hilbert.h

#pragma once
 
#include <dsplib/delay.h>
#include <dsplib/fir.h>
 
namespace dsplib {
 
// calculation of the analytical signal using DFT
arr_cmplx hilbert(span_real x);
 
// uses an n-point FFT
arr_cmplx hilbert(span_real x, int n);
 
class HilbertFilter
{
public:
    //default bandpass filter IR
    //flen - FIR filter length
    //tw - transition bandwidth
    explicit HilbertFilter(int flen = 51, real_t tw = 0.01);
 
    explicit HilbertFilter(span_real h);
 
    //main processing
    arr_cmplx process(span_real s);
 
    //impulse response
    [[nodiscard]] span_real impz() const;
 
    arr_cmplx operator()(span_real x) {
        return this->process(x);
    }
 
    // Design complex Hilbert FIR (Window Method)
    // see: https://www.dsprelated.com/freebooks/sasp/Filtering_Windowing_Ideal_Hilbert_Transform.html
    // flen - FIR filter length
    // fs - sample rate (Hz)
    // f1 - lower pass-band limit = transition bandwidth (Hz)
    static arr_cmplx design_fir(int flen, real_t fs, real_t f1);
 
private:
    FirFilter<real_t> _fir;   
    DelayReal _d;             
};
 
}   // namespace dsplib