Adjust inductance for antenna with capacitor

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: http://www.ti.com/product/RI-STU-MRD...arch=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="../imgqa/eboard/Antenna/rf-0zf55g4nfmp.png"><img src="../imgqa/eboard/Antenna/rf-hqdmjww5feh.jpg" alt="antenna.png" /></a>

Regards

Use LC Resonsnce formula to calculate. http://en.wikipedia.org/wiki/LC_circuit

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.

http://www.ti.com/lit/pdf/scbu049