122 lines
3.9 KiB
Fortran
122 lines
3.9 KiB
Fortran
subroutine syncjs8d(cd0,icos,i0,delf,sync)
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! Compute sync power for a complex, downsampled JS8 signal.
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!include 'js8_params.f90'
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parameter(NP=NMAX/NDOWN, NP2=NN*NDOWNSPS)
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complex cd0(0:NP-1)
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complex csynca(0:6,NDOWNSPS),csyncb(0:6,NDOWNSPS),csyncc(0:6,NDOWNSPS)
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complex csync2a(NDOWNSPS),csync2b(NDOWNSPS),csync2c(NDOWNSPS)
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complex ctwk(NDOWNSPS)
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complex z1,z2,z3
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real delf
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logical first
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integer icos
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data first/.true./
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save first,twopi,csynca,csyncb,csyncc
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p(z1)=(real(z1)**2 + aimag(z1)**2) !Statement function for power
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integer icos7a(0:6), icos7b(0:6), icos7c(0:6)
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if(icos.eq.1) then
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icos7a = (/4,2,5,6,1,3,0/) !Beginning Costas 7x7 tone pattern
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icos7b = (/4,2,5,6,1,3,0/) !Middle Costas 7x7 tone pattern
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icos7c = (/4,2,5,6,1,3,0/) !End Costas 7x7 tone pattern
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else
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icos7a = (/0,6,2,3,5,4,1/) !Beginning Costas 7x7 tone pattern
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icos7b = (/1,5,0,2,3,6,4/) !Middle Costas 7x7 tone pattern
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icos7c = (/2,5,0,6,4,1,3/) !End Costas 7x7 tone pattern
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endif
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if(NWRITELOG.eq.1) then
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write(*,*) '<DecodeDebug> syncjs8d costas', icos7a, icos7b, icos7c
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flush(6)
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endif
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! Set some constants and compute the csync array.
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if( first ) then
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twopi=8.0*atan(1.0)
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fs2=12000.0/NDOWN !Sample rate after downsampling
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dt2=1/fs2 !Corresponding sample interval
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taus=NDOWNSPS*dt2 !Symbol duration
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baud=1.0/taus !Keying rate
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do i=0,6
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phia=0.0
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phib=0.0
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phic=0.0
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dphia=twopi*icos7a(i)*baud*dt2
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dphib=twopi*icos7b(i)*baud*dt2
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dphic=twopi*icos7c(i)*baud*dt2
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do j=1,NDOWNSPS
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csynca(i,j)=cmplx(cos(phia),sin(phia)) !Waveform for Beginning 7x7 Costas array
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csyncb(i,j)=cmplx(cos(phib),sin(phib)) !Waveform for Middle 7x7 Costas array
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csyncc(i,j)=cmplx(cos(phic),sin(phic)) !Waveform for End 7x7 Costas array
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phia=mod(phia+dphia,twopi)
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phib=mod(phib+dphib,twopi)
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phic=mod(phia+dphic,twopi)
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if(NWRITELOG.eq.1) then
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write(*,*) '<DecodeDebug> computing costas waveforms', i, j, phia, phib, phic, dphia, dphib, dphic
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flush(6)
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endif
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enddo
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enddo
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first=.false.
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endif
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! compute the ctwk samples at the delta frequency to by used to detect peaks
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! at frequencies +/- delf so we can align the decoder for the best possible
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! chance at decoding.
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!
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! NOTE: this does not need to compute the entire set of samples for the
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! costas arrays...it only needs to do it for the delta frequency
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! whose conjugate is multiplied against each csync arrays for those
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! coastas signals
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if(delf.ne.0.0) then
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fs2=12000.0/NDOWN
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dt2=1.0/fs2
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dphi=twopi*delf*dt2
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phi=0.0
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do i=1,NDOWNSPS
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ctwk(i)=cmplx(cos(phi),sin(phi))
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phi=mod(phi+dphi,twopi)
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enddo
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endif
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sync=0
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do i=0,6
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i1=i0+i*NDOWNSPS
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i2=i1+36*NDOWNSPS
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i3=i1+72*NDOWNSPS
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z1=0.
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z2=0.
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z3=0.
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csync2a=csynca(i,1:NDOWNSPS)
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if(delf.ne.0.0) csync2a=ctwk*csync2a
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if(i1.ge.0 .and. i1+NDOWNSPS-1.le.NP2-1) z1=sum(cd0(i1:i1+NDOWNSPS-1)*conjg(csync2a))
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csync2b=csyncb(i,1:NDOWNSPS)
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if(delf.ne.0.0) csync2b=ctwk*csync2b
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if(i2.ge.0 .and. i2+NDOWNSPS-1.le.NP2-1) z2=sum(cd0(i2:i2+NDOWNSPS-1)*conjg(csync2b))
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csync2c=csyncc(i,1:NDOWNSPS)
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if(delf.ne.0.0) csync2c=ctwk*csync2c
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if(i3.ge.0 .and. i3+NDOWNSPS-1.le.NP2-1) z3=sum(cd0(i3:i3+NDOWNSPS-1)*conjg(csync2c))
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sync = sync + p(z1) + p(z2) + p(z3)
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if(NWRITELOG.eq.1) then
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write(*,*) '<DecodeDebug> sync computation', i, sync
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flush(6)
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endif
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enddo
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return
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end subroutine syncjs8d
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