how to get gain from directivity ?

Status
Not open for further replies.

waqas jaan

Member level 1
Dear All.

i have designed an antenna with directivity of 6.907dBi. what will the value of gain here ? i mean how to get gain from this respective directivity ?
while the radiation efficiency of such antenna is -2.056dB.

Vengateswaran

Member level 5
whether the directivity you have calculated is maximum directivity..?? if so, u can get maximum gain as, G=radiation efficiency * Directivity... But for your calculation, u'll be getting negative gain...

waqas jaan

Member level 1

yes it is the maximum directivity.
but as you mentioned, that G = rad eff * dir. so whether shall i multiply it in the value of dB or to convert it from dB and than multiply it ?

albbg

You have to operate in linear, that is convert dB to lin, multiply and then convert back, the result, to dB.

G=10^(6.907/10)*10^(-2.056/10) = 3.056 lin
G(dBi) = 10*log(3.056) = 4.85 dBi

waqas jaan

Member level 1
Thank you so much, i got it.

what do you think ? is it good or not ? i mean 4.85dBi or 6.40dBi is a good gain or not ?

Vengateswaran

Member level 5
I don't think it is good... it can be used for low end applications..

waqas jaan

Member level 1
actually it is microstrip patch antenna at resonant freq of 5.2GHz.

Vengateswaran

Member level 5
I think it is partially less when looking at your design... But i dont know exactly...

albbg

If that directivity you wanted to achive is OK (this means the angle over which the power is radiated, mainly) then is only matter of efficiency.
You reached -2.056dB, that is 62%. Usually patch antennas have efficiency ranging rouglhly from 50 to 90% then you are inside it. This depends from factors like substrate losses, material conductivity, etc.

However if you could increase the efficiency up to the ideal 100 % the gain will increase 10*log10(100/62)=2 dB; not so much.

Status
Not open for further replies.