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157 lines
5.5 KiB
C++
157 lines
5.5 KiB
C++
// Copyright 2020 Mobilinkd LLC.
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#pragma once
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#include "FirFilter.h"
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#include "PhaseEstimator.h"
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#include "DeviationError.h"
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#include "FrequencyError.h"
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#include "SymbolEvm.h"
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#include <array>
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#include <tuple>
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namespace modemm17
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{
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namespace detail
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{
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static const auto rrc_taps = std::array<float, 79>{
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-0.009265784007800534, -0.006136551625729697, -0.001125978562075172, 0.004891777252042491,
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0.01071805138282269, 0.01505751553351295, 0.01679337935001369, 0.015256245142156299,
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0.01042830577908502, 0.003031522725559901, -0.0055333532968188165, -0.013403099825723372,
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-0.018598682349642525, -0.01944761739590459, -0.015005271935951746, -0.0053887880354343935,
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0.008056525910253532, 0.022816244158307273, 0.035513467692208076, 0.04244131815783876,
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0.04025481153629372, 0.02671818654865632, 0.0013810216516704976, -0.03394615682795165,
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-0.07502635967975885, -0.11540977897637611, -0.14703962203941534, -0.16119995609538576,
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-0.14969512896336504, -0.10610329539459686, -0.026921412469634916, 0.08757875030779196,
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0.23293327870303457, 0.4006012210123992, 0.5786324696325503, 0.7528286479934068,
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0.908262741447522, 1.0309661131633199, 1.1095611856548013, 1.1366197723675815,
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1.1095611856548013, 1.0309661131633199, 0.908262741447522, 0.7528286479934068,
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0.5786324696325503, 0.4006012210123992, 0.23293327870303457, 0.08757875030779196,
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-0.026921412469634916, -0.10610329539459686, -0.14969512896336504, -0.16119995609538576,
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-0.14703962203941534, -0.11540977897637611, -0.07502635967975885, -0.03394615682795165,
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0.0013810216516704976, 0.02671818654865632, 0.04025481153629372, 0.04244131815783876,
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0.035513467692208076, 0.022816244158307273, 0.008056525910253532, -0.0053887880354343935,
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-0.015005271935951746, -0.01944761739590459, -0.018598682349642525, -0.013403099825723372,
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-0.0055333532968188165, 0.003031522725559901, 0.01042830577908502, 0.015256245142156299,
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0.01679337935001369, 0.01505751553351295, 0.01071805138282269, 0.004891777252042491,
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-0.001125978562075172, -0.006136551625729697, -0.009265784007800534
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};
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static const auto evm_b = std::array<float, 3>{0.02008337, 0.04016673, 0.02008337};
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static const auto evm_a = std::array<float, 3>{1.0, -1.56101808, 0.64135154};
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} // detail
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struct Fsk4Demod
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{
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using demod_result_t = std::tuple<double, double, int, double>;
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using result_t = std::tuple<double, double, int, double, double, double, double>;
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BaseFirFilter<std::tuple_size<decltype(detail::rrc_taps)>::value> rrc = makeFirFilter(detail::rrc_taps);
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PhaseEstimator phase = PhaseEstimator(48000, 4800);
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DeviationError<10> deviation;
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FrequencyError<32> frequency;
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SymbolEvm<std::tuple_size<decltype(detail::evm_b)>::value> symbol_evm = makeSymbolEvm(makeIirFilter(detail::evm_b, detail::evm_a));
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double sample_rate = 48000;
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double symbol_rate = 4800;
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double unlock_gain = 0.02;
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double lock_gain = 0.001;
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std::array<float, 3> samples{0};
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double t = 0;
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double dt = symbol_rate / sample_rate;
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double ideal_dt = dt;
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bool sample_now = false;
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double estimated_deviation = 1.0;
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double estimated_frequency_offset = 0.0;
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double evm_average = 0.0;
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Fsk4Demod(
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double sample_rate,
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double symbol_rate,
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double unlock_gain = 0.02,
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double lock_gain = 0.001
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) :
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sample_rate(sample_rate),
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symbol_rate(symbol_rate),
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unlock_gain(unlock_gain * symbol_rate / sample_rate),
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lock_gain(lock_gain * symbol_rate / sample_rate),
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dt(symbol_rate / sample_rate),
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ideal_dt(dt)
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{
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samples.fill(0.0);
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}
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demod_result_t demod(bool lock)
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{
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estimated_deviation = deviation(samples[1]);
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for (auto& sample : samples) sample *= estimated_deviation;
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estimated_frequency_offset = frequency(samples[1]);
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for (auto& sample : samples) sample -= estimated_frequency_offset;
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auto phase_estimate = phase(samples);
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if (samples[1] < 0) phase_estimate *= -1;
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dt = ideal_dt - (phase_estimate * (lock ? lock_gain : unlock_gain));
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t += dt;
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symbol_evm(samples[1]);
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int symbol;
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float evm;
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std::tie(symbol, evm) = symbol_evm(samples[1]);
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evm_average = symbol_evm.evm();
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samples[0] = samples[2];
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return std::make_tuple(samples[1], phase_estimate, symbol, evm);
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}
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/**
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* Process the sample. If a symbol is ready, return a tuple
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* containing the sample used, the estimated phase, the decoded
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* symbol, the EVM, the deviation error and the frequency error
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* (sample, phase, symbol, evm, ed, ef), otherwise None.
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*/
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result_t operator()(double sample, bool lock)
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{
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auto filtered_sample = rrc(sample);
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if (sample_now)
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{
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samples[2] = filtered_sample;
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sample_now = false;
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double prev_sample;
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double phase_estimate;
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int symbol;
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double evm;
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std::tie(prev_sample, phase_estimate, symbol, evm) = demod(lock);
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return std::make_tuple(
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prev_sample,
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phase_estimate,
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symbol,
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evm,
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estimated_deviation,
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estimated_frequency_offset,
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evm_average
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);
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}
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t += dt;
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if (t < 1.0)
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{
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samples[0] = filtered_sample;
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}
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else
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{
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t -= 1.0;
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samples[1] = filtered_sample;
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sample_now = true;
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}
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return result_t{0, 0, 0, 0, 0, 0, 0};
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}
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};
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} // modemm17
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