2020-09-18 15:36:27 +00:00
|
|
|
///////////////////////////////////////////////////////////////////////////////////
|
2023-11-19 05:43:20 +00:00
|
|
|
// Copyright (C) 2012 maintech GmbH, Otto-Hahn-Str. 15, 97204 Hoechberg, Germany //
|
|
|
|
|
// written by Christian Daniel //
|
|
|
|
|
// Copyright (C) 2015-2020 Edouard Griffiths, F4EXB <f4exb06@gmail.com> //
|
|
|
|
|
// Copyright (C) 2020 Jon Beniston, M7RCE <jon@beniston.com> //
|
2020-09-18 15:36:27 +00:00
|
|
|
// //
|
|
|
|
|
// This program is free software; you can redistribute it and/or modify //
|
|
|
|
|
// it under the terms of the GNU General Public License as published by //
|
|
|
|
|
// the Free Software Foundation as version 3 of the License, or //
|
|
|
|
|
// (at your option) any later version. //
|
|
|
|
|
// //
|
|
|
|
|
// This program is distributed in the hope that it will be useful, //
|
|
|
|
|
// but WITHOUT ANY WARRANTY; without even the implied warranty of //
|
|
|
|
|
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the //
|
|
|
|
|
// GNU General Public License V3 for more details. //
|
|
|
|
|
// //
|
|
|
|
|
// You should have received a copy of the GNU General Public License //
|
|
|
|
|
// along with this program. If not, see <http://www.gnu.org/licenses/>. //
|
|
|
|
|
///////////////////////////////////////////////////////////////////////////////////
|
|
|
|
|
|
|
|
|
|
#ifndef INCLUDE_DSP_FMPREEMPHASIS_H_
|
|
|
|
|
#define INCLUDE_DSP_FMPREEMPHASIS_H_
|
|
|
|
|
|
|
|
|
|
#include "dsp/dsptypes.h"
|
|
|
|
|
#include "export.h"
|
|
|
|
|
|
|
|
|
|
#define FMPREEMPHASIS_TAU_EU 50e-6f
|
|
|
|
|
#define FMPREEMPHASIS_TAU_US 75e-6f
|
|
|
|
|
|
|
|
|
|
/** FM preemphasis filter.
|
|
|
|
|
* Amplifies frequencies above ~3.2k (tau=50e-6 in EU) or ~2.1k (tau=75e-6 in US)
|
|
|
|
|
* at ~6dB per octave, and then flattens at 12k (highFreq).
|
|
|
|
|
* Frequency response:
|
|
|
|
|
* highFreq
|
|
|
|
|
* -------
|
|
|
|
|
* /
|
|
|
|
|
* /
|
|
|
|
|
* -------/
|
|
|
|
|
* 1/(2*pi*tau)
|
|
|
|
|
*/
|
|
|
|
|
class SDRBASE_API FMPreemphasis
|
|
|
|
|
{
|
|
|
|
|
public:
|
|
|
|
|
|
|
|
|
|
FMPreemphasis(int sampleRate, Real tau = FMPREEMPHASIS_TAU_EU, Real highFreq = 12000.0);
|
|
|
|
|
|
|
|
|
|
void configure(int sampleRate, Real tau = FMPREEMPHASIS_TAU_EU, Real highFreq = 12000.0);
|
|
|
|
|
|
|
|
|
|
Real filter(Real sampleIn);
|
|
|
|
|
|
|
|
|
|
private:
|
|
|
|
|
Real m_z; // Delay element
|
|
|
|
|
Real m_b0; // IIR numerator taps
|
|
|
|
|
Real m_b1;
|
|
|
|
|
Real m_a1; // IIR denominator taps
|
|
|
|
|
};
|
|
|
|
|
|
|
|
|
|
#endif /* INCLUDE_DSP_FMPREEMPHASIS_H_ */
|
