/* * Copyright (C) 2014 Jared Boone, ShareBrained Technology, Inc. * * This file is part of PortaPack. * * 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; either version 2, 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 for more details. * * You should have received a copy of the GNU General Public License * along with this program; see the file COPYING. If not, write to * the Free Software Foundation, Inc., 51 Franklin Street, * Boston, MA 02110-1301, USA. */ #include "channel_decimator.hpp" buffer_c16_t ChannelDecimator::execute_decimation(const buffer_c8_t& buffer) { const buffer_c16_t work_baseband_buffer { work_baseband.data(), work_baseband.size() }; const buffer_s16_t work_audio_buffer { (int16_t*)work_baseband.data(), sizeof(work_baseband) / sizeof(int16_t) }; /* 3.072MHz complex<int8_t>[2048], [-128, 127] * -> Shift by -fs/4 * -> 3rd order CIC: -0.1dB @ 0.028fs, -1dB @ 0.088fs, -60dB @ 0.468fs * -0.1dB @ 86kHz, -1dB @ 270kHz, -60dB @ 1.44MHz * -> gain of 256 * -> decimation by 2 * -> 1.544MHz complex<int16_t>[1024], [-32768, 32512] */ auto stage_0_out = execute_stage_0(buffer, work_baseband_buffer); if( decimation_factor == DecimationFactor::By2 ) { return stage_0_out; } /* 1.536MHz complex<int16_t>[1024], [-32768, 32512] * -> 3rd order CIC: -0.1dB @ 0.028fs, -1dB @ 0.088fs, -60dB @ 0.468fs * -0.1dB @ 43kHz, -1dB @ 136kHz, -60dB @ 723kHz * -> gain of 1 * -> decimation by 2 * -> 768kHz complex<int16_t>[512], [-8192, 8128] */ auto cic_1_out = cic_1.execute(stage_0_out, work_baseband_buffer); if( decimation_factor == DecimationFactor::By4 ) { return cic_1_out; } /* 768kHz complex<int16_t>[512], [-32768, 32512] * -> 3rd order CIC decimation by 2, gain of 1 * -> 384kHz complex<int16_t>[256], [-32768, 32512] */ auto cic_2_out = cic_2.execute(cic_1_out, work_baseband_buffer); if( decimation_factor == DecimationFactor::By8 ) { return cic_2_out; } /* 384kHz complex<int16_t>[256], [-32768, 32512] * -> 3rd order CIC decimation by 2, gain of 1 * -> 192kHz complex<int16_t>[128], [-32768, 32512] */ auto cic_3_out = cic_3.execute(cic_2_out, work_baseband_buffer); if( decimation_factor == DecimationFactor::By16 ) { return cic_3_out; } /* 192kHz complex<int16_t>[128], [-32768, 32512] * -> 3rd order CIC decimation by 2, gain of 1 * -> 96kHz complex<int16_t>[64], [-32768, 32512] */ auto cic_4_out = cic_4.execute(cic_3_out, work_baseband_buffer); return cic_4_out; } buffer_c16_t ChannelDecimator::execute_stage_0( const buffer_c8_t& buffer, const buffer_c16_t& work_baseband_buffer ) { if( fs_over_4_downconvert ) { return translate.execute(buffer, work_baseband_buffer); } else { return cic_0.execute(buffer, work_baseband_buffer); } }