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More work on block detection for dpsk.

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git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@8644 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
This commit is contained in:
Steven Franke 2018-04-28 22:18:19 +00:00
parent 073d7d01c9
commit 8149fe24be
1 changed files with 78 additions and 14 deletions
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92
lib/fsk4hf/wsprdpskd.f90
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@ -38,6 +38,7 @@ program wsprdpskd
integer*1,target :: idat(9)
integer*1 decoded(68),apmask(204),cw(204)
integer*1 hbits(232),hbits1(232),hbits3(232)
integer*1 b(14),bbest(14)
data ipreamble/1,1,1,1,0,0,0,0,0,0,0,0,1,1,1,1/
data iuniqueword0/z'30C9E8AD'/
@ -64,12 +65,7 @@ program wsprdpskd
isync2(113:116)=0
isync2(117:216)=isync(101:200)
! data sync tone
! 0 0 0
! 0 1 1
! 1 0 2
! 1 1 3
dphi=twopi*baud*(h/2.0)*dt*20 ! dt*10 is samp interval after downsample
dphi=twopi*baud*(h/2.0)*dt*20 ! dt*20 is samp interval after downsample
do j=0,1
if(j.eq.0) then
dphi0=-3*dphi
@ -150,24 +146,76 @@ program wsprdpskd
fb=10.0
fs=12000.0/30.0
npts=120*12000.0/30.0
nsync=16
call getcandidate2(c2,npts,fs,fa,fb,ncand,candidates) !First approx for freq
! call getcandidate2(c2,npts,fs,fa,fb,ncand,candidates) !First approx for freq
ncand=1
candidates(1,1)=0.0
candidates(1,2)=-28
ndecodes=0
do icand=1,ncand
fc0=candidates(icand,1)
xsnr=candidates(icand,2)
fc0=0.0
call dsdpsk(c2,fc0,cd)
i0=40
do i=0,231
cs(i)=cd(i0+10*i)
enddo
cs(i)=cd(i0+10*i)/5e4
enddo
! 2-bit differential detection
do i=1,231
sbits(i)=-real(cs(i)*conjg(cs(i-1)))/5e4
sbits(i)=-real(cs(i)*conjg(cs(i-1)))
enddo
rxdata(1:100)=sbits(1:100)
rxdata(101:200)=sbits(132:231);
! detect a differentially encoded block of symbols using the
! Divsalar and Simon approach, except that we estimate only
! the central symbol of the block and then step the block forward
! by one symbol.
!
sbits3=sbits
goto 100
nbit=13 ! number of decoded bits to be derived from nbit+1 symbols
numseq=2**nbit
il=(nbit+1)/2
ih=231-nbit/2
do isym=il,ih
rmax=-1e32
b=0
do iseq=0,numseq-1
do i=1,nbit
b(i)=merge(1,0,iand(iseq,2**(nbit-i))>0)
enddo
b(1:nbit)=2*b(1:nbit)-1
i1=isym-(nbit+1)/2
csum=cs(i1)
do i=1,nbit
bb=1
do m=1,i
bb=bb*b(m)
enddo
csum=csum+bb*cs(i1+i)
enddo
ps(iseq)=abs(csum)**2
if(ps(iseq).gt.rmax) then
bbest=b
rmax=ps(iseq)
endif
enddo
if(isym.eq.il) then
do i=1,isym-1
call getmetric(2**(nbit-i),ps,numseq,xmet)
sbits3(i)=-xmet
enddo
endif
call getmetric(2**((nbit-1)/2),ps,numseq,xmet)
sbits3(isym)=-xmet
if(isym.eq.ih) then
do i=ih+1,231
call getmetric(2**(231-i),ps,numseq,xmet)
sbits3(i)=-xmet
enddo
endif
enddo
100 continue
rxdata(1:100)=sbits3(1:100)
rxdata(101:200)=sbits3(132:231);
rxav=sum(rxdata(1:200))/200.0
rx2av=sum(rxdata(1:200)*rxdata(1:200))/200.0
rxsig=sqrt(rx2av-rxav*rxav)
@ -227,6 +275,22 @@ program wsprdpskd
999 end program wsprdpskd
subroutine getmetric(ib,ps,ns,xmet)
real ps(0:ns-1)
xm1=-1e32
xm0=-1e32
do i=0,ns-1
if( iand(i/ib,1) .eq. 1 .and. ps(i) .gt. xm1 ) then
xm1=ps(i)
endif
if( iand(i/ib,1) .eq. 0 .and. ps(i) .gt. xm0 ) then
xm0=ps(i)
endif
enddo
xmet=xm1-xm0
return
end subroutine getmetric
subroutine dsdpsk(ci,f0,co)
parameter(NI=240*200,NH=NI/2,NO=NI/20) ! downsample from 200 samples per symbol to 10
complex ci(0:NI-1),ct(0:NI-1)