Multiwire Lines Research Articles

Coherent radiation of active Josephson traveling-wave antennas

The dynamics of large superwavelength open systems which are free-standing multi-wire lines with a large number of Josephson junctions, DC bias batteries and other lumped elements is analyzed using direct numerical simulation. Such systems represent the simplest version of the active Josephson antennas proposed in our earlier studies and show promise as terahertz and subterahertz radiation sources. We have studied dependences of the radiation characteristics on the antenna geometry, number of junctions, DC bias current and the lumped elements position and parameters. Detailed simulation results reveal a multitude of phase transitions between the dynamical states, which differ in the number of Josephson junctions synchronized by the excited waves of current and, hence, in the radiation power emitted into open space also as in radiation patterns. It is shown that, in the absence of noise, the Josephson antennas can emit completely coherent radiation.

Determining electromagnetic fields generated by overhead power transmission lines

Under actual operating conditions of electrical networks, it is hard to obtain experimental data that correspond to the maximum levels of the electromagnetic field strengths generated by overhead power transmission lines. Therefore, the analysis of the electromagnetic environment in electric power systems, both at the operated and newly created facilities, is recommended to be performed on the basis of mathematical modeling. The modeling methods and tools developed in IrGUPS and the Fazonord software package implemented on their basis make it possible, after determining the power system mode, to calculate the electromagnetic field strengths generated by multi-wire power transmission lines. In this case, the analyzed lines are considered in close connection with a complex electric power system. To check the adequacy of the simulation, measurements of electric and magnetic field strengths were performed, including comparative calculations for a 110 kV double-circuit line with a ground-wire located within the city. The comparison carried out in rather complex conditions is indicative of the correctness of the method of calculating a multi-wire line electromagnetic field developed in IrGUPS.

Modal analysis of multi-connected waveguides

A general analysis for the modal characterization of multiconnected uniform, hollow, conducting waveguides is presented. It is relevant to waveguides with an 'outer' conductor for which analytical Green's functions are known and 'inner' conductors described by integral equations. The transverse electromagnetic (TEM)-mode space is analyzed, and singularities of the integral equations are studied to determine the higher-order modes. The cases of parallel wires into rectangular waveguides and above a ground plane are addressed in detail; experimental results about a complex multiwire line are reported. Mixed coaxial and circular offset coaxial waveguides are also analyzed. Spurious solutions arise due to the structure of the integral equations for multiconnected waveguides. Criteria to discard such modes are presented. >

Lumped‐element representations of lossy multi‐wire lines

AbstractLumped‐element representations are derived for lossy multiwire lines using simple circuit matrix with the assumptions that (1) phase constants of all transmission modes are identical, and (2) their attenuation constants are independent of frequencies. Since these assumptions are valid in the limited frequency range, simplified representations of lossy multiwire lines are derived in the vicinity of a quarter‐wavelength frequency. As an application of narrowband equivalent representations, analysis and design of lossy interdigital‐line filters of narrow‐band are investigated.

Theory of microwave coupled-line networks

The multiwire line forms the basis of many practical microwave filtering and coupling circuits. It also has considerable importance as a circuit element in formal synthesis procedures. This paper is concerned with a tutorial presentation of the various methods of analysis for such multiwire lines leading to a number of different equivalent circuits, and with the use of these for synthesis and design. The treatment is restricted to the case of uniform commensurate lines with homogeneous dielectric. Where possible, a unifying approach based on general equivalent circuits is used and this permits the design of some well-known microwave structures to be seen from a somewhat different viewpoint. Some gaps in the existing design procedures for some components are identified and it may be that the methods of analysis and synthesis presented here could lead to new solutions.

Bearing errors in the VHF omnirange due to scattering from wires

Scattering from obstacles in the vicinity of a VHF omnirange can cause bearing errors in aircraft receivers. A general formula is developed for the bearing error due to an arbitrary scatterer in terms of its scattering radiation pattern. The theory is then applied to get specific results for a long horizontal wire. The current distribution on the wire, the scattered field, and the bearing error are computed by a transform method, and all integrals are evaluated asymptotically by the saddle point method. The final result clearly shows the dependence of the bearing error on all system parameters. The theoretical conclusions are all found to be consistent with the results of numerous experiments carried out by the Federal Aviation Administration (FAA). Some results and speculations are presented for multiwire lines.

Early schemes for television

More than a dozen schemes for sending visual images by electricity appeared from 1877 to 1884. Some used multiwire lines and mosaic arrays; others used single lines and a scanning method-autographic, spiral, linear. Selenium cells and incandescent filaments were common elements. Basic ideas on scanning speed, repetition frequency, synchronism, picture elements, and beam modulation evolved during these years. Some schemes employed magnetooptic effects, others used polarized light, and an optical equivalent of the cathode-ray tube was proposed for one receiver. Mechanical problems were finally solved by the scanning disk, which, 40 years later, with the aid of electronic techniques, became the foundation for practical mechanical television. Both facsimile and television proposals were covered, partly because they were inseparable during this era and partly to show the continuity of developments.

On multi-wire non-uniform transmission lines†

Solutions and transmission matrices are obtained in terms of ’ hyperbolic functions ’ for three classes of multi-wire non-uniform transmission lines. Theorems have also been proposed, whereby knowing the solutions for any class of multi-wire line, another class may be derived whose solutions are related to those of the original class. The inter-relationships of the matrix parameters of the new class with those of the original class are also given. These results represent generalizations of those obtained by Swamy and Bhattacharyya, and by Berger for the two-wire case.

High-Frequency Polyphase Transmission Line

The problems of the polyphase transmission line and the single-phase multiwire line have been formulated, based upon the vector-potential method. The transmission-line equations that determine the current and voltage relationships on these lines have been derived and solved. Formulas for the characteristic impedance of the lines have been thus obtained. They are useful in designing lines to feed polyphase radiating systems, and in computing the input impedance of triple-folded dipoles and other antennas.