Surface-wave Transmission Line Research Articles

Effects of supports on a surface-wave transmission line

A method of calculating the effect of supports on the amplitude characteristics of a Goubau line is given in this paper. The results from this method agree well with experimental data and thus predictions for a line one mile in length were made. It is shown that supports can cause limitations in the line length and in the available bandwidth.

The Surface-Wave Transmission Line and Its Use in Communicating with High-Speed Vehicles

The potential use of surface waves for the communication and control link with high-speed trains is being studied for the U. S. Department of Transportation, Office of High-Speed Ground Transportation. The results are presented for the first part of this study, which dealt with the feasibility of using the surfacewave transmission line (SWTL) as this link, including its characteristics, launching energy onto the line, coupling to and from the line, and communication capacity. The SWTL shows promise in providing the bandwidth and economy required to meet the demands of a high-speed ground transportation system, without requiring the allocation of space in the crowded radio spectrum.

Measurement of waveguide attenuation by resonance methods

It is shown that attenuation coefficients obtained from Qfactor measurements on resonant waveguides containing more than one homogeneous dielectric medium would be subject to significant error if certain forms of the expression relating the Qfactor to the attenuation coefficient were applied. In particular, results for the Goubau surface-wave transmission line are examined.

Calculations on surface-wave transmission lines with unrestricted radial dimensions

Accurate expressions for power flow, power loss per unit length and attenuation coefficient are derived by the perturbation method. It is shown that the approximations used by Goubau, and hitherto generally applied, result in errors which increase rapidly for large values of phase-velocity reduction. Computations based on the accurate expressions for the TM01 mode are presented in the form of a design chart.

Radiation from corners in surface-wave lines

Theory of radiation from corners in surface-wave transmission lines is developed, and a relatively simple analytical expression for the radiation pattern is obtained. This is in good agreement with experimental results for corners involving a change in direction not exceeding approximately 100°.

Mode of millimeter wave two-wire surface wave transmission line fields

Mode of millimeter wave two-wire surface wave transmission line fields

Attenuation coefficient of millimetre-wave two-wire surface-wave transmission lines

The two-wire line is shown to have an attenuation coefficient in millimetre wavelengths which is about the same as the attenuation constant of RG-98/U rectangular waveguide. The attenuation coefficient is also shown to agree with Sommerfeld's equation. The field extent is shown to be of reasonable value.

Periodic Cylinder Arrays as Transmission Lines

Periodic structures of conducting cylinders have been used as radiators (Yagi antennas), and, more recently, as slow-wave lines in traveling-wave tubes and masers. In this report it is shown that a nonresonant structure may have interesting capabilities as an open surface-wave transmission line. By means of a relatively simple matching network, efficient excitation of a surface wave on the periodic line is obtained. Response is flat over a 20 per cent frequency range at X band for several combinations of cylinder lengths and spacings. Total insertion losses are less than 3 db and largely independent of length of transmission line. Conducting cylinders are embedded in styrofoam. The effects of bends and twists in the line have also been investigated. It is shown experimentally that a guided wave on this periodic structure can follow a circular path having 1.5/spl lambda/ radius of curvature with very little loss. The plane of polarization can be rotated 90/spl deg/ by inserting a short twisted section. By terminating the transmission line with short circuits at both ends, a discrete series of transmission maxima is observed. Since these resonant peaks of transmission are of high Q factor, the dispersion characteristic of the line is obtained with very good accuracy. This type of open transmission line may offer advantages over heavy-weight and bulky conventional waveguides for some specialized applications.

Some characteristics of surface-wave transmission lines for long-distance transmission

Some characteristics of surface-wave transmission lines for long-distance transmission

Investigations with a model surface wave transmission line

This paper summarizes the results of experimental studies conducted with a scale model of a surface wave transmission line (swt line) for long-distance transmission. The purpose of the experiments was to determine the effect of supports, bends, and sags on the transmission loss of such a line. Also, the coupling between parallel identical lines has been measured and compared with the theory. Formulas and other information are given which may be applied to the design of a swt line for long-distance transmission.

Open Wire Lines

The properties of two-wire lines and single wire lines (surface wave transmission lines) are discussed on a comparative basis. The two-wire line is actually a system of two coupled single wire lines and thus requires a high degree of symmetry to maintain the desired wave mode. While the single wire line is more affected by bends it has the advantages that it is simpler in construction and is less susceptible to weather conditions. The main domain of the two-wire lines lies in the frequency range below 100 mc and that of the single wire line in the range above 100 mc.

Loss Measurements of Surface Wave Transmission Lines

Loss measurements were made on ten dielectric coated wires used as surface wave transmission lines at a frequency of 9365 mc/sec. The purpose of these measurements was (1) to develop a satisfactory method for making the loss measurements, and (2) to compare the measured loss with the calculated or predicted value obtained from theoretical analysis made by Goubau. A resonance method, in which the Q of a resonator formed by short circuiting both ends of a length of line is determined, was found to be most desirable. The loss in the resonator end plates was taken into account in determining the wire loss. A description of the apparatus required and the experimental procedures used is given. A brief discussion of alternative methods for making the loss measurements, some of which have been tried, is also given. The losses of the wires measured ranged from about 3.0 db/100 feet for thin dielectric coatings to about 11.5 db/100 feet for thick dielectric coatings. The agreement between measured and calculated losses of wires for which the constants of the dielectric coating are known is considered good.

A UHF Surface-Wave Transmission Line

A description is given of a surface-wave transmissionline unit developed to meet a requirement for an efficient, easy to install and maintain antenna feed line.

The launching of electromagnetic waves on a cylindrical conductor

The transmission of waves along a straight cylindrical conductor is discussed and an analysis made of the method of launching by means of a conical horn. It is shown that the efficiency of launching depends on the horn angle and aperture and that the launching loss is probably due to the generation of complementary waves which dissipate their energy as heat in the conductor. Details are given of experiments on a surface-wave transmission line at a wavelength of 6.5 cm, and suggestions are made for reducing the launching loss.

Interaction Between Surface-Wave Transmission Lines

An important question connected with surface-wave transmission lines is the interaction between them or with other wires which act like surface waveguides. An analysis is made of two parallel lines with the provision that the coupling is small. When the two lines are identical, there is maximum interaction, and under suitable conditions, complete power transfer from one line to the other occurs. The analysis is supplemented by typical examples.

Investigation of a surface-wave line for long distance transmission

The surface-wave line discussed in this paper is a single conductor with a dielectric coat. The energy is propagated along the surface of the line in a wave mode similar to that in a coaxial line. The phase velocity of this wave is reduced by 1 to 5% from the velocity of light, depending on the thickness of' the dielectric layer. Because of this reduction in phase velocity, no outer conductor is necessary for the return of the current. The conduction current in the outer conductor of a coaxial line is replaced by a displacement current through the air. The experiments demonstrated that the single conductor surface-wave transmission line is practical for long-distance, wide-band communication. They also indicated possible improvements: (a) The use of "copperweld" conductor rather than a conductor with segmental structure in order to reduce the conductivity loss. The ~eat mechanical strength of this cable would permit an increase in the span to at least 250 feet; (b) Avoiding unnecessary curves; (o) Omitting the· messenger wire..