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https://github.com/saitohirga/WSJT-X.git
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a0d471cb0b
(i) SNR no longer saturates at +20 dB (ii) a large signal in the passband no longer causes the SNR of weaker signals to be biased low.
44 lines
1.0 KiB
Fortran
44 lines
1.0 KiB
Fortran
subroutine get_spectrum_baseline(dd,nfa,nfb,sbase)
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include 'ft8_params.f90'
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parameter(NST=NFFT1/2,NF=NMAX/NST-1)
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real s(NH1,NF)
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real savg(NH1)
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real sbase(NH1)
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real x(NFFT1)
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real window(NFFT1)
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complex cx(0:NH1)
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real dd(NMAX)
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equivalence (x,cx)
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logical first
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data first/.true./
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save first,window
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if(first) then
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first=.false.
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pi=4.0*atan(1.)
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window=0.
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call nuttal_window(window,NFFT1)
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window=window/sum(window)*NSPS*2/300.0
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endif
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! Compute symbol spectra, stepping by NSTEP steps.
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savg=0.
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df=12000.0/NFFT1
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do j=1,NF
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ia=(j-1)*NST + 1
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ib=ia+NFFT1-1
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if(ib.gt.NMAX) exit
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x=dd(ia:ib)*window
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call four2a(x,NFFT1,1,-1,0) !r2c FFT
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s(1:NH1,j)=abs(cx(1:NH1))**2
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savg=savg + s(1:NH1,j) !Average spectrum
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enddo
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if(nfa.lt.nint(200.0)) nfa=nint(200.0)
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if(nfb.gt.nint(4910.0)) nfb=nint(4910.0)
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call baseline(savg,nfa,nfb,sbase)
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return
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end subroutine get_spectrum_baseline
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