In this Inside Wireless episode, Tasos explains the subject of gain - one of the most important parameters of an antenna.

Gain says how strongly an antenna radiates in any direction. Gain can be visualized through radiation diagram. The gain radiation diagram instantly and graphically informs about the directional properties of given antenna.

Typically gain is measured in dBi, decibels compared to an isotropic antenna. Isotropic antenna is an abstract antenna that radiates with the same strength in any direction. Therefore, its radiation diagram is a sphere - each point on it has the same distance to the origin where the antenna is positioned.

Comparing the radiation strength of any antenna to the isotropic antenna, and converting it to logarithmic scale, any antenna gain can be expressed in dBi. The logarithmic scale is very useful to understand - it lets us work with huge numbers differing by orders of magnitude without needing to handle too many zeros.

X is an absolute gain in linear scale and you can convert it to Y given in decibels using equation:

Y = 20 * log (X)

Logarithm is a standard function on any calculator these days. What you will notice though is that doubling gain in linear scale means adding 3 dB in logarithmic scale. The confusion often comes when comparing the logarithmic numbers. For example, the difference between 15 dB and 30 dB is not double but 32x more of the measured variable.

RF power is also usually given in dB, but in this case dBm, where the 'm' says the reference value is 1 mW of power.

In antenna datasheets you will most often find gain given as a single number. This is the maximum gain at a particular frequency. Today however, this information is rather insufficient. With computational power so easily accessible, it is easy to provide wideband information, or at least a 3D radiation pattern of an antenna, such as in this datasheet: [ Ссылка ]

Visit [ Ссылка ] to find out more about RF elements Antennas technology.

0:00 Gain definition
0:23 Decibels explained
1:30 Gain & dBi
1:55 Radio power & dBm

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