# How to calculate gain from radiation pattern?

Status
Not open for further replies.

#### cakalhunter

##### Junior Member level 1 Can anybody explain how i can compute gain from radiation pattern? I could not obtain a satisfactory solution for this problem.

#### plasma The gain G of antenna is a power ratio, function of directivity D and efficiency K :

G = K*(P max/Pin avg) = k*D (G is expressed in dB)

The directivity of an antenna is the maximum gain measured compared to its gain averaged in all directions. The directivity D of an antenna is given by the next relation : D = P (max)/ Pin (avg)

To compare performance of a 20 dB gain antenna over an isotropic, let's image that this antenna radiates its 20 dB gain (in fact 20 dBi) from the center of a sphere. This energy will travel through a surface 100 times smaller than the total surface of the sphere, or 41253squer° / 100 = 41squer° of beamwidth.

This calc. it's for 100% efficiency antenna

Gmax =K/Δθ1 Δθ2

Practical
values of K fall in the range 25000–35000 (with the beamwidth angles in degrees.)

#### cakalhunter

##### Junior Member level 1 how to calculate radiation of entana

My friend, thanks for your help

but is there a way to obtain gain from radiation pattern? All i have is a radiation pattern.

regards

#### svarun

##### Full Member level 5 how to calculate the radiation patterns

Let P(Θ,Φ) denote the far field radiation pattern with respect to power. You need to square if you have the field pattern. . Find P(Θ,Φ)max. Then find the average of P(Θ,Φ) by taking a grid of say 50 by 50 points or even finer. Find 10log(P(Θ,Φ)max/P(Θ,Φ)ave) That will give your gain.

svarun

#### snkhan

##### Full Member level 6 svarun said:
Let P(Θ,Φ) denote the far field radiation pattern with respect to power. You need to square if you have the field pattern. . Find P(Θ,Φ)max. Then find the average of P(Θ,Φ) by taking a grid of say 50 by 50 points or even finer. Find 10log(P(Θ,Φ)max/P(Θ,Φ)ave) That will give your gain.

svarun

Hi:
Please clarify the difference between radiation pattern and field pattern. Because we measure the field pattern (e.g. azimuth) in anheonic chamber which is power measurement.

##### Junior Member level 3 its too difficult!

#### snkhan

##### Full Member level 6 its too difficult!

Is it too difficult to explain or too difficult to calculate.

Regards

#### dowjones

##### Full Member level 2 simply you can't.

from the pattern you get the directivity, which differs from the gain in the loss of the antenna. To have a measure of the gain you need a standard gain antenna and make a power measurement (which is out of your means if I understand properly), or an estimate of the loss of your antenna. Assumed this is the case, you have the loss (estimate) and the directivity (pattern), so you have the gain...

btw field pattern, radiation pattern is all the same.

rgdz

#### snkhan

##### Full Member level 6 Hi
The definition given by plasma makes sense.
G = K*(P max/Pin avg) = k*D (G is expressed in dB)

Actually measuring the radiation pattern using an antenna of known gain (usually horn antenna) is an estimation of loss in a specific plane. I think we can measure the gain by subtracting the gain of known receiving antenna to one obtained from above definition.
please let me know if i am wrong

#### VSMVDD

##### Banned yes you can do this be measuing using a soft media like a snow material

or a terain that is a simulation of snow

you need nec pro this has such terrain sims built in

dont listen to no it cant be done

ANYTHING can be done in a simulation with rf

you just need to filter out the idiots first

simply put
you need a buffer media and detract it from real life terrain
this way you can duduce gain over a given terrain region

actual gain is given over an isotropic for a perfect sim

but i think this isnt what you want

so nec pro is....

Status
Not open for further replies.