module fst4_decode type :: fst4_decoder procedure(fst4_decode_callback), pointer :: callback contains procedure :: decode end type fst4_decoder abstract interface subroutine fst4_decode_callback (this,nutc,sync,nsnr,dt,freq, & decoded,nap,qual,ntrperiod,lwspr,fmid,w50) import fst4_decoder implicit none class(fst4_decoder), intent(inout) :: this integer, intent(in) :: nutc real, intent(in) :: sync integer, intent(in) :: nsnr real, intent(in) :: dt real, intent(in) :: freq character(len=37), intent(in) :: decoded integer, intent(in) :: nap real, intent(in) :: qual integer, intent(in) :: ntrperiod logical, intent(in) :: lwspr real, intent(in) :: fmid real, intent(in) :: w50 end subroutine fst4_decode_callback end interface contains subroutine decode(this,callback,iwave,nutc,nQSOProgress,nfqso, & nfa,nfb,nsubmode,ndepth,ntrperiod,nexp_decode,ntol, & emedelay,lapcqonly,mycall,hiscall,nfsplit,iwspr) use timer_module, only: timer use packjt77 use, intrinsic :: iso_c_binding include 'fst4/fst4_params.f90' parameter (MAXCAND=100) class(fst4_decoder), intent(inout) :: this procedure(fst4_decode_callback) :: callback character*37 decodes(100) character*37 msg,msgsent character*77 c77 character*12 mycall,hiscall character*12 mycall0,hiscall0 complex, allocatable :: c2(:) complex, allocatable :: cframe(:) complex, allocatable :: c_bigfft(:) !Complex waveform real llr(240),llra(240),llrb(240),llrc(240),llrd(240) real candidates(100,4) real bitmetrics(320,4) real s4(0:3,NN) real minsync logical lapcqonly integer itone(NN) integer hmod integer*1 apmask(240),cw(240) integer*1 hbits(320) integer*1 message101(101),message74(74),message77(77) integer*1 rvec(77) integer apbits(240) integer nappasses(0:5) ! # of decoding passes for QSO states 0-5 integer naptypes(0:5,4) ! (nQSOProgress,decoding pass) integer mcq(29),mrrr(19),m73(19),mrr73(19) logical badsync,unpk77_success,single_decode logical first,nohiscall,lwspr,ex integer*2 iwave(30*60*12000) data mcq/0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0/ data mrrr/0,1,1,1,1,1,1,0,1,0,0,1,0,0,1,0,0,0,1/ data m73/0,1,1,1,1,1,1,0,1,0,0,1,0,1,0,0,0,0,1/ data mrr73/0,1,1,1,1,1,1,0,0,1,1,1,0,1,0,1,0,0,1/ data rvec/0,1,0,0,1,0,1,0,0,1,0,1,1,1,1,0,1,0,0,0,1,0,0,1,1,0,1,1,0, & 1,0,0,1,0,1,1,0,0,0,0,1,0,0,0,1,0,1,0,0,1,1,1,1,0,0,1,0,1, & 0,1,0,1,0,1,1,0,1,1,1,1,1,0,0,0,1,0,1/ data first/.true./ save first,apbits,nappasses,naptypes,mycall0,hiscall0 this%callback => callback dxcall13=hiscall ! initialize for use in packjt77 mycall13=mycall fMHz=1.0 if(iwspr.ne.0.and.iwspr.ne.1) return if(first) then mcq=2*mod(mcq+rvec(1:29),2)-1 mrrr=2*mod(mrrr+rvec(59:77),2)-1 m73=2*mod(m73+rvec(59:77),2)-1 mrr73=2*mod(mrr73+rvec(59:77),2)-1 nappasses(0)=2 nappasses(1)=2 nappasses(2)=2 nappasses(3)=2 nappasses(4)=2 nappasses(5)=3 ! iaptype !