mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2024-11-13 15:41:50 -05:00
67 lines
1.6 KiB
Fortran
67 lines
1.6 KiB
Fortran
subroutine subtractft4(dd,itone,f0,dt)
|
|
|
|
! Subtract an ft4 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 timer_module, only: timer
|
|
|
|
parameter (NMAX=21*3456,NSPS=576,NFFT=NMAX,NFILT=1400)
|
|
parameter (NFRAME=(103+2)*NSPS)
|
|
real*4 dd(NMAX), window(-NFILT/2:NFILT/2), xjunk
|
|
complex cref,camp,cfilt,cw
|
|
integer itone(103)
|
|
logical first
|
|
data first/.true./
|
|
common/heap4/cref(NFRAME),camp(NMAX),cfilt(NMAX),cw(NMAX),xjunk(NFRAME)
|
|
save first
|
|
|
|
nstart=dt*12000+1-NSPS
|
|
nsym=103
|
|
fs=12000.0
|
|
icmplx=1
|
|
bt=1.0
|
|
nss=NSPS
|
|
call gen_ft4wave(itone,nsym,nss,fs,f0,cref,xjunk,icmplx,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)-2*REAL(cfilt(i)*cref(i))
|
|
enddo
|
|
|
|
return
|
|
end subroutine subtractft4
|
|
|