Directivity

About this film

Combining colour, animation and sound to clarify principles of radio-wave transmission, this film illustrates how antennas propagate radio waves and how they may be adapted to increase the directivity of transmissions. The theoretical concepts are emphasized.

Did you know?

Directivity

In electromagnetics, directivity is a parameter of an antenna or optical system which measures the degree to which the radiation emitted is concentrated in a single direction. It is the ratio of the radiation intensity in a given direction from the antenna to the radiation intensity averaged over all directions. Therefore, the directivity of a hypothetical isotropic radiator, a source of electromagnetic waves which radiates the same power in all directions, is 1, or 0 dBi.

Learn more

Radio wave

Radio waves are a type of electromagnetic radiation with the lowest frequencies and the longest wavelengths in the electromagnetic spectrum, typically with frequencies below 300 gigahertz (GHz) and wavelengths greater than 1 millimeter, about the diameter of a grain of rice. Radio waves with frequencies above about 1 GHz and wavelengths shorter than 30 centimeters are called microwaves. Like all electromagnetic waves, radio waves in a vacuum travel at the speed of light, and in the Earth's atmosphere at a slightly lower speed. Radio waves are generated by charged particles undergoing acceleration, such as time-varying electric currents. Naturally occurring radio waves are emitted by lightning and astronomical objects, and are part of the blackbody radiation emitted by all warm objects.

Learn more

Evolved antenna

In radio communications, an evolved antenna is an antenna designed fully or substantially by an automatic computer design program that uses an evolutionary algorithm that mimics Darwinian evolution. This procedure has been used since the early 2000s to design antennas for mission-critical applications involving stringent, conflicting, or unusual design requirements, such as unusual radiation patterns, for which none of the many existing antenna types are adequate.

Learn more

The Magic School Bus (TV series)

The Magic School Bus is an animated educational children's television series, based on the book series of the same name by Joanna Cole and Bruce Degen. Originally broadcast on PBS from September 11, 1994 to December 8, 1997, the series received critical acclaim for its use of celebrity voice talent, as well as combining entertainment with an educational series. The series stars Lily Tomlin as the voice of Ms. Frizzle. The theme song is performed by Little Richard.

Learn more

Color

Color is the visual perception produced by the activation of the different types of cone cells in the eye caused by light. Though color is not an inherent property of matter, color perception is related to an object's light absorption, emission, reflection and transmission. For most humans, visible wavelengths of light are the ones perceived in the visible light spectrum, with three types of cone cells (trichromacy). Other animals may have a different number of cone cell types or have eyes sensitive to different wavelengths, such as bees that can distinguish ultraviolet, and thus have a different color sensitivity range. Animal perception of color originates from different light wavelength or spectral sensitivity in cone cell types, which is then processed by the brain.

Learn more

Theoretical physics

Theoretical physics is a branch of physics that uses mathematical models and abstractions of physical objects and systems to explain and predict natural phenomena. It is, in the broadest sense, the attempt to say why things happen the way they do, not merely to record that they do. This is in contrast to experimental physics, which tests and refines those explanations through direct measurement and observation. In practice, the two feed each other constantly: a theoretical prediction suggests an experiment, and an unexpected experimental result sends theorists back to the drawing board.

Learn more

More films you might like

Bandwidth

Bandwidth

Hightech in Space: The Secrets of Hidden Data Transmission

Hightech in Space: The Secrets of Hidden Data Transmission