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# [SOLVED]125 Khz Coil antenna design

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#### guytoub

##### Full Member level 2
Hello,
I want to built a 125khz coil antenna but i don't know how to calculate it.
do someone have any idea please?
i want to simulate i in CST

Thanks

125 kHz has become a frequency often used for RFID. Ordinarily a long wire suspended outdoors is recommended to pick up radio broadcasts at a distance.
If you're interested in RFID system, the link below relates to the same question as yours.

It states: "LF RFID is primarily near field inductive power transfer."
Which is saying electromagnetic waves are not a chief ingredient.

The discussion advises trial and error.

I want to built a 125khz coil antenna but i don't know how to calculate it.
Which purpose, e.g. RFID reader, RFID tag, radio receiver, proximity switch, wireless energy transmission?

Good morning,
the object of my study is for RFID tag reading.
the idea is to make a coil to capture this frequency at 125 khz but that it is small.
I want to model it on CST or ADS. I know how to make miscrostrip antennas but I have never done this kind of study at low frequency.
Should I make a representation in R,LC?
if you have examples of study and modeling even on different frequencies I am interested.

Common practice is to tune a coil & capacitor tank circuit so it resonates at your desired frequency. Since you want high Q this is achieved with a high L:C ratio.

Selection of values depends on how much current is available to operate (or drive) the LC pair.
Say it's a few mA and 0.1 V. Suitable values to start with: 16 uH, 100 nF.

Simulation shows it has a pronounced peak at 125 kHz.

Common practice is to tune a coil & capacitor tank circuit so it resonates at your desired frequency. Since you want high Q this is achieved with a high L:C ratio.

Selection of values depends on how much current is available to operate (or drive) the LC pair.
Say it's a few mA and 0.1 V. Suitable values to start with: 16 uH, 100 nF.

Simulation shows it has a pronounced peak at 125 kHz.
Thanks ,

i tried it and it works well.

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