113 lines
3.0 KiB
Fortran
113 lines
3.0 KiB
Fortran
|
subroutine subtract65(dd,npts,f0,dt)
|
||
|
|
|
||
|
|
! Subtract a jt65 signal
|
||
|
|
!
|
||
|
|
! Measured signal : dd(t) = a(t)cos(2*pi*f0*t+theta(t))
|
||
|
|
! Reference signal : cref(t) = exp( j*(2*pi*f0*t+phi(t)) )
|
||
|
|
! Complex amp : cfilt(t) = LPF[ dd(t)*CONJG(cref(t)) ]
|
||
|
|
! Subtract : dd(t) = dd(t) - 2*REAL{cref*cfilt}
|
||
|
|
|
||
|
|
use packjt
|
||
|
|
use timer_module, only: timer
|
||
|
|
|
||
|
|
integer correct(63)
|
||
|
|
parameter (NMAX=60*12000) !Samples per 60 s
|
||
|
|
parameter (NFILT=1600)
|
||
|
|
real*4 dd(NMAX), window(-NFILT/2:NFILT/2)
|
||
|
|
complex cref,camp,cfilt,cw
|
||
|
|
integer nprc(126)
|
||
|
|
real*8 dphi,phi
|
||
|
|
logical first
|
||
|
|
data nprc/ &
|
||
|
|
1,0,0,1,1,0,0,0,1,1,1,1,1,1,0,1,0,1,0,0, &
|
||
|
|
0,1,0,1,1,0,0,1,0,0,0,1,1,1,0,0,1,1,1,1, &
|
||
|
|
0,1,1,0,1,1,1,1,0,0,0,1,1,0,1,0,1,0,1,1, &
|
||
|
|
0,0,1,1,0,1,0,1,0,1,0,0,1,0,0,0,0,0,0,1, &
|
||
|
|
1,0,0,0,0,0,0,0,1,1,0,1,0,0,1,0,1,1,0,1, &
|
||
|
|
0,1,0,1,0,0,1,1,0,0,1,0,0,1,0,0,0,0,1,1, &
|
||
|
|
1,1,1,1,1,1/
|
||
|
|
data first/.true./
|
||
|
|
common/chansyms65/correct
|
||
|
|
common/heap1/cref(NMAX),camp(NMAX),cfilt(NMAX),cw(NMAX)
|
||
|
|
save first
|
||
|
|
|
||
|
|
pi=4.0*atan(1.0)
|
||
|
|
|
||
|
|
! Symbol duration is 4096/11025 s.
|
||
|
|
! Sample rate is 12000/s, so 12000*(4096/11025)=4458.23 samples/symbol.
|
||
|
|
! For now, call it 4458 samples/symbol. Over the message duration, we'll be off
|
||
|
|
! by about (4458.23-4458)*126=28.98 samples; 29 samples, or 0.7% of 1 symbol.
|
||
|
|
! Could eliminate accumulated error by injecting one extra sample every
|
||
|
|
! 5 or so symbols... Maybe try this later.
|
||
|
|
|
||
|
|
nstart=dt*12000+1;
|
||
|
|
nsym=126
|
||
|
|
ns=4458
|
||
|
|
nref=nsym*ns
|
||
|
|
nend=nstart+nref-1
|
||
|
|
phi=0.0
|
||
|
|
iref=1
|
||
|
|
ind=1
|
||
|
|
isym=1
|
||
|
|
call timer('subtr_1 ',0)
|
||
|
|
do k=1,nsym
|
||
|
|
if( nprc(k) .eq. 1 ) then
|
||
|
|
omega=2*pi*f0
|
||
|
|
else
|
||
|
|
omega=2*pi*(f0+2.6917*(correct(isym)+2))
|
||
|
|
isym=isym+1
|
||
|
|
endif
|
||
|
|
dphi=omega/12000.0
|
||
|
|
do i=1,ns
|
||
|
|
cref(ind)=cexp(cmplx(0.0,phi))
|
||
|
|
phi=modulo(phi+dphi,2*pi)
|
||
|
|
id=nstart-1+ind
|
||
|
|
if(id.ge.1) camp(ind)=dd(id)*conjg(cref(ind))
|
||
|
|
ind=ind+1
|
||
|
|
enddo
|
||
|
|
enddo
|
||
|
|
call timer('subtr_1 ',1)
|
||
|
|
|
||
|
|
call timer('subtr_2 ',0)
|
||
|
|
! Smoothing filter: do the convolution by means of FFTs. Ignore end-around
|
||
|
|
! cyclic effects for now.
|
||
|
|
|
||
|
|
nfft=564480
|
||
|
|
|
||
|
|
if(first) then
|
||
|
|
! Create and normalize the filter
|
||
|
|
sum=0.0
|
||
|
|
do j=-NFILT/2,NFILT/2
|
||
|
|
window(j)=cos(pi*j/NFILT)**2
|
||
|
|
sum=sum+window(j)
|
||
|
|
enddo
|
||
|
|
cw=0.
|
||
|
|
do i=-NFILT/2,NFILT/2
|
||
|
|
j=i+1
|
||
|
|
if(j.lt.1) j=j+nfft
|
||
|
|
cw(j)=window(i)/sum
|
||
|
|
enddo
|
||
|
|
call four2a(cw,nfft,1,-1,1)
|
||
|
|
first=.false.
|
||
|
|
endif
|
||
|
|
|
||
|
|
nz=561708
|
||
|
|
cfilt(1:nz)=camp(1:nz)
|
||
|
|
cfilt(nz+1:nfft)=0.
|
||
|
|
call four2a(cfilt,nfft,1,-1,1)
|
||
|
|
fac=1.0/float(nfft)
|
||
|
|
cfilt(1:nfft)=fac*cfilt(1:nfft)*cw(1:nfft)
|
||
|
|
call four2a(cfilt,nfft,1,1,1)
|
||
|
|
call timer('subtr_2 ',1)
|
||
|
|
|
||
|
|
! Subtract the reconstructed signal
|
||
|
|
call timer('subtr_3 ',0)
|
||
|
|
do i=1,nref
|
||
|
|
j=nstart+i-1
|
||
|
|
if(j.ge.1 .and. j.le.npts) dd(j)=dd(j)-2*REAL(cfilt(i)*cref(i))
|
||
|
|
enddo
|
||
|
|
call timer('subtr_3 ',1)
|
||
|
|
|
||
|
|
return
|
||
|
|
end subroutine subtract65
|