sinad() function verification problems

Question

獻霆黃 2024-8-6

回答： arushi 2024-8-6

Hi, I am doing DSP with sinad() function.

I wonder :

1.How sinad() verify the "wanted signal" and how is the notch filter decided?

It seems that if I put some different 1k audio raw datas into sinad(), it has different notch bandwidth

2. sinad() use a periodogram and kaiser window with beta=38, how is this decided?

Answer 1

arushi 2024-8-6

Hi ,

The sinad() function identifies the "wanted signal" by locating the fundamental frequency component of the input signal. :

Fundamental Frequency Identification: The function first estimates the fundamental frequency of the signal. This is typically done using a Fast Fourier Transform (FFT) to find the frequency with the highest power, which is assumed to be the fundamental frequency of the signal.
Notch Filter Design: Once the fundamental frequency is identified, the function designs a notch filter to remove the fundamental frequency component from the signal. This is done to isolate the noise and distortion components.
Dynamic Notch Bandwidth: The bandwidth of the notch filter can vary depending on the characteristics of the input signal. Different signals, even if centered around the same frequency (e.g., 1 kHz), may have different spectral characteristics, which can lead to variations in the notch filter bandwidth. The notch filter is designed to effectively remove the fundamental frequency while preserving the noise and distortion components for accurate SINAD calculation.

Hope this helps.