Hi,
I'm designing a Sigma Delta Modulator and I'd like to calculate its SNR (or more accurately, SINAD).
I reviewed the spectrum assistant AN, which was quite helpful, but I still don't have answers to all my questions, as follows:
1. The input to my modulator is DC (i.e. quasi-static input). However, I can't figure how to let VIVA know that. Instead, it detects another frequency as the signal, and I can't control it. In my case, I'm using the Hann window, so there is a leakage to the first frequency bin as well (see the example below, the signal leaked to the first frequency bin @14Hz, as highlighted). Yet, the tool doesn't detect even the leakage as the signal.
2. Following the modulator, I will implement a digital filter, such that high frequency components will be eliminated. Therefore, I want the SNR calculation to integrated only until a certain frequency. How could that be accomplished?
For example, refer to the following figure
Thanks!!