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Rf Antenna inductance&impedance

suleymancskn , 11-02-2020, 03:28 AM
Hello, I want to design an RF antenna. I am using TRF7970 IC. I want to design my own antenna. I can calculate the inductance value of the antenna. But I don't know how many ohms the antenna is impedance. Is there a need to calculate impedance for the antenna? Otherwise, I will find a balance with the capacitor and resistors determined in the Q circuit in the photo.
In summary, I can calculate the inductance for the antenna. However, I am not sure if it is necessary to calculate impedance.
I am waiting for your suggestions on the subject.
Thank you.
suleymancskn , 11-02-2020, 03:43 AM
I am based on the values entered in the TI source document. When I calculate the standard single ended 50R impedance of Altium, it is not 50 ohms. Should we use a different calculation method?
robertferanec , 11-06-2020, 03:02 AM
I am not RF expert. However I can tell, that every single software where I try to calculate impedance will give me different results. Of course, the results should be similar, but they are never exactly the same - that is the reason why I trust the numbers which are provided by the PCB manufacturer.

In your case, to route 50OHMs I would try to ask PCB manufacturer for their recommendation. If it is not possible ... then I usually go with the free Saturn PCB Toolkit calculation: https://saturnpcb.com/pcb_toolkit/

PS: I do not know how accurate is the Altium calculation. I do not trust any Altiums calculations as they just keep changing everything (including calculations). But I need to add, that when I checked Altium impedance calculations last time, they were close to what I was getting also in different software.

jebin , 12-08-2020, 10:44 AM
Hi Robert,
I agree with you. Better to get impedance details from PCB manufacture, its makes life easy.

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