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Calculating Power_radiated, Directivity and Gain

 
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Ahsan
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Joined: 03 Jul 2016
Posts: 2

PostPosted: Sun Jul 03, 2016 12:49 pm    Post subject: Calculating Power_radiated, Directivity and Gain Reply with quote

I am using a rfxepert instrument to measure my test antenna. All I got in output data is E_theta_amplitude, E_theta_phase, Ephi_Amplitude and Ephi_phase. Now based on this data I want to calculate power radiated, directivity and gain. I know for calculating gain you need to consider losses so lets just stick to power radiated and directivity.

To calculate power radiated I calculated first Etotal=sqrt(|E_theta|^2+|E_phi|^2), then
Powerpattern=Etotal*Etotal, then for all theta and phi points
I used this formula from antenna theory site.[/img][http://www.antenna-theory.com/definitions/trp.php].

I integrate it over whole sphere and also multipying each point with sin theta. BUt i am not getting correct answer. do anybody knows what did i miss. Is it the wave impedence i forgot to divide power pattern with and also with 2 as for power density you need to divide with waveimpedence and 2. I even tried it but answer is not correct. any help will be appreciated.thank you.
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Parna
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Joined: 14 Apr 2015
Posts: 8
Location: Canada

PostPosted: Mon Jul 04, 2016 5:15 pm    Post subject: Reply with quote

How do you know you are not getting the correct answer?

If you have pattern values at every degree, you can use this for Directivity (in dBi):

https://www.wolframalpha.com/input/?i=10log10(4*180%5E2%2F(pi*sum(sum((10%5E(C%2F10)%2B10%5E(X%2F10))*sin(theta),0,179),0,359)))

C and X are your E_theta_amplitude and Ephi_Amplitude normalized and in dB. If your amplitudes aren't in dB then they can replace the whole 10^(C or X/10), but you would still need to divide them by the peak value to normalize them.

Hope this helps
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