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added biquad notch filter

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This commit is contained in:
Ahmet Inan 2019-02-22 19:32:09 +01:00
commit a87ee25f66
2 changed files with 17 additions and 0 deletions
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1
README.md
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@ -39,6 +39,7 @@ The following [infinite impulse response](https://en.wikipedia.org/wiki/Infinite
* [second-order Butterworth low or high pass filter](https://en.wikipedia.org/wiki/Butterworth_filter)
* [2n-order Butterworth cascade of second-order low or high pass filters](https://en.wikipedia.org/wiki/Butterworth_filter)
* [second-order notch filter](https://en.wikipedia.org/wiki/Band-stop_filter)
### [phasor.hh](phasor.hh)

16
biquad.hh
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@ -53,6 +53,22 @@ public:
a1a0 = a1 / a0;
a2a0 = a2 / a0;
}
void notch(int n, int N, VALUE Q)
{
VALUE alpha = UnitCircle<VALUE>::sin(n, N) / (VALUE(2) * Q),
cn = UnitCircle<VALUE>::cos(n, N),
b0 = VALUE(1),
b1 = -VALUE(2) * cn,
b2 = VALUE(1),
a0 = VALUE(1) + alpha,
a1 = -VALUE(2) * cn,
a2 = VALUE(1) - alpha;
b0a0 = b0 / a0;
b1a0 = b1 / a0;
b2a0 = b2 / a0;
a1a0 = a1 / a0;
a2a0 = a2 / a0;
}
TYPE operator()(TYPE x0)
{
TYPE y0 = b0a0*x0 + b1a0*x1 + b2a0*x2