96 lines
2.6 KiB
Plaintext
96 lines
2.6 KiB
Plaintext
|
subroutine xcor4(s2,ipk,nsteps,nsym,lag1,lag2,ich,mode4,ccf,ccf0, &
|
||
|
|
lagpk,flip)
|
||
|
|
|
||
|
|
! Computes ccf of the 4_FSK spectral array s2 and the pseudo-random
|
||
|
|
! array pr2. Returns peak of CCF and the lag at which peak occurs.
|
||
|
|
! The CCF peak may be either positive or negative, with negative
|
||
|
|
! implying the "OOO" message.
|
||
|
|
|
||
|
|
parameter (NHMAX=1260) !Max length of power spectra
|
||
|
|
parameter (NSMAX=525) !Max number of half-symbol steps
|
||
|
|
real s2(NHMAX,NSMAX) !2d spectrum, stepped by half-symbols
|
||
|
|
real a(NSMAX)
|
||
|
|
real ccf(-5:540)
|
||
|
|
integer nch(7)
|
||
|
|
integer npr2(207)
|
||
|
|
real pr2(207)
|
||
|
|
logical first
|
||
|
|
data lagmin/0/ !Silence compiler warning
|
||
|
|
data first/.true./
|
||
|
|
data npr2/ &
|
||
|
|
0,0,0,0,1,1,0,0,0,1,1,0,1,1,0,0,1,0,1,0,0,0,0,0,0,0,1,1,0,0, &
|
||
|
|
0,0,0,0,0,0,0,0,0,0,1,0,1,1,0,1,1,0,1,0,1,1,1,1,1,0,1,0,0,0, &
|
||
|
|
1,0,0,1,0,0,1,1,1,1,1,0,0,0,1,0,1,0,0,0,1,1,1,1,0,1,1,0,0,1, &
|
||
|
|
0,0,0,1,1,0,1,0,1,0,1,0,1,0,1,1,1,1,1,0,1,0,1,0,1,1,0,1,0,1, &
|
||
|
|
0,1,1,1,0,0,1,0,1,1,0,1,1,1,1,0,0,0,0,1,1,0,1,1,0,0,0,1,1,1, &
|
||
|
|
0,1,1,1,0,1,1,1,0,0,1,0,0,0,1,1,0,1,1,0,0,1,0,0,0,1,1,1,1,1, &
|
||
|
|
1,0,0,1,1,0,0,0,0,1,1,0,0,0,1,0,1,1,0,1,1,1,1,0,1,0,1/
|
||
|
|
data nch/1,2,4,9,18,36,72/
|
||
|
|
save
|
||
|
|
|
||
|
|
if(first) then
|
||
|
|
do i=1,207
|
||
|
|
pr2(i)=2*npr2(i)-1
|
||
|
|
enddo
|
||
|
|
first=.false.
|
||
|
|
endif
|
||
|
|
|
||
|
|
ccfmax=0.
|
||
|
|
ccfmin=0.
|
||
|
|
nw=nch(ich)
|
||
|
|
|
||
|
|
do j=1,nsteps
|
||
|
|
n=2*mode4
|
||
|
|
if(mode4.eq.1) then
|
||
|
|
a(j)=max(s2(ipk+n,j),s2(ipk+3*n,j)) - max(s2(ipk ,j),s2(ipk+2*n,j))
|
||
|
|
else
|
||
|
|
kz=max(1,nw/2)
|
||
|
|
ss0=0.
|
||
|
|
ss1=0.
|
||
|
|
ss2=0.
|
||
|
|
ss3=0.
|
||
|
|
wsum=0.
|
||
|
|
do k=-kz+1,kz-1
|
||
|
|
w=float(kz-iabs(k))/nw
|
||
|
|
wsum=wsum+w
|
||
|
|
ss0=ss0 + w*s2(ipk +k,j)
|
||
|
|
ss1=ss1 + w*s2(ipk+ n+k,j)
|
||
|
|
ss2=ss2 + w*s2(ipk+2*n+k,j)
|
||
|
|
ss3=ss3 + w*s2(ipk+3*n+k,j)
|
||
|
|
enddo
|
||
|
|
a(j)=(max(ss1,ss3) - max(ss0,ss2))/sqrt(wsum)
|
||
|
|
endif
|
||
|
|
enddo
|
||
|
|
|
||
|
|
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)*pr2(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 subroutine xcor4
|