mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2024-11-29 15:48:38 -05:00
65 lines
2.1 KiB
Fortran
65 lines
2.1 KiB
Fortran
subroutine sync8d(cd0,i0,ctwk,itwk,itype,sync)
|
|
|
|
! Compute sync power for a complex, downsampled FT8 signal.
|
|
! itype specifies which Costas array to use
|
|
|
|
parameter(NP2=2812,NDOWN=60)
|
|
complex cd0(0:3199)
|
|
complex csync_1(0:6,32),csync_2(0:6,32)
|
|
complex csync2(32)
|
|
complex ctwk(32)
|
|
complex z1,z2,z3
|
|
logical first
|
|
integer icos7_1(0:6),icos7_2(0:6)
|
|
data icos7_1/2,5,6,0,4,1,3/
|
|
data icos7_2/3,1,4,0,6,5,2/
|
|
data first/.true./
|
|
save first,twopi,fs2,dt2,taus,baud,csync_1,csync_2
|
|
|
|
p(z1)=real(z1)**2 + aimag(z1)**2 !Statement function for power
|
|
|
|
! Set some constants and compute the csync array.
|
|
if( first ) then
|
|
twopi=8.0*atan(1.0)
|
|
fs2=12000.0/NDOWN !Sample rate after downsampling
|
|
dt2=1/fs2 !Corresponding sample interval
|
|
taus=32*dt2 !Symbol duration
|
|
baud=1.0/taus !Keying rate
|
|
do i=0,6
|
|
phi1=0.0
|
|
phi2=0.0
|
|
dphi1=twopi*icos7_1(i)*baud*dt2
|
|
dphi2=twopi*icos7_2(i)*baud*dt2
|
|
do j=1,32
|
|
csync_1(i,j)=cmplx(cos(phi1),sin(phi1)) !Waveform for 7x7 Costas array
|
|
csync_2(i,j)=cmplx(cos(phi2),sin(phi2)) !Waveform for 7x7 Costas array
|
|
phi1=mod(phi1+dphi1,twopi)
|
|
phi2=mod(phi2+dphi2,twopi)
|
|
enddo
|
|
enddo
|
|
first=.false.
|
|
endif
|
|
|
|
sync=0
|
|
do i=0,6 !Sum over 7 Costas frequencies and
|
|
i1=i0+i*32 !three Costas arrays
|
|
i2=i1+36*32
|
|
i3=i1+72*32
|
|
if(itype.eq.1) then
|
|
csync2=csync_1(i,1:32)
|
|
else
|
|
csync2=csync_2(i,1:32)
|
|
endif
|
|
if(itwk.eq.1) csync2=ctwk*csync2 !Tweak the frequency
|
|
z1=0.
|
|
z2=0.
|
|
z3=0.
|
|
if(i1.ge.0 .and. i1+31.le.NP2-1) z1=sum(cd0(i1:i1+31)*conjg(csync2))
|
|
if(i2.ge.0 .and. i2+31.le.NP2-1) z2=sum(cd0(i2:i2+31)*conjg(csync2))
|
|
if(i3.ge.0 .and. i3+31.le.NP2-1) z3=sum(cd0(i3:i3+31)*conjg(csync2))
|
|
sync = sync + p(z1) + p(z2) + p(z3)
|
|
enddo
|
|
|
|
return
|
|
end subroutine sync8d
|