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Adjust inductance for antenna with capacitor

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F-Moura

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Hello all,

so, maybe this is a simple question, but I dont know for where start.

I have a electronic that need 47uH, 134.5kHz to work well. I only have a 49uH coil.
I read that I can use a capacitor to reduce inductance, but how calculate the value for it?

I can use impedance relation?

I´m starter with RF technology, so any help is much.


Regards.
 

your 47uH is shunting or seriesing?
Could you give the circuit SCH?
 
Hi tony,

I use Series 2000 Micro Reader by Texas Instruments.
link: https://www.ti.com/product/RI-STU-MRD2?keyMatch=RI-STU-MRD2&tisearch=Search-EN

When I said coil, I meant antenna, sorry for this.
The Microreader need a 47uH antenna to work, and I did it, but now, I need use a antenna of 49 uH, for this I want use other passive components to make 49uH work with 47uH.

<a title="antenna.png" href="http://obrazki.elektroda.pl/3828776300_1403095611.png"><img src="http://obrazki.elektroda.pl/3828776300_1403095611_thumb.jpg" alt="antenna.png" /></a>

Regards
 

I suggest to read the reader's reference manual, chapter 5.2 Adapting the Inductance Range. Oops!
 

work out the reactance of your coil at its operating frequency (Xl = 2 X PI X L X F) = Xml, repeat for the specified coil (Xsl). If you have done it correctly subtracting Xsl from Xml should give you a figure (Xtoo much). You need a capacitor whose reactance at the operating frequency equals Xtoo much and put it in series with your coil. (Xc = 1/2 X PI X F X C).
Frank
 

Hello guys,

sorry for disappearing.
Using LC ressonance formula I solved easily.

FvM, I no find the book that you talk about. Can you give the full name and author?
If someone have tips of bibliography about RF, I´m grad with suggestions.

Tnx for all.
 

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