mirror of https://github.com/saitohirga/WSJT-X.git
87 lines
2.5 KiB
Fortran
87 lines
2.5 KiB
Fortran
subroutine decode65a(dd,npts,newdat,nqd,f0,nflip,mode65,ntrials, &
|
|
naggressive,ndepth,mycall,hiscall,hisgrid,nexp_decode,sync2, &
|
|
a,dt,nft,qual,nhist,decoded)
|
|
|
|
! Apply AFC corrections to a candidate JT65 signal, then decode it.
|
|
|
|
use timer_module, only: timer
|
|
|
|
parameter (NMAX=60*12000) !Samples per 60 s
|
|
real*4 dd(NMAX) !92 MB: raw data from Linrad timf2
|
|
complex cx(NMAX/8) !Data at 1378.125 samples/s
|
|
complex c5x(NMAX/32) !Data at 344.53125 Hz
|
|
complex c5a(512)
|
|
real s2(66,126)
|
|
real a(5)
|
|
logical first
|
|
character decoded*22
|
|
character mycall*12,hiscall*12,hisgrid*6
|
|
data first/.true./,jjjmin/1000/,jjjmax/-1000/
|
|
data nhz0/-9999999/
|
|
save
|
|
|
|
! Mix sync tone to baseband, low-pass filter, downsample to 1378.125 Hz
|
|
call timer('filbig ',0)
|
|
call filbig(dd,npts,f0,newdat,cx,n5,sq0)
|
|
call timer('filbig ',1)
|
|
|
|
! NB: cx has sample rate 12000*77125/672000 = 1378.125 Hz
|
|
|
|
! Find best DF, drift, curvature, and DT. Start by downsampling to 344.53125 Hz
|
|
call timer('fil6521 ',0)
|
|
call fil6521(cx,n5,c5x,n6)
|
|
call timer('fil6521 ',1)
|
|
|
|
fsample=1378.125/4.
|
|
|
|
call timer('afc65b ',0)
|
|
! Best fit for DF, drift, banana-coefficient, and dt. fsample = 344.53125 S/s
|
|
dtbest=dt
|
|
call afc65b(c5x,n6,fsample,nflip,a,ccfbest,dtbest)
|
|
call timer('afc65b ',1)
|
|
|
|
sync2=3.7e-4*ccfbest/sq0 !Constant is empirical
|
|
|
|
! Apply AFC corrections to the time-domain signal
|
|
! Now we are back to using the 1378.125 Hz sample rate, enough to
|
|
! accommodate the full JT65C bandwidth.
|
|
a(3)=0
|
|
call timer('twkfreq ',0)
|
|
call twkfreq65(cx,n5,a)
|
|
call timer('twkfreq ',1)
|
|
|
|
! Compute spectrum for each symbol.
|
|
nsym=126
|
|
nfft=512
|
|
j=int(dtbest*1378.125)
|
|
|
|
c5a=cmplx(0.0,0.0)
|
|
call timer('sh_ffts ',0)
|
|
do k=1,nsym
|
|
do i=1,nfft
|
|
j=j+1
|
|
if(j.ge.1 .and. j.le.NMAX/8) then
|
|
c5a(i)=cx(j)
|
|
else
|
|
c5a(i)=0.
|
|
endif
|
|
enddo
|
|
call four2a(c5a,nfft,1,1,1)
|
|
do i=1,66
|
|
jj=i
|
|
if(mode65.eq.2) jj=2*i-1
|
|
if(mode65.eq.4) jj=4*i-3
|
|
s2(i,k)=real(c5a(jj))**2 + aimag(c5a(jj))**2
|
|
enddo
|
|
enddo
|
|
call timer('sh_ffts ',1)
|
|
|
|
call timer('dec65b ',0)
|
|
call decode65b(s2,nflip,mode65,ntrials,naggressive,ndepth, &
|
|
mycall,hiscall,hisgrid,nexp_decode,nqd,nft,qual,nhist,decoded)
|
|
dt=dtbest !return new, improved estimate of dt
|
|
call timer('dec65b ',1)
|
|
|
|
return
|
|
end subroutine decode65a
|