mirror of https://github.com/saitohirga/WSJT-X.git
44 lines
837 B
Fortran
44 lines
837 B
Fortran
subroutine lorentzian_fading(c,npts,fs,fspread)
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!
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! npts is the total length of the simulated data vector
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!
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complex c(0:npts-1)
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complex cspread(0:npts-1)
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complex z
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twopi=8.0*atan(1.0)
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df=fs/npts
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nh=npts/2
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cspread(0)=1.0
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cspread(nh)=0.
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b=6.0
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do i=1,nh
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f=i*df
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x=b*f/fspread
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z=0.
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a=0.
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if(x.lt.3.0) then
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a=sqrt(1.111/(1.0+x*x)-0.1)
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phi1=twopi*rran()
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z=a*cmplx(cos(phi1),sin(phi1))
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endif
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cspread(i)=z
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z=0.
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if(x.lt.3.0) then
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phi2=twopi*rran()
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z=a*cmplx(cos(phi2),sin(phi2))
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endif
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cspread(npts-i)=z
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enddo
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call four2a(cspread,npts,1,1,1)
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s=sum(abs(cspread)**2)
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avep=s/npts
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fac=sqrt(1.0/avep)
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cspread=fac*cspread
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c=cspread*c
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return
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end subroutine lorentzian_fading
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