------------------------ ! 1 CQ ??? ??? (29 ap bits) ! 2 MyCall ??? ??? (29 ap bits) ! 3 MyCall DxCall ??? (58 ap bits) ! 4 MyCall DxCall RRR (77 ap bits) ! 5 MyCall DxCall 73 (77 ap bits) ! 6 MyCall DxCall RR73 (77 ap bits) !******** naptypes(0,1:4)=(/1,2,0,0/) ! Tx6 selected (CQ) naptypes(1,1:4)=(/2,3,0,0/) ! Tx1 naptypes(2,1:4)=(/2,3,0,0/) ! Tx2 naptypes(3,1:4)=(/3,6,0,0/) ! Tx3 naptypes(4,1:4)=(/3,6,0,0/) ! Tx4 naptypes(5,1:4)=(/3,1,2,0/) ! Tx5 mycall0='' hiscall0='' first=.false. endif l1=index(mycall,char(0)) if(l1.ne.0) mycall(l1:)=" " l1=index(hiscall,char(0)) if(l1.ne.0) hiscall(l1:)=" " if(mycall.ne.mycall0 .or. hiscall.ne.hiscall0) then apbits=0 apbits(1)=99 apbits(30)=99 if(len(trim(mycall)) .lt. 3) go to 10 nohiscall=.false. hiscall0=hiscall if(len(trim(hiscall0)).lt.3) then hiscall0=mycall ! use mycall for dummy hiscall - mycall won't be hashed. nohiscall=.true. endif msg=trim(mycall)//' '//trim(hiscall0)//' RR73' i3=-1 n3=-1 call pack77(msg,i3,n3,c77) call unpack77(c77,1,msgsent,unpk77_success) if(i3.ne.1 .or. (msg.ne.msgsent) .or. .not.unpk77_success) go to 10 read(c77,'(77i1)') message77 message77=mod(message77+rvec,2) call encode174_91(message77,cw) apbits=2*cw-1 if(nohiscall) apbits(30)=99 10 continue mycall0=mycall hiscall0=hiscall endif !************************************ hmod=2**nsubmode if(nfqso+nqsoprogress.eq.-999) return Keff=91 nmax=15*12000 single_decode=iand(nexp_decode,32).eq.32 if(ntrperiod.eq.15) then nsps=720 nmax=15*12000 ndown=18/hmod !nss=40,80,160,400 if(hmod.eq.4) ndown=4 if(hmod.eq.8) ndown=2 nfft1=int(nmax/ndown)*ndown else if(ntrperiod.eq.30) then nsps=1680 nmax=30*12000 ndown=42/hmod !nss=40,80,168,336 nfft1=359856 !nfft2=8568=2^3*3^2*7*17 if(hmod.eq.4) then ndown=10 nfft1=nmax endif if(hmod.eq.8) then ndown=5 nfft1=nmax endif else if(ntrperiod.eq.60) then nsps=3888 nmax=60*12000 ndown=96/hmod !nss=36,81,162,324 if(hmod.eq.1) ndown=108 nfft1=7500*96 ! nfft2=7500=2^2*3*5^4 else if(ntrperiod.eq.120) then nsps=8200 nmax=120*12000 ndown=200/hmod !nss=40,82,164,328 if(hmod.eq.1) ndown=205 nfft1=7200*200 ! nfft2=7200=2^5*3^2*5^2 else if(ntrperiod.eq.300) then nsps=21504 nmax=300*12000 ndown=512/hmod !nss=42,84,168,336 nfft1=7020*512 ! nfft2=7020=2^2*3^3*5*13 else if(ntrperiod.eq.900) then nsps=66560 nmax=900*12000 ndown=1664/hmod !nss=40,80,160,320 nfft1=6480*1664 ! nfft2=6480=2^4*3^4*5 else if(ntrperiod.eq.1800) then nsps=134400 nmax=1800*12000 ndown=3360/hmod !nss=40,80,160,320 nfft1=6426*3360 ! nfft2=6426=2*3^3*7*17 end if nss=nsps/ndown