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DAC38RF80: 6.5Gb/s with QAM/CAP modulation on cat6a

JNV
Prodigy 80 points
Part Number: DAC38RF80
Other Parts Discussed in Thread: DAC38RF82, , ADC32RF45

Hello,

I’m trying to design a high debit transmission line on a twisted pair cat6a. I would like to transfer data at 6.5Gb/s in the best case (may be reduce to 3.2Gb/s). The twisted pair measures less than 10 meters (I do not yet know the cable cut off frequency, but I assume it will be at least 500MHz).

I saw that the ADSL (in the first versions) used CAP modulation (Carrierless Amplitude and Phase Modulation), a variant of QAM. Theoretically, it’s possible to get very large transfer data rate on a 500MHz bandwidth channel with this kind of modulation.

CAP uses FIR filters (root squared cosine filter) which must run at the DAC and ADC sample rate (here around 5Gsps). Because I’m using a FPGA limited to 200-300MHz, I must externalize these filters. I saw that several DAC offer the possibility to use built in sinc filter (examples: DAC38RF8x)

My questions:

Is there ADC offering also the possibility to use sinc filter (I only saw DDC and low pass filter)?

Did you already saw or work on an application with these kinds of problematic?

Best Regards,

JNV

  • 0
    TI__Expert 3505 points
    Hi JNV, There are a total of 12 pin for pin compatible family members in the DAC38RF80 Series. They offer options for integrated balun output or a current output and there are variations in interpolation settings. To study the differences please look under the description tab in the product folder. A table there will allow you to review all 12 products at once. My suggestion is to look at the DAC38RF82 which offers a current output and you can bypass the interpolation. Regards, Mark
  • 0 in reply to high speed guy
    TI__Expert 3505 points
    HI JNV, As additional information I am not aware of any ADC which offers the inverse sinx(x) correction. Your analysis of primarily finding DDC functionality as additional feature is correct. In some instances there are features like the NCOs available in the RF Sampling ADC32RF45 product family. Regards, Mark