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Improve dt estimation in ft8b so that dt refinement procedure in subtractft8.f90 can be done with 4 calls to sqf instead of 7.

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This commit is contained in:
Steven Franke 2020-02-29 13:46:59 -06:00
parent 877878ea88
commit 037805ca8f
4 changed files with 38 additions and 23 deletions
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27
lib/ft8/ft8b.f90
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@ -17,6 +17,7 @@ subroutine ft8b(dd0,newdat,nQSOProgress,nfqso,nftx,ndepth,nzhsym,lapon, &
real bmeta(174),bmetb(174),bmetc(174),bmetd(174)
real llra(174),llrb(174),llrc(174),llrd(174),llrz(174) !Soft symbols
real dd0(15*12000)
real ss(9)
integer*1 message77(77),apmask(174),cw(174)
integer apsym(58),aph10(10)
integer mcq(29),mcqru(29),mcqfd(29),mcqtest(29),mcqww(29)
@ -28,6 +29,7 @@ subroutine ft8b(dd0,newdat,nQSOProgress,nfqso,nftx,ndepth,nzhsym,lapon, &
integer ncontest,ncontest0
logical one(0:511,0:8)
integer graymap(0:7)
integer iloc(1)
complex cd0(0:3199)
complex ctwk(32)
complex csymb(32)
@ -106,17 +108,15 @@ subroutine ft8b(dd0,newdat,nQSOProgress,nfqso,nftx,ndepth,nzhsym,lapon, &
i0=nint((xdt+0.5)*fs2) !Initial guess for start of signal
smax=0.0
do idt=i0-8,i0+8 !Search over +/- one quarter symbol
do idt=i0-10,i0+10 !Search over +/- one quarter symbol
call sync8d(cd0,idt,ctwk,0,sync)
if(sync.gt.smax) then
smax=sync
ibest=idt
endif
enddo
xdt2=ibest*dt2 !Improved estimate for DT
! Now peak up in frequency
i0=nint(xdt2*fs2)
smax=0.0
do ifr=-5,5 !Search over +/- 2.5 Hz
delf=ifr*0.5
@ -126,7 +126,7 @@ subroutine ft8b(dd0,newdat,nQSOProgress,nfqso,nftx,ndepth,nzhsym,lapon, &
ctwk(i)=cmplx(cos(phi),sin(phi))
phi=mod(phi+dphi,twopi)
enddo
call sync8d(cd0,i0,ctwk,1,sync)
call sync8d(cd0,ibest,ctwk,1,sync)
if( sync .gt. smax ) then
smax=sync
delfbest=delf
@ -135,9 +135,22 @@ subroutine ft8b(dd0,newdat,nQSOProgress,nfqso,nftx,ndepth,nzhsym,lapon, &
a=0.0
a(1)=-delfbest
call twkfreq1(cd0,NP2,fs2,a,cd0)
xdt=xdt2
f1=f1+delfbest !Improved estimate of DF
call sync8d(cd0,i0,ctwk,0,sync)
call timer('ft8_down',0)
call ft8_downsample(dd0,.false.,f1,cd0) !Mix f1 to baseband and downsample
call timer('ft8_down',1)
smax=0.0
do idt=-4,4 !Search over +/- one quarter symbol
call sync8d(cd0,ibest+idt,ctwk,0,sync)
ss(idt+5)=sync
enddo
smax=maxval(ss)
iloc=maxloc(ss)
ibest=iloc(1)-5+ibest
xdt=(ibest-1)*dt2
sync=smax
do k=1,NN
i1=ibest+(k-1)*32
@ -421,7 +434,7 @@ subroutine ft8b(dd0,newdat,nQSOProgress,nfqso,nftx,ndepth,nzhsym,lapon, &
if(lsubtract) call subtractft8(dd0,itone,f1,xdt,.false.)
! write(21,3001) nzhsym,npasses,nqsoprogress,ipass,iaptype,lsubtract, &
! f1,xdt,msg37(1:22); flush(21)
!3001 format(5i3,L3,f7.1,f7.2,2x,a22)
!3001 format(5i3,L3,f7.1,f9.4,2x,a22)
xsig=0.0
xnoi=0.0
do i=1,79

23
lib/ft8/subtractft8.f90
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@ -41,19 +41,24 @@ subroutine subtractft8(dd0,itone,f0,dt,ldt)
call gen_ft8wave(itone,79,1920,2.0,12000.0,f0,cref,xjunk,1,NFRAME)
if(ldt) then !Are we refining DT ?
sqa=sqf(-300)
sqb=sqf(300)
sq0=sqf(0) !Do the subtraction with idt=0
call peakup(sqa,sq0,sqb,dx)
if(abs(dx).gt.1.0) return !No acceptable minimum: do not subtract
i1=nint(300.0*dx) !First approximation of best idt
sqa=sqf(i1-60)
sqb=sqf(i1+60)
! sqa=sqf(-300)
! sqb=sqf(300)
! sq0=sqf(0) !Do the subtraction with idt=0
! call peakup(sqa,sq0,sqb,dx)
! if(abs(dx).gt.1.0) return !No acceptable minimum: do not subtract
! i1=nint(300.0*dx) !First approximation of best idt
i1=0
! sqa=sqf(i1-60)
! sqb=sqf(i1+60)
sqa=sqf(i1-90)
sqb=sqf(i1+90)
sq0=sqf(i1)
call peakup(sqa,sq0,sqb,dx)
if(abs(dx).gt.1.0) return !No acceptable minimum: do not subtract
i2=nint(60.0*dx) + i1 !Best estimate of idt
! i2=nint(60.0*dx) + i1 !Best estimate of idt
i2=nint(90.0*dx) + i1 !Best estimate of idt
sq0=sqf(i2) !Do the subtraction with idt=i2
!write(*,*) 'subtract - i2= ',i2,dt
else
sq0=sqf(0) !Do the subtraction with idt=0
endif

3
lib/ft8/sync8.f90
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@ -106,7 +106,7 @@ subroutine sync8(dd,nfa,nfb,syncmin,nfqso,maxcand,s,candidate, &
if(red(n).lt.syncmin.or.isnan(red(n)).or.k.eq.maxcand) exit
k=k+1
candidate0(1,k)=n*df
candidate0(2,k)=(jpeak(n)-1)*tstep
candidate0(2,k)=(jpeak(n)-0.5)*tstep
candidate0(3,k)=red(n)
enddo
ncand=k
@ -144,5 +144,6 @@ subroutine sync8(dd,nfa,nfb,syncmin,nfqso,maxcand,s,candidate, &
endif
enddo
ncand=k-1
return
end subroutine sync8

8
lib/ft8/sync8d.f90
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@ -12,20 +12,16 @@ subroutine sync8d(cd0,i0,ctwk,itwk,sync)
integer icos7(0:6)
data icos7/3,1,4,0,6,5,2/
data first/.true./
save first,twopi,fs2,dt2,taus,baud,csync
save first,twopi,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=12000.0/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
dphi=twopi*icos7(i)/32.0
do j=1,32
csync(i,j)=cmplx(cos(phi),sin(phi)) !Waveform for 7x7 Costas array
phi=mod(phi+dphi,twopi)