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on1
Joined: 27 May 2008
Posts: 42
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 01 Jun 2008 10:08 Double Ground Plane? |
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Hi to all!I'm trying to simulate a 3 band microstrip monopole for GSM/GPRS/UMTS usb modem. The problem is that the monopole is connected to the pcb but there is another pcb under the first one; I've done several simulation and I see that the second PCB has a big influence on the results: do i have to consider or not? I post some photos to see the details, sorry for bad quality but I have to make with my WebCam. NOTE: the second GND_plane doesn't extend under the antenna obviously.
Thanks.
Bye
Francesco
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FvM
Joined: 22 Jan 2008
Posts: 5160
Helped: 767
Location: Bochum, Germany
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01 Jun 2008 10:23 Re: Double Ground Plane? |
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| I didn't recocnize much details from your photos, but in general, a ground plane below a monopole that has dimensions similar to the monopole can't be actually regarded as a ground plane?! It's rather some kind of dipole. So it's plausible, that the second plane has a considerable effect on antenna impedance, radiation pattern, whatever.
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on1
Joined: 27 May 2008
Posts: 42
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01 Jun 2008 10:49 Re: Double Ground Plane? |
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Thanks for answer first. Of course the effect of GND is surely important but pay attention to the fact that this second GND doesn't extend under the monopole.
thanks
Francesco
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FvM
Joined: 22 Jan 2008
Posts: 5160
Helped: 767
Location: Bochum, Germany
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01 Jun 2008 11:56 Re: Double Ground Plane? |
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| Yes, i considered this fact. I prefer to regard the monopole and the ground plane as a kind of dipole. Whatever you assume as a model for the ground plane, because of it's small dimension it will be exited and radiate somehow. So the second plane must have a coupling with the antenna.
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on1
Joined: 27 May 2008
Posts: 42
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01 Jun 2008 12:13 Re: Double Ground Plane? |
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Yes I think so, infact considering both the GND plane the plot of S11db shows that the antenna seems to resonate at 2 frequency (1.6 and 2 Ghz). Considering only one PCB you can see only a resonance with modest bandwith at 1.7 Ghz. Now I'm doing several simulation varying the length of the monopole 'cause I want to discover the efficace index of air-PVC multistrate interface.
thanks
Francesco
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