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2x Interpolation on dac3484

Brian Sun
Prodigy 210 points
Other Parts Discussed in Thread: DAC3484

Hello,

   I'm having trouble accomplishing 2x interpolation on the dac3484 i created a tone and changed the dac3484.ini file for the HSDCpro and selected 2x interpolation on the DAC348x gui and the tone works fine. I then uploaded my waveform that has a small bandwidth attached to it and the waveform had a bunch of side lobes and odd looking waveforms (see attached). is there a setting i'm missing?

Thanks in advance for any advice,

Brian

  • 0
    TI__Guru* 78174 points

    Hi Brian,

    For 2x interpolation, you should only need to change the DAC3484 Configuration file to 2x interpolation and change the FPGA clock to a higher clock ratio. There is no need to change the dac3484.ini file within the HSDC PRO.

    Fullscreen DAC3484_FDAC_2xint_NCOoff_QMCoff.txt Download 
       x00	   xF184
   x01	   x0100
   x02	   x8002
   x03	   xA001
   x04	   x4DF1
   x05	   x0000
   x06	   x3400
   x07	   xFFFF
   x08	   x0000
   x09	   x8000
   x0A	   x0000
   x0B	   x0000
   x0C	   x0400
   x0D	   x0400
   x0E	   x0400
   x0F	   x0400
   x10	   x0000
   x11	   x0000
   x12	   x0000
   x13	   x0000
   x14	   x0000
   x15	   x0640
   x16	   x0000
   x17	   x0640
   x18	   x205F
   x19	   x10F0
   x1A	   x8820
   x1B	   x0800
   x1C	   x0000
   x1D	   x0000
   x1E	   x1111
   x1F	   x8882
   x20	   x2201
   x22	   x1B1B
   x23	   x001F
   x24	   x1000
   x25	   x787A
   x26	   xB6B6
   x27	   xEAA8
   x28	   x4541
   x29	   x1A1A
   x2A	   x1616
   x2B	   xAAA2
   x2C	   xC4C4
   x2D	   x0004
   x2E	   x0000
   x2F	   x0000
   x30	   x6020
   x7F	   x0001
CDCE62005 Registers
Freq:0.000000MHz
Address	Data
00		80400000
01		803C0001
02		81400002
03		C1840003
04		00040004
05		29F01A55
06		44AF0006
07		165294A7
08		20001808

    You may use the example 2x interpolation setting file on the DAC348x GUI to try out your waveform.

    Please keep in mind that the maximum input data rate for the DAC348x is 312.5MSPS per channel. With 2x interpolation, the max DAC sample rate is 625MSPS. This means that the output signal is limited to within the first Nyquist zone of DC to 312.5MHz. I see your signal is center at 500MHz or so, perhaps you are running is at 1.25GSPS with signal centered around Fs/2, and you are seeing the Nyquist image. You will definitely need to reduce your overall DAC sample rate to be compliant to DAC's specification. 

  • 0 in reply to Kang Hsia
    Prodigy 210 points

    Alright. I tried the file sent and I reverted the .ini file for HSDC pro  and I placed my waveform centered at 80MHz which put my upper limit at about 130MHz I put the signal through the dac and got a lot of non sense. I then created a 100MHz tone using HSDC pro and i ended up getting the following.   

    what am i doing wrong? i put my clock at 1250MHz and my data rate is 312.5M and my tone is at 100MHz.

    Brian

  • 0 in reply to Brian Sun
    TI__Guru* 78174 points
    Brian,

    Please elaborate the end-goal of your setup. I cannot provide feedback unless you can also help provide detail information and questions. Some snapshots in the attachments will be very helpful.
    It seems like you plan to operate the DAC3484 in 4x interpolation. If so, please load the 4x interpolation file as oppose to the 2x interpolation file that I had provided before.

    -Kang
  • 0 in reply to Kang Hsia
    Prodigy 210 points
    ok I will PM you the details and start a discussion that way

    Thanks,
    Brian