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# How to calculate gain from radiation pattern?

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#### 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.

cakalhunter said:
Can anybody explain how i can compute gain from radiation pattern? I could not obtain a satisfactory solution for this problem.

Measure Half power beam width in the E-plane and H-plane. Multiply them and invert and again multiply with 4*pi. The result will be approximate far field directivity. Now multiply directivity with efficiency to calculate Gain. Efficiency is anoter parameter that you have to know.

:!::idea::?:

and the attachment

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

If you have AZ and EL pattern take -3dB beam width for example

θaz=20° and θel=25° Assuming efficiency 60% we get k=30000

Gain=30000/20*25=60 ----> transform to dB Gain[dB]=10*log60=17.18dB

read pages 497 and 498 in Attachment

PL

As plasma mentioned,the method is one shortcut to calculate the Gain,but it is for directivity,and not very accurate.

Hello,

if you have the complete pattern (full theta-phi measurement) you can get the directivity to high accuracy, however you will not have efficiency and therefore no gain info.

To get the gain you need to know the ohmic losses of the antenna (conductor and dielectric loss) , or at least a good estimate. In case you know or assume a low loss antenna, then directivity equals the gain.

regards

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