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I am trying to design a system to sample an RF signal using a 10MSPS 12 bit ADC (ADC12010CIVYX/NOPB). During frequency planning I observed that, to get a proper sample with out aliasing the input frequency should be at 9Mhz (or 19,29,39 etc) i.e. in the second (or even) Nyquist zone. My problem is that the RF signal is at UHF (409 MHz, so it would fall in the 82 nd Nyquist zone) and I would to know if there is an upper limit for the Nyquist zone that can be safely under sampled by the ADC.

Any help is greatly appreciated.

Thanks.

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Take a look at the datasheet:

enter image description here

enter image description here

So about 100 MHz, give or take depending on how much SNR you want to give up. For 450 MHz, you probably want to buy the faster (pin compatible) version of the chip here:

https://www.ti.com/product/ADC12L066

Which lists:

enter image description here

So that would enable you to subsample 409 MHz with nearly full sensitivity.

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The concept is an old subject as microwave oscilloscopes used a pin diode to sample the signal at HF rates so that low frequency scopes could display microwave signals.

The limitation in harmonics you requested is actually a recursive notch filter with the bandwidth null equal to the inverse of the pulse sample interval with harmonics of the sampling rate. Thus, the larger the ratio of the sampling interval / S&H acquisition time, the higher the harmonic that can be achieved.

Keysight uses still uses this method in some cases in their instrumentation. They use pseudo random triggers (PRBS) to spread the spectrum of the trigger signal.

https://rfmw.em.keysight.com/DigitalPhotonics/flexdca/UG/Content/Topics/Quick%20Start/theory_sampling.htm

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