fs=12000.0 !Sample rate fs2=fs/ndown nspsec=nint(fs2) dt=1.0/fs !Sample interval (s) dt2=1.0/fs2 tt=nsps*dt !Duration of "itone" symbols (s) baud=1.0/tt sigbw=4.0*hmod*baud nfft2=nfft1/ndown !make sure that nfft1 is exactly nfft2*ndown nfft1=nfft2*ndown nh1=nfft1/2 allocate( c_bigfft(0:nfft1/2) ) allocate( c2(0:nfft2-1) ) allocate( cframe(0:160*nss-1) ) if(ndepth.eq.3) then nblock=4 jittermax=2 norder=3 elseif(ndepth.eq.2) then nblock=1 if(hmod.eq.1) nblock=3 jittermax=0 norder=3 elseif(ndepth.eq.1) then nblock=1 jittermax=0 norder=3 endif ndropmax=1 npct=nexp_decode/256 call blanker(iwave,nfft1,ndropmax,npct,c_bigfft) ! The big fft is done once and is used for calculating the smoothed spectrum ! and also for downconverting/downsampling each candidate. call four2a(c_bigfft,nfft1,1,-1,0) !r2c ! call blank2(nfa,nfb,nfft1,c_bigfft,iwave) if(hmod.eq.1) then if(fMHz.lt.2.0) then nsyncoh=8 ! Use N=8 for sync nhicoh=1 ! Use N=1,2,4,8 for symbol estimation else nsyncoh=4 ! Use N=4 for sync nhicoh=0 ! Use N=1,2,3,4 for symbol estimation endif else if(hmod.eq.2) nsyncoh=1 if(hmod.eq.4) nsyncoh=-2 if(hmod.eq.8) nsyncoh=-4 endif if( single_decode ) then fa=max(100,nint(nfqso+1.5*hmod*baud-ntol)) fb=min(4800,nint(nfqso+1.5*hmod*baud+ntol)) else fa=max(100,nfa) fb=min(4800,nfb) endif if(hmod.eq.1) then if(ntrperiod.eq.15) minsync=1.15 if(ntrperiod.gt.15) minsync=1.20 elseif(hmod.gt.1) then minsync=1.2 endif ! Get first approximation of candidate frequencies call get_candidates_fst4(c_bigfft,nfft1,nsps,hmod,fs,fa,fb, & minsync,ncand,candidates,base) ndecodes=0 decodes=' ' isbest=0 fc2=0. do icand=1,ncand fc0=candidates(icand,1) detmet=candidates(icand,2) ! Downconvert and downsample a slice of the spectrum centered on the ! rough estimate of the candidates frequency. ! Output array c2 is complex baseband sampled at 12000/ndown Sa/sec. ! The size of the downsampled c2 array is nfft2=nfft1/ndown call fst4_downsample(c_bigfft,nfft1,ndown,fc0,sigbw,c2) call timer('sync240 ',0) fc1=0.0 if(emedelay.lt.0.1) then ! search offsets from 0 s to 2 s is0=1.5*nspsec ishw=1.5*nspsec else ! search plus or minus 1.5 s centered on emedelay is0=nint((emedelay+1.0)*nspsec) ishw=1.5*nspsec endif smax=-1.e30 do if=-12,12 fc=fc1 + 0.1*baud*if do istart=max(1,is0-ishw),is0+ishw,4*hmod call sync_fst4(c2,istart,fc,hmod,nsyncoh,nfft2,nss, & ntrperiod,fs2,sync) if(sync.gt.smax) then fc2=fc isbest=istart smax=sync endif enddo enddo fc1=fc2 is0=isbest ishw=4*hmod isst=1*hmod smax=0.0 do if=-7,7 fc=fc1 + 0.02*baud*if do istart=max(1,is0-ishw),is0+ishw,isst call sync_fst4(c2,istart,fc,hmod,nsyncoh,nfft2,nss, & ntrperiod,fs2,sync) if(sync.gt.smax) then fc2=fc