152 lines
3.8 KiB
Plaintext
152 lines
3.8 KiB
Plaintext
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subroutine ft8b(dd0,newdat,nfqso,ndepth,icand,sync0,f1,xdt,nharderrors, &
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dmin,nbadcrc,message,xsnr)
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use timer_module, only: timer
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include 'ft8_params.f90'
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parameter(NRECENT=10,NP2=2812)
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character message*22,msgsent*22
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character*12 recent_calls(NRECENT)
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real a(5)
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real s1(0:7,ND),s2(0:7,NN)
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real ps(0:7)
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real rxdata(3*ND),llr(3*ND) !Soft symbols
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real dd0(15*12000)
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integer*1 decoded(KK),apmask(3*ND),cw(3*ND)
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integer itone(NN)
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complex cd0(3200)
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complex ctwk(32)
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complex csymb(32)
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logical newdat
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max_iterations=40
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norder=2
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if(ndepth.eq.3 .and. abs(nfqso-f1).lt.10.0) norder=3
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fs2=12000.0/NDOWN
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dt2=1.0/fs2
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twopi=8.0*atan(1.0)
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delfbest=0.
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ibest=0
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call timer('ft8_down',0)
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call ft8_downsample(dd0,newdat,f1,cd0) !Mix f1 to baseband and downsample
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call timer('ft8_down',1)
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i0=nint(xdt*fs2) !Initial guess for start of signal
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smax=0.0
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do idt=i0-16,i0+16 !Search over +/- half a symbol
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call sync8d(cd0,idt,ctwk,0,sync)
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if(sync.gt.smax) then
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smax=sync
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ibest=idt
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endif
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enddo
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xdt2=ibest*dt2 !Improved estimate for DT
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! Now peak up in frequency
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i0=nint(xdt2*fs2)
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smax=0.0
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do ifr=-5,5 !Search over +/- 2.5 Hz
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delf=ifr*0.5
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dphi=twopi*delf*dt2
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phi=0.0
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do i=1,32
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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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call sync8d(cd0,i0,ctwk,1,sync)
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if( sync .gt. smax ) then
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smax=sync
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delfbest=delf
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endif
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enddo
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a=0.0
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a(1)=-delfbest
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call twkfreq1(cd0,NP2,fs2,a,cd0)
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xdt=xdt2
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f1=f1+delfbest !Improved estimate of DF
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call sync8d(cd0,i0,ctwk,2,sync)
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j=0
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do k=1,NN
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i1=ibest+(k-1)*32
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csymb=cmplx(0.0,0.0)
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if( i1.ge.1 .and. i1+31 .le. NP2 ) csymb=cd0(i1:i1+31)
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call four2a(csymb,32,1,-1,1)
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s2(0:7,k)=abs(csymb(1:8))
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enddo
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j=0
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do k=1,NN
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if(k.le.7) cycle
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if(k.ge.37 .and. k.le.43) cycle
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if(k.gt.72) cycle
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j=j+1
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s1(0:7,j)=s2(0:7,k)
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enddo
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do j=1,ND
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ps=s1(0:7,j)
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where (ps.gt.0.0) ps=log(ps)
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r1=max(ps(1),ps(3),ps(5),ps(7))-max(ps(0),ps(2),ps(4),ps(6))
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r2=max(ps(2),ps(3),ps(6),ps(7))-max(ps(0),ps(1),ps(4),ps(5))
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r4=max(ps(4),ps(5),ps(6),ps(7))-max(ps(0),ps(1),ps(2),ps(3))
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rxdata(3*j-2)=r4
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rxdata(3*j-1)=r2
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rxdata(3*j)=r1
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enddo
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rxav=sum(rxdata)/(3.0*ND)
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rx2av=sum(rxdata*rxdata)/(3.0*ND)
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var=rx2av-rxav*rxav
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if( var .gt. 0.0 ) then
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rxsig=sqrt(var)
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else
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rxsig=sqrt(rx2av)
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endif
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rxdata=rxdata/rxsig
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ss=0.84
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llr=2.0*rxdata/(ss*ss)
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apmask=0
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cw=0
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call timer('bpd174 ',0)
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call bpdecode174(llr,apmask,max_iterations,decoded,cw,nharderrors)
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call timer('bpd174 ',1)
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dmin=0.0
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if(nharderrors.lt.0) then
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call timer('osd174 ',0)
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call osd174(llr,norder,decoded,cw,nharderrors,dmin)
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call timer('osd174 ',1)
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endif
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nbadcrc=1
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message=' '
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xsnr=-99.0
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if(count(cw.eq.0).eq.174) go to 900 !Reject the all-zero codeword
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if( nharderrors.ge.0 .and. dmin.le.30.0 .and. nharderrors .lt. 30) then
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call chkcrc12a(decoded,nbadcrc)
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else
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nharderrors=-1
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go to 900
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endif
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if(nbadcrc.eq.0) then
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call extractmessage174(decoded,message,ncrcflag,recent_calls,nrecent)
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call genft8(message,msgsent,itone)
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! call subtractft8(dd0,itone,f1,xdt2)
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xsig=0.0
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xnoi=0.0
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do i=1,79
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xsig=xsig+s2(itone(i),i)**2
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ios=mod(itone(i)+4,7)
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xnoi=xnoi+s2(ios,i)**2
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enddo
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xsnr=0.001
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if( xnoi.gt.0 .and. xnoi.lt.xsig ) xsnr=xsig/xnoi-1.0
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xsnr=10.0*log10(xsnr)-27.0
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if( xsnr .lt. -24.0 ) xsnr=-24.0
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! write(50,3050) icand,sync0,f1,xdt,nharderrors,dmin,message
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!3050 format(i3,3f10.3,i5,f10.3,2x,a22)
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endif
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900 continue
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return
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end subroutine ft8b
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