ADF7021 4FSK Modulation Problem

Hello,

I have a problem when trying 4FSK modulation using ADF7021, transmitted data is different with received data even though the modulation and demodulation configuration is same.

For my test, I am using 2 pair of EVAL-ADF7021DBJZ and EVAL-ADF70XXMBZ2 boards, also using ADF7021 Evaluation software. For checking the data, i am using oscilloscope and logic analyzer, and the data input is from STM32 microcontroller.

Here's my configuration.

Tx configuration:

Rx Configuration:

Here's the data monitored by oscilloscope (upper tx, lower rx)

The transmitted data is different with received data. Previously i've tried using 2FSK modulation and succeed.

please help me, maybe my configuration is wrong or something.

Regards,

Indra



image reupload
[edited by: indraak at 2:56 AM (GMT 0) on 3 Apr 2020]
  • +1
    •  Analog Employees 
    on Apr 3, 2020 3:44 AM 4 months ago

    Hi Indra,

    From the images, it looks like you haven't updated the registers. Please update the registers highlighted in green by clicking the update buttons on each register. Note that It’s important to update Register 13 when using 4FSK. Also note that the GUI is asking for the symbol rate (not the bit rate). For 4FSK, the symbol rate is half or 0.5x of the bit rate.

    Regards,

    Aldrich

  • Thanks Aldrich,

    I took the screenshot for posting image only. What registers should be updated? all the green highlighted registers? I usually use Program Register 0 to 4 button to update those registers only. 

    For the symbol rate, the input data bitrate is 8kbps, is that right?

  • 0
    •  Analog Employees 
    on Apr 3, 2020 4:36 AM 4 months ago in reply to indraak

    Hi Indra,

    Please refer to the datasheet for more info on the registers. I would suggest updating each register that highlight green when changing configurations from the GUI.

    Yes, that is correct.

    Regards,

    Aldrich

  • Hi Aldrich,

    Thank you, I've tried 4FSK modulation successfully with 8kbps and 16kbps data rate.

    However, when I've tried 32kbps data rate, i have a problem.

    The evaluation software had a problem with timeout error when I configured the receive module, I've tried it many times but the result always be the same. Here's the error screenshot

    How to solve this problem?

    Regards,

    Indra

  • 0
    •  Analog Employees 
    on Apr 6, 2020 3:34 PM 3 months ago in reply to indraak

    Hi Indra,

    Glad you were able to make it work.

    Your combination of data rate and frequency deviation with 4FSK is not possible. I would suggest you to follow the examples in the datasheet. Note that for 4FSK, the data rate used is only up to 19.6 kbps. To support 32.8 kbps. it is suggested to use raised cosine filtering with an alpha = 0.7, inner frequency deviation = 1.78 kHz, and the POST_DEMOD_BW = 24.6 kHz, as discussed in the datasheet, under the Specifications section.

    Regards,

    Aldrich