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Original question:

AWR1642BOOST: Getting error: SAMPLING RATE IS NOT WITHIN [2, 37.5] Msps when I used a sampling rate of 10,000 ksps

RTOS/AWR1642BOOST: Sampling Rate of AWR1642

Samuel Miller99
Expert 1005 points
Part Number: AWR1642BOOST
Other Parts Discussed in Thread: AWR1642

Tool/software: TI-RTOS

If the maximum sampling rate of the ADC on the AWR1642 for complex data is 6.25 Msps, then this means that the sampling rate of real data is 3.125 Msps and the sampling rate of imaginary data is 3.125 Msps. Are you already taking Nyquist into account here or is the maximum frequency of the signal that can be accurately sampled half of the sampling rate for real and imaginary - 1.5625 MHz? If this is true, then how am I supposed to utilize the full 3MHz bandwidth of the ADC? 

  • 0
    TI__Expert 7215 points
    Hi,

    IF BW on AWR1642 is 5 MHz.

    If you are using Sampling rate of 6.25msps, You would get 5MHz IF Bandwidth in Complex 1x mode. In this mode, negative IF frequency(Noise) is not sampled out.

    Regards,
    Kaushal
  • 0 in reply to Kaushal Kukkar
    Expert 1005 points
    Sorry, I believe I am still a little confused. Based on the sampling rate of 6.25 msps, the real component of the signal is sampled 3.125 MHz and the imaginary component of the signal is sampled 3.125 MHz, correct? Then, given these sampling rates, shouldn't the maximum detectable frequency only be 1.5625 MHz due to Nyquist? Even if the IF BW is 5 MHz, wouldn't a 5MHz signal be too frequent to accurately sample, according to the Nyquist criterion, with a 6.25 Msps sampling rate?
  • 0 in reply to Kaushal Kukkar
    Expert 1005 points
    Please see reply below
  • 0 in reply to Samuel Miller99
    TI__Guru 58035 points
    Hello Samuel,
    When the ADC sampling rate is set to 6.25Msps each of the I and Q ADCs sample at 6.25Mhz each. So you actually get a signal of either -3.125 Mhz to +3.125Mhz in the regular complex 2X mode OR 0 - 6.25Mhz in complex 1x mode (its the same total BW but shifted).
    Accounting for filter roll off the usage BW is 5Mhz in this case.

    regards,
    Vivek