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RDS passband.

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Jean-François DEL NERO 2022-11-27 11:24:45 +01:00
parent a2c5d80f6c
commit c61d30a7f0
2 changed files with 248 additions and 0 deletions
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209
src/broadcast_fm/fir_filters/FIR_RDS_Passband_Filter.c Normal file
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#include "FIR_RDS_Passband_Filter.h"
static double filter_taps[FIR_RDS_PASSBAND_FILTER_TAP_NUM] = {
0.0011758952792351321,
0.0022825939806044066,
-0.0019570074010951343,
-0.00027851461513982113,
0.001982028200159741,
-0.0003389431241327098,
-0.0024417117605763056,
0.0016466166949177271,
0.00218694860144487,
-0.0030376302189676335,
-0.0011800497713823548,
0.004168106876686315,
-0.0005791258713967658,
-0.00458555303109236,
0.0028139691227342402,
0.003940288276590675,
-0.0050234537734311566,
-0.002119154734838742,
0.006593028363423018,
-0.0006727491736447931,
-0.00695399400792946,
0.0039020880903873115,
0.0057750793411364245,
-0.00681158899151599,
-0.003107033394127733,
0.008620882212666705,
-0.0005794133751050271,
-0.008750162638389876,
0.004479315885893972,
0.0070169617420127485,
-0.007649884221502565,
-0.003740197001726764,
0.009281335614837303,
-0.0003149505855050032,
-0.0089577356517151,
0.0041390587641292,
0.006802841753806556,
-0.006771677505037472,
-0.003472861768043537,
0.007602360659868646,
-0.00002158539801443246,
-0.0065901492892861515,
0.0026352213902105784,
0.004304698762062282,
-0.0036461187111267385,
-0.0017527583320990098,
0.0029247978193551695,
0.000045375309167217514,
-0.0010211980056331939,
8.161836662908323e-7,
-0.0009758278121958338,
0.0017878150467851178,
0.0017849398746189002,
-0.00479767892252991,
-0.000419447058223516,
0.007723187364492702,
-0.0034049324700813023,
-0.008959729595498423,
0.009016826051129821,
0.007132775033388645,
-0.014845503678668026,
-0.0016410722787915503,
0.018797163709037834,
-0.006974139283513686,
-0.01886428994137313,
0.016983931436409156,
0.013800947035325157,
-0.025799279635182262,
-0.0036593927759145765,
0.03062151969130689,
-0.00999748811830927,
-0.029253805215330695,
0.02431922013866165,
0.02083281348651543,
-0.03580207822554663,
-0.006253984979073887,
0.04117741905917765,
-0.011858329290914316,
-0.03833083360406418,
0.02966478887325469,
0.026988906545642496,
-0.04301062709660084,
-0.008948772365378355,
0.048486879453607246,
-0.012229670009599255,
-0.044344388567933726,
0.03202505232497606,
0.031024500923222363,
-0.04604032280096179,
-0.01113548747503351,
0.05109759172117753,
-0.01113548747503351,
-0.04604032280096179,
0.031024500923222363,
0.03202505232497606,
-0.044344388567933726,
-0.012229670009599255,
0.048486879453607246,
-0.008948772365378355,
-0.04301062709660084,
0.026988906545642496,
0.02966478887325469,
-0.03833083360406418,
-0.011858329290914316,
0.04117741905917765,
-0.006253984979073887,
-0.03580207822554663,
0.02083281348651543,
0.02431922013866165,
-0.029253805215330695,
-0.00999748811830927,
0.03062151969130689,
-0.0036593927759145765,
-0.025799279635182262,
0.013800947035325157,
