mirror of https://github.com/saitohirga/WSJT-X.git
226 lines
6.5 KiB
Fortran
226 lines
6.5 KiB
Fortran
subroutine timf2(k,nxpol,nfft,nwindow,nb,peaklimit,iqadjust,iqapply,faclim, &
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cx0,cy0,gainx,gainy,phasex,phasey,cx1,cy1,slimit,lstrong,px,py,nzap)
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! Sequential processing of time-domain I/Q data, using Linrad-like
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! "first FFT" and "first backward FFT".
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! cx0,cy0 - complex input data
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! nfft - length of FFTs
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! nwindow - 0 for no window, 2 for sin^2 window
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! iqapply - 0/1 determines if I/Q phase and amplitude corrections applied
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! gainx,y - gain error in Q channel, relative to I
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! phasex,y - phase error
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! cx1,cy1 - output data
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! Non-windowed processing means no overlap, so kstep=nfft.
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! Sin^2 window has 50% overlap, kstep=nfft/2.
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! Frequencies with strong signals are identified and separated. The back
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! transforms are done separately for weak and strong signals, so that
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! noise blanking can be applied to the weak-signal portion. Strong and
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! weak are finally re-combined in the time domain.
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parameter (MAXFFT=1024,MAXNH=MAXFFT/2)
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parameter (MAXSIGS=100)
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complex cx0(0:nfft-1),cx1(0:nfft-1)
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complex cy0(0:nfft-1),cy1(0:nfft-1)
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complex cx(0:MAXFFT-1),cxt(0:MAXFFT-1)
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complex cy(0:MAXFFT-1),cyt(0:MAXFFT-1)
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complex cxs(0:MAXFFT-1),covxs(0:MAXNH-1) !Strong X signals
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complex cys(0:MAXFFT-1),covys(0:MAXNH-1) !Strong Y signals
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complex cxw(0:MAXFFT-1),covxw(0:MAXNH-1) !Weak X signals
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complex cyw(0:MAXFFT-1),covyw(0:MAXNH-1) !Weak Y signals
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real*4 w(0:MAXFFT-1)
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real*4 s(0:MAXFFT-1),stmp(0:MAXFFT-1)
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logical*1 lstrong(0:MAXFFT-1),lprev
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integer ia(MAXSIGS),ib(MAXSIGS)
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complex h,u,v
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logical first
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data first/.true./
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data k0/99999999/
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save w,covxs,covxw,covys,covyw,s,ntc,ntot,nh,kstep,fac,first,k0
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if(first) then
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pi=4.0*atan(1.0)
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do i=0,nfft-1
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w(i)=(sin(i*pi/nfft))**2
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enddo
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s=0.
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ntc=0
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ntot=0
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nh=nfft/2
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kstep=nfft
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if(nwindow.eq.2) kstep=nh
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fac=1.0/nfft
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slimit=1.e30
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first=.false.
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endif
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if(k.lt.k0) then
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covxs=0.
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covxw=0.
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covys=0.
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covyw=0.
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endif
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k0=k
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cx(0:nfft-1)=cx0
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if(nwindow.eq.2) cx(0:nfft-1)=w(0:nfft-1)*cx(0:nfft-1)
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call four2a(cx,nfft,1,1,1) !First forward FFT
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if(nxpol.ne.0) then
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cy(0:nfft-1)=cy0
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if(nwindow.eq.2) cy(0:nfft-1)=w(0:nfft-1)*cy(0:nfft-1)
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call four2a(cy,nfft,1,1,1) !First forward FFT
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endif
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if(iqapply.ne.0) then !Apply I/Q corrections
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h=gainx*cmplx(cos(phasex),sin(phasex))
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v=0.
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do i=0,nfft-1
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u=cx(i)
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if(i.gt.0) v=cx(nfft-i)
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x=real(u) + real(v) - (aimag(u) + aimag(v))*aimag(h) + &
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(real(u) - real(v))*real(h)
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y=aimag(u) - aimag(v) + (aimag(u) + aimag(v))*real(h) + &
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(real(u) - real(v))*aimag(h)
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cxt(i)=0.5*cmplx(x,y)
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enddo
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else
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cxt(0:nfft-1)=cx(0:nfft-1)
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endif
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if(nxpol.ne.0) then
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if(iqapply.ne.0) then !Apply I/Q corrections
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h=gainy*cmplx(cos(phasey),sin(phasey))
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v=0.
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do i=0,nfft-1
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u=cy(i)
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if(i.gt.0) v=cy(nfft-i)
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x=real(u) + real(v) - (aimag(u) + aimag(v))*aimag(h) + &
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(real(u) - real(v))*real(h)
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y=aimag(u) - aimag(v) + (aimag(u) + aimag(v))*real(h) + &
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(real(u) - real(v))*aimag(h)
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cyt(i)=0.5*cmplx(x,y)
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enddo
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else
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cyt(0:nfft-1)=cy(0:nfft-1)
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endif
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endif
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! Identify frequencies with strong signals, copy frequency-domain
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! data into array cs (strong) or cw (weak).
