71 lines
2.4 KiB
C
71 lines
2.4 KiB
C
/*
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* Licensed to the OpenAirInterface (OAI) Software Alliance under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The OpenAirInterface Software Alliance licenses this file to You under
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* the OAI Public License, Version 1.1 (the "License"); you may not use this file
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* except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.openairinterface.org/?page_id=698
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*-------------------------------------------------------------------------------
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* For more information about the OpenAirInterface (OAI) Software Alliance:
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* contact@openairinterface.org
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*/
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#include <stdint.h>
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#include <math.h>
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#include "tools_defs.h"
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#define LUT_SIN_RESOL 128
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// look-up table for the sine (cosine) function
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static uint16_t LUTSin[LUT_SIN_RESOL + 1];
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void InitSinLUT(void)
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{
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for (int i = 0; i < (LUT_SIN_RESOL + 1); i++) {
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LUTSin[i] = round(sin((M_PI * i) / (2 * LUT_SIN_RESOL)) * (1 << 14)); // Format: Q14
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}
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}
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// fast calculation of e^{i*2*pi*phase}
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// ret.r == cosinus << 14
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// ret.i == sinus << 14
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c16_t get_sin_cos(double phase)
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{
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int index;
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if (phase < 0) {
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index = (int)(-phase * 4 * LUT_SIN_RESOL + 0.5) % (4 * LUT_SIN_RESOL);
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index = 4 * LUT_SIN_RESOL - index;
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} else {
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index = (int)(phase * 4 * LUT_SIN_RESOL + 0.5) % (4 * LUT_SIN_RESOL);
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}
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c16_t ret;
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if (index < 2 * LUT_SIN_RESOL) { // check for 1st and 2nd Quadrant
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if (index < LUT_SIN_RESOL) { // 1st Quadrant
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ret.r = LUTSin[LUT_SIN_RESOL - index];
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ret.i = LUTSin[index];
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} else { // 2nd Quadrant
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ret.r = -LUTSin[index - LUT_SIN_RESOL];
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ret.i = LUTSin[2 * LUT_SIN_RESOL - index];
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}
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} else { // 3rd and 4th Quadrant
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if (index < 3 * LUT_SIN_RESOL) { // 3rd Quadrant
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ret.r = -LUTSin[3 * LUT_SIN_RESOL - index];
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ret.i = -LUTSin[index - 2 * LUT_SIN_RESOL];
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} else { // 4th Quadrant
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ret.r = LUTSin[index - 3 * LUT_SIN_RESOL];
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ret.i = -LUTSin[4 * LUT_SIN_RESOL - index];
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}
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}
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return ret;
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}
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