Errors in AN5457 (RF Matching Network Design)

[tve]

I'm looking at Appending A.1.10 of AN5457 where the PA matching impedance measurements for the UFQFPN48 package @14dBm and 915Mhz are shown. I cannot match up the points 1 through 5 in figure 80 with the rows 1 through 5 in table 14 below the figure.

For example, point 5 in the chart is between the 22mA and 23mA lines but the table lists 27.38. There are 3 points above the 25mA contour in the chart but only 2 in the table. Etc.

[Imen GH]

​Hello,

I will check and get back to you.

Imen

[Hamilton DC · Accepted solution]

Hi @tve​,

You're right. It was a mistake when putting my original text in the official format.

I'll ask the tech writer to correct these errors.

FYI:

Figure 80 - The graph is correct, but the points aren't

Table 11, values are:

1 - 11.36 + j0.37

2 - 15.27 + j1.27

3 - 11.58 + j3.67

4 - 7.924 + j1.97

5 - 15.80 + j5.16

Always use the online version of this document to make sure you have the latest one.

Don't hesitate if you have other questions.

Thank you for you cooperation.

Kind regards,

Hamilton

[tve]

Thanks for the quick reply!

[Hamilton DC]

Hi Thorsten,

The AN is being modified by tech writers.

I'll let you know as soon as it's published.

Br,

Hamilton

[Hamilton DC]

FYI, the online version has been updated:

https://www.st.com/resource/en/application_note/dm00690797-rf-matching-network-design-guide-for-stm32wl-series-stmicroelectronics.pdf

[Electronica77]

Dear all,

As you know, Nucleo -WL55JC1 activates both Hi and Lo Power modes for Tx. I reviewed the matching network for both Hi and Lo Power P.A outputs and filtering and matching elements values(capacitors & inductors) are not associated with calculating formulas given in AN5457. Therefore, I do not know what is the approximate P.A output impedance determining the specific matching network.

What is the maximum attenuation that would be inserted from the filtering/matching network between P.A output and antenna socket when this circuit resonates at 868MHz?

For my business case, we want to provide an average TX power output of 17 dBm before the antenna. So, if I attach a helical antenna(50Ohms) with its gain of 3dBi, the accumulative total radiated power will be 20 dBi(EiRP). Because of range of P.A TX power in Hi mode varies from 15dBm up to 22 dBm, I will centralize(maximum resonance) the TX power at 17dBm@868MHz and manage low losses mismatching as much as possible for down side and up side TX power around 17dBm.

I am a little bit confused about how to calculate the elements(capacitors&inductors) for matching/filtering network following AN5457 document.

Best Regards,

Stavros