CC1310: AWR Receive Front-End Simulation

Not sure what you are trying to do.
As stated in the datasheet, 44+j15 is the optimal differential impedance seen from the RF pins into the balun and filter. S-parameters are only valid for small signal. When in Tx, s-parameters are not valid since the voltage swings are large. The impedance is a tradeoff between what the PA want to see and what the LNA want to see. Having a low S22 would potentially make sense if you looked at a perfect match for a LNA but not for LNA + PA.

But: 0850BM14E0016 provides the wanted impedance and provide a 50 ohm interface on the other side. The IPC contains balun + filter and you can connect an antenna to the output and pass regulations (www.ti.com/.../swra524a.pdf)

If you want to design more filtering, simulate single ended from a 50 ohm point since the IPC has a 50 ohm port. Why do you plan to add a bandpass filter?

Hello,

Thank you for the response. I believe that I am evaluating small-signal, as I am looking at the RX bypass chain (see below). The AWR model that I made is basically everything in blue.

You will notice that I estimate the insertion loss of the RF switches to be around 0.25 dB in the model. Also, I convert the RF_N/RF_P differential combination to single-ended using AWRs MMCONV. At port 2, I am looking for the 44 + j15 impedance. Port 1, where the antenna is, is set to 50 ohm.

Based on the fact that the 44 + j15 impedance is optimized for both the internal LNA and PA of the CC1310, it now makes sense that S22 is not as good. I guess I shouldn't worry about it, as the IPC is matched properly. Instead, I have now set port 2 to 50 ohms prior to the balun. Attached are the updated schematic and plot, which both look just fine.

Since the IPC already contains a filter, do you think I should get rid of the bandpass filter in the bypass chain? Maybe even the external LNA?

6012.RX_Chain_Bypass_SCH.pdf

8640.RX_Chain_Bypass_PLT.pdf

Thanks for the app note.

There are a couple reasons I am not using a FEM. I am a university student and would like to acquire more RF experience, so research, impedance matching, and simulation are all valuable skills to know. From a functional standpoint, the LNA I selected has much higher gain and low NF compared to most FEMs, and my PA can go up to 30 dBm (the FCC limit). With the bypass path I can turn off the LNA and PA to save power, and also avoid the low PA efficiency at reduced input power.

Ok, makes sense.