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Replace some hardwired parameters with variables in wsprd_exp.

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git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@5625 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
This commit is contained in:
Steven Franke 2015-06-21 22:32:22 +00:00
parent 8c706f7f29
commit 4d176c846a
1 changed files with 31 additions and 22 deletions
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51
lib/wsprd/wsprd_exp.c
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@ -389,8 +389,8 @@ void subtract_signal2(double *id, double *qd, long np,
float f0, int shift0, float drift0, unsigned char* channel_symbols)
{
double dt=1.0/375.0, df=375.0/256.0;
int i, j, k, ii, nfilt=256; //nfilt must be even number.
double pi=4.*atan(1.0),twopidt;
double pi=4.*atan(1.0), twopidt, phi=0, dphi, cs;
int i, j, k, ii, nsym=162, nspersym=256, nfilt=256; //nfilt must be even number.
double refi[45000],refq[45000];
double ci[45000],cq[45000],cfi[45000],cfq[45000];
@ -401,26 +401,30 @@ void subtract_signal2(double *id, double *qd, long np,
memset(cfi,0,sizeof(double)*45000);
memset(cfq,0,sizeof(double)*45000);
double phi=0, dphi;
// double dphi, cdphi, sdphi;
twopidt=2.0*pi*dt;
// measured signal is: s(t)=a(t)*exp( j*theta(t) )
// reference is: r(t) = exp( j*phi(t) )
// complex amplitude is estimated as: c(t)=LPF[s(t)*conjugate(r(t))]
// so c(t) has phase angle theta-phi
// multiply r(t) by c(t) and subtract from s(t), i.e. s'(t)=s(t)-c(t)r(t)
/******************************************************************************
Measured signal: s(t)=a(t)*exp( j*theta(t) )
Reference is: r(t) = exp( j*phi(t) )
Complex amplitude is estimated as: c(t)=LPF[s(t)*conjugate(r(t))]
so c(t) has phase angle theta-phi
Multiply r(t) by c(t) and subtract from s(t), i.e. s'(t)=s(t)-c(t)r(t)
*******************************************************************************/
// create reference wspr signal vector, centered on f0.
for (i=0; i<162; i++) {
//
for (i=0; i<nsym; i++) {
cs=(double)channel_symbols[i];
dphi=twopidt*
(
f0 + ((float)drift0/2.0)*((float)i-81.0)/81.0
+ ((double)channel_symbols[i]-1.5)*df
f0 + ((float)drift0/2.0)*((float)i-(float)nsym/2.0)/((float)nsym/2.0)
+ (cs-1.5)*df
);
for ( j=0; j<256; j++ ) {
ii=256*i+j;
for ( j=0; j<nspersym; j++ ) {
ii=nspersym*i+j;
refi[ii]=refi[ii]+cos(phi); //cannot precompute sin/cos because dphi is changing
refq[ii]=refq[ii]+sin(phi);
phi=phi+dphi;
@ -428,9 +432,11 @@ void subtract_signal2(double *id, double *qd, long np,
}
// s(t) * conjugate(r(t))
// place signal 1 impulse response width in so that we don't have to deal
// with partial convolutions at the beginning when applying LPF.
for (i=0; i<41472; i++) {
// beginning of first symbol in reference signal is at i=0
// beginning of first symbol in received data is at shift0.
// filter transient lasts nfilt samples
// leave nfilt zeros as a pad at the beginning of the unfiltered reference signal
for (i=0; i<nsym*nspersym; i++) {
k=shift0+i;
if( (k>0) & (k<np) ) {
ci[i+nfilt] = id[k]*refi[i] + qd[k]*refq[i];
@ -457,13 +463,16 @@ void subtract_signal2(double *id, double *qd, long np,
}
}
// subtract c(t)*ref(i) here
// subtract c(t)*r(t) here
// (ci+j*cq)(refi+j*refq)=(ci*refi-cq*refq)+j(ci*refq)+cq*refi)
// beginning of first symbol in reference signal is at i=nfilt
// beginning of first symbol in received data is at shift0.
for (i=0; i<41472; i++) {
k=shift0+i;
j=i+nfilt;
if( (k>0) & (k<np) ) {
id[k]=id[k] - (cfi[i+nfilt]*refi[i]-cfq[i+nfilt]*refq[i]);
qd[k]=qd[k] - (cfi[i+nfilt]*refq[i]+cfq[i+nfilt]*refi[i]);
id[k]=id[k] - (cfi[j]*refi[i]-cfq[j]*refq[i]);
qd[k]=qd[k] - (cfi[j]*refq[i]+cfq[j]*refi[i]);
}
}
return;