ADF7021 Transmit Signal Problem


I have a problem in transmission using ADF7021 modules, I use EVAL-ADF7021DBJZ boards.

I set up the transceiver with 2FSK RC Modulation, 24kbps data rate, 450Mhz channel frequency, 6KHz frequency deviation, etc.

Here is my detailed register configuration:

reg_0_data = 0x12B00000;
reg_1_data = 0x575011;
reg_2_data = 0x4275D0D2;
reg_3_data = 0x29903453;
reg_4_data = 0x80C6A694;
reg_5_data = 0x01915;
reg_6_data = 0x504C986;
reg_15_data = 0xE000F;

When I transmitted the data, there is an unwanted signal (like spurious) within 100MHz span, and the signal is getting more within time.

Here the picture, the signal I mentioned is marked in red.

Can you explain what is that signal? How that signal can be generated?



Parents Reply Children
  • Hi Edwinu,

    We are using this RF module for TDM/TDMA application. It must be turning the PA on and off continuously.

    Do you know how to reduce that signal?  Do you have an advice how to use the RF module for TDM/TDMA application properly?

    It also mentioned in this forum that the RF module is possible to use for TDM/TDMA application.



  • +1
    •  Analog Employees 
    on Sep 2, 2020 4:27 AM 7 months ago in reply to indraak

    Hi Indra,

    Please refer to PA Ramping of the Transmitter Section on page 26 of the datasheet to understand more about this PA splatter. 

    To answer your question whether the part can be used in TDM/TDMA, the answer is still yes. 

    Transmit spectrum and PA splatter are measured using different methods that are usually outlined in the standard. I would recommend that you refer to the standard (depends on what you're using) and verify whether the ADF7021 would meet the PA splatter limit.



  • Hi Edwinu,

    I have used PA Ramp in mode 7 (the slowest) but the PA splatter is still happened.

    Is this the only way to reduce PA splatter in this RF module?

    I will also check the standard limit.