What is a Lens Antenna?

A lens antenna uses the convergence and divergence properties of a lens to transmit and receive signals. These antennas consist of a dipole or horn antenna followed by a lens. The size of the lens used depends on the operating frequency - the higher the frequency the smaller the lens. Due to this lens antennas are used at high frequencies as they can be quite bulky at lower frequencies.

Image 1: Tx and Rx Modes of a Lens Antenna

While transmitting, the lens is placed in such a way that the feeding antennas is located at its focal point, this way we get collimated or parallel rays at the output of the lens. The feed is usually a horn antenna that generates a spherical wavefront or an antenna array that produces a cylindrical wavefront. While receiving, when the incident rays strike the lens they get refracted and get converged to the focal point where the receptor is located.

These types of antennas are used for high-frequency applications that require wide bandwidths.

There are two main types of lens antennas: Di-electric lens or Delay lens Antennas and Metal plate lens antennas.

Di-electric lens antennas are those where the Travelling waves are delayed by lens media. The lens, in this case, is usually made up of polystyrene or Lucite and polyethylene. These types of antennas are usually used Microwave and mm-Wave frequencies as for frequencies less than 3 GHz they become heavy and bulky.

Image 2: Dielectric Lens Antenna

Image 3: Metal Plate Lens Antenna