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# Tag Info

Accepted

### Transfer function of second order notch filter

For digital notch filters, I like to use the following form for a notch filter at DC ( $\omega$=0): $$H(z) = \frac{1+a}{2}\frac{(z-1)}{(z-a)}$$ where $a$ is a real positive number < 1. The ...
• 36.2k
Accepted

• 26.6k
Accepted

### How to test the FIR filter in C++?

The first basic test could be to use a unit impulse as an input signal and see if the output signal equals the impulse response (i.e. the filter coefficients). Another simple test signal is a unit ...
• 79.3k
Accepted

### Why Butterworth filter always starts my signal from from zero mark (amplitude)?

Filters do have a delay (a lag) since they do not act immediately on your signal. Also all samples before the time 0 are zeros, thus in general you will start from the "zero mark", as you said (just ...
• 10.4k