113 lines
2.9 KiB
Fortran
113 lines
2.9 KiB
Fortran
|
subroutine decode4(dat,npts,dtx,nfreq,flip,mode4,ndepth,neme,minw, &
|
||
|
|
mycall,hiscall,hisgrid,decoded,nfano,deepbest,qbest,ichbest)
|
||
|
|
|
||
|
|
! Decodes JT4 data, assuming that DT and DF have already been determined.
|
||
|
|
! Input dat(npts) has already been downsampled by 2: rate = 11025/2.
|
||
|
|
! ### NB: this initial downsampling should be removed in WSJT-X, since
|
||
|
|
! it restricts the useful bandwidth to < 2.7 kHz.
|
||
|
|
|
||
|
|
use jt4
|
||
|
|
real dat(npts) !Raw data
|
||
|
|
character decoded*22,deepmsg*22,deepbest*22
|
||
|
|
character*12 mycall,hiscall
|
||
|
|
character*6 hisgrid
|
||
|
|
real*8 dt,df,phi,f0,dphi,twopi,phi1,dphi1
|
||
|
|
complex*16 cz,cz1,c0,c1
|
||
|
|
real*4 sym(207)
|
||
|
|
|
||
|
|
twopi=8*atan(1.d0)
|
||
|
|
dt=2.d0/11025 !Sample interval (2x downsampled data)
|
||
|
|
df=11025.d0/2520.d0 !Tone separation for JT4A mode
|
||
|
|
nsym=206
|
||
|
|
amp=15.0
|
||
|
|
istart=nint((dtx+0.8)/dt) !Start index for synced FFTs
|
||
|
|
if(istart.lt.0) istart=0
|
||
|
|
nchips=0
|
||
|
|
qbest=0.
|
||
|
|
qtop=0.
|
||
|
|
deepmsg=' '
|
||
|
|
ichbest=-1
|
||
|
|
c0=0.
|
||
|
|
k=istart
|
||
|
|
phi=0.d0
|
||
|
|
phi1=0.d0
|
||
|
|
|
||
|
|
ich1=minw+1
|
||
|
|
do ich=1,7
|
||
|
|
if(nch(ich).le.mode4) ich2=ich
|
||
|
|
enddo
|
||
|
|
|
||
|
|
do ich=ich1,ich2
|
||
|
|
nchips=min(nch(ich),70)
|
||
|
|
nspchip=1260/nchips
|
||
|
|
k=istart
|
||
|
|
phi=0.d0
|
||
|
|
phi1=0.d0
|
||
|
|
fac2=1.e-8 * sqrt(float(mode4))
|
||
|
|
do j=1,nsym+1
|
||
|
|
if(flip.gt.0.0) then
|
||
|
|
f0=nfreq + (npr(j))*mode4*df
|
||
|
|
f1=nfreq + (2+npr(j))*mode4*df
|
||
|
|
else
|
||
|
|
f0=nfreq + (1-npr(j))*mode4*df
|
||
|
|
f1=nfreq + (3-npr(j))*mode4*df
|
||
|
|
endif
|
||
|
|
dphi=twopi*dt*f0
|
||
|
|
dphi1=twopi*dt*f1
|
||
|
|
sq0=0.
|
||
|
|
sq1=0.
|
||
|
|
do nc=1,nchips
|
||
|
|
phi=0.d0
|
||
|
|
phi1=0.d0
|
||
|
|
c0=0.
|
||
|
|
c1=0.
|
||
|
|
do i=1,nspchip
|
||
|
|
k=k+1
|
||
|
|
phi=phi+dphi
|
||
|
|
phi1=phi1+dphi1
|
||
|
|
cz=dcmplx(cos(phi),-sin(phi))
|
||
|
|
cz1=dcmplx(cos(phi1),-sin(phi1))
|
||
|
|
if(k.le.npts) then
|
||
|
|
c0=c0 + dat(k)*cz
|
||
|
|
c1=c1 + dat(k)*cz1
|
||
|
|
endif
|
||
|
|
enddo
|
||
|
|
sq0=sq0 + real(c0)**2 + aimag(c0)**2
|
||
|
|
sq1=sq1 + real(c1)**2 + aimag(c1)**2
|
||
|
|
enddo
|
||
|
|
sq0=fac2*sq0
|
||
|
|
sq1=fac2*sq1
|
||
|
|
rsym=amp*(sq1-sq0)
|
||
|
|
if(j.ge.1) then
|
||
|
|
rsymbol(j,ich)=rsym
|
||
|
|
sym(j)=rsym
|
||
|
|
endif
|
||
|
|
enddo
|
||
|
|
|
||
|
|
call extract4(sym,ncount,decoded) !Do the convolutional decode
|
||
|
|
nfano=0
|
||
|
|
if(ncount.ge.0) then
|
||
|
|
nfano=1
|
||
|
|
ichbest=ich
|
||
|
|
exit
|
||
|
|
endif
|
||
|
|
|
||
|
|
qual=0. !Now try deep search
|
||
|
|
! if(ndepth.ge.1) then
|
||
|
|
if(iand(ndepth,32).eq.32) then
|
||
|
|
call deep4(sym(2),neme,flip,mycall,hiscall,hisgrid,deepmsg,qual)
|
||
|
|
if(qual.gt.qbest) then
|
||
|
|
qbest=qual
|
||
|
|
deepbest=deepmsg
|
||
|
|
ichbest=ich
|
||
|
|
endif
|
||
|
|
endif
|
||
|
|
enddo
|
||
|
|
if(qbest.gt.qtop) then
|
||
|
|
qtop=qbest
|
||
|
|
endif
|
||
|
|
qual=qbest
|
||
|
|
|
||
|
|
return
|
||
|
|
end subroutine decode4
|