Antenna parameters you should know about | applied electronics engineering

# Antenna parameters you should know about

By Applied Electronics - Wednesday, September 14, 2016 No Comments
Antenna are used in any wireless communication devices. Wireless routers, modems, cell phones, satellite, home dish etc all have antenna. As a communication system designer or electronics engineer you should be familiar with types of antenna and some important antenna parameters. Antenna parameters includes radiation intensity, directivity, directive gain, antenna gain or antenna power gain etc.

Antenna types are huge so it is not possible to list them all here. But some of the important ones are dipole antenna, mono-pole antenna, loop antenna, horn antenna, parabolic antenna and lens antenna. These are illustrate below.

Figure(a) shows dipole antenna, figure(b) shows monopole antenna, figure(c) shows loop antenna, figure(d) is a horn antenna, figure(e) shows parabolic antenna and figure(f) shows lens antenna.

Furthermore, the modern cell phones uses patch antenna.

Antenna Parameters are as follows:

Power Density Wrad is the power per unit area(Wrad). Power radiation(U) is the power radiated by the antenna per unit solid angle. These two quantities are related. Power radiation at a distance r from the antenna is given by the following equation.

Directive Gain and Directivity

The ability of an antenna to direct its power along some direction is called directivity. Antenna capability of radiating power at some specific direction is measured using antenna directive gain and directivity.

An antenna that radiates power uniformly in all spherical direction is called isotropic antenna. The power radiation by mono-pole antenna is close to isotropic radiation and can be considered to be an isotropic antenna. However this is only approximation since no antenna in practice can generate and radiate perfectly spherical radiation in all direction.

The directive gain(DG) is the ratio of Power Radiation Intensity(U) of the test antenna to the Power Radiation Intensity(Uo) of a hypothetical isotropic antenna.

where U is the radiation intensity due to the test antenna in watts per unit solid angle, U0 the radiation intensity due to the isotropic antenna in watts per unit solid angle, and Prad the total power radiated in watts.

The radiation intensity U is a function of θ and φ.

The directivity is same as directive gain but the difference is that the directivity is a measure or maximum radiation intensity to the isotropic radiation intensity.

Antenna Gain or antenna power gain is defined as the ratio of radiation intensity(U) of the antenna at a point to the radiation intensity at the same point measured in terms of isotropic antenna when same input power is supplied.

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