subroutine sync8d(cd0,i0,ctwk,itwk,sync) ! Compute sync power for a complex, downsampled FT8 signal. parameter(NP2=2812,NDOWN=20) complex cd0(3125) complex csync(0:6,32) complex csync2(32) complex ctwk(32) complex z1,z2,z3 logical first integer icos7(0:6) data icos7/2,5,6,0,4,1,3/ 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=4000.0/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 phi=0.0 dphi=twopi*icos7(i)*baud*dt2 do j=1,32 csync(i,j)=cmplx(cos(phi),sin(phi)) !Waveform for 7x7 Costas array phi=mod(phi+dphi,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 csync2=csync(i,1:32) if(itwk.eq.1) csync2=ctwk*csync2 !Tweak the frequency z1=0. z2=0. z3=0. if(i1.ge.1 .and. i1+31.le.NP2) z1=sum(cd0(i1:i1+31)*conjg(csync2)) if(i2.ge.1 .and. i2+31.le.NP2) z2=sum(cd0(i2:i2+31)*conjg(csync2)) if(i3.ge.1 .and. i3+31.le.NP2) z3=sum(cd0(i3:i3+31)*conjg(csync2)) sync = sync + p(z1) + p(z2) + p(z3) enddo return end subroutine sync8d