AFE7952: How to get the great sampling at 4th Nyquest??

Gordon Liu

Intellectual 825 points

Part Number: AFE7952

Hi ,

The chip suport 12GHz at RF signal but sampling is only 3Gsps.

How to get the great sampling at 4th Nyquest??

Example:

Input Signal= 11.8GHz~12GHz , What 's output EVM value at digital domain??

over 1 year ago

0 Gordon Liu over 1 year ago

Intellectual 825 points

Sorry, it's 8th Nyquest Zone.

0 Ali Syed over 1 year ago in reply to Gordon Liu

TI__Expert 4110 points

Hi,

The RF sampling is based 'band-limited' sampling of the input signal. So that if the input signal (11.8G - 12G = 200M BW), then ADC sampling at ~3GHz will not result in aliasing within the 200MHz channel BW. I will draw this out in a plot to demonstrate.

regards,

Ali

0 Gordon Liu over 1 year ago in reply to Ali Syed

Intellectual 825 points

Hi Syed,

I find out a good tool in TI; https://www.ti.com/tool/FREQ-DDC-FILTER-CALC

I set Fs=3000MHz, Interleave=1, Fc=11900MHz, BW=200MHz.

I get: Rx band=50~150MHz, HD2=100~300MHz, HD3=150~450MHz,

The HD2 have interfere the Rx band,

I guess the Rx EVM is not good Does it correct??

+1 Kang Hsia over 1 year ago in reply to Gordon Liu

TI__Guru 68534 points

Gordon,

If possible, please move Fc around such that HD2 and HD3 does not land in-band as the RX band. You may also want to consider using our HD2 correction/calibration, available on the AFE7952 to correct the HD2 to lower level to not impact the in band signal. Thank you.

-Kang

RF & microwave

RF & microwave forum

AFE7952: How to get the great sampling at 4th Nyquest??