Lens Antenna

lens antenna

[′lenz an‚ten·ə]
(electromagnetism)
A microwave antenna in which a dielectric lens is placed in front of the dipole or horn radiator to concentrate the radiated energy into a narrow beam or to focus received energy on the receiving dipole or horn.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Lens Antenna

 

an antenna whose directivity pattern is a result of the difference between the phase velocity of propagation of an electromagnetic wave in air and that in the lens material.

Lens antennas are used in radar and metering equipment that operates in the centimeter wavelength range. A lens antenna consists of a lens proper and of a feed. The shape of the lens depends on the refractive index n (the ratio of the phase velocity of propagation of a radio wave in a vacuum to that in the lens). A decelerating lens antenna, as in optics, is one for which n > 1. An accelerating lens antenna (without an optical analogy) is one for which n < 1. The feed is usually a horn antenna that generates a spherical wave front or an antenna array that produces a cylindrical wave front.

Decelerating lens antennas are made of high-quality low-loss homogeneous dielectrics (polystyrene, fluoroplastics) or synthetic dielectrics (systems of variously shaped metallic particles suspended in air or in a homogeneous dielectric with a relative dielectric constant approaching unity). The refractive index can change within wide limits with extremely low losses.

Accelerating lens antennas are made of shaped metal sheets. There is no analogy in optics. The principle of operation derives from the fact that the phase velocity of an electromagnetic wave propagating between parallel metal sheets depends on the distance between them if the electric field vector is parallel to the sheets. In such a case the phase velocity is greater than the speed of light, and the refractive index is less than unity.

Zoning the surfaces of a lens antenna reduces its weight and dimensions. The shape and height in profile of the individual zones are chosen such that the electromagnetic waves refracted by adjacent zones leave the lens with a phase shift of 360°. The field at the aperture remains cophasal.

With aplanatic and Lüneberg lens antennas it is possible to control the directivity pattern virtually without distortion.

O. N. TERESHIN and G. K. GALIMOV

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
The technology involves the use of a compact focal lens antenna made with metamaterials to achieve advanced beamforming (maximum gain of 31 dBi) that concentrates radio waves in a specified direction for long-distance transmission.
Munro, "Electronically scanned Rotman lens antenna with liquid crystal phase shifters," Electronics Letters, vol.
1 indicate that the focusing MSs can be applied to the design of high gain planar lens antenna by properly locating feed sources over the surfaces [10].
These COWs will feature some of the highest capacity antennas in AT&T's fleet, including the Giant Eyeball Antenna (also known as the Luneburg Lens Antenna), AT&T added.
The geometrical structure considered in the proposed electromagnetic model consists of a dielectric lens antenna placed on a perfectly electric conductor (PEC) circular plate having radius [r.sub.d] (see Figure 1).
In general, the lens antenna can be implemented as a dielectric lens, a Fresnel lens, or a lens-array.
It also provides reliable signal reflection even from solids with a steep angle of repose and is highly resistant to material build-up due to the unique lens antenna.
Singhal, "A review on the development of Rotman lens antenna," Chinese Journal of Engineering, vol.
In this paper, we propose a multi-beam lens antenna design in which the beam symmetry is controlled by acting on the lens shape, with the goal of generating circular footprints in the whole covered area.
Yoon, "Beamforming lens antenna on a high resistivity silicon wafer for 60 GHz WPAN," IEEE Trans.