isbest=istart smax=sync endif enddo enddo call timer('sync240 ',1) fc_synced = fc0 + fc2 dt_synced = (isbest-fs2)*dt2 !nominal dt is 1 second so frame starts at sample fs2 candidates(icand,3)=fc_synced candidates(icand,4)=isbest enddo ! remove duplicate candidates do icand=1,ncand fc=candidates(icand,3) isbest=nint(candidates(icand,4)) do ic2=1,ncand fc2=candidates(ic2,3) isbest2=nint(candidates(ic2,4)) if(ic2.ne.icand .and. fc2.gt.0.0) then if(abs(fc2-fc).lt.0.10*baud) then ! same frequency if(abs(isbest2-isbest).le.2) then candidates(ic2,3)=-1 endif endif endif enddo enddo ic=0 do icand=1,ncand if(candidates(icand,3).gt.0) then ic=ic+1 candidates(ic,:)=candidates(icand,:) endif enddo ncand=ic xsnr=0. do icand=1,ncand sync=candidates(icand,2) fc_synced=candidates(icand,3) isbest=nint(candidates(icand,4)) xdt=(isbest-nspsec)/fs2 if(ntrperiod.eq.15) xdt=(isbest-real(nspsec)/2.0)/fs2 call fst4_downsample(c_bigfft,nfft1,ndown,fc_synced,sigbw,c2) do ijitter=0,jittermax if(ijitter.eq.0) ioffset=0 if(ijitter.eq.1) ioffset=1 if(ijitter.eq.2) ioffset=-1 is0=isbest+ioffset if(is0.lt.0) cycle cframe=c2(is0:is0+160*nss-1) bitmetrics=0 if(hmod.eq.1) then call get_fst4_bitmetrics(cframe,nss,hmod,nblock,nhicoh,bitmetrics,s4,badsync) else call get_fst4_bitmetrics2(cframe,nss,hmod,nblock,bitmetrics,s4,badsync) endif if(badsync) cycle hbits=0 where(bitmetrics(:,1).ge.0) hbits=1 ns1=count(hbits( 1: 16).eq.(/0,0,0,1,1,0,1,1,0,1,0,0,1,1,1,0/)) ns2=count(hbits( 77: 92).eq.(/1,1,1,0,0,1,0,0,1,0,1,1,0,0,0,1/)) ns3=count(hbits(153:168).eq.(/0,0,0,1,1,0,1,1,0,1,0,0,1,1,1,0/)) ns4=count(hbits(229:244).eq.(/1,1,1,0,0,1,0,0,1,0,1,1,0,0,0,1/)) ns5=count(hbits(305:320).eq.(/0,0,0,1,1,0,1,1,0,1,0,0,1,1,1,0/)) nsync_qual=ns1+ns2+ns3+ns4+ns5 ! if(nsync_qual.lt. 46) cycle !### Value ?? ### scalefac=2.83 llra( 1: 60)=bitmetrics( 17: 76, 1) llra( 61:120)=bitmetrics( 93:152, 1) llra(121:180)=bitmetrics(169:228, 1) llra(181:240)=bitmetrics(245:304, 1) llra=scalefac*llra llrb( 1: 60)=bitmetrics( 17: 76, 2) llrb( 61:120)=bitmetrics( 93:152, 2) llrb(121:180)=bitmetrics(169:228, 2) llrb(181:240)=bitmetrics(245:304, 2) llrb=scalefac*llrb llrc( 1: 60)=bitmetrics( 17: 76, 3) llrc( 61:120)=bitmetrics( 93:152, 3) llrc(121:180)=bitmetrics(169:228, 3) llrc(181:240)=bitmetrics(245:304, 3) llrc=scalefac*llrc llrd( 1: 60)=bitmetrics( 17: 76, 4) llrd( 61:120)=bitmetrics( 93:152, 4) llrd(121:180)=bitmetrics(169:228, 4) llrd(181:240)=bitmetrics(245:304, 4) llrd=scalefac*llrd apmag=maxval(abs(llra))*1.1 ntmax=nblock+nappasses(nQSOProgress) if(lapcqonly) ntmax=nblock+1 if(ndepth.eq.1) ntmax=nblock apmask=0 if(iwspr.eq.1) then ! 