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DATV demod: apply commit dd2d9b97025a34a1b168439d60528826b6c9ebf6 Fix RRC amplitude.

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f4exb 2020-04-21 01:22:50 +02:00
parent 9cff60f143
commit 8f46029457
1 changed files with 5 additions and 6 deletions
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11
plugins/channelrx/demoddatv/leansdr/filtergen.h
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@ -88,7 +88,7 @@ int lowpass(int order, float Fcut, T **coeffs, float gain = 1)
// https://en.wikipedia.org/wiki/Root-raised-cosine_filter // https://en.wikipedia.org/wiki/Root-raised-cosine_filter
template <typename T> template <typename T>
int root_raised_cosine(int order, float Fs, float rolloff, T **coeffs) int root_raised_cosine(int order, float Fs, float rolloff, T **coeffs, float gain=1)
{ {
float B = rolloff, pi = M_PI; float B = rolloff, pi = M_PI;
int ncoeffs = (order + 1) | 1; int ncoeffs = (order + 1) | 1;
@ -98,19 +98,18 @@ int root_raised_cosine(int order, float Fs, float rolloff, T **coeffs)
int t = i - ncoeffs / 2; int t = i - ncoeffs / 2;
float c; float c;
if (t == 0) if (t == 0)
c = sqrt(Fs) * (1 - B + 4 * B / pi); c = (1 - B + 4*B/pi);
else else
{ {
float tT = t * Fs; float tT = t * Fs;
float den = pi * tT * (1 - (4 * B * tT) * (4 * B * tT)); float den = pi * tT * (1 - (4 * B * tT) * (4 * B * tT));
if (!den) if (!den)
c = B * sqrt(Fs / 2) * ((1 + 2 / pi) * sin(pi / (4 * B)) + (1 - 2 / pi) * cos(pi / (4 * B))); c = B/sqrtf(2) * ( (1+2/pi)*sinf(pi/(4*B)) + (1-2/pi)*cosf(pi/(4*B)) );
else else
c = sqrt(Fs) * (sin(pi * tT * (1 - B)) + 4 * B * tT * cos(pi * tT * (1 + B))) / den; c = ( sinf(pi*tT*(1-B)) + 4*B*tT*cosf(pi*tT*(1+B)) ) / den;
} }
(*coeffs)[i] = c; (*coeffs)[i] = Fs * c * gain;
} }
normalize_dcgain(ncoeffs, *coeffs);
return ncoeffs; return ncoeffs;
} }