Form Of And Function Of Military Antennas

By Patty Goff


In professional satellite communications transmitters, it is common for a single antenna to work with two orthogonal polarizations simultaneously, so that the available bandwidth for the signal on the link is doubled (military antennas). To do this, standing next to one ortho-mode transducer feeder, which has a circular waveguide port connected to the horn and two orthogonal rectangular waveguide ports, each of which works in a different polarization.

Within the transmission we can define co-polar diagram that represents the communication from to a desired polarity and polarized radiation pattern with the opposite polarity to that you already have. The most important parameters of the radiation pattern are: pointing direction: The maximum radiation. Directivity and Gain. Main lobe constitutes angular range around the direction of maximum radiation. Side lobes are other relative maxima, lower the principal value.

This relationship also can be seen from another point of view, indicating how good the antenna in the rejection of signals from the rear. Rarely is really important, because the interference from the rear do not usually happen, but it can happen. The F / B ratio is not a very useful number because often varies greatly from one channel to another. Of course, if it is the radiation pattern, then the F / B is not needed.

Loops are only effective at resonance, and must therefore be geared to operate, high q, very narrow bandwidth. All within about 10 wavelengths (near field) of an antenna may affect its radiation patterns. An antenna is the most "sensitive" in its main cones, there where it has "gain" in a free field radiation pattern.

The antenna resistance is the sum of the transmission resistance and loss resistance. The antennas are called resonant when its input reactance vanishes. Beam is a radiation parameter, linked to a radiation pattern. May define the beam width at -3 dB, which is angular range within which the radiated power density is equal to half of maximum power (in main direction of radiation).

You can also define the beam width between zero, which is the angular range of the main beam of a radiation pattern between two adjacent zeros to maximum. Create antennas radiated electromagnetic fields. Polarized electromagnetic defined in a certain direction, as the geometric shape that traces the edge of electric field vector at a certain distance from the antenna, to change the time.

Every day use of aerials to transmit and receive signals (data) throughout the world by millions of people is ordinary. General: Everything is connected without cables using in some degree antennas for the exchange of information (data). An aerial is a (metal wire) device designed for the purpose of emitting or receiving electromagnetic waves into free space. A transmitter antenna transforms electrical energy into electromagnetic waves, and a receiver performs the inverse function.

The wire transmitters are analyzed from the electrical currents of the conductors. Aperture aerials are those that use surfaces or openings to direct the electromagnetic beam which concentrate their transmission and reception antenna system in one direction.




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