Trying to figure an antenna for the Si4012 RF chip. Page 26 of https://www.silabs.com/documents/public/application-notes/AN639.pdf talks about feeding the two sides of the loop antenna through two pull-up inductors (LP and LM) which it fails to provide any values for.
There is also a Word document named Panic Button Differential Loop(Printed) Along the PCBCircumference in the 434 MHz Differential Antenna Matrix (WES0042-01) whose link I can not find anymore that presents a diagram figuring the same two inductors with "tbd" values. And they never got discussed.
Lastly, I have found this document: https://www.silabs.com/documents/public/application-notes/AN436.pdf that on page 3 (as well as throughout the file) gives a diagram and some values for a pull-up inductor
Lchoke that appears to have the same purpose as the one I am asking about.
Thing is this one is for a single ended antenna while my design comprises a differential antenna. Would it be safe to take out the value from this pdf and use it on my design ? And another detail - I suppose THT inductors (as well as caps / resistors) are out of question on this side of the PCB and 434 MHz, correct ?
I still don't get how to size the RF choke. In the https://www.silabs.com/documents/public/application-notes/AN436.pdf they ate giving the example of 315 MHz. |Z_load| here is around 56 ohm and the recommended inductance for the choke is 270 - 390 nH, thus making for an impedance |Z_choke| of 534 - 771 ohm, roughly tenfold compared to Z_load.
In my design, however, |Z_load| is somewhere between 500 and 600 ohm (434 MHz differential antenna). Wouldn't it be required to pick an inductor having its impedance in the 5k - 6k ohm interval in order to actually be effective at blocking the fundamental + first few armonics ?