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4734790518
Simplify calculation of gate masks. Use entire symbol period to compute symbol value. Correct error sign based on symbol value.
71 lines
2.1 KiB
C++
71 lines
2.1 KiB
C++
/*
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* Copyright (C) 2016 Jared Boone, ShareBrained Technology, Inc.
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*
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* This file is part of PortaPack.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; see the file COPYING. If not, write to
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* the Free Software Foundation, Inc., 51 Franklin Street,
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* Boston, MA 02110-1301, USA.
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*/
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#ifndef __PHASE_DETECTOR_HPP__
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#define __PHASE_DETECTOR_HPP__
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#include <cstdint>
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#include <cstddef>
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#include <cmath>
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class PhaseDetectorEarlyLateGate {
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public:
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using history_t = uint32_t;
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using symbol_t = bool;
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using error_t = int;
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struct result_t {
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symbol_t symbol;
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error_t error;
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};
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constexpr PhaseDetectorEarlyLateGate(
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const size_t samples_per_symbol
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) : sample_threshold { samples_per_symbol / 2 },
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late_mask { (1UL << sample_threshold) - 1UL },
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early_mask { late_mask << sample_threshold }
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{
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}
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result_t operator()(const history_t symbol_history) const {
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static_assert(sizeof(history_t) == sizeof(unsigned long), "popcountl size mismatch");
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// history = ...0111, early
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// history = ...1110, late
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const size_t late_side = __builtin_popcountl(symbol_history & late_mask);
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const size_t early_side = __builtin_popcountl(symbol_history & early_mask);
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const size_t total_count = late_side + early_side;
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const auto lateness = static_cast<int>(late_side) - static_cast<int>(early_side);
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const symbol_t symbol = (total_count >= sample_threshold);
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const error_t error = symbol ? -lateness : lateness;
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return { symbol, error };
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}
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private:
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const size_t sample_threshold;
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const history_t late_mask;
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const history_t early_mask;
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};
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#endif/*__PHASE_DETECTOR_HPP__*/
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