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oliver
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Joined: 09 Sep 2009
Posts: 3

 Posted: Wed Sep 09, 2009 4:11 pm    Post subject: shorting pin effect to resonant frequency of PIFA 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

Joined: 03 Jan 2007
Posts: 210

 Posted: Wed Sep 09, 2009 7:47 pm    Post subject: Shorting Pin 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.
oliver
Antenna-Theory.com Newbie

Joined: 09 Sep 2009
Posts: 3

 Posted: Wed Sep 09, 2009 11:44 pm    Post subject: 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

Joined: 03 Jan 2007
Posts: 210

 Posted: Thu Sep 10, 2009 4:51 am    Post subject: ? Not sure what you are talking about.
oliver
Antenna-Theory.com Newbie

Joined: 09 Sep 2009
Posts: 3

 Posted: Thu Sep 10, 2009 6:51 am    Post subject: 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!

Joined: 03 Jan 2007
Posts: 210

 Posted: Fri Sep 11, 2009 4:01 am    Post subject: 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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