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TSW38J84EVM: Parasitic modulation of output signal when used with custom file.

Yuyi Shen
Prodigy 10 points

Part Number: TSW38J84EVM

Hello,

I'm using the TSW38J84EVM with the TSW14J56EVM to transmit BLE preambles by loading a csv into HS DC Pro, and upon reading the TSW38J84EVM output with an AD9082-FMCA-EBZ evaluation board, performing coarse frequency compensation in Matlab, and correlating the received signal with the known preamble sequence, it seems that the transmitted preambles have had some sort of parasitic phase modulation relative to the reference preamble sequence. I've checked the AD9082 receiver board and it hasn't had issues receiving this type of signal in the past, so I'm thinking there's something wrong with my configuration of the TSW37J84EVM.

I have attached the csv file I used. It's a 1 MHz BW signal centered at a 10 MHz IF, and the waveforms shown in HS DC Pro after loading it in as an external pattern file are consistent with the file contents.

I've extracted the transmitted preambles and divided them by the reference preamble sequence to find the relative phase shift in the signal space over the duration of the preambles, which is plotted below:

There seems to be a distinctive sinusoidal phase shift that consistently shows up. The two plots are from two different readouts of the AD9082 eval board, taken some hours apart.

The TSW38J84EVM is configured as described in the user guide with a 10 MHz reference to CLK_IN, and the PLL1 and PLL2 LEDs mentioned are lit. Here is a screenshot of the "Alarms and Errors" page of the TSW3XJ8X GUI. As far as I can tell the right firmware (DAC3XJ84_LMF_442) is loaded into the TSW14J56EVM.

Are there any particular alarms that stand out?

BLE.csv

  • 0
    Prodigy 10 points

    Btw, "TSW37J84EVM" is a typo. It should be "TSW38J84EVM."

  • 0
    Prodigy 10 points

    The relative phase shift between the transmitted preambles and the preamble reference sequence also varies significantly across preambles transmitted by the TSW38J84EVM:

    This is the case for using the TRF3722 and the TRF3705 (with a 2.4 GHz LO from a N5181A signal generator):

    In the case of using the TRF3705, the phase difference between preambles seems to be consistently ~90 degrees.

    The csv file I'm using only contains the IQ samples for one BLE preamble, so I think the TSW38J84EVM is looping the file over and over between preambles.

  • 0 in reply to Yuyi Shen
    TI__Guru 72329 points

    Hi, 

    the HSDC PRO can only transmit Pre-amble only once upon the clicking of the "send" button. The HSDC PRo will continuously playback the same waveform excluding pre-amble cycle after cycle. 

    If you have specific RF performance questions or JESD204 related issue, we can help support and please do feel free to list them Unfortunately, we cannot support you on your software defined radio project with modulation and demodulation. You have way too many arithmetic and cross correlation questions that need to be resolved in your university Communications Courses. This is too system specific and we cannot get into the details.

    -Kang