Traveling-Wave Antenna

traveling-wave antenna

[′trav·əl·iŋ ¦wāvan′ten·ə]
(electromagnetism)
An antenna in which the current distributions are produced by waves of charges propagated in only one direction in the conductors. Also known as progressive-wave antenna.

Traveling-Wave Antenna

 

a directional antenna in which a traveling wave of electromagnetic oscillations is propagated along its geometric axis. Traveling-wave antennas are made either with discrete radiators placed along the axis at a certain distance from one another or in the form of a continuous radiator that extends in the direction of the axis. (The latter is considered as the sum of discrete radiators adjoining one another.) The Yagi antenna and the helical antenna belong to the first category; the dielectric rod antenna and the Beverage antenna belong to the second. There are also traveling-wave antennas consisting of several elements, each of which is a traveling-wave antenna of the second type (the rhombic antenna and others). This type of antenna is used in receiving and transmitting installations for all wavelengths of the radio band.

The traveling-wave antenna has its maximum radiation (reception) in the direction of its axis. The directivity is D = kl/λ where / is the length of the antenna, λ is the wavelength, and k is a coefficient that depends on the directivity of the individual radiating element, the phase velocity of the traveling wave, the relationships of the current amplitudes in the radiating elements, and other factors. The value of k usually lies in a range from 4 to 8. The directivity reaches a maximum when the phase velocity v of the traveling wave is somewhat less than the velocity of light c and equal to

v = c • 2l/(2/ + λ)

The typical characteristics of a traveling-wave antenna are the axially symmetrical shape of its three-dimensional radiation pattern (that is, the shape of the pattern is the same in any plane passing through the antenna’s axis) and the maintenance of adequate directivity (in the majority of traveling-wave antennas) over a broad wavelength range. The first characteristic becomes increasingly evident with an increase in the ratio l/λ and the axial symmetry of the radiation pattern of each radiating element.

REFERENCE

Aizenberg, G. Z. Antenny ul’trakorotkikh voln [part 1]. Moscow, 1957.

G. Z. AIZENBERG and O. N. TERESHIN

References in periodicals archive ?
Zhang, "Transmission characteristics of a twisted radio wave based on circular traveling-wave antenna," IEEE Trans.
Zhang, "Transmission characteristics of a twisted radio wave based on circular traveling-wave antenna," Institute of Electrical and Electronics Engineers.
The zig-zag antenna's input impedance measurements with and without feed fingers as a function of frequency are also presented.[8] These measurements are carried out to avoid the costly and bulky impedance transformers that are normally used to match the input impedance of such a traveling-wave antenna to the characteristic impedance of the feeding cable.
However, in practice, the maximum gain obtainable from a traveling-wave antenna is no more than 18 dB, and arrays are normally employed for higher gain applications.[9] These specifications are used in the preliminary stages of designing such antennas in L-band.
In practice, a traveling-wave antenna is only capable of achieving 18 dB gain, and arrays are normally employed for higher gain applications.
The length of the notch can be increased to create a traveling-wave antenna, similar to the linear-tapered slot antenna.|14~ The flare of the notch antenna is another important design parameter, as seen with the exponentially-tapered Vivaldi antenna.|15~ Important work has been reported on the impedance and radiation characteristics.|16-18~ The design flexibility of this type of antenna makes it useful for many diverse applications.
Traveling-wave antennas typically are divided into two classes: leaky wave and surface wave.
Milligan, "Traveling-wave antennas," in Modern Antenna Design, chaper 10, John Wiley & Sons, Hoboken, NJ, USA, 2nd edition, 2005.
Wiesbeck, "Design Considerations for Comb-Line Microstrip Traveling-wave Antennas," 1992 IEEE International Symposium on Antennas and Propagation, Chicago, IL, pp.
Chapter 5 focuses on high frequency RCS prediction techniques and includes geometric and physical optics, diffraction theory and surface traveling-wave antennas. Chapter 6, on phenomenological examples, has been rewritten since the First Edition.