50-bit msgs, no ap decoding nblock=4 ntmax=nblock endif do itry=1,ntmax if(itry.eq.1) llr=llra if(itry.eq.2.and.itry.le.nblock) llr=llrb if(itry.eq.3.and.itry.le.nblock) llr=llrc if(itry.eq.4.and.itry.le.nblock) llr=llrd if(itry.le.nblock) then apmask=0 iaptype=0 endif if(itry.gt.nblock) then llr=llra if(nblock.gt.1) then if(hmod.eq.1) llr=llrd if(hmod.eq.2) llr=llrb if(hmod.eq.4) llr=llrc if(hmod.eq.8) llr=llrd endif iaptype=naptypes(nQSOProgress,itry-nblock) if(lapcqonly) iaptype=1 if(iaptype.ge.2 .and. apbits(1).gt.1) cycle ! No, or nonstandard, mycall if(iaptype.ge.3 .and. apbits(30).gt.1) cycle ! No, or nonstandard, dxcall if(iaptype.eq.1) then ! CQ apmask=0 apmask(1:29)=1 llr(1:29)=apmag*mcq(1:29) endif if(iaptype.eq.2) then ! MyCall ??? ??? apmask=0 apmask(1:29)=1 llr(1:29)=apmag*apbits(1:29) endif if(iaptype.eq.3) then ! MyCall DxCall ??? apmask=0 apmask(1:58)=1 llr(1:58)=apmag*apbits(1:58) endif if(iaptype.eq.4 .or. iaptype.eq.5 .or. iaptype .eq.6) then apmask=0 apmask(1:77)=1 llr(1:58)=apmag*apbits(1:58) if(iaptype.eq.4) llr(59:77)=apmag*mrrr(1:19) if(iaptype.eq.5) llr(59:77)=apmag*m73(1:19) if(iaptype.eq.6) llr(59:77)=apmag*mrr73(1:19) endif endif dmin=0.0 nharderrors=-1 unpk77_success=.false. if(iwspr.eq.0) then maxosd=2 Keff=91 norder=3 call timer('d240_101',0) call decode240_101(llr,Keff,maxosd,norder,apmask,message101, & cw,ntype,nharderrors,dmin) call timer('d240_101',1) elseif(iwspr.eq.1) then maxosd=2 call timer('d240_74 ',0) Keff=64 norder=4 call decode240_74(llr,Keff,maxosd,norder,apmask,message74,cw, & ntype,nharderrors,dmin) call timer('d240_74 ',1) endif if(nharderrors .ge.0) then if(count(cw.eq.1).eq.0) then nharderrors=-nharderrors cycle endif if(iwspr.eq.0) then write(c77,'(77i1)') mod(message101(1:77)+rvec,2) call unpack77(c77,1,msg,unpk77_success) else write(c77,'(50i1)') message74(1:50) c77(51:77)='000000000000000000000110000' call unpack77(c77,1,msg,unpk77_success) endif if(unpk77_success) then idupe=0 do i=1,ndecodes if(decodes(i).eq.msg) idupe=1 enddo if(idupe.eq.1) goto 2002 ndecodes=ndecodes+1 decodes(ndecodes)=msg if(iwspr.eq.0) then call get_fst4_tones_from_bits(message101,itone,0) else call get_fst4_tones_from_bits(message74,itone,1) endif inquire(file='plotspec',exist=ex) fmid=-999.0 if(ex) then call write_ref(itone,iwave,nsps,nmax,ndown,hmod, & isbest,fc_synced,fmid,w50) endif xsig=0 do i=1,NN xsig=xsig+s4(itone(i),i)**2 enddo arg=400.0*(xsig/base)-1.0 if(arg.gt.0.0) then xsnr=10*log10(arg)-21.0-11.7*log10(nsps/800.0) else xsnr=-99.9 endif else cycle endif nsnr=nint(xsnr) qual=0. fsig=fc_synced - 1.5*hmod*baud if(ex) then write(21,'(i6.6,8i6,f7.1,f10.2,f7.1,1x,f7.2,1x,f7.1,1x,a37,f5.3)') & nutc,icand,itry,nsyncoh,iaptype,ijitter,ntype,nsync_qual, & nharderrors,dmin,sync,xsnr,xdt,fsig,msg,w50 