numerical "shooting" methods are employed in obtaining the dispersion curves of a coaxial waveguide loaded with a radially inhomogeneous dielectric. The utility of this technique is tested by comparing results with known analytical solutions. The method is also used to find the dispersion curves of a coaxial waveguide loaded with a radially Gaussian-distributed plasma.     

Transmission Modes in a Braided Coaxial Cable and Coupling to a Tunnel Environment

Radio frequency transmission in a semicircular tunnel containing a braided coaxial cable is considered. The general formulation accounts for both the ohmic losses in the tunnel wall and a thin lossy film layer on the outer surface of the dielectric jacket of the cable. Using a quasi-static approximation, it is found that the propagation constants of the low-frequency transmission line modes are obtained through the solution of a cubic equation. However, for the special case when the conductivity thickness product of the Iossy film layer vanishes, this cubic equation reduces to a quadratic. The spatially dispersive form of the braid transfer impedance is also accounted for. It is shown that the quasistatic theory is well justified for frequencies as high as 100 MHz for typical tunnel geometries. Finally, special characteristic impedances are derived for the various modes of the equivalent multiconductor transmission line.     

Calculated Channel Characteristics of a Braided Coaxial Cable in a Mine Tunnel

The braided coaxial cable is studied as a communication scheme in a mine tunnel. A simplified rectangular waveguide model is adopted for the tunnel, and the shield of the cable is assumed to behave as a single inductive transfer impedance. Specific results on the attenuation of the monofilar and bifilar (or coaxial) modes of propagation, taking into account the possible existence of a thin lossy film on the cable, are presented. In order to estimate the maximum possible range of communication, we consider the coupling factors of these modes to transmitting and receiving dipoles inside the tunnel, and we present results on these factors for various cable parameters and over a wide range of frequencies.     

A Coaxial to Microstrip Transition (Short Papers)

A method of obtaining an improved transition, from 0.141-in (3.55-mm) semirigid coaxial to microstrip is described. Further improvements by means of compensation include two fixed types having a reflection coefficient less than 0.005 and an adjustable form capable of producing a "transparent" transition.     

Coaxial Impedance Inverter Design (Short Papers)

It is shown that the effects of discontinuity capacitances associated with the abrupt change in the center conductor diameter of a coaxial bandpass filter can readily be anticipated at the designing stage.     

Coaxial E-Field Probe for High-Power Microwave Measurement (Short Papers)

Open-ended semirigid coaxial cable is characterized for use as a coupling element for the measurement of high-power microwaves. There are many high-power microwave experiments where a high vacuum must be maintained, and yet it is necessary to measure the power and frequency of the microwave energy in a cavity or waveguide. Semirigid coaxial cable which is left open-ended and inserted no more than fresh with the inner waveguide wall is a convenient way to couple out a known sample of the power. The cable is inserted into the waveguide in a direction parallel to the electric field. The coupling value is expressed in terms of an area multiplier which is applied to the area of the end of the center conductor. The induced charge Q on the center conductor is then determined from Q =/rarr over D· and/n·(effective area), and the coupled power is calculated from P = ( omega Q)/ sup 2//(2Z/sub 0/). For a flush mounted Z/sub 0/=50-Omega with PTFE dielectric, the area multiplier is shown to be 3.846 theoretically and 3.77 experimentally. The area multiplier is also determined for various withdrawal depths of the coax into the waveguide wall.     

Inductance of Nonstraight Conductors Close to Ground Return Plane (Short Papers)

Measurement and calculation of the inductance of a nonstraight conductor close to ground return plane are considered. An equivalent circuit model solution is given, and the results are compared to measurements for a corner-type geometry. Much larger changes in inductance as a function of frequency have been observed for the corner-type geometry than for the equivalent straight-conductor geometry. The circuit model can be used to predict the inductance for other configurations.     

