WSJT-X/lib/spec_qra65.f90

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subroutine spec_qra65(c0,nsps,s3,LL,NN)
! Compute synchronized symbol spectra.
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complex c0(0:85*nsps-1) !Synchronized complex data at 6000 S/s
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complex, allocatable :: cs(:) !Complex symbol spectrum
real s3(LL,NN) !Synchronized symbol spectra
real xbase0(LL),xbase(LL) !Work arrays
integer isync(22) !Indices of sync symbols
data isync/1,9,12,13,15,22,23,26,27,33,35,38,46,50,55,60,62,66,69,74,76,85/
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allocate(cs(0:nsps-1))
fac=1.0/nsps
j=0
n=1
do k=1,84
if(k.eq.isync(n)) then
n=n+1
cycle
endif
j=j+1
ja=(k-1)*nsps
jb=ja+nsps-1
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cs=fac*c0(ja:jb)
call four2a(cs,nsps,1,-1,1) !c2c FFT to frequency
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do ii=1,LL
i=ii-65
if(i.lt.0) i=i+nsps
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s3(ii,j)=real(cs(i))**2 + aimag(cs(i))**2
enddo
enddo
df=6000.0/nsps
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do i=1,LL
call pctile(s3(i,1:NN),NN,45,xbase0(i)) !Get baseline for passband shape
enddo
nh=9
xbase(1:nh-1)=sum(xbase0(1:nh-1))/(nh-1.0)
xbase(LL-nh+1:LL)=sum(xbase0(LL-nh+1:LL))/(nh-1.0)
do i=nh,LL-nh
xbase(i)=sum(xbase0(i-nh+1:i+nh))/(2*nh+1) !Smoothed passband shape
enddo
do i=1,LL
s3(i,1:NN)=s3(i,1:NN)/(xbase(i)+0.001) !Apply frequency equalization
enddo
return
end subroutine spec_qra65