Multiconductor Antenna Transmission Lines with Arbitrarily Positioned Load Impedances in an Incident Field

The problem considered is that of a multiple conductor transmission line with arbitrarily positioned impedances in series with each wire. The objective is to determine the currents in each of the loads in terms of the amplitude of the incident electric field. The groundwork is laid in this paper for a very general theory for N wire structures when the impedances are situated at the centers of the conductors. If the load elements are in echelon rather than centrally positioned, it appears necessary to abandon the simultaneous integral equation approach employed and resort to the use of two network theorems: superposition and compensation. It is demonstrated that the results depend on a synthesis of antenna and transmission line behavior. This work is an extension to the theory of end-loaded conductors published previously in the G-EMC TRANSACTIONS.     

Impedance Characteristics of a Class of Multiconductor Transmission Lines

The characteristics of TEM modes propagating along a conical transmission line consisting of equiangular strips and exhibiting N-fold symmetry are investigated. Impedance eigenvalues for the eigenmodes of such structures are evaluated using no integral equation approach. Two techniques of calculating the eigenvalues are investigated and compared for this class of transmission line. The results are also compared to exact results available for self-complementary structures. Transverse field distributions along the conical line are also presented for the case N=6.     

Frequency Response of Multiconductor Transmission Lines Illuminated by an Electromagnetic Field

A well-known result [1], [2] for the response of a two-wire transmission line illuminated by a nonuniform electromagnetic field is extended to multiconductor lines. A simple matrix equation for the currents induced in arbitrary termination networks is obtained. Air Development Center.     

Multiconductor Transmission Lines in Inhomogeneous Bi-Anisotropic Media

An analysis method for multiconductor transmission lines embedded in inhomogeneous bi-anisotropic media is presented. The Maxwell-Boffi equations, accompanied by the Maxwell-Minkowski ones, are expressed as Taylor series of the operating frequency where the zeroth- and first-order terms are retained. The reduced problem is solved using the potential formulation through the static 2-D free-space Green's function. The method of moments is employed to numerically solve the set of quasi-TEM integral equations, to produce the Telegrapher's equations, and to derive the circuit parameters in matrix form. The procedure is augmented by providing in closed form the field-coupling integrals.     

Transient Response of Multiconductor Transmission Lines Excited by a Nonuniform Electromagnetic Field

The time-domain transmission-line equations for uniform multiconductor transmission lines in a conductive, homogeneous medium excited by a transient, nonuniform electromagnetic (EM) field, are derived from Maxwell's equations. Depending on how the line voltage is defined, two formulations are possible. One of these formulations is considerably more convenient to apply than the other. The assumptions made in the derivation of the transmission-line equations and the boundary conditions at the terminations are discussed. For numerical calculations, the transmission -line equations are represented by finite-difference techniques, and numerical examples are included.     

Characteristic Impedances of Multiconductor Strip Transmission Lines

The design of certain log-periodic microwave circuit elements requires a knowledge of the characteristic impedances of a system of four-coupled strip transmission lines. The system of four strip conductors between parallel ground planes is capable of supporting four different TEM modes which have different characteristic impedances. In this paper, the characteristic impedances of the four modes are determined by a variational method. The variational solution is an upper bound to the exact characteristic impedance of the line. In general, the coplanar strip conductors are located at an arbitrary (but identical) displacement from the parallel ground planes. When the separation between the broadside-coupled strips is precisely one-half the spacing between the parallel ground planes, two of the mode impedances may be determined exactly by means of conformal mapping. The variational solutions are compared to the exact solutions for this special case. Because of the "cell image" principle which holds for the problem, the mode solutions presented here also apply to various single- and two-conductor strip transmission lines with arbitrary displacements. As a result, solutions for the following strip line configurations are available from the analysis: a single strip conductor in a trough, or between parallel ground planes; two coplanar strips between ground planes; two broadside-coupled strips in a trough, or between parallel ground planes. An extensive set of curves are presented which show the characteristic impedances of the four modes as a function of the relative dimensions of the strip transmission line.     

Multiconductor Transmission Lines In Multilayered Dielectric Media

A method for computing the capacitance matrix and inductance matrix for a multiconductor transmission line in a multilayered dielectric region is presented. The number of conductors and the number of dielectric layers are arbitrary. Some of the conductors may be of finite cross section and others may be infinitesimally thin. The conductors are either above a single ground plane or between two parallel ground planes. The formulation is obtained by rising a free-space Green's function in conjunction with total charge on the conductor-to-dielectric interfaces and polarization charge on the dielectric-to-dielectric interfaces. The solution is effected by the method of moments using pulses for expansion and point matching for testing. Computed results are given for some cases where all conducting lines are of finite cross section and other cases where they are infinitesimally thin.     

Periodically Loaded Transmission Lines

In this paper equations for the transmission parameters of a periodically loaded line are derived in closed form with no restriction on the size, type or number of discontinuities. The equations also take into consideration any attenuation that may exist on the line. Several plots of the input reflection coefficient are presented and compared with experimental results. The agreement is very good.     

