WSJT-X/sync65.f

167 lines
5.1 KiB
FortranFixed
Raw Normal View History

subroutine sync65(dat,jz,DFTolerance,NFreeze,MouseDF,
+ mode65,dtx,dfx,snrx,snrsync,ccfblue,ccfred,flip,width)
C Synchronizes JT65 data, finding the best-fit DT and DF.
C NB: at this stage, submodes ABC are processed in the same way.
parameter (NP2=60*11025) !Size of data array
parameter (NFFTMAX=2048) !Max length of FFTs
parameter (NHMAX=NFFTMAX/2) !Max length of power spectra
parameter (NSMAX=320) !Max number of half-symbol steps
integer DFTolerance !Range of DF search
real dat(jz)
real psavg(NHMAX) !Average spectrum of whole record
real s2(NHMAX,NSMAX) !2d spectrum, stepped by half-symbols
real ccfblue(-5:540) !CCF with pseudorandom sequence
real ccfred(-224:224) !Peak of ccfblue, as function of freq
real tmp(450)
save
C Do FFTs of symbol length, stepped by half symbols. Note that we have
C already downsampled the data by factor of 2.
nsym=126
nfft=2048
nsteps=2*jz/nfft - 1
nh=nfft/2
df=0.5*11025.0/nfft
C Compute power spectrum for each step and get average
call zero(psavg,nh)
do j=1,nsteps
k=(j-1)*nh + 1
call limit(dat(k),nfft)
call ps(dat(k),nfft,s2(1,j))
if(mode65.eq.4) call smooth(s2(1,j),nh)
call add(psavg,s2(1,j),psavg,nh)
enddo
call flat1(psavg,s2,nh,nsteps,NHMAX,NSMAX) !Flatten the spectra
C Find the best frequency channel for CCF
famin= 670.46
fbmax=1870.46
fa=famin
fb=fbmax
if(NFreeze.eq.1) then
fa=max(famin,1270.46+MouseDF-DFTolerance)
fb=min(fbmax,1270.46+MouseDF+DFTolerance)
else
fa=max(famin,1270.46+MouseDF-600)
fb=min(fbmax,1270.46+MouseDF+600)
endif
ia=fa/df
ib=fb/df
i0=nint(1270.46/df)
lag1=-5
lag2=59
syncbest=-1.e30
syncbest2=-1.e30
call zero(ccfred,449)
do i=ia,ib
call xcor(s2,i,nsteps,nsym,lag1,lag2,
+ ccfblue,ccf0,lagpk0,flip,0.0)
j=i-i0
if(j.ge.-224 .and. j.le.224) ccfred(j)=ccf0
C Find rms of the CCF, without the main peak
call slope(ccfblue(lag1),lag2-lag1+1,lagpk0-lag1+1.0)
sync=abs(ccfblue(lagpk0))
ppmax=psavg(i)-1.0
C Find the best sync value
if(sync.gt.syncbest2) then
ipk2=i
lagpk2=lagpk0
syncbest2=sync
endif
C We are most interested if snrx will be more than -30 dB.
if(ppmax.gt.0.2938) then !Corresponds to snrx.gt.-30.0
if(sync.gt.syncbest) then
ipk=i
lagpk=lagpk0
syncbest=sync
endif
endif
enddo
C If we found nothing with snrx > -30 dB, take the best sync that *was* found.
if(syncbest.lt.-10.) then
ipk=ipk2
lagpk=lagpk2
syncbest=syncbest2
endif
C Peak up in frequency to fraction of channel
base=0.25*(psavg(ipk-3)+psavg(ipk-2)+psavg(ipk+2)+psavg(ipk+3))
! call peakup(psavg(ipk-1),psavg(ipk),psavg(ipk+1),dx)
! if(dx.lt.-1.0) dx=-1.0
! if(dx.gt.1.0) dx=1.0
dx=0.
dfx=(ipk+dx-i0)*df
C Peak up in time, at best whole-channel frequency
call xcor(s2,ipk,nsteps,nsym,lag1,lag2,
+ ccfblue,ccfmax,lagpk,flip,0.0)
xlag=lagpk
if(lagpk.gt.lag1 .and. lagpk.lt.lag2) then
call peakup(ccfblue(lagpk-1),ccfmax,ccfblue(lagpk+1),dx2)
xlag=lagpk+dx2
endif
C Find rms of the CCF, without the main peak
call slope(ccfblue(lag1),lag2-lag1+1,xlag-lag1+1.0)
sq=0.
nsq=0
do lag=lag1,lag2
if(abs(lag-xlag).gt.2.0) then
sq=sq+ccfblue(lag)**2
nsq=nsq+1
endif
enddo
rms=sqrt(sq/nsq)
snrsync=abs(ccfblue(lagpk))/rms - 1.1 !Empirical
dt=2.0/11025.0
istart=xlag*nh
dtx=istart*dt
snrx=-99.0
! ppmax=psavg(ipk)/base-1.0
ppmax=psavg(ipk)-1.0
C Plus 3 dB because sync tone is on half the time. (Don't understand
C why an additional +2 dB is needed ...)
if(ppmax.gt.0.0001) snrx=db(ppmax*df/2500.0) + 5.0 !###
if(mode65.eq.4) snrx=snrx + 2.0
if(snrx.lt.-33.0) snrx=-33.0
C Compute width of sync tone to outermost -3 dB points
call pctile(ccfred(ia-i0),tmp,ib-ia+1,45,base)
jpk=ipk-i0
stest=base + 0.5*(ccfred(jpk)-base) ! -3 dB
do i=-10,0
if(jpk+i.ge.-223) then
if(ccfred(jpk+i).gt.stest) go to 30
endif
enddo
i=0
30 x1=i-1+(stest-ccfred(jpk+i-1))/(ccfred(jpk+i)-ccfred(jpk+i-1))
do i=10,0,-1
if(jpk+i.le.223) then
if(ccfred(jpk+i).gt.stest) go to 32
endif
enddo
i=0
32 x2=i+1-(stest-ccfred(jpk+i+1))/(ccfred(jpk+i)-ccfred(jpk+i+1))
width=x2-x1
if(width.gt.1.2) width=sqrt(width**2 - 1.44)
width=df*width
width=max(0.0,min(99.0,width))
return
end