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ntot=ntot+1
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if(mod(ntot,128).eq.5) then
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call pctile(s,stmp,1024,50,xmedian)
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slimit=faclim*xmedian
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endif
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if(ntc.lt.96000/nfft) ntc=ntc+1
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uu=1.0/ntc
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smax=0.
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do i=0,nfft-1
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p=real(cxt(i))**2 + aimag(cxt(i))**2
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if(nxpol.ne.0) p=p + real(cyt(i))**2 + aimag(cyt(i))**2
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s(i)=(1.0-uu)*s(i) + uu*p
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lstrong(i)=(s(i).gt.slimit)
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if(s(i).gt.smax) smax=s(i)
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enddo
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nsigs=0
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lprev=.false.
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iwid=1
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ib=-99
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do i=0,nfft-1
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if(lstrong(i) .and. (.not.lprev)) then
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if(nsigs.lt.MAXSIGS) nsigs=nsigs+1
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ia(nsigs)=i-iwid
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if(ia(nsigs).lt.0) ia(nsigs)=0
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endif
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if(.not.lstrong(i) .and. lprev) then
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ib(nsigs)=i-1+iwid
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if(ib(nsigs).gt.nfft-1) ib(nsigs)=nfft-1
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endif
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lprev=lstrong(i)
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enddo
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if(nsigs.gt.0) then
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do i=1,nsigs
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ja=ia(i)
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jb=ib(i)
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if(ja.lt.0 .or. ja.gt.nfft-1 .or. jb.lt.0 .or. jb.gt.nfft-1) then
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cycle
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endif
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if(jb.eq.-99) jb=ja + min(2*iwid,nfft-1)
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lstrong(ja:jb)=.true.
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enddo
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endif
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do i=0,nfft-1
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if(lstrong(i)) then
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cxs(i)=fac*cxt(i)
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cxw(i)=0.
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if(nxpol.ne.0) then
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cys(i)=fac*cyt(i)
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cyw(i)=0.
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endif
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else
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cxw(i)=fac*cxt(i)
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cxs(i)=0.
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if(nxpol.ne.0) then
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cyw(i)=fac*cyt(i)
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cys(i)=0.
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endif
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endif
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enddo
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call four2a(cxw,nfft,1,-1,1) !Transform weak and strong X
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call four2a(cxs,nfft,1,-1,1) !back to time domain, separately
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if(nxpol.ne.0) then
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call four2a(cyw,nfft,1,-1,1) !Transform weak and strong Y
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call four2a(cys,nfft,1,-1,1) !back to time domain, separately
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endif
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if(nwindow.eq.2) then
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cxw(0:nh-1)=cxw(0:nh-1)+covxw(0:nh-1) !Add previous segment's 2nd half
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covxw(0:nh-1)=cxw(nh:nfft-1) !Save 2nd half
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cxs(0:nh-1)=cxs(0:nh-1)+covxs(0:nh-1) !Ditto for strong signals
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covxs(0:nh-1)=cxs(nh:nfft-1)
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if(nxpol.ne.0) then
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cyw(0:nh-1)=cyw(0:nh-1)+covyw(0:nh-1) !Add previous segment's 2nd half
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covyw(0:nh-1)=cyw(nh:nfft-1) !Save 2nd half
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cys(0:nh-1)=cys(0:nh-1)+covys(0:nh-1) !Ditto for strong signals
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covys(0:nh-1)=cys(nh:nfft-1)
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endif
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endif
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! Apply noise blanking to weak data
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if(nb.ne.0) then
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do i=0,kstep-1
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peak=abs(cxw(i))
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if(nxpol.ne.0) peak=max(peak,abs(cyw(i)))
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if(peak.gt.peaklimit) then
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cxw(i)=0.
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if(nxpol.ne.0) cyw(i)=0.
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nzap=nzap+1
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endif
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enddo
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endif
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! Compute power levels from weak data only
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do i=0,kstep-1
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px=px + real(cxw(i))**2 + aimag(cxw(i))**2
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if(nxpol.ne.0) py=py + real(cyw(i))**2 + aimag(cyw(i))**2
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enddo
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cx1(0:kstep-1)=cxw(0:kstep-1) + cxs(0:kstep-1) !Recombine weak + strong
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if(nxpol.ne.0) then
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cy1(0:kstep-1)=cyw(0:kstep-1) + cys(0:kstep-1) !Weak + strong
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endif
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return
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end subroutine timf2
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