mirror of
https://github.com/pavel-demin/ft8d.git
synced 2024-11-27 14:58:43 -05:00
66 lines
1.5 KiB
Fortran
66 lines
1.5 KiB
Fortran
subroutine subtractft8(dd,itone,f0,dt)
|
|
|
|
! Subtract an ft8 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}
|
|
|
|
parameter (NMAX=15*4000,NFRAME=640*79)
|
|
parameter (NFFT=NMAX,NFILT=1400)
|
|
real*4 window(-NFILT/2:NFILT/2),xjunk
|
|
complex dd(NMAX)
|
|
complex cref,camp,cfilt,cw
|
|
integer itone(79)
|
|
logical first
|
|
data first/.true./
|
|
common/heap8/cref(NFRAME),camp(NMAX),cfilt(NMAX),cw(NMAX),xjunk(NFRAME)
|
|
save first
|
|
|
|
if(f0.lt.2000.0) then
|
|
f=f0+2000.0
|
|
else
|
|
f=f0-2000.0
|
|
endif
|
|
nstart=dt*4000+1
|
|
call gen_ft8wave(itone,79,640,2.0,4000.0,f,cref,xjunk,1,NFRAME)
|
|
camp=0.
|
|
do i=1,nframe
|
|
id=nstart-1+i
|
|
if(id.ge.1.and.id.le.NMAX) camp(i)=dd(id)*conjg(cref(i))
|
|
enddo
|
|
|
|
if(first) then
|
|
! Create and normalize the filter
|
|
pi=4.0*atan(1.0)
|
|
fac=1.0/float(nfft)
|
|
sum=0.0
|
|
do j=-NFILT/2,NFILT/2
|
|
window(j)=cos(pi*j/NFILT)**2
|
|
sum=sum+window(j)
|
|
enddo
|
|
cw=0.
|
|
cw(1:NFILT+1)=window/sum
|
|
cw=cshift(cw,NFILT/2+1)
|
|
call four2a(cw,nfft,1,-1,1)
|
|
cw=cw*fac
|
|
first=.false.
|
|
endif
|
|
|
|
cfilt=0.0
|
|
cfilt(1:nframe)=camp(1:nframe)
|
|
call four2a(cfilt,nfft,1,-1,1)
|
|
cfilt(1:nfft)=cfilt(1:nfft)*cw(1:nfft)
|
|
call four2a(cfilt,nfft,1,1,1)
|
|
|
|
! Subtract the reconstructed signal
|
|
do i=1,nframe
|
|
j=nstart+i-1
|
|
if(j.ge.1 .and. j.le.NMAX) dd(j)=dd(j)-cfilt(i)*cref(i)
|
|
enddo
|
|
|
|
return
|
|
end subroutine subtractft8
|
|
|