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Typical antenna parameters are gain, bandwidth, radiation pattern, beamwidth, polarization, impedance; These are imperative communicative means. The antenna pattern is the response of the antenna to a plane wave incident from a given direction or the relative power density of the wave transmitted by the antenna in a given direction. For a ...
Antenna reactance may be removed using lumped elements, such as capacitors or inductors in the main path of current traversing the antenna, often near the feedpoint, or by incorporating capacitive or inductive structures into the conducting body of the antenna to cancel the feedpoint reactance – such as open-ended "spoke" radial wires, or ...
A lens antenna is made from a layer of dielectric, or a metal screen, or multiple waveguide structure of varying thickness, mounted in front of a feed antenna. The waveguide / screen / dialectric refracts the radio waves, focusing them on the feed antenna, similar to a focusing lens placed in front of a flashlight. Dielectric resonator
The second antenna is a reference antenna, which points rigidly at the first antenna. Each antenna is alternately connected to a transmitter having a particular source impedance, and a receiver having the same input impedance (the impedance may differ between the two antennas).
This will often be a half-wave dipole, a very well understood and repeatable antenna that can be easily built for any frequency. The directive gain of a half-wave dipole with respect to the isotropic radiator is known to be 1.64 and it can be made nearly 100% efficient.
The beam waveguide antenna addresses these problems by locating the feed antenna in a "feed house" at the base of the antenna, instead of in front of the dish. The radio waves collected by the dish are focused into a beam and reflected by metal surfaces in a path through the supporting structure to the stationary feed antenna at the base.
Electromagnetic waves are radiated by electric charges when they are accelerated. [2] [10] In a transmitting antenna, radio waves are generated by time varying electric currents, consisting of electrons accelerating as they flow back and forth in the metal antenna, driven by the electric field due to the oscillating voltage applied to the antenna by the radio transmitter.
In radio and telecommunication, a traveling-wave antenna is a class of antenna that uses a traveling wave on a guiding structure as the main radiating mechanism. Its distinguishing feature is that the radio-frequency current that generates the radio waves travels through the antenna in one direction.