mirror of https://github.com/saitohirga/WSJT-X.git
85 lines
2.3 KiB
Fortran
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(-5:28)
|
|
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
|