QUESTION

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Clearance under M20047

I have tunned my antenna correctly with a VNA (lifting components, matching on final design, etc), but it doesn´t always get a fix or takes too long compared to an external patch antenna, and if it is cloudy it can only get the time or nothing at all. Since matching has been solved correctly and I followed design rules of clearance below the antenna and size of the board,

a) How deep the clearance below the antenna should be? As you can see in the image, I have nothing under the antenna for at least 1.6mm before my metal structure is present
b) Antennas work only one at a time, could it be that radiation pattern changed dramaticaly due to the metal structure?
c) Do you have other type of GNSS antenna with higher gain on top side of the antenna, so it is no longer omnidirectional?

Thank you for your advice in advance.
 

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1 Answer

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Best answer

Hi Eddy,

Let me answer your questions first:

a) How deep the clearance below the antenna should be? As you can see in the image, I have nothing under the antenna for at least 1.6mm before my metal structure is present.

We recommend at least 5mm from any metal structure to prevent the antenna from being detuned.


b) Antennas work only one at a time, could it be that radiation pattern changed dramaticaly due to the metal structure?

Yes, the antenna pattern will be affected by the metal below the antenna.  It usually acts like a reflector and any signal on the other side of the metal object will be blocked reducing the radiated performance.


c) Do you have other type of GNSS antenna with higher gain on top side of the antenna, so it is no longer omnidirectional?

Yes, the Beltii SR4G013 is designed to operate on a ground plane with no widow or copper cut out beneath the antenna. It also has a higher peak gain than the M20047.

Best regards,

Geoff S.

commented by
Thanks for your kind and informative answer, I´ll have a look.
Best regards,

Eddy

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