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added AM demodulator with AGC

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Ahmet Inan 2019-02-08 20:21:42 +01:00
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README.md
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@ -48,6 +48,10 @@ The following [infinite impulse response](https://en.wikipedia.org/wiki/Infinite
[Frequency modulation](https://en.wikipedia.org/wiki/Frequency_modulation) [demodulation](https://en.wikipedia.org/wiki/Demodulation) with and without [atan2](https://en.wikipedia.org/wiki/Atan2).
### [amd.hh](amd.hh)
[Amplitude modulation](https://en.wikipedia.org/wiki/Amplitude_modulation) [demodulation](https://en.wikipedia.org/wiki/Demodulation) with [automatic gain control](https://en.wikipedia.org/wiki/Automatic_gain_control).
### [atan2.hh](atan2.hh)
[atan](https://en.wikipedia.org/wiki/Inverse_trigonometric_functions) and [atan2](https://en.wikipedia.org/wiki/Atan2).

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amd.hh Normal file
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@ -0,0 +1,43 @@
/*
AM Demodulation
Copyright 2019 Ahmet Inan <inan@aicodix.de>
*/
#pragma once
namespace DSP {
template <typename TYPE>
class AMD1
{
typedef TYPE complex_type;
typedef typename complex_type::value_type value_type;
value_type avg, att, dec, lo, hi, idx;
public:
AMD1() : avg(0), att(0), dec(0), lo(0.001), hi(1), idx(1)
{
}
void index(value_type modidx)
{
idx = modidx;
}
void agc(value_type attack, value_type decay, value_type low = value_type(0.001), value_type high = value_type(1))
{
att = attack;
dec = decay;
lo = low;
hi = high;
}
value_type operator()(complex_type input)
{
value_type amp = abs(input);
avg = lerp(amp < avg ? dec : att, avg, amp);
avg = min(max(avg, lo), hi);
amp /= avg;
return (amp * (value_type(1)+idx) - value_type(1)) / idx;
}
};
}