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AFE58JD48: Down-conversion

Sun Youli
Prodigy 30 points

Part Number: AFE58JD48

         Hello, I have a question about the down-conversion.

       According to the signal processing theory, when the down-conversion is disabled, we can get a real signal instead of a complex signal.

But, in the figure 106( OCTOBER 2019– REVISED DECEMBER 2019), the Q-phase always exist. When the down-conversion disabled the Q-phase become 0s. Will the Q-phase data be output? Is that correct？

         However, according to the Table 50, we can't see the Q-phase data in the frame. As I understand it, when down-conversion disabled, there will be no Q-

phase data output, even if it is 0s. Am I right?

         Looking forward to your response.

  • 0
    TI__Expert 7140 points

    Hi Sun,

    Yes, you are right the Q-phase data is replaced with 0s when DWN_CN_BYPASS is enabled as shown in the figure 106.

    However, the data compression logic for the two cases, that is with DWN_CNV_BYPASS = 0 and DWN_CNV_BYPASS = 1 are different.

     

    For down-conversion enable case, you can refer to section 10.3.7.4.3.2 Channel-compression operation with Table 26 along with subsequent examples.

    For the down-conversion disable case, please refere to 10.3.7.4.4 Operation of Channel-compression without Down-conversion with Table 43 along woth subsequent examples.

    Hence, the Q-phase data will not be placed on the compression data line and consequently it won’t be output.

    Thanks & regards,

    Abhishek

  • 0 in reply to Abhishek Vishwa1
    Prodigy 30 points

    Thanks for your reply.

    I have another question,

    In the figure Figure 146 shows SPI Write Timing Diagram to Access Demodulator Memory, how to read 112bits?

  • 0 in reply to Sun Youli
    TI__Expert 7140 points

    Hi Sun,

    In order to read the coefficients from the demodulator memory, we have provided a specific mode in which the programmed coefficients can be streamed out on the data out lines.

    The coefficient test mode allows coefficients to be streamed through the demodulator output. In this mode, the demodulator input is replaced by a sequence of one impulse and zero samples, where one impulse (that is, 4000h) is followed by 16 × M of zeros (where M is a decimation factor value). This mode is useful to check the decimation filter coefficients.

    Please refer to the section 10.3.7.4.2.1.3 Coefficient Test Mode in the device datasheet.

    If you have further questions regarding the device 58JD48, then I would recommend you to please send us a mail on support_us_afe_tx@list.ti.com since the device is NDA restricted and we would like to keep the content internal. 

    If you wish to reach out directly to me, please send me a mail on abhishek.vishwa27@ti.com. 

    Thanks & regards,

    Abhishek