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Antenna parameters
Frequency
It is the range of electromagnetic wave frequencies that antenna operates on. Electromagnetic waves propagate with velocity of light, so if the frequency of the wave is bigger the length of it is smaller. In Wi-fi there are two standards: 802.11b(g) and 802.11a. They specify different frequencies. 802.11b(g) - range from 2.4 GHz to 2.4835 GHz, 802.11a - from 5.150 GHz to 5.350 GHz, from 5.450 GHz to 5725 GHz and from 5.725 GHz to 5.825 GHz.
Gain
Antenna gain is normally given in isotropic decibels (dBi). It is the maximum of power densities in all directions and is the logarithm comparison to an isotropic antenna. Directivity of the antenna define how narrowly it radiates in specified direction. The higher antenna gain the more it is directional.
Polarization
Polarization of the antenna can be linear or nonlinear. In linear polarization vector of electric (and magnetic)
field propagates in a plane. If the plane of electric vector is horizontal we say that the polarization is horizontal. In vertical plane case - the polarization is vertical. It is worth mentioning that electric and magnetic vectors are always orthogonal (perpendicular).
Beamwidth
Beamwidth is the part of the main lobe in radiation pattern. The unit of the beamwidth is degree, and the borders
are in 3dB density power decrease. In general the radiation pattern is three dimensional. When radiation pattern is crossed over by horizontal (vertica) plane - the horizontal (vertical) radiation pattern is achieved. From those the horizontal and vertical beamwidth can be obtained.
VSWR - Voltage Standing Wave Ratio
VSWR denotes energy radiating effectivity.
Impedance
The value of the impedance to which the antenna is matched.
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