WSJT-X/lib/jtmsk_short.f90
Joe Taylor 27d1c9ca5c Further improvements to decoder for short JTMSK messages.
In mainwindow.cpp, return after executing call to fastSink().  ###???###


git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6464 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
2016-02-04 16:10:55 +00:00

162 lines
4.4 KiB
Fortran

subroutine jtmsk_short(cdat,npts,narg,tbest,idfpk,decoded)
! Decode short-format messages in JTMSK mode.
parameter (NMAX=15*12000,NSAVE=100)
character*22 msg,decoded,msgsent
character*3 rpt(0:7)
complex cdat(0:npts-1)
complex cw(0:209,0:4095) !Waveforms of possible messages
complex cb11(0:65) !Complex waveform of Barker 11
complex cd(0:511)
complex z1,z2a,z2b
real*8 dt,twopi,freq,phi,dphi0,dphi1,dphi
real r1(0:NMAX-1)
real r2(0:4095)
real r1save(NSAVE)
integer itone(234) !Message bits
integer jgood(NSAVE)
integer indx(NSAVE)
integer narg(0:14)
logical first
data rpt /'26 ','27 ','28 ','R26','R27','R28','RRR','73 '/
data first/.true./,nrxfreq0/-1/,ttot/0.0/
save first,cw,cb11,nrxfreq0,ttot
nrxfreq=narg(10) !Target Rx audio frequency (Hz)
ntol=narg(11) !Search range, +/- ntol (Hz)
nhashcalls=narg(12)
if(first .or. nrxfreq.ne.nrxfreq0) then
dt=1.d0/12000.d0
twopi=8.d0*atan(1.d0)
freq=nrxfreq
dphi0=twopi*(freq-500.d0)*dt !Phase increment, lower tone
dphi1=twopi*(freq+500.d0)*dt !Phase increment, upper tone
nsym=35 !Number of symbols
nspm=6*nsym !Samples per message
msg="<C1ALL C2ALL> 73"
do imsg=0,4095 !Generate all possible message waveforms
ichk=10000+imsg
call genmsk(msg,ichk,msgsent,itone,itype) !Encode the message
k=-1
phi=0.d0
do j=1,nsym
dphi=dphi0
if(itone(j).eq.1) dphi=dphi1
do i=1,6
k=k+1
phi=phi + dphi
if(phi.gt.twopi) phi=phi-twopi
xphi=phi
cw(k,imsg)=cmplx(cos(xphi),sin(xphi))
enddo
enddo
enddo
cb11=cw(0:65,0)
first=.false.
nrxfreq0=nrxfreq
endif
r1thresh=0.80
maxdecodes=999
r1max=0.
do j=0,npts-210 !Find the B11 sync vectors
z1=0.
ss=0.
do i=0,65
ss=ss + real(cdat(j+i))**2 + aimag(cdat(j+i))**2
z1=z1 + cdat(j+i)*conjg(cb11(i)) !Signal matching B11
enddo
ss=sqrt(ss/66.0)*66.0
r1(j)=abs(z1)/(0.908*ss) !Goodness-of-fit to B11
if(r1(j).gt.r1max) then
r1max=r1(j)
jpk=j
endif
enddo
k=0
do j=1,npts-211
if(r1(j).gt.r1thresh .and. r1(j).ge.r1(j-1) .and. r1(j).ge.r1(j+1) ) then
k=k+1
jgood(k)=j
r1save(k)=r1(j)
if(k.ge.NSAVE) exit
endif
enddo
kmax=k
call indexx(r1save,kmax,indx)
df=12000.0/512.0
ibest2=-1
idfbest=0
u1best=0.
do kk=1,min(kmax,10)
k=indx(kmax+1-kk)
j=jgood(k)
if(j.lt.144 .or. j.gt.npts-210) cycle
t=j/12000.0
u1=0.
u2=0.
r2max=0.
ibest=-1
do iidf=0,10
idf=20*((iidf+1)/2)
if(idf.gt.ntol) exit
if(iand(iidf,1).eq.1) idf=-idf
call tweak1(cdat(j-144:j+209),354,float(-idf),cd)
cd(354:)=0.
do imsg=0,4095
ssa=0.
ssb=0.
do i=0,209
ssa=ssa + real(cd(144+i))**2 + aimag(cd(144+i))**2
ssb=ssb + real(cd(i))**2 + aimag(cdat(i))**2
enddo
z2a=dot_product(cw(0:209,imsg),cd(144:353))
z2b=dot_product(cw(0:65,imsg),cdat(144:209)) + &
dot_product(cw(66:209,imsg),cdat(0:143))
ssa=sqrt(ssa/210.0)*210.0
ssb=sqrt(ssb/210.0)*210.0
r2(imsg)=max(abs(z2a)/ssa,abs(z2b)/ssb)
if(r2(imsg).gt.r2max) then
r2max=r2(imsg)
ibest=imsg
u2=u1
u1=r2max
idfpk=idf
t2=t
n=0
if(imsg.eq.2296 .or. imsg.eq.2302) n=1
endif
enddo
enddo
r1_r2=r1(j)/r2max
if(u1.ge.0.71 .and. u2/u1.lt.0.91 .and. r1_r2.lt.1.3) then
if(u1.gt.u1best) then
irpt=iand(ibest,7)
ihash=ibest/8
narg(13)=ibest
decoded="<...> "//rpt(irpt)
tbest=t
r1best=r1(j)
u1best=u1
u2best=u2
ibest2=ibest
idfbest=idfpk
r1_r2best=r1_r2
nn=0
if(ihash.eq.narg(12) .and. iand(ibest2,7).eq.0) nn=1
endif
endif
enddo
return
end subroutine jtmsk_short