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shorting pin effect to resonant frequency of PIFA

 
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oliver
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PostPosted: Wed Sep 09, 2009 4:11 pm    Post subject: shorting pin effect to resonant frequency of PIFA Reply with quote

Dear Sir,

Would you please advise why shorting pin of PIFA if acts inductive reactance will reduce resonant frequency and if acts capacitive reactance will increase resonant frequency?

Thanks and best regards,
Oliver
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admin
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PostPosted: Wed Sep 09, 2009 7:47 pm    Post subject: Shorting Pin Reply with quote

The shorting pin acts as an inductive reactance: it can be viewed as a short circuited transmission line that is a small portion of a wavelength long. It resonates with the open circuited end (capacitive).

The shorting pin is required so that the PIFA can be a quarter wavelength long. Without it, the antenna would be a patch antenna and would have to be approximately a half-wavelength long.
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oliver
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PostPosted: Wed Sep 09, 2009 11:44 pm    Post subject: Reply with quote

Hi Sir,
Thanks a lot for your prompt response!
May I conclude the effect of shorting pin to resonant frequency as below,
1. pure inductive has lower resonant frequency since longer shorted end transmission line
2. indcutive and capacitive is the original resonant frequency since mid shorted end transmission line
3. pure capacitive has higher resonant frequency since there is no shorted end transmission line (open end)

Thanks and best regards,
Oliver
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admin
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PostPosted: Thu Sep 10, 2009 4:51 am    Post subject: ? Reply with quote

Not sure what you are talking about.
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oliver
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PostPosted: Thu Sep 10, 2009 6:51 am    Post subject: Reply with quote

Sorry for confusion!

Since I'm don't quite understand why shorting pin viewed as open circuited end (capacitive) will increase resonant frequency, could you please explain more detailed?

Thanks for your patience!
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admin
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PostPosted: Fri Sep 11, 2009 4:01 am    Post subject: Reply with quote

Don't think about capacitive or inductive loading - just think of the PIFA as a quarter-wavelength structure that radiates. The shorting pin enables the antenna to radiate with only a quarter-wavelength size.

If you wanted to further reduce the resonate frequency, then you could think about capacitive loading the open circuited end.
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