0.016983931436409156,
-0.01886428994137313,
-0.006974139283513686,
0.018797163709037834,
-0.0016410722787915503,
-0.014845503678668026,
0.007132775033388645,
0.009016826051129821,
-0.008959729595498423,
-0.0034049324700813023,
0.007723187364492702,
-0.000419447058223516,
-0.00479767892252991,
0.0017849398746189002,
0.0017878150467851178,
-0.0009758278121958338,
8.161836662908323e-7,
-0.0010211980056331939,
0.000045375309167217514,
0.0029247978193551695,
-0.0017527583320990098,
-0.0036461187111267385,
0.004304698762062282,
0.0026352213902105784,
-0.0065901492892861515,
-0.00002158539801443246,
0.007602360659868646,
-0.003472861768043537,
-0.006771677505037472,
0.006802841753806556,
0.0041390587641292,
-0.0089577356517151,
-0.0003149505855050032,
0.009281335614837303,
-0.003740197001726764,
-0.007649884221502565,
0.0070169617420127485,
0.004479315885893972,
-0.008750162638389876,
-0.0005794133751050271,
0.008620882212666705,
-0.003107033394127733,
-0.00681158899151599,
0.0057750793411364245,
0.0039020880903873115,
-0.00695399400792946,
-0.0006727491736447931,
0.006593028363423018,
-0.002119154734838742,
-0.0050234537734311566,
0.003940288276590675,
0.0028139691227342402,
-0.00458555303109236,
-0.0005791258713967658,
0.004168106876686315,
-0.0011800497713823548,
-0.0030376302189676335,
0.00218694860144487,
0.0016466166949177271,
-0.0024417117605763056,
-0.0003389431241327098,
0.001982028200159741,
-0.00027851461513982113,
-0.0019570074010951343,
0.0022825939806044066,
0.0011758952792351321
};
void FIR_RDS_Passband_Filter_init(FIR_RDS_Passband_Filter* f) {
int i;
for(i = 0; i < FIR_RDS_PASSBAND_FILTER_TAP_NUM; ++i)
f->history[i] = 0;
f->last_index = 0;
}
void FIR_RDS_Passband_Filter_put(FIR_RDS_Passband_Filter* f, double input) {
f->history[f->last_index++] = input;
if(f->last_index == FIR_RDS_PASSBAND_FILTER_TAP_NUM)
f->last_index = 0;
}
double FIR_RDS_Passband_Filter_get(FIR_RDS_Passband_Filter* f) {
double acc = 0;
int index = f->last_index, i;
for(i = 0; i < FIR_RDS_PASSBAND_FILTER_TAP_NUM; ++i) {
index = index != 0 ? index-1 : FIR_RDS_PASSBAND_FILTER_TAP_NUM-1;
acc += f->history[index] * filter_taps[i];
};
return acc;
}

39
src/broadcast_fm/fir_filters/FIR_RDS_Passband_Filter.h Normal file
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@ -0,0 +1,39 @@
#ifndef FIR_RDS_PASSBAND_FILTER_H_
#define FIR_RDS_PASSBAND_FILTER_H_
/*
FIR filter designed with
http://t-filter.appspot.com
sampling frequency: 200000 Hz
* 0 Hz - 53500 Hz
  gain = 0
  desired attenuation = -45 dB
  actual attenuation = -47.361757711285 dB
* 55000 Hz - 59000 Hz
  gain = 1
  desired ripple = 5 dB
  actual ripple = 3.1644314706123344 dB
* 60500 Hz - 100000 Hz
  gain = 0
  desired attenuation = -45 dB
  actual attenuation = -47.320695886416395 dB
*/
#define FIR_RDS_PASSBAND_FILTER_TAP_NUM 181
typedef struct {
double history[FIR_RDS_PASSBAND_FILTER_TAP_NUM];
unsigned int last_index;
} FIR_RDS_Passband_Filter;
void FIR_RDS_Passband_Filter_init(FIR_RDS_Passband_Filter* f);
void FIR_RDS_Passband_Filter_put(FIR_RDS_Passband_Filter* f, double input);
double FIR_RDS_Passband_Filter_get(FIR_RDS_Passband_Filter* f);
#endif