How can we calculate the gain of an antenna?

[mani_sohail]

Antenna Gain

How we calculate the gain of antenna?
high gain antenna is highy directional antenna?
the gain of Yaggi antenna is zero?

 

[electronics_kumar]

Re: Antenna Gain

Antenna Gain= (Radiation resistance)/(loss resiatance+Radiation resistance)
loss resiatance calculated from eddy current loss,copperloss etc..
actually there exists many more formulas to fing Gain of a antenna...
2)high directional antenna will have maximum radiation intensity in particulat direction..that why it is called as high directional antenna
in terms of radiation intensity in particular direction with that of isotropic antennsalso,Gain can be calculated

 

[albert22]

Re: Antenna Gain

The gain of an antenna takes account of the antenna efficiency as well as its directivity. The formal definition of gain in any direction is "power density radiated in that direction divided by the power density which would have been radiated at that direction by a lossless (perfect) isotropic radiator having the same total accepted input power."
The gain is specified as a ratio (in Decibels) relative to a reference antenna. Being reference antennas the isotropic and the dipole.
If the gain is specified with the isotropic as a ref. it is expressed as dBi. If the ref. is a dipole you use dBd.
An isotropic antenna is a theoretical antenna with radiates equally in all directions. It is just a point in the free space.
For example a dipole antena has a gain of 2.2 dBi that is 1.6 times that of the ref.
The dipole is directive and the isotropic not, so you are achieving gain by concentrating the radiated energy in one direction.
A yagi rated at 7.2dBd will give you 2.15dB more gain than the one that is rated at 7.2dBi.
There are simulation programs that allow you to calculate gain and radiation pattern. Like those based on NEC as the EZNEC and MININEC. The data you should enter is the geometry of the antenna and the surrounding objets (if not on the free space).
Also there are programs to calculate yagi uda antennas.
The efficiency depends on its resistive losses in the antenna structure, and by resistive loss in objects which may lie near the antenna

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