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John_li
Joined: 06 Aug 2005
Posts: 188
Helped: 5
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 28 Aug 2008 0:06 Why i got the test different S11 with different ground? |
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Hi all,
I measured 5.8G helix antenna(S11 parameter) soldered with different gounds as photoes.And I got the different results,i do not know what cause the different results,anyone can help me?
Thank you
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FvM
Joined: 22 Jan 2008
Posts: 2695
Helped: 439
Location: Bochum, Germany
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| 28 Aug 2008 11:09 Why i got the test different S11 with different ground? |
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At 5.8 GHz, your feeding cable to PCB interface can be expected to have already a considerable reflection coefficient. It can't be identical for the three cases.
The cable position also affects the antenna impedance to some extent.
Generally, the effects could be better understood from a S11 frequency sweep, it would reveal e. g. resonances.
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John_li
Joined: 06 Aug 2005
Posts: 188
Helped: 5
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| 28 Aug 2008 15:47 Why i got the test different S11 with different ground? |
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| Thank you for reply.And any criteria to obey?and how to select the correct point ?Any theoretics to explain the differnce?
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