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IF sampling with wide channel bandwidth

Sindbad
Prodigy 250 points
Other Parts Discussed in Thread: ADS6143, ADS6142, ADS6144

Hi,

Could somebody answer my question, please. Is there any way to digitize a signal with the bandwidth 10 MHz (single channel) directly at IF, which is 70 MHz for further processing in DSP. I consider that for the proper processing in DSP (I need to find the convolution) the sampling rate should be at least 10 times higher than the highest frequency in the signal spectrum, which is 70+10/5 = 75 MHz. But sampling rate as high as 750 MHz is a problem. Is the down conversion to 0-10 MHz the only way to solve the problem?

Thank you in advance.

  • 0
    TI__Intellectual 1960 points

    Sindbad,

    It is very common to sample only 10MHz of BW at 70MHz of BW.  Recommendation is a sample rate that puts this near the middle of a nyquist band for symmetrical anti-alias analog fitering design.  I suggest a clock rate near 40MSPS, 56MSPS or 93MSPS.  The higher the rate, the more room you will have for an easier anti-alias filter.  The lower rate will be cheaper and lower power for the ADC.  You will have to discuss your DSP requirements with the DSP support team.  I am not knowledgeable as to what you require there.  But the ADC needed for this bandwidth and IF should be covered by one of these 3 rates (or near these rates).  I suggest looking at ADS6142/6122 up to 65MSPS, ADS6143/6123 up to 80MSPS or ADS6144/6124 up to 105MSPS (all pincompatible).  These ADCs have the option of CMOS or DDR LVDS output.  I suspect the CMOS will be required for direct connection to the DSP.  (look for the uPP - universal parallel port on TI DSPs).  The uPP may be limited to 80MSPS but please confirm that with DSP team.

    Philip Pratt

  • 0 in reply to Philip Pratt
    Prodigy 250 points

    Philip,

    Thank you very much for your response with so much details and references! This will definitely help.

    Sindbad