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subroutine syncjs8d(cd0,icos,i0,delf,sync)
! Compute sync power for a complex, downsampled JS8 signal.
!include 'js8_params.f90'
parameter(NP=NMAX/NDOWN, NP2=NN*NDOWNSPS)
complex cd0(0:NP-1)
complex csynca(0:6,NDOWNSPS),csyncb(0:6,NDOWNSPS),csyncc(0:6,NDOWNSPS)
complex csync2a(NDOWNSPS),csync2b(NDOWNSPS),csync2c(NDOWNSPS)
complex ctwk(NDOWNSPS)
complex z1,z2,z3
real delf
logical first
integer icos
data first/.true./
save first,twopi,csynca,csyncb,csyncc
p(z1)=(real(z1)**2 + aimag(z1)**2) !Statement function for power
integer icos7a(0:6), icos7b(0:6), icos7c(0:6)
if(icos.eq.1) then
icos7a = (/4,2,5,6,1,3,0/) !Beginning Costas 7x7 tone pattern
icos7b = (/4,2,5,6,1,3,0/) !Middle Costas 7x7 tone pattern
icos7c = (/4,2,5,6,1,3,0/) !End Costas 7x7 tone pattern
else
icos7a = (/0,6,2,3,5,4,1/) !Beginning Costas 7x7 tone pattern
icos7b = (/1,5,0,2,3,6,4/) !Middle Costas 7x7 tone pattern
icos7c = (/2,5,0,6,4,1,3/) !End Costas 7x7 tone pattern
endif
if(NWRITELOG.eq.1) then
write(*,*) '<DecodeDebug> syncjs8d costas', icos7a, icos7b, icos7c
flush(6)
endif
! 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=NDOWNSPS*dt2 !Symbol duration
baud=1.0/taus !Keying rate
do i=0,6
phia=0.0
phib=0.0
phic=0.0
dphia=twopi*icos7a(i)*baud*dt2
dphib=twopi*icos7b(i)*baud*dt2
dphic=twopi*icos7c(i)*baud*dt2
do j=1,NDOWNSPS
csynca(i,j)=cmplx(cos(phia),sin(phia)) !Waveform for Beginning 7x7 Costas array
csyncb(i,j)=cmplx(cos(phib),sin(phib)) !Waveform for Middle 7x7 Costas array
csyncc(i,j)=cmplx(cos(phic),sin(phic)) !Waveform for End 7x7 Costas array
phia=mod(phia+dphia,twopi)
phib=mod(phib+dphib,twopi)
phic=mod(phia+dphic,twopi)
if(NWRITELOG.eq.1) then
write(*,*) '<DecodeDebug> computing costas waveforms', i, j, phia, phib, phic, dphia, dphib, dphic
flush(6)
endif
enddo
enddo
first=.false.
endif
! compute the ctwk samples at the delta frequency to by used to detect peaks
! at frequencies +/- delf so we can align the decoder for the best possible
! chance at decoding.
!
! NOTE: this does not need to compute the entire set of samples for the
! costas arrays...it only needs to do it for the delta frequency
! whose conjugate is multiplied against each csync arrays for those
! coastas signals
if(delf.ne.0.0) then
fs2=12000.0/NDOWN
dt2=1.0/fs2
dphi=twopi*delf*dt2
phi=0.0
do i=1,NDOWNSPS
ctwk(i)=cmplx(cos(phi),sin(phi))
phi=mod(phi+dphi,twopi)
enddo
endif
sync=0
do i=0,6
i1=i0+i*NDOWNSPS
i2=i1+36*NDOWNSPS
i3=i1+72*NDOWNSPS
z1=0.
z2=0.
z3=0.
csync2a=csynca(i,1:NDOWNSPS)
if(delf.ne.0.0) csync2a=ctwk*csync2a
if(i1.ge.0 .and. i1+NDOWNSPS-1.le.NP2-1) z1=sum(cd0(i1:i1+NDOWNSPS-1)*conjg(csync2a))
csync2b=csyncb(i,1:NDOWNSPS)
if(delf.ne.0.0) csync2b=ctwk*csync2b
if(i2.ge.0 .and. i2+NDOWNSPS-1.le.NP2-1) z2=sum(cd0(i2:i2+NDOWNSPS-1)*conjg(csync2b))
csync2c=csyncc(i,1:NDOWNSPS)
if(delf.ne.0.0) csync2c=ctwk*csync2c
if(i3.ge.0 .and. i3+NDOWNSPS-1.le.NP2-1) z3=sum(cd0(i3:i3+NDOWNSPS-1)*conjg(csync2c))
sync = sync + p(z1) + p(z2) + p(z3)
if(NWRITELOG.eq.1) then
write(*,*) '<DecodeDebug> sync computation', i, sync
flush(6)
endif
enddo
return
end subroutine syncjs8d
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