WSJT-X/xcor.f
Joe Taylor 06291ab964 First good compile with map65a running inside map65.
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/map65@334 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
2007-01-11 21:25:52 +00:00

85 lines
2.3 KiB
Fortran

subroutine xcor(s2,ipk,nsteps,nsym,lag1,lag2,
+ ccf,ccf0,lagpk,flip,fdot)
C Computes ccf of a row of s2 and the pseudo-random array pr. Returns
C peak of the CCF and the lag at which peak occurs. For JT65, the
C CCF peak may be either positive or negative, with negative implying
C the "OOO" message.
parameter (NHMAX=1024) !Max length of power spectra
parameter (NSMAX=320) !Max number of half-symbol steps
real s2(NHMAX,NSMAX) !2d spectrum, stepped by half-symbols
real a(NSMAX),a2(NSMAX)
real ccf(-5:540)
include 'prcom.h'
common/clipcom/ nclip
data lagmin/0/ !Silence g77 warning
save
df=11025.0/4096.
dtstep=0.5/df
fac=dtstep/(60.0*df)
do j=1,nsteps
ii=nint((j-nsteps/2)*fdot*fac)+ipk
a(j)=s2(ii,j)
enddo
C If requested, clip the spectrum that will be cross correlated.
nclip=0 !Turn it off
if(nclip.gt.0) then
call pctile(a,a2,nsteps,50,base)
alow=a2(nint(nsteps*0.16))
ahigh=a2(nint(nsteps*0.84))
rms=min(base-alow,ahigh-base)
clip=4.0-nclip
atop=base+clip*rms
abot=base-clip*rms
do i=1,nsteps
if(nclip.lt.4) then
a(i)=min(a(i),atop)
a(i)=max(a(i),abot)
else
if(a(i).ge.base) then
a(i)=1.0
else
a(i)=-1.0
endif
endif
enddo
endif
ccfmax=0.
ccfmin=0.
do lag=lag1,lag2
x=0.
do i=1,nsym
j=2*i-1+lag
if(j.ge.1 .and. j.le.nsteps) x=x+a(j)*pr(i)
enddo
ccf(lag)=2*x !The 2 is for plotting scale
if(ccf(lag).gt.ccfmax) then
ccfmax=ccf(lag)
lagpk=lag
endif
if(ccf(lag).lt.ccfmin) then
ccfmin=ccf(lag)
lagmin=lag
endif
enddo
ccf0=ccfmax
flip=1.0
if(-ccfmin.gt.ccfmax) then
do lag=lag1,lag2
ccf(lag)=-ccf(lag)
enddo
lagpk=lagmin
ccf0=-ccfmin
flip=-1.0
endif
return
end