Lens Antenna

  • Source: eahison
  • Date:04/12/2019

Lens antenna, an antenna capable of converting a spherical wave or a cylindrical wave of a point source or a line source into a plane wave by electromagnetic waves to obtain a pen-shaped, sector-shaped or other shaped beams. The phase velocity of the electromagnetic wave is adjusted by appropriately designing the lens surface shape and refractive index to obtain a plane wavefront on the radiation aperture.

lens-antenna

Lens antennas have absorbed a lot of optical information engineering technology, which has been widely used in communication and military fields and has attracted more attention from the industry. According to the theory of geometric optics, a spherical wave radiated from a point source at the focal point of the lens condenses through the lens to form a plane wave. This is the general idea of lens antenna design. The lens antenna is composed of a lens and an electromagnetic radiator. Electromagnetic waves have wave-particle duality. During the process of transmission, refraction occurs when different media are not parallel. Mounting the lens in front of the radiator allows the radiant energy to concentrate and the beam to narrow.

The lens antenna has two types of a medium deceleration lens antenna and a metal acceleration lens antenna.

new--4-18-3

Cylindrical wave lens antenna

Media deceleration lens antenna

The dielectric deceleration lens antenna is made of the low-loss high-frequency medium, thick in the middle and then around. The spherical wave emitted from the radiation source is decelerated as it passes through the dielectric lens. Therefore, the spherical wave is decelerated in the middle portion of the lens, and the path decelerated in the peripheral portion is short. Therefore, the spherical wave becomes a plane wave after passing through the lens, that is, the radiation becomes directional.

It is characterized by a thick inner lining and a thin edge. Electromagnetic waves released from the electromagnetic radiation source are pressed while passing through the lens. This pressing is more effective at the center of the lens, and the pressing path is long; while the pressing effect at the edge of the lens is weak, the pressing path is short. The result of this suppression is that a spherical wave is formed by a spherical wave to form a plane wave, and the directivity of the electromagnetic radiation is enhanced.

metal-accelerating-lens-antenna

The metal accelerating lens antenna is formed by placing a plurality of metal plates of different lengths in parallel. The metal plate is perpendicular to the ground, and the shorter the metal plate is, the closer it is to the middle. The electric waves are accelerated as they propagate through the parallel metal plates. When the spherical wave emitted from the radiation source passes through the metal lens, the closer to the edge of the lens, the longer the path is accelerated, and the path that is accelerated in the middle is short. Therefore, the spherical wave passing through the metal lens becomes a plane wave.

In the next issue we will introduce [the characteristics of the lens antenna and its advantages]

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