mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2024-11-19 10:32:02 -05:00
69 lines
1.8 KiB
Fortran
69 lines
1.8 KiB
Fortran
subroutine ccf1(cx,cy,n5,nflip,a,ccfmax,dtmax)
|
|
|
|
parameter (NMAX=60*96000) !Approx samples per half symbol
|
|
complex cx(n5)
|
|
complex cy(n5)
|
|
real a(5)
|
|
complex w,wstep,za,zb,z
|
|
real ss(2600)
|
|
complex csx(0:NMAX/64),csy(0:NMAX/64)
|
|
data twopi/6.283185307/a1,a2,a3/99.,99.,99./
|
|
save
|
|
|
|
if(a(1).ne.a1 .or. a(2).ne.a2 .or. a(3).ne.a3) then
|
|
a1=a(1)
|
|
a2=a(2)
|
|
a3=a(3)
|
|
|
|
C Mix and integrate the complex X and Y signals
|
|
csx(0)=0.
|
|
csy(0)=0.
|
|
w=1.0
|
|
x0=0.5*(n5+1)
|
|
s=2.0/n5
|
|
do i=1,n5
|
|
x=s*(i-x0)
|
|
if(mod(i,1000).eq.1) then
|
|
p2=1.5*x*x - 0.5
|
|
! p3=2.5*(x**3) - 1.5*x
|
|
! p4=4.375*(x**4) - 3.75*(x**2) + 0.375
|
|
dphi=(a(1) + x*a(2) + p2*a(3)) * (twopi/1378.125)
|
|
wstep=cmplx(cos(dphi),sin(dphi))
|
|
endif
|
|
w=w*wstep
|
|
csx(i)=csx(i-1) + w*cx(i)
|
|
csy(i)=csy(i-1) + w*cy(i)
|
|
enddo
|
|
endif
|
|
|
|
C Compute 1/2-symbol powers at 1/16-symbol steps.
|
|
n6=n5/32
|
|
fac=1.e-4
|
|
pol=a(4)/57.2957795
|
|
aa=cos(pol)
|
|
bb=sin(pol)
|
|
fsample=1378.125
|
|
baud=11025.0/4096.0
|
|
nsph=nint(0.5*fsample/baud) !Samples per half symbol
|
|
do i=1,n6
|
|
j=32*i
|
|
k=j-nsph
|
|
ss(i)=0.
|
|
if(k.ge.1) then
|
|
za=csx(j)-csx(k)
|
|
zb=csy(j)-csy(k)
|
|
z=aa*za + bb*zb
|
|
ss(i)=fac*(real(z)**2 + aimag(z)**2)
|
|
endif
|
|
enddo
|
|
|
|
ccfmax=0.
|
|
call ccf2(ss,n6,nflip,ccf,lagpk)
|
|
if(ccf.gt.ccfmax) then
|
|
ccfmax=ccf
|
|
dtmax=0.5*lagpk*(512.0/11025.0)
|
|
endif
|
|
|
|
return
|
|
end
|