mirror of
https://github.com/f4exb/sdrangel.git
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116 lines
2.7 KiB
C++
116 lines
2.7 KiB
C++
/*
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* Filters from Fldigi.
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*/
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#ifndef _FFTFILT_H
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#define _FFTFILT_H
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#include <complex>
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#include "gfft.h"
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#include "export.h"
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#undef M_PI
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#define M_PI 3.14159265358979323846
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//----------------------------------------------------------------------
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class SDRBASE_API fftfilt {
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enum {NONE, BLACKMAN, HAMMING, HANNING};
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public:
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typedef std::complex<float> cmplx;
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fftfilt(float f1, float f2, int len);
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fftfilt(float f2, int len);
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~fftfilt();
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// f1 < f2 ==> bandpass
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// f1 > f2 ==> band reject
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void create_filter(float f1, float f2);
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void create_dsb_filter(float f2);
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void create_asym_filter(float fopp, float fin); //!< two different filters for in band and opposite band
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void create_rrc_filter(float fb, float a); //!< root raised cosine. fb is half the band pass
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int noFilt(const cmplx& in, cmplx **out);
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int runFilt(const cmplx& in, cmplx **out);
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int runSSB(const cmplx& in, cmplx **out, bool usb, bool getDC = true);
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int runDSB(const cmplx& in, cmplx **out, bool getDC = true);
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int runAsym(const cmplx & in, cmplx **out, bool usb); //!< Asymmetrical fitering can be used for vestigial sideband
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protected:
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int flen;
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int flen2;
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g_fft<float> *fft;
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cmplx *filter;
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cmplx *filterOpp;
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cmplx *data;
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cmplx *ovlbuf;
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cmplx *output;
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int inptr;
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int pass;
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int window;
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inline float fsinc(float fc, int i, int len)
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{
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int len2 = len/2;
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return (i == len2) ? 2.0 * fc:
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sin(2 * M_PI * fc * (i - len2)) / (M_PI * (i - len2));
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}
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inline float _blackman(int i, int len)
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{
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return (0.42 -
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0.50 * cos(2.0 * M_PI * i / len) +
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0.08 * cos(4.0 * M_PI * i / len));
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}
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/** RRC function in the frequency domain. Zero frequency is on the sides with first half in positive frequencies
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* and second half in negative frequencies */
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inline cmplx frrc(float fb, float a, int i, int len)
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{
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float x = i/(float)len; // normalize to [0..1]
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x = 0.5-fabs(x-0.5); // apply symmetry: now both halves overlap near 0
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float tr = fb*a; // half the transition zone
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if (x < fb-tr)
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{
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return 1.0; // in band
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}
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else if (x < fb+tr) // transition
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{
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float y = ((x-(fb-tr)) / (2.0*tr))*M_PI;
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return (cos(y) + 1.0f)/2.0f;
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}
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else
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{
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return 0.0; // out of band
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}
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}
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void init_filter();
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void init_dsb_filter();
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};
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/* Sliding FFT filter from Fldigi */
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class SDRBASE_API sfft {
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#define K1 0.99999
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public:
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typedef std::complex<float> cmplx;
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sfft(int len);
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~sfft();
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void run(const cmplx& input);
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void fetch(float *result);
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private:
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int fftlen;
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int first;
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int last;
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int ptr;
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struct vrot_bins_pair;
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vrot_bins_pair *vrot_bins;
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cmplx *delay;
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float k2;
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};
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#endif
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