[signal] 最簡單的方式實做 FIR Low Pass FIlter using numpy

這篇文章用了一個非常淺顯易懂的方式, 描述利用 numpy 實做 FIR Low Pass Filter.
裡面提供了

1. fc: cut-off frequency 是 sampling rate 的一個比例觀念
=>
 For example, if the sampling rate is 10 kHz, then fc=0.1 will result in the frequencies above 1 kHz being removed. The central part of a sinc filter with fc=0.1 is illustrated in Figure 1.

2. 利用 window 解決無限長度的問題, 而 window 長度 N 如何計算
=>
是由 Transition Bandwidth b 決定.
N = int(np.ceil((4 / b)))
if not N % 2: N += 1  # Make sure that N is odd.

3. delay 的計算
=> delay = (N-1)/2
因此可以做 shift 的補償

https://tomroelandts.com/articles/how-to-create-a-simple-low-pass-filter

Enjoy!

by Jing.