LC tuning circuit for RF 868Mhz Antenna circuit.

Thread Starter

abc14

Joined Oct 15, 2017
117
Hi Guys,

I am doing a custom PCB for an RF transceiver IC operating at 868Mhz. I understand most of the concepts laid out in the data sheet, But I need some clarity on the LC tuning circuit, how the resonant frequency is calculated. LC tuning part of my schematic is attached as screenshot.

upload_2019-4-30_12-34-38.png


I think frequency is calculated as 2*pi*F= 1/sqrt(L*C). I have attached the datasheet as well.


https://www.semtech.com/uploads/documents/sx1231.pdf
 

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cariban

Joined Aug 14, 2018
69
Hi Guys,

I am doing a custom PCB for an RF transceiver IC operating at 868Mhz. I understand most of the concepts laid out in the data sheet, But I need some clarity on the LC tuning circuit, how the resonant frequency is calculated. LC tuning part of my schematic is attached as screenshot.

View attachment 176327


I think frequency is calculated as 2*pi*F= 1/sqrt(L*C). I have attached the datasheet as well.


https://www.semtech.com/uploads/documents/sx1231.pdf
They are not used as resonance purpose. Except L2 is RF choke, the rest are used for impedance matching or filtering purpose. Different working band needs different values. That is reflected in the datasheet.
 

Thread Starter

abc14

Joined Oct 15, 2017
117
They are not used as resonance purpose. Except L2 is RF choke, the rest are used for impedance matching or filtering purpose. Different working band needs different values. That is reflected in the datasheet.
Thanks for reply, Ok they acting as filters. I made a mistake in the schematic L2 wasn't connected properly.

upload_2019-4-30_13-35-59.png
 
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