subroutine mskrtd(id2,nutc0,tsec,ntol,line) ! Real-time decoder for MSK144. ! Analysis block size = NZ = 7168 samples, t_block = 0.597333 s ! Called from hspec() at half-block increments, about 0.3 s parameter (NZ=7168) !Block size parameter (NSPM=864) !Number of samples per message frame parameter (NFFT1=8192) !FFT size for making analytic signal parameter (NAVGMAX=7) !Coherently average up to 7 frames parameter (NPTSMAX=7*NSPM) !Max points analyzed at once integer*2 id2(NZ) !Raw 16-bit data character*22 msgreceived !Decoded message character*80 line !Formatted line with UTC dB T Freq Msg complex cdat(NFFT1) !Analytic signal complex cdat2(NFFT1) !Signal shifted to baseband complex c(NSPM) !Coherently averaged complex data complex ct(NSPM) complex ct2(2*NSPM) complex cs(NSPM) complex cb(42) !Complex waveform for sync word complex cc(0:NSPM-1) ! integer*8 count0,count1,count2,count3,clkfreq integer s8(8) integer iloc(1) integer ipeaks(10) integer nav(6) real cbi(42),cbq(42) real d(NFFT1) real xcc(0:NSPM-1) real xccs(0:NSPM-1) real pp(12) !Half-sine pulse shape logical first data first/.true./ data s8/0,1,1,1,0,0,1,0/ data nav/1,2,3,5,7,9/ save first,cb,fs,pi,twopi,dt,s8,pp,t03,t12,nutc00 ! call system_clock(count0,clkfreq) if(first) then pi=4.0*atan(1.0) twopi=8.0*atan(1.0) fs=12000.0 dt=1.0/fs do i=1,12 !Define half-sine pulse angle=(i-1)*pi/12.0 pp(i)=sin(angle) enddo ! Define the sync word waveforms s8=2*s8-1 cbq(1:6)=pp(7:12)*s8(1) cbq(7:18)=pp*s8(3) cbq(19:30)=pp*s8(5) cbq(31:42)=pp*s8(7) cbi(1:12)=pp*s8(2) cbi(13:24)=pp*s8(4) cbi(25:36)=pp*s8(6) cbi(37:42)=pp(1:6)*s8(8) cb=cmplx(cbi,cbq) first=.false. t03=0.0 t12=0.0 nutc00=-1 endif msgreceived=' ' max_iterations=10 niterations=0 d(1:NZ)=id2 rms=sqrt(sum(d(1:NZ)*d(1:NZ))/NZ) if(rms.lt.1.0) return fac=1.0/rms d(1:NZ)=fac*d(1:NZ) d(NZ+1:NFFT1)=0. call analytic(d,NZ,NFFT1,cdat) !Convert to analytic signal and filter nmessages=0 line=' ' nshort=0 npts=7168 nsnr=-4 !### Temporary ### do iavg=1,5 navg=nav(iavg) ndf=nint(7.0/navg) + 1 xmax=0.0 bestf=0.0 ! call system_clock(count1,clkfreq) do ifr=-ntol,ntol,ndf !Find freq that maximizes sync ferr=ifr call tweak1(cdat,NPTS,-(1500+ferr),cdat2) c=0 do i=1,navg ib=(i-1)*NSPM+1 ie=ib+NSPM-1 c(1:NSPM)=c(1:NSPM)+cdat2(ib:ie) enddo cc=0 ct2(1:NSPM)=c ct2(NSPM+1:2*NSPM)=c do ish=0,NSPM-1 cc(ish)=dot_product(ct2(1+ish:42+ish)+ct2(336+ish:377+ish),cb(1:42)) enddo xcc=abs(cc) xb=maxval(xcc)/(48.0*sqrt(float(navg))) if(xb.gt.xmax) then xmax=xb bestf=ferr cs=c xccs=xcc endif enddo ! call system_clock(count2,clkfreq) fest=1500+bestf c=cs xcc=xccs ! Find 2 largest peaks do ipk=1,2 iloc=maxloc(xcc) ic2=iloc(1) ipeaks(ipk)=ic2 xcc(max(0,ic2-7):min(NSPM-1,ic2+7))=0.0 enddo do ipk=1,2 do is=1,3 ic0=ipeaks(ipk) if(is.eq.2) ic0=max(1,ic0-1) if(is.eq.3) ic0=min(NSPM,ic0+1) ct=cshift(c,ic0-1) call msk144decodeframe(ct,msgreceived,nsuccess) if(nsuccess .gt. 0) then write(*,*) nsuccess,msgreceived write(line,1020) nutc0,nsnr,tsec,nint(fest),msgreceived,char(0) 1020 format(i6.6,i4,f5.1,i5,' ^ ',a22,a1) goto 999 endif enddo !Slicer dither enddo !Peak loop enddo msgreceived=' ' ndither=-98 999 continue ! call system_clock(count3,clkfreq) ! t12=t12 + float(count2-count1)/clkfreq ! t03=t03 + float(count3-count0)/clkfreq ! if(navg.gt.7) navg=0 ! write(*,3002) nutc0,tsec,t12,t03,xmax,nint(bestf),navg, & ! nbadsync,niterations,ipk,is,msgreceived(1:19) ! write(62,3002) nutc0,tsec,t12,t03,xmax,nint(bestf),navg, & ! nbadsync,niterations,ipk,is,msgreceived(1:19) !3002 format(i6,f6.2,2f7.2,f6.2,i5,5i3,1x,a19) return end subroutine mskrtd