From c61d30a7f08492d4045ec51b695fab13abab3bfd Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Jean-Fran=C3=A7ois=20DEL=20NERO?= Date: Sun, 27 Nov 2022 11:24:45 +0100 Subject: [PATCH] RDS passband. --- .../fir_filters/FIR_RDS_Passband_Filter.c | 209 ++++++++++++++++++ .../fir_filters/FIR_RDS_Passband_Filter.h | 39 ++++ 2 files changed, 248 insertions(+) create mode 100644 src/broadcast_fm/fir_filters/FIR_RDS_Passband_Filter.c create mode 100644 src/broadcast_fm/fir_filters/FIR_RDS_Passband_Filter.h diff --git a/src/broadcast_fm/fir_filters/FIR_RDS_Passband_Filter.c b/src/broadcast_fm/fir_filters/FIR_RDS_Passband_Filter.c new file mode 100644 index 0000000..028ae9f --- /dev/null +++ b/src/broadcast_fm/fir_filters/FIR_RDS_Passband_Filter.c @@ -0,0 +1,209 @@ +#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; +} + diff --git a/src/broadcast_fm/fir_filters/FIR_RDS_Passband_Filter.h b/src/broadcast_fm/fir_filters/FIR_RDS_Passband_Filter.h new file mode 100644 index 0000000..815e20b --- /dev/null +++ b/src/broadcast_fm/fir_filters/FIR_RDS_Passband_Filter.h @@ -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