AX8052F143 - How to configurate RX and TX outside AXRadioLab limits

Hello,

I’m currently designing new device to work at 900MHz, but to full fill FCC requirements, I have to set the TX parameters value to be outside AX_RadioLab interface. However, there are many registers I don’t understand, hope you guys will help me to solve this.

Firstly, because I have to expand the 6dB bandwidth to have minimum 500kHz, so I changed the TX deviation frequency to at least 115 kHz and at least I can archive it. Besides that, I also have to full fill the requirements about Power Spectral Density, for this I try to increase the bitrate to higher to try to flat the signal to reduce the peak value. At some point, it works, but the problem is that when I try to test the system with new value, the receiver device does not work (it cannot receive the message from transmitter device).

If I changed only FSKDEV => 115 kHz, both devices work.
But when I changed FSKDEV and TXRATE (to be 150 kBits/s), they do not work anymore.

I am using:

  • Modulation: FSK
  • Fxtal: 16,369 MHz
  • HDLC framming.

If you have any idea or need more information, please comment. Any help is appreciated.
Thanks!

Hi @nhut.tran, I don’t fully understand, are you modifying your PHY values in AX-RadioLAB only or you are also trying to manually change registers values via the Edit Registers (Advanced) or directly on the AX_Radio_Lab_output\config.c file?
You should be able to input all your requirements in the GUI and get a working example, but note that the AX8052F143 has an upper datarate limit of 125 kbps (as stated in the datasheet). The 115 kHz deviation is not a problem as the RX BW can be as large as 200 kHz.
For a deeper understanding on the registers you can CTRL-F through the AX5043 Programming Manual.

Hi Georgi,

Thanks for your reply.

I’ve modified both PHY values in AX-RadioLAB and via Edit Registers also, but I didn’t changed anything in config.c file.

AxRadioLab has its limits, so that I cannot go over the limits (e.g max bitrate in AX_RadioLAB is 125 kbps) . The question is about how to set Receiver parameters according to TX settings? (For example, how to set RX BW?)

Do you know what would be invoked in RX parameters? Just because I’m not an expert in this field, so it would be very help full to know all necessary in calculating and setting Radio parameters.

Thanks.

Hi @nhut.tran ,

AxRadioLab has its limits, so that I cannot go over the limits (e.g max bitrate in AX_RadioLAB is 125 kbps) .

This is a limit of the AX5043 radio, and AX-RadioLab will only allow to set what is possible. Additionally AX-RadioLab has some built-in ‘error checking’ that will highlight in red whatever field is not optimally programmed (e.g. suggesting you an optimal RX BW for the selected data-rate and AFC).

The question is about how to set Receiver parameters according to TX settings? (For example, how to set RX BW?)

RadioLab will throw an error (highlight RX BW in red) when the set RX BW is not fulfilling the simplified Carlson`s rule (from Carson bandwidth rule - Wikipedia), so if you wish to use 125 kbps signal with a 115 kHz deviation, following the
BW=2(\Delta f+DR)= 2(115kHz + 125 kHz) = 480 kHz >>200kHz
(Ax-RadioLab uses slightly different equations depending on the selected modulation. For GFSK the check would be BW < (1+1.5h) BR ).

You may still be able to get some radio communication (as some power will still fall within the RX BW), but to run at good sensitivity you should decrease your data-rate and/or modulation factor).

Do you know what would be invoked in RX parameters?

A good place to start learning more about the capabilities of our radio is via the AX-RadioLab User Manual that you can access directly in RadioLab as shown below. In addition the AX5043 Programming Manual dives deeper into details of the radio’s registers.

Hi @georgi.gorine ,

Thanks for your reply and sorry for my late.

“You may still be able to get some radio communication (as some power will still fall within the RX BW), but to run at good sensitivity you should decrease your data-rate and/or modulation factor).”

This is exactly what I want to ask more, because my receiver device still can get the radio communication from transmitter device, but I want to improve the sensitivity of the receiver device and I still don’t know how to improve it by setting RX’s registers.

And another question is about how to extend the RX BW? how to extend the RX BW to 500kHz?

I’ve read Programming Manual, but there are so many registers invoked in RX. If you know which registers are critical/main affect to receiver sensitivity/ RX BW, please help me with. Or if you have more documents about how to improve receiver of AX8052F143 sensitivity/ RX BW, please send me too.

I will read more about Programming Manual in the mean time.

Thank you.

Hi @nhut.tran ,

And another question is about how to extend the RX BW? how to extend the RX BW to 500kHz?

If you are allowed to change your protocol, reducing your modulation factor will allow you to fit within the 220kHz 3dB bandwidth of the receiver, thus increasing your sensitivity. Dropping the datarate will also allow the same benefit. Both changes can be done in Ax-RadioLab to generate the proper set of registers.

And another question is about how to extend the RX BW? how to extend the RX BW to 500kHz?

The maximum RX BW (channel filter) of our AX8052F143 is 200kHz (of 220kHz 3dB BW). This is a hardware limitation of our narrow-band AX8052F143. If you are interested in a wide-band radio check out our AX8052F151 based on the wide-band AX5051 TRX that has a 600kHz max RX BW.

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Hi @georgi.gorine,

I very appreciate your helps. Thanks a lot.