flush(21) endif call this%callback(nutc,smax1,nsnr,xdt,fsig,msg, & iaptype,qual,ntrperiod,lwspr,fmid,w50) goto 2002 endif enddo ! metrics enddo ! istart jitter 2002 enddo !candidate list return end subroutine decode subroutine sync_fst4(cd0,i0,f0,hmod,ncoh,np,nss,ntr,fs,sync) ! Compute sync power for a complex, downsampled FST4 signal. use timer_module, only: timer include 'fst4/fst4_params.f90' complex cd0(0:np-1) complex csync1,csync2,csynct1,csynct2 complex ctwk(3200) complex z1,z2,z3,z4,z5 integer hmod,isyncword1(0:7),isyncword2(0:7) real f0save common/sync240com/csync1(3200),csync2(3200),csynct1(3200),csynct2(3200) data isyncword1/0,1,3,2,1,0,2,3/ data isyncword2/2,3,1,0,3,2,0,1/ data f0save/-99.9/,nss0/-1/,ntr0/-1/ save twopi,dt,fac,f0save,nss0,ntr0 p(z1)=(real(z1*fac)**2 + aimag(z1*fac)**2)**0.5 !Compute power nz=8*nss call timer('sync240a',0) if(nss.ne.nss0 .or. ntr.ne.ntr0) then twopi=8.0*atan(1.0) dt=1/fs k=1 phi1=0.0 phi2=0.0 do i=0,7 dphi1=twopi*hmod*(isyncword1(i)-1.5)/real(nss) dphi2=twopi*hmod*(isyncword2(i)-1.5)/real(nss) do j=1,nss csync1(k)=cmplx(cos(phi1),sin(phi1)) csync2(k)=cmplx(cos(phi2),sin(phi2)) phi1=mod(phi1+dphi1,twopi) phi2=mod(phi2+dphi2,twopi) k=k+1 enddo enddo fac=1.0/(8.0*nss) nss0=nss ntr0=ntr f0save=-1.e30 endif if(f0.ne.f0save) then dphi=twopi*f0*dt phi=0.0 do i=1,nz ctwk(i)=cmplx(cos(phi),sin(phi)) phi=mod(phi+dphi,twopi) enddo csynct1(1:nz)=ctwk(1:nz)*csync1(1:nz) csynct2(1:nz)=ctwk(1:nz)*csync2(1:nz) f0save=f0 nss0=nss endif call timer('sync240a',1) i1=i0 !Costas arrays i2=i0+38*nss i3=i0+76*nss i4=i0+114*nss i5=i0+152*nss s1=0.0 s2=0.0 s3=0.0 s4=0.0 s5=0.0 if(ncoh.gt.0) then nsec=8/ncoh do i=1,nsec is=(i-1)*ncoh*nss z1=0 if(i1+is.ge.1) then z1=sum(cd0(i1+is:i1+is+ncoh*nss-1)*conjg(csynct1(is+1:is+ncoh*nss))) endif z2=sum(cd0(i2+is:i2+is+ncoh*nss-1)*conjg(csynct2(is+1:is+ncoh*nss))) z3=sum(cd0(i3+is:i3+is+ncoh*nss-1)*conjg(csynct1(is+1:is+ncoh*nss))) z4=sum(cd0(i4+is:i4+is+ncoh*nss-1)*conjg(csynct2(is+1:is+ncoh*nss))) z5=0 if(i5+is+ncoh*nss-1.le.np) then z5=sum(cd0(i5+is:i5+is+ncoh*nss-1)*conjg(csynct1(is+1:is+ncoh*nss))) endif s1=s1+abs(z1)/nz s2=s2+abs(z2)/nz s3=s3+abs(z3)/nz s4=s4+abs(z4)/nz s5=s5+abs(z5)/nz enddo else nsub=-ncoh nps=nss/nsub do i=1,8 do isub=1,nsub is=(i-1)*nss+(isub-1)*nps z1=0.0 if(i1+is.ge.1) then z1=sum(cd0(i1+is:i1+is+nps-1)*conjg(csynct1(is+1:is+nps))) endif z2=sum(cd0(i2+is:i2+is+nps-1)*conjg(csynct2(is+1:is+nps))) z3=sum(cd0(i3+is:i3+is+nps-1)*conjg(csynct1(is+1:is+nps))) z4=sum(cd0(i4+is:i4+is+nps-1)*conjg(csynct2(is+1:is+nps))) z5=0.0 if(i5+is+ncoh*nss-1.le.np) then