WSJT-X/lib/qra/q65/q65_sync.f90
2021-01-06 15:48:21 +00:00

345 lines
9.5 KiB
Fortran

subroutine q65_sync(nutc,iwave,ntrperiod,mode_q65,codewords,ncw,nsps, &
nfqso,ntol,ndepth,lclearave,emedelay,xdt,f0,snr1,width,dat4,snr2,idec)
! Detect and align with the Q65 sync vector, returning time and frequency
! offsets and SNR estimate.
! Input: iwave(0:nmax-1) Raw data
! mode_q65 Tone spacing 1 2 4 8 16 (A-E)
! nsps Samples per symbol at 12000 Sa/s
! nfqso Target frequency (Hz)
! ntol Search range around nfqso (Hz)
! Output: xdt Time offset from nominal (s)
! f0 Frequency of sync tone
! snr1 Relative SNR of sync signal
use packjt77
use timer_module, only: timer
parameter (NSTEP=8) !Step size nsps/NSTEP
parameter (LN=2176*63) !LN=LL*NN; LL=64*(mode_q65+2), NN=63
parameter (PLOG_MIN=-240.0) !List decoding threshold
integer*2 iwave(0:12000*ntrperiod-1) !Raw data
integer isync(22) !Indices of sync symbols
integer itone(85)
integer codewords(63,206)
integer dat4(13)
integer ijpk(2)
logical lclearave
character*37 decoded
real, allocatable :: s1(:,:) !Symbol spectra, 1/8-symbol steps
real, allocatable :: s3(:,:) !Data-symbol energies s3(LL,63)
real, allocatable :: ccf(:,:) !CCF(freq,lag)
real, allocatable :: ccf1(:) !CCF(freq) at best lag
real, allocatable :: ccf2(:) !CCF(freq) at any lag
real sync(85) !sync vector
complex, allocatable :: c0(:) !Complex spectrum of symbol
data isync/1,9,12,13,15,22,23,26,27,33,35,38,46,50,55,60,62,66,69,74,76,85/
data sync(1)/99.0/
save sync
idec=-1
snr1=0.
dat4=0
LL=64*(2+mode_q65)
nfft=nsps
df=12000.0/nfft !Freq resolution = baud
istep=nsps/NSTEP
iz=5000.0/df !Uppermost frequency bin, at 5000 Hz
txt=85.0*nsps/12000.0
jz=(txt+1.0)*12000.0/istep !Number of quarter-symbol steps
if(nsps.ge.6912) jz=(txt+2.0)*12000.0/istep !For TR 60 s and higher
ia=ntol/df
ia2=max(ia,10*mode_q65,nint(100.0/df))
nsmo=int(0.7*mode_q65*mode_q65)
if(nsmo.lt.1) nsmo=1
allocate(s1(iz,jz))
allocate(s3(-64:LL-65,63))
allocate(c0(0:nfft-1))
allocate(ccf(-ia2:ia2,-53:214))
allocate(ccf1(-ia2:ia2))
allocate(ccf2(-ia2:ia2))
if(sync(1).eq.99.0) then !Generate the sync vector
sync=-22.0/63.0 !Sync tone OFF
do k=1,22
sync(isync(k))=1.0 !Sync tone ON
enddo
endif
fac=1/32767.0
do j=1,jz !Compute symbol spectra at step size
i1=(j-1)*istep
i2=i1+nsps-1
k=-1
do i=i1,i2,2 !Load iwave data into complex array c0, for r2c FFT
xx=iwave(i)
yy=iwave(i+1)
k=k+1
c0(k)=fac*cmplx(xx,yy)
enddo
c0(k+1:)=0.
call four2a(c0,nfft,1,-1,0) !r2c FFT
do i=1,iz
s1(i,j)=real(c0(i))**2 + aimag(c0(i))**2
enddo
! For large Doppler spreads, should we smooth the spectra here?
