In the datasheet of AD9684 , the noise density is disclosed -155 dBFS/Hz at 500 MSPS.
Is this number including 8 times aliased noise floor within 2 GHz bandwidth?
Unless otherwise noted the specifications in Table 2 reflect performance with a 1.7Vp-p full-scale differential input. Lowering your Input Signal full-scale to 1.46Vp-p might slightly degrade full-scale SNR, probably by only a fraction of a dB since the inherent ADC noise stays the same but your input signal gets smaller.
The AD9684 datasheet lists typical noise density at -153dBFS/Hz in the Features section on Page 1, and again in spec table 2 on page 5.
The noise density figure is calculated as follows:
Thermal Noise: 10log(500M/2)= 84dBFS
Round to closest integer.... -153dBFS/Hz
For additional info on how we measure and calculate the various ADC specifications presented in the datasheet please refer to our app note (AN-835)http://www.analog.com/media/en/technical-documentation/application-notes/AN-835.pdf
Thanks for the reply.
Does the SNR specification in Table 2 stay same when the full scale reduces to 1.46Vpp? I am trying to sample 1.43 GHz signal.
You can look at figure 92 of the AD9680 datasheet (page 31) to see the SNR/SFDR response. The AD9684 shares the same core with the AD9680.
Retrieving data ...