Influence of Spatial Dispersion of the Shield Transfer Impedance of a Braided Coaxial Cable (Letters)

The effect of the dependence of the braid transfer impedance on the propagation constant is discussed for a coaxial cable located in a circular tunnel.     

Exact Wave Resistance of Coaxial Regular Polygonal Conductors (Short Papers)

There are various cases in which one can evaluate exactly the wave resistance of coaxial conductors such that each of the inner and outer conductors is a regular polygon. They are obtained by conformal mapping using complete elliptic integrals. Such typical examples each with exact wave resistances are shown.     

Field Propagation in an Open-Beam Waveguide (Short Papers)

A new method is described for the investigation of the open-beam waveguides, which may be applied even when the optical elements are not inserted in absorbing screens.     

Wave Propagation on Nonuniform Transmission Lines (Short Papers)

The problem of wave propagation on nonuniform transmission lines is studied. Equations are presented not only for the reflection coefficient but for the transmission and admittance properties as well. They are valid under the assumption that only one mode of propagation exists on the line and that the properties do not change so rapidly that the fundamental transmission line equations are no longer applicable. Since all equations are derived for arbitrary load conditions, an extremely versatile solution of the problem has been obtained.     

疏编织漏泄同轴电缆空间场分布的研究

通过对SLYWV-75-10型疏编织漏泄同轴电缆的空间场分布进行实际测量,并对测试结果和数据进行分析,证明SLYWV-75-10型疏编织漏泄同轴电缆完全能够作为户外周界入侵探测报警系统的探测传感器,同时对电缆间距、最大单元警戒范围以及系统的响应时间等给出了具体的参考指标,对户外周界入侵探测报警系统的研制和开发具有重要指导意义.     

Propagation on a Ported Coaxial Cable Buried in Flat Earth

Consider a horizontal coaxial cable with periodic slots in the outer conductor. This ?leaky cable? is buried in the earth as one component of an intruder detection system. We develop the theory for surface-wave propagation on the cable in the presence of the planar air-earth interface. Numerical results are included for the phase velocity and attenuation constant as functions of the various parameters. Data are presented for the electric-field strength at the air-earth interface, and the electric-field distribution in the air region above the buried cable.     

Microwave Propagation in Rectangular Vtaveguide Containing a Semiconductor Subject to a Transverse Magnetic Field (Short Papers)

The propagation constant of waveguide partially loaded with a semiconductor in the H plane is evaluated using a three-mode approximation analysis. As the waveguide is progressively filled, a large peak occurs in the attenuation coefficient due to higher order mode propagation. In the presence of a transverse magnetic field, propagation becomes nonreciprocal and this nonreciprocal effect is shown to be significantly increased in the region of the peak. The theoretical results are verified using n-type germanium samples in 26.5-40 -GHz waveguide.     

A Design Method of Bandpass Filters Using Dielectric-Filled Coaxial Resonators (Short Papers)

Design formulas for capacitively coupled bandpass filters using dielectric-filled coaxial resonators are derived and experimentally verified. The most important advantage of this filter is its ability to provide wide stopband characteristics for harmonics suppression. Its features can be obtained from the configuration using both quarter-wavelength uniform impedance resonators (UIR's) and stepped impedance resonators (SIR's).     

Slotted Line Measurements for Propagation Constant in Lossy Waveguide (Short Papers)

The propagation coefficient in a slotted waveguide partially loaded with a lossy dielectric can be determined accurately, in terms of the measured standing-wave pattern, by means of a computer program solving a set of transcendental equations. This determination is a necessary step in a permittivity measurement technique which was recently proposed by several authors.     

Slow-Wave Propagation in Two Types of Cylindrical Waveguides Loaded with a Semiconductor (Short Papers)

For a parallel-plate waveguide and a microstripline loaded with a semiconductor slab of resistive (or active) character, the complex propagation constant gamma is determined. Gamma is found for higher order branches for microwave and millimeter-wave frequencies between 10 and 140 GHz, representing a study of phase velocity slowing (and attenuation).