do i=1,nsmo
call smo121(s1(1:iz,j),iz)
enddo
enddo
i0=nint(nfqso/df) !Target QSO frequency
if(i0-64.lt.1 .or. i0-65+LL.gt.iz) go to 900
call pctile(s1(i0-64:i0-65+LL,1:jz),LL*jz,40,base)
s1=s1/base
! Apply fast AGC
s1max=20.0 !Empirical choice
do j=1,jz !### Maybe wrong way? ###
smax=maxval(s1(i0-64:i0-65+LL,j))
if(smax.gt.s1max) s1(i0-64:i0-65+LL,j)=s1(i0-64:i0-65+LL,j)*s1max/smax
enddo
dtstep=nsps/(NSTEP*12000.0) !Step size in seconds
lag1=-1.0/dtstep
lag2=1.0/dtstep + 0.9999
if(nsps.ge.3600 .and. emedelay.gt.0) lag2=4.0/dtstep + 0.9999 !Include EME
j0=0.5/dtstep
if(nsps.ge.7200) j0=1.0/dtstep !Nominal start-signal index
if(ncw.lt.1) go to 100
!######################################################################
! Try list decoding via "Deep Likelihood".
ipk=0
jpk=0
ccf_best=0.
imsg_best=-1
do imsg=1,ncw
i=1
k=0
do j=1,85
if(j.eq.isync(i)) then
i=i+1
itone(j)=-1
else
k=k+1
itone(j)=codewords(k,imsg)
endif
enddo
! Compute 2D ccf using all 85 symbols in the list message
ccf=0.
iia=200.0/df
do lag=lag1,lag2
do k=1,85
j=j0 + NSTEP*(k-1) + 1 + lag
if(j.ge.1 .and. j.le.jz) then
do i=-ia2,ia2
ii=i0+mode_q65*itone(k)+i
if(ii.ge.iia .and. ii.le.iz) ccf(i,lag)=ccf(i,lag) + s1(ii,j)
enddo
endif
enddo
enddo
ccfmax=maxval(ccf(-ia:ia,:))
if(ccfmax.gt.ccf_best) then
ccf_best=ccfmax
ijpk=maxloc(ccf(-ia:ia,:))
ipk=ijpk(1)-ia-1
jpk=ijpk(2)-53-1
f0=nfqso + (ipk-mode_q65)*df
xdt=jpk*dtstep
imsg_best=imsg
ccf1=ccf(:,jpk)
endif
enddo ! imsg
i1=i0+ipk-64
i2=i1+LL-1
j=j0+jpk-7
n=0
do k=1,85
j=j+8
if(sync(k).gt.0.0) then
cycle
endif
n=n+1
if(j.ge.1 .and. j.le.jz) then
do i=0,LL-1
s3(i-64,n)=s1(i+i1,j)
enddo
endif
enddo
nsubmode=0
if(mode_q65.eq.2) nsubmode=1
if(mode_q65.eq.4) nsubmode=2
if(mode_q65.eq.8) nsubmode=3
if(mode_q65.eq.16) nsubmode=4
nFadingModel=1
baud=12000.0/nsps
ibwa=1.8*log(baud*mode_q65) + 2
ibwb=min(10,ibwa+4)
do ibw=ibwa,ibwb
b90=1.72**ibw
b90ts=b90/baud
call timer('dec1 ',0)
call q65_dec1(s3,nsubmode,b90ts,codewords,ncw,esnodb,irc,dat4,decoded)
call timer('dec1 ',1)
if(irc.ge.0) then
snr2=esnodb - db(2500.0/baud) + 3.0 !Empirical adjustment
idec=1
ic=ia2/4;
base=(sum(ccf1(-ia2:-ia2+ic)) + sum(ccf1(ia2-ic:ia2)))/(2.0+2.0*ic);
ccf1=ccf1-base
smax=maxval(ccf1)
if(smax.gt.10.0) ccf1=10.0*ccf1/smax
base=(sum(ccf2(-ia2:-ia2+ic)) + sum(ccf2(ia2-ic:ia2)))/(2.0+2.0*ic);
ccf2=ccf2-base
smax=maxval(ccf2)
if(smax.gt.10.0) ccf2=10.0*ccf2/smax
go to 100
endif
enddo
irc=-2
dat4=0
!######################################################################
! Compute the 2D CCF using sync symbols only
100 ccf=0.