z5=sum(cd0(i5+is:i5+is+nps-1)*conjg(csynct1(is+1:is+nps))) endif s1=s1+abs(z1)/(8*nss) s2=s2+abs(z2)/(8*nss) s3=s3+abs(z3)/(8*nss) s4=s4+abs(z4)/(8*nss) s5=s5+abs(z5)/(8*nss) enddo enddo endif sync = s1+s2+s3+s4+s5 return end subroutine sync_fst4 subroutine fst4_downsample(c_bigfft,nfft1,ndown,f0,sigbw,c1) ! Output: Complex data in c(), sampled at 12000/ndown Hz complex c_bigfft(0:nfft1/2) complex c1(0:nfft1/ndown-1) df=12000.0/nfft1 i0=nint(f0/df) ih=nint( ( f0 + 1.3*sigbw/2.0 )/df) nbw=ih-i0+1 c1=0. c1(0)=c_bigfft(i0) nfft2=nfft1/ndown do i=1,nbw if(i0+i.le.nfft1/2) c1(i)=c_bigfft(i0+i) if(i0-i.ge.0) c1(nfft2-i)=c_bigfft(i0-i) enddo c1=c1/nfft2 call four2a(c1,nfft2,1,1,1) !c2c FFT back to time domain return end subroutine fst4_downsample subroutine get_candidates_fst4(c_bigfft,nfft1,nsps,hmod,fs,fa,fb, & minsync,ncand,candidates,base) complex c_bigfft(0:nfft1/2) !Full length FFT of raw data integer hmod !Modulation index (submode) integer im(1) !For maxloc real candidates(100,4) !Candidate list real, allocatable :: s(:) !Low resolution power spectrum real, allocatable :: s2(:) !CCF of s() with 4 tones real xdb(-3:3) !Model 4-tone CCF peaks real minsync data xdb/0.25,0.50,0.75,1.0,0.75,0.50,0.25/ nh1=nfft1/2 df1=fs/nfft1 baud=fs/nsps !Keying rate df2=baud/2.0 nd=df2/df1 !s() sums this many bins of big FFT ndh=nd/2 ia=nint(max(100.0,fa)/df2) !Low frequency search limit ib=nint(min(4800.0,fb)/df2) !High frequency limit signal_bw=4*(12000.0/nsps)*hmod analysis_bw=min(4800.0,fb)-max(100.0,fa) xnoise_bw=10.0*signal_bw !Is this a good compromise? if(analysis_bw.gt.xnoise_bw) then ina=ia inb=ib else fcenter=(fa+fb)/2.0 !If noise_bw > analysis_bw, fl = max(100.0,fcenter-xnoise_bw/2.)/df2 !we'll search over noise_bw fh = min(4800.0,fcenter+xnoise_bw/2.)/df2 ina=nint(fl) inb=nint(fh) endif nnw=nint(48000.*nsps*2./fs) allocate (s(nnw)) s=0. !Compute low-resloution power spectrum do i=ina,inb ! noise analysis window includes signal analysis window j0=nint(i*df2/df1) do j=j0-ndh,j0+ndh s(i)=s(i) + real(c_bigfft(j))**2 + aimag(c_bigfft(j))**2 enddo enddo ina=max(ina,1+3*hmod) !Don't run off the ends inb=min(inb,nnw-3*hmod) allocate (s2(nnw)) s2=0. do i=ina,inb !Compute CCF of s() and 4 tones s2(i)=s(i-hmod*3) + s(i-hmod) +s(i+hmod) +s(i+hmod*3) enddo call pctile(s2(ina+hmod*3:inb-hmod*3),inb-ina+1-hmod*6,30,base) s2=s2/base !Normalize wrt noise level ncand=0 candidates=0 if(ia.lt.3) ia=3 if(ib.gt.nnw-2) ib=nnw-2 ! Find candidates, using the CLEAN algorithm to remove a model of each one ! from s2() after it has been found. pval=99.99 do while(ncand.lt.100) im=maxloc(s2(ia:ib)) iploc=ia+im(1)-1 !Index of CCF peak