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70 lines
1.8 KiB
Fortran
70 lines
1.8 KiB
Fortran
subroutine watterson(c,npts,nsig,fs,delay,fspread)
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!
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! npts is the total length of the simulated data vector
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! nsig is the number of points that are occupied by signal
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!
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complex c(0:npts-1)
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complex c2(0:npts-1)
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complex cs1(0:npts-1)
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complex cs2(0:npts-1)
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nonzero=0
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df=fs/npts
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if(fspread.gt.0.0) then
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do i=0,npts-1
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xx=gran()
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yy=gran()
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cs1(i)=0.707*cmplx(xx,yy)
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xx=gran()
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yy=gran()
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cs2(i)=0.707*cmplx(xx,yy)
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enddo
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call four2a(cs1,npts,1,-1,1) !To freq domain
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call four2a(cs2,npts,1,-1,1)
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do i=0,npts-1
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f=i*df
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if(i.gt.npts/2) f=(i-npts)*df
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x=(f/(0.5*fspread))**2
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a=0.
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if(x.le.50.0) then
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a=exp(-x)
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endif
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cs1(i)=a*cs1(i)
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cs2(i)=a*cs2(i)
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if(abs(f).lt.10.0) then
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p1=real(cs1(i))**2 + aimag(cs1(i))**2
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p2=real(cs2(i))**2 + aimag(cs2(i))**2
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if(p1.gt.0.0) nonzero=nonzero+1
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! write(62,3101) f,p1,p2,db(p1+1.e-12)-60,db(p2+1.e-12)-60
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!3101 format(f10.3,2f12.3,2f10.3)
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endif
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enddo
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call four2a(cs1,npts,1,1,1) !Back to time domain
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call four2a(cs2,npts,1,1,1)
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cs1(0:npts-1)=cs1(0:npts-1)/npts
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cs2(0:npts-1)=cs2(0:npts-1)/npts
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endif
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nshift=nint(0.001*delay*fs)
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if(delay.gt.0.0) then
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c2(0:npts-1)=cshift(c(0:npts-1),-nshift) !negative shifts are right shifts
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else
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c2(0:npts-1)=0.0
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endif
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sq=0.
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do i=0,npts-1
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if(nonzero.gt.1) then
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c(i)=0.5*(cs1(i)*c(i) + cs2(i)*c2(i))
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else
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c(i)=0.5*(c(i) + c2(i))
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endif
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sq=sq + real(c(i))**2 + aimag(c(i))**2
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! write(61,3001) i/12000.0,c(i)
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!3001 format(3f12.6)
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enddo
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rms=sqrt(sq/nsig)
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c=c/rms
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return
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end subroutine watterson
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