do lag=lag1,lag2
do k=1,85
n=NSTEP*(k-1) + 1
j=n+lag+j0
if(j.ge.1 .and. j.le.jz) then
do i=-ia2,ia2
if(i0+i.lt.1 .or. i0+i.gt.iz) cycle
ccf(i,lag)=ccf(i,lag) + sync(k)*s1(i0+i,j)
enddo
endif
enddo
enddo
ijpk=maxloc(ccf(-ia:ia,:))
ipk=ijpk(1)-ia-1
jpk=ijpk(2)-53-1
do i=-ia2,ia2
ccf2(i)=maxval(ccf(i,:))
enddo
sq=0.
nsq=0
jd=(lag2-lag1)/4
do i=-ia2,ia2
do j=lag1,lag2
if(abs(j-jpk).gt.jd .and. abs(i-ipk).gt.ia/2) then
sq=sq + ccf(i,j)**2
nsq=nsq+1
endif
enddo
enddo
rms=sqrt(sq/nsq)
smax=ccf(ipk,jpk)
snr1=smax/rms
ccf2=ccf2/rms
if(snr1.gt.10.0) ccf2=(10.0/snr1)*ccf2
if(irc.le.0) then
f0=nfqso + ipk*df
xdt=jpk*dtstep
ccf1=ccf(:,jpk)/rms
if(snr1.gt.10.0) ccf1=(10.0/snr1)*ccf1
if(iand(ndepth,16).eq.16) then
! Fill s3() from s1() here, then call q65_avg().
i1=i0+ipk-64
i2=i1+LL-1
if(snr1.ge.2.8 .and. i1.ge.1 .and. i2.le.iz) then
j=j0+jpk-7
n=0
do k=1,85
j=j+8
if(sync(k).gt.0.0) then
cycle
endif
n=n+1
if(j.ge.1 .and. j.le.jz) s3(-64:LL-65,n)=s1(i1:i2,j)
enddo
call q65_avg(nutc,ntrperiod,LL,nfqso,ntol,lclearave,xdt,f0,snr1,s3)
endif
endif
endif
smax=maxval(ccf1)
i1=-9999
i2=-9999
do i=-ia,ia
if(i1.eq.-9999 .and. ccf1(i).ge.0.5*smax) i1=i
if(i2.eq.-9999 .and. ccf1(-i).ge.0.5*smax) i2=-i
enddo
width=df*(i2-i1)
do i=-ia2,ia2
freq=nfqso + i*df
write(17,1100) freq,ccf1(i),xdt,ccf2(i)
1100 format(4f10.3)
enddo
close(17)
900 return
end subroutine q65_sync
subroutine q65_dec1(s3,nsubmode,b90ts,codewords,ncw,esnodb,irc,dat4,decoded)
use q65
use packjt77
real s3prob(0:63,63) !Symbol-value probabilities
integer codewords(63,206)
integer dat4(13)
character c77*77,decoded*37
logical unpk77_success
nFadingModel=1
decoded=' '
call q65_intrinsics_ff(s3,nsubmode,b90ts,nFadingModel,s3prob)
call q65_dec_fullaplist(s3,s3prob,codewords,ncw,esnodb,dat4,plog,irc)
if(sum(dat4).le.0) irc=-2
if(irc.ge.0 .and. plog.gt.PLOG_MIN) then
write(c77,1000) dat4(1:12),dat4(13)/2
1000 format(12b6.6,b5.5)
call unpack77(c77,0,decoded,unpk77_success) !Unpack to get msgsent
else
irc=-1
endif
return
end subroutine q65_dec1
subroutine q65_dec2(s3,nsubmode,b90ts,esnodb,irc,dat4,decoded)
use q65
use packjt77
real s3prob(0:63,63) !Symbol-value probabilities
integer dat4(13)
character c77*77,decoded*37
logical unpk77_success
nFadingModel=1
decoded=' '
call q65_intrinsics_ff(s3,nsubmode,b90ts,nFadingModel,s3prob)
call q65_dec(s3,s3prob,APmask,APsymbols,esnodb,dat4,irc)
if(sum(dat4).le.0) irc=-2
if(irc.ge.0) then
write(c77,1000) dat4(1:12),dat4(13)/2
1000 format(12b6.6,b5.5)
call unpack77(c77,0,decoded,unpk77_success) !Unpack to get msgsent
endif
return
end subroutine q65_dec2