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ADC31RF80: How to distinguish different Nyquist Zone Image

Part Number: ADC31RF80
Other Parts Discussed in Thread: TRF371135

Team.

Customer would like to use ADC31RF80 for single-ended RFin 300Mhz - 4GHz and has question how to distinguish signal > = fs/2? 

If it's not feasible, could we add solution like TRF371135 in front? They are now surveying LTC5586 as well. Here is the comparison below. The advantages of LTC is single-ended so that they can save a bulun and higher IF BW. If we can use ADC31RF80 without demodulator, that would be great. Thanks.

 

TRF371135

LTC5586

Frequency Range

1700MHz to 6000 MHz

300MHz to 6GHz

IF Bandwidth

30MHz

DC to 1GHz

RF input Type

Differential

Single-ended

Output Type

Differential

Differential

Allan

  • Allan,

    I didn't fully understand your question. The ADC analog input BW will support up to 4GHz, but will need matching. The ADC doesn't distinguish whether input is < or > FS/2; so input above the FS/2 will fold in. Are they targeting 3GPP bands with in the .3 to 4 GHz?

    Regards,
    satish.
  • Dear Satish,

    The application used ADC31RF80 scan frequency 300MHz~4GHz. The RF frequency is wideband if RF frequency 1000MHz, 2900MHz and 3045MHz into ADC31RF80, baseband has three tones. How to Identify input frequency1000MHz, 2900MHz and 3045MHz on ADC31RF80.

    Regards,
    Shuen-Jeng Lin
  • Hi,

    There's no method to identify whether the output is aliased or not after digitazation.
    One way to approach this problem is to band pass filter the input into the ADC where the pass bands are split into 3 nyq zones. e.g., If you clock the ADC at 3GHz, input into channel A can be conditioned (filtered) for the 1st nyq zone (upto 1.5G), input to channel B can be conditioned for the 2nd nyq zone (1.5-3 G) and use channel A of another ADC for the 3rd nyq zone. There's still the challenge for the transition region.

    Regards,
    satish.
  • Dear Satish,

    Do you know the solution for transition region? what's batters solution for transition bandwidth 380MHz at fs/2 and fs?

    Thanks,
    Shuen-Jeng Lin
  • Hi,
    Like I mentioned a band pass filter is one solution.
    Regards,
    satish.