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Working RRC filter design

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This commit is contained in:
ha7ilm 2017-04-30 22:23:21 +02:00
parent d1af45a588
commit bfc6f5dea0
2 changed files with 17 additions and 12 deletions
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17
csdr.c
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@ -3039,22 +3039,26 @@ int main(int argc, char *argv[])
{
if(argc<=2) return badsyntax("required parameter <matched_filter_type> is missing.");
matched_filter_type_t type = matched_filter_get_type_from_string(argv[2]);
int samples_per_symbol = 0;
int samples_per_symbol = 0;
if(argc<=3) return badsyntax("required parameter <samples_per_symbol> is missing.");
sscanf(argv[3],"%d",&samples_per_symbol);
int num_taps = 0;
if(argc<=4 && type!=MATCHED_FILTER_COSINE)
return badsyntax("required parameter <num_taps> is missing.");
if(type!=MATCHED_FILTER_COSINE)
{
if(argc<=4) return badsyntax("required parameter <num_taps> is missing.");
sscanf(argv[4],"%d",&num_taps);
}
else num_taps = (2*samples_per_symbol)+1;
float beta = 0;
if(argc<=5 && type==MATCHED_FILTER_RRC)
return badsyntax("required parameter <beta> is missing.");
if(type==MATCHED_FILTER_RRC)
{
if(argc<=5) return badsyntax("required parameter <beta> is missing.");
sscanf(argv[5],"%f",&beta);
}
if(type==MATCHED_FILTER_COSINE) num_taps = (2*samples_per_symbol)+1;
float* taps = (float*)malloc(sizeof(float)*num_taps);
switch(type)
{
@ -3065,6 +3069,7 @@ int main(int argc, char *argv[])
firdes_cosine_f(taps, num_taps, samples_per_symbol);
break;
}
//fprintf(stderr, "beta = %f, num_taps = %d, samples_per_symbol = %d\n", beta, num_taps, samples_per_symbol);
if(!sendbufsize(initialize_buffers())) return -2;

8
libcsdr.c
View file

@ -2371,13 +2371,13 @@ int firdes_rrc_f(float* taps, int taps_length, int samples_per_symbol, float bet
{
//needs an odd taps_length
int middle_i=taps_length/2;
taps[middle_i]=(1/samples_per_symbol)*(1+beta*(4/PI-1));
for(int i=1;i<taps_length/2;i++)
taps[middle_i]=(1/(float)samples_per_symbol)*(1+beta*(4/PI-1));
for(int i=1;i<1+taps_length/2;i++)
{
if(i==samples_per_symbol/(4*beta))
taps[middle_i+i]=taps[middle_i-i]=(beta/(samples_per_symbol*sqrt(2)))*((1+(2/PI))*sin(PI/(4*beta))+(1-(2/PI)*cos(PI/(4*beta))));
taps[middle_i+i]=taps[middle_i-i]=(beta/(samples_per_symbol*sqrt(2)))*((1+(2/PI))*sin(PI/(4*beta))+(1-(2/PI))*cos(PI/(4*beta)));
else
taps[middle_i+i]=taps[middle_i-i]=(1/samples_per_symbol)*
taps[middle_i+i]=taps[middle_i-i]=(1/(float)samples_per_symbol)*
(sin(PI*(i/(float)samples_per_symbol)*(1-beta)) + 4*beta*(i/(float)samples_per_symbol)*cos(PI*(i/(float)samples_per_symbol)*(1+beta)))/
(PI*(i/(float)samples_per_symbol)*(1-powf(4*beta*(i/(float)samples_per_symbol),2)));
}