A few months ago, as part of my summer internship, I had performed interfacing of an ADC with FPGA (Zynq-7000). The goal was to take an analog signal from a signal generator, feed it to the ADC and present the digitized output to the FPGA. The FPGA was supposed to perform FFT on the data through an algorithm which we had written on Vivado Suite. The magnitude spectrum was successfully obtained on the waveform viewer.
We then decided to calculate the SNR and SFDR values from the data. The way I proceeded for computing SFDR was to record the value of the amplitude of fundamental frequency (which kept fluctuating, but not much) and value of the next highest peak (the highest spur) in the first Nyquist zone. The ratio of these two values would fetch me the SFDR.
The input to the ADC was a 200 kHz sinewave. To check for consistency, we performed three different sized FFTs, 2k-, 8k- and 32k- and in each trial the strength of the analog signal was varied from -60 dBm to 0 dBm (in steps of 10dBm). The value of SFDR always hovered around 23 dBc.
The value of SFDR given in the ADC datasheet is around 80 to 90 dBc, but we ended up with a value much less than that (23dBc).
I understand that the conditions under which the datasheet values were calculated were quite different from ours in terms of strength and frequency of input signal.
My major concern which I wish to clarify from the experts sitting on this platform is whether or not my procedure was proper enough, or atleast worth appreciating? Was there any major flaw(s) which I may have failed to notice in my approach? I am sure there certainly were. This concern arises because whenever I think of mentioning this project in my resume, I wonder if the examiner will ridicule me of missing anything fundamental. There wasn't a subject expert at that time who could point out if I was going on the right path.