On the Quasi-TEM Modes in Inhomogeneous Multiconductor Transmission Lines

We consider the general inhomogeneous shielded N-conductor transmission line and derive several properties for the quasi-TEM modes. The concept of quasi-TEM is deduced through an asymptotic series expansion of the fields and conditions for the propagation constant as well as the construction of the field are presented. It is seen that the problem is reduced to two static two-dimensional boundary value problems. The concepts of propagating modes and impedance modes are introduced and it is shown, that in the general case, these are not the same. The special cases of propagating impedance modes are finally discussed and are seen to exist under certain symmetry conditions of the multiconductor line.     

Losses on Multiconductor Transmission Lines in Multilayered Dielectric Media

For the transmission-line modes, a multiconductor transmission line in a multilayered dielectric medium can be characterized by four matrix parameters the capacitance matrices [C], the inductance matrix [L], the shunt conductance matrix [G], and the series resistance matrix [R]. The first two matrices [C] and [L] can be obtained from equivalent electrostatic and magnetostatic problems. The conductance matrix [G] can be obtained by changing all dielectric constants epsilon/sub i/ to complex dielectric constants /angle over epsilon/sub i/ in the equivalent electrostatic problem. The resistance matrix [R] can be obtained by applying a perturbation method to each mode of the transmission line. A computer program has been written for an arbitrary line, and sample computations are presented.     

Analysis of a Class of Cylindrical Multiconductor Transmission Lines Using an Iterative Approaclh

A class of cylindrical multiconductor transmission lines is theoretically analyzed, and useful parameters, e.g., characteristic impedance and effective dielectric constant, are derived. Discretization of the continuous functions and exploitation of the periodicity of the cylindrical structure lead to a discrete convolution which can be carried out numerically rigorously and efficiently using the FFT algorithm. An iterative technique is employed in the spectral domain to derive the solution of integral equations for the charge distribution. Numerical results are presented and compared with available data.     

Experimental Characterization of Multiconductor Transmission Lines in the Frequency Domain

Although a number of papers have been published on the experimental characterization of multiconductor transmission lines, they are limited to the time domain for lossless multiconductor lines in homogeneous media. This paper presents a method for the characterization of multiconductor transmission lines in inhomogeneous media. The experimental technique for the measurement of multiconductor line parameters is presented and the appropriate multiconductor line equations are solved to obtain these parameters. The experimental method involves only the short-and open-circuit impedance measurements for different configurations. The experimental results for a four-conductor line are found to be in good agreement with computed results and a low-frequency lumped model.     

In Inhomogeneous Theory of Time-Domain Quasi-TEM Modes Multiconductor Lines

Theory for quasi-TEM modes propagating in a transversely inhomogeneous (multidielectric), longitudinally uniform transmission line, previously derived for time-harmonic waves, is derived for transient signals. It is seen that, while the starting point for the theory is completely different, the result is similar to the time-harmonic theory, and previously derived properties for propagating modes also apply in the transient case. The range of applicability is discussed with a simple example.     

Transmission Lines Loaded at Regular Intervals

By a mathematical analysis, the switching time of an incident wave is predicted for a terminated net in which equal, lumped capacitive loads are repeated a finite number of times at regular intervals. The analysis is valid even for the ease of only a few Ioads, for which the distributed load approximation is poor. An APL program has been developed to compute the delay; its use is demonstrated by an example. The results are extended to include complex loads.     

Transmission Line Coupled to a Cylinder in an Incident Field

An approximate formula is derived for the currents in the loads terminating a two-wire line located parallel to and near a circular conducting cylinder of finite length. The line and the cylinder are illuminated by an incident plane wave. The analysis takes account of the coupling between the line and the cylinder and hence of the effects of possible axial resonances in the latter. The configuration simulates exposed conductors used to interconnect the electronic apparatus in a rocket. The analysis is directed toward determining possible hazards due to induced currents.     

任意截面的非平行多导体传输线瞬态分析

以分析多导体传输线的时域有限差分(FDTD)法为基础,在考虑任意截面传输线分布参数无法直接计算的情况下,提出MOM-FDTD 混合方法对不平行多导体传输线进行瞬态分析。首先,利用FDTD建立多导体传输线时域差分模型,然后用MOM 法计算任意截面形状的非平行传输线的分布参数,并且与FDTD法混合进行瞬态分析计算。此算法相对于全波算法,在时间与存储空间消耗上具有很大的优势,并且满足精度要求。最后通过同轴传输线与矩形带状线的例子验证这个方法是正确有效的。     

Experimental Characterization of Multiconductor Transmission Lines in Inhomogeneous Media Using Time-Domain Techniques

An effective method for the time-domain characterization of lossless multiconductor transmission lines with cross-sectionally inhomogeneous dielectrics is presented. Lines of this type are characterized by multiple propagation modes having different velocities. Time-domain reflectometry is used to obtain the characteristics impedance and the modal velocities of the line. A pulse or step-function response of the line is used to obtain the modal amplitudes which, in turn, determine the velocity matrix. The appropriate multiconductor transmission-line equations are solved to obtain the per-unit-length inductance and capacitance matrices in terms of the measured characteristic-impedance and velocity matrices. The method is concise and complete and identifies the propagation modes in a way that permits direct physical interpretation of the results. The time-domain experimental results for a four-conductor transmission line are presented and are found to be in good agreement with independent frequency-domain measurements.