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Ground plane For Monopole antenna.

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bugsbunnyboss

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Hi,

How to calculate the size of the ground plane when using a monopole antenna? Is it w.r.t. the frequency that we use or the physical length of the antenna or any other factor?

I want to use a monopole antenna in 434.7 MHz transmitter and the antenna's physical length is 16 Cm. I checked the antenna with SWR meter , but it did not match for 434.7MHz, and I was told that it is a monopole antenna and needs ground plane to work. what should be the size(area or volume) of the ground plane that I should use with this antenna?

Is there any calculation for the size of the ground plane?


Thanks in advance.
 

davenn

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it can be as large as you like, but the minimum size should be a 1/4 wave out to the edge in any direction away from the base (feedpoint) of the monopole

Dave
 

bugsbunnyboss

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Thanks for your reply Dave. Can you please explain what u meant by "1/4 wave out to the edge in any direction"?
Do you mean I should have at least 4 cm(16/4) in all directions(x,x',y,y',z & z'), from the antenna feedpoint?
If yes, then how can you put ground plane above the antenna (sorry if that is a stupid question!)
 

AndreyG

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Both electrodes of the antenna can be any size. Such antenna will not be resonant by itself, but can be resonated using discrete components for example.
Once I tuned antenna for RFID tag on 435 MHz. The whole device: antenna and ground plane - 1" diameter and 1/8" thick.

The efficiency of small antenna will be low, the bandwidth can be very low but this is different story.
My Tag when tuned worked just fine for the application.
 

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