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STWLC03 wireless receiver tuning mistakes

Question asked by Christophe HARDOUIN on Feb 7, 2018

Hi,

 

I want to compute the resonant circuit formula to have the right value for C :

I use the STEVAL-ISB039V1 kit with transmitter and receiver board

First mistakes with inductive and capacitors values :

If I use the fomula for resonant frequency :

Fd = 1 / ( 2 * pi * racine ( L1 * ( 1 /( 1/C1 +1/C2 ) ) ) from STM STWLC03 datasheet, page 49/56

with the kit values : L1 is 12.3uH and C1= 304nF, C2=3.3nF

L1+C1+C2 form a serial circuit and 1 / (1/C1 + 1/C2) is a basic formula to have Ceq from 2 Capacitor in serial..

 

But Fd gives : 794 KHz !! (I use the kit's values !)

 

If I compute the transmitter Fs I have 138KHz (That's the right value I think..)

 

Do you have any idea about the mistakes ??

 

My goal is to change the Rx antenna and compute new capacitor tuning value at receiver side, but first, with kit's value I don't have the right value..

 

Thanks you for your help

Sincerely

 

Christophe

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