pval=s2(iploc) !Peak value if(pval.lt.minsync) exit do i=-3,+3 !Remove 0.9 of a model CCF at k=iploc+2*hmod*i !this frequency from s2() if(k.ge.ia .and. k.le.ib) then s2(k)=max(0.,s2(k)-0.9*pval*xdb(i)) endif enddo ncand=ncand+1 candidates(ncand,1)=df2*iploc !Candidate frequency candidates(ncand,2)=pval !Rough estimate of SNR enddo return end subroutine get_candidates_fst4 subroutine write_ref(itone,iwave,nsps,nmax,ndown,hmod,i0,fc,fmid,w50) ! On "plotspec" special request, compute Doppler spread for a decoded signal include 'fst4/fst4_params.f90' complex, allocatable :: cwave(:) !Reconstructed complex signal complex, allocatable :: g(:) !Channel gain, g(t) in QEX paper real,allocatable :: ss(:) !Computed power spectrum of g(t) integer itone(160) !Tones for this message integer*2 iwave(nmax) !Raw Rx data integer hmod !Modulation index data ncall/0/ save ncall ncall=ncall+1 nfft=2*nmax nwave=max(nmax,(NN+2)*nsps) allocate(cwave(0:nwave-1)) allocate(g(0:nfft-1)) wave=0 fsample=12000.0 call gen_fst4wave(itone,NN,nsps,nwave,fsample,hmod,fc,1,cwave,wave) cwave=cshift(cwave,-i0*ndown) fac=1.0/32768 g(0:nmax-1)=fac*float(iwave)*conjg(cwave(:nmax-1)) g(nmax:)=0. call four2a(g,nfft,1,-1,1) !Forward c2c FFT df=12000.0/nfft ia=1.0/df smax=0. do i=-ia,ia !Find smax in +/- 1 Hz around 0. j=i if(j.lt.0) j=i+nfft s=real(g(j))**2 + aimag(g(j))**2 smax=max(s,smax) enddo ia=10.1/df allocate(ss(-ia:ia)) !Allocate space for +/- 10 Hz sum1=0. sum2=0. nns=0 do i=-ia,ia j=i if(j.lt.0) j=i+nfft ss(i)=(real(g(j))**2 + aimag(g(j))**2)/smax f=i*df if(f.ge.-4.0 .and. f.le.-2.0) then sum1=sum1 + ss(i) !Power between -2 and -4 Hz nns=nns+1 else if(f.ge.2.0 .and. f.le.4.0) then sum2=sum2 + ss(i) !Power between +2 and +4 Hz endif enddo avg=min(sum1/nns,sum2/nns) !Compute avg from smaller sum sum1=0. do i=-ia,ia f=i*df if(abs(f).le.1.0) sum1=sum1 + ss(i)-avg !Power in abs(f) < 1 Hz enddo ia=nint(1.0/df) + 1 sum2=0.0 xi1=-999 xi2=-999 xi3=-999 sum2z=0. do i=-ia,ia !Find freq range that has 50% of signal power sum2=sum2 + ss(i)-avg if(sum2.ge.0.25*sum1 .and. xi1.eq.-999.0) then xi1=i - 1 + (sum2-0.25*sum1)/(sum2-sum2z) endif if(sum2.ge.0.50*sum1 .and. xi2.eq.-999.0) then xi2=i - 1 + (sum2-0.50*sum1)/(sum2-sum2z) endif if(sum2.ge.0.75*sum1) then xi3=i - 1 + (sum2-0.75*sum1)/(sum2-sum2z) exit endif sum2z=sum2 enddo xdiff=sqrt(1.0+(xi3-xi1)**2) !Keep small values from fluctuating too widely w50=xdiff*df !Compute Doppler spread fmid=xi2*df !Frequency midpoint of signal powere do i=-ia,ia !Save the spectrum for plotting f=i*df y=0.99*ss(i+nint(xi2)) + ncall-1 write(52,1010) f,y 1010 format(f12.6,f12.6) enddo return end subroutine write_ref end module fst4_decode