mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2024-09-17 10:46:33 -04:00
55 lines
1.6 KiB
Fortran
55 lines
1.6 KiB
Fortran
subroutine sync4d(cd0,i0,ctwk,itwk,sync)
|
|
|
|
! Compute sync power for a complex, downsampled FT4 signal.
|
|
! 20 samples per symbol
|
|
|
|
include 'ft4_params.f90'
|
|
parameter(NP=NMAX/16)
|
|
complex cd0(0:NP-1)
|
|
complex csync(80)
|
|
complex csync2(80)
|
|
complex ctwk(80)
|
|
complex z1,z2,z3
|
|
logical first
|
|
integer icos4(0:3)
|
|
data icos4/0,1,3,2/
|
|
data first/.true./
|
|
save first,twopi,fs2,dt2,taus,baud,csync
|
|
|
|
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=20*dt2 !Symbol duration
|
|
baud=1.0/taus !Keying rate
|
|
k=1
|
|
phi=0.0
|
|
do i=0,3
|
|
! dphi=(twopi/2.0)*(2*icos4(i)-3)*baud*dt2
|
|
dphi=twopi*icos4(i)*baud*dt2
|
|
do j=1,20
|
|
csync(k)=cmplx(cos(phi),sin(phi)) !Waveform for 7x7 Costas array
|
|
phi=mod(phi+dphi,twopi)
|
|
k=k+1
|
|
enddo
|
|
enddo
|
|
first=.false.
|
|
endif
|
|
|
|
sync=0
|
|
i1=i0 !three Costas arrays
|
|
i2=i0+36*20-1
|
|
i3=i0+72*20-1
|
|
csync2=csync
|
|
if(itwk.eq.1) csync2=ctwk*csync2 !Tweak the frequency
|
|
if(i1.ge.0 .and. i1+79.le.NP-1) z1=sum(cd0(i1:i1+79)*conjg(csync2))
|
|
if(i2.ge.0 .and. i2+79.le.NP-1) z2=sum(cd0(i2:i2+79)*conjg(csync2))
|
|
if(i3.ge.0 .and. i3+79.le.NP-1) z3=sum(cd0(i3:i3+79)*conjg(csync2))
|
|
sync = sync + p(z1) + p(z2) + p(z3)
|
|
|
|
return
|
|
end subroutine sync4d
|