mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2024-11-06 01:11:18 -05:00
122 lines
3.6 KiB
Fortran
122 lines
3.6 KiB
Fortran
subroutine ccf65(ss,nhsym,ssmax,sync1,ipol1,jpz,dt1,flipk, &
|
|
syncshort,snr2,ipol2,dt2)
|
|
|
|
parameter (NFFT=512,NH=NFFT/2)
|
|
real ss(4,322) !Input: half-symbol powers, 4 pol'ns
|
|
real s(NFFT) !CCF = ss*pr
|
|
complex cs(0:NH) !Complex FT of s
|
|
real s2(NFFT) !CCF = ss*pr2
|
|
complex cs2(0:NH) !Complex FT of s2
|
|
real pr(NFFT) !JT65 pseudo-random sync pattern
|
|
complex cpr(0:NH) !Complex FT of pr
|
|
real pr2(NFFT) !JT65 shorthand pattern
|
|
complex cpr2(0:NH) !Complex FT of pr2
|
|
real tmp1(322)
|
|
real ccf(-11:54,4)
|
|
logical first
|
|
integer npr(126)
|
|
data first/.true./
|
|
equivalence (s,cs),(pr,cpr),(s2,cs2),(pr2,cpr2)
|
|
save
|
|
|
|
! The JT65 pseudo-random sync pattern:
|
|
data npr/ &
|
|
1,0,0,1,1,0,0,0,1,1,1,1,1,1,0,1,0,1,0,0, &
|
|
0,1,0,1,1,0,0,1,0,0,0,1,1,1,0,0,1,1,1,1, &
|
|
0,1,1,0,1,1,1,1,0,0,0,1,1,0,1,0,1,0,1,1, &
|
|
0,0,1,1,0,1,0,1,0,1,0,0,1,0,0,0,0,0,0,1, &
|
|
1,0,0,0,0,0,0,0,1,1,0,1,0,0,1,0,1,1,0,1, &
|
|
0,1,0,1,0,0,1,1,0,0,1,0,0,1,0,0,0,0,1,1, &
|
|
1,1,1,1,1,1/
|
|
|
|
if(first) then
|
|
! Initialize pr, pr2; compute cpr, cpr2.
|
|
fac=1.0/NFFT
|
|
do i=1,NFFT
|
|
pr(i)=0.
|
|
pr2(i)=0.
|
|
k=2*mod((i-1)/8,2)-1
|
|
if(i.le.NH) pr2(i)=fac*k
|
|
enddo
|
|
do i=1,126
|
|
j=2*i
|
|
pr(j)=fac*(2*npr(i)-1)
|
|
! Not sure why, but it works significantly better without the following line:
|
|
! pr(j-1)=pr(j)
|
|
enddo
|
|
call four2a(pr,NFFT,1,-1,0)
|
|
call four2a(pr2,NFFT,1,-1,0)
|
|
first=.false.
|
|
endif
|
|
|
|
! Look for JT65 sync pattern and shorthand square-wave pattern.
|
|
ccfbest=0.
|
|
ccfbest2=0.
|
|
ipol1=1
|
|
ipol2=1
|
|
do ip=1,jpz !Do jpz polarizations
|
|
do i=1,nhsym-1
|
|
! s(i)=ss(ip,i)+ss(ip,i+1)
|
|
s(i)=min(ssmax,ss(ip,i)+ss(ip,i+1))
|
|
enddo
|
|
call pctile(s,nhsym-1,50,base)
|
|
s(1:nhsym-1)=s(1:nhsym-1)-base
|
|
s(nhsym:NFFT)=0.
|
|
call four2a(s,NFFT,1,-1,0) !Real-to-complex FFT
|
|
do i=0,NH
|
|
cs2(i)=cs(i)*conjg(cpr2(i)) !Mult by complex FFT of pr2
|
|
cs(i)=cs(i)*conjg(cpr(i)) !Mult by complex FFT of pr
|
|
enddo
|
|
call four2a(cs,NFFT,1,1,-1) !Complex-to-real inv-FFT
|
|
call four2a(cs2,NFFT,1,1,-1) !Complex-to-real inv-FFT
|
|
|
|
do lag=-11,54 !Check for best JT65 sync
|
|
j=lag
|
|
if(j.lt.1) j=j+NFFT
|
|
ccf(lag,ip)=s(j)
|
|
if(abs(ccf(lag,ip)).gt.ccfbest) then
|
|
ccfbest=abs(ccf(lag,ip))
|
|
lagpk=lag
|
|
ipol1=ip
|
|
flipk=1.0
|
|
if(ccf(lag,ip).lt.0.0) flipk=-1.0
|
|
endif
|
|
enddo
|
|
|
|
do lag=-11,54 !Check for best shorthand
|
|
ccf2=s2(lag+28)
|
|
if(ccf2.gt.ccfbest2) then
|
|
ccfbest2=ccf2
|
|
lagpk2=lag
|
|
ipol2=ip
|
|
endif
|
|
enddo
|
|
|
|
enddo
|
|
|
|
! Find rms level on baseline of "ccfblue", for normalization.
|
|
sum=0.
|
|
do lag=-11,54
|
|
if(abs(lag-lagpk).gt.1) sum=sum + ccf(lag,ipol1)
|
|
enddo
|
|
base=sum/50.0
|
|
sq=0.
|
|
do lag=-11,54
|
|
if(abs(lag-lagpk).gt.1) sq=sq + (ccf(lag,ipol1)-base)**2
|
|
enddo
|
|
rms=sqrt(sq/49.0)
|
|
sync1=ccfbest/rms - 4.0
|
|
dt1=lagpk*(2048.0/11025.0) - 2.5
|
|
|
|
! Find base level for normalizing snr2.
|
|
do i=1,nhsym
|
|
tmp1(i)=ss(ipol2,i)
|
|
enddo
|
|
call pctile(tmp1,nhsym,40,base)
|
|
snr2=0.398107*ccfbest2/base !### empirical
|
|
syncshort=0.5*ccfbest2/rms - 4.0 !### better normalizer than rms?
|
|
dt2=2.5 + lagpk2*(2048.0/11025.0)
|
|
|
|
return
|
|
end subroutine ccf65
|