2016-02-23 14:37:38 -05:00
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subroutine degrade_snr(d2,npts,db,bw)
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2015-11-23 13:20:55 -05:00
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2017-05-18 11:59:30 -04:00
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! Degrade S/N by specified number of dB.
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2015-11-23 13:20:55 -05:00
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2017-05-18 11:59:30 -04:00
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integer*2 d2(npts)
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p0=0.
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do i=1,npts
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x=d2(i)
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p0=p0 + x*x
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enddo
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p0=p0/npts
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2016-02-23 14:37:38 -05:00
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if(bw.gt.0.0) p0=p0*6000.0/bw
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2015-11-23 13:20:55 -05:00
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s=sqrt(p0*(10.0**(0.1*db) - 1.0))
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2016-10-07 11:34:55 -04:00
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fac=sqrt(p0/(p0+s*s))
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2015-11-23 13:20:55 -05:00
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do i=1,npts
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2017-05-18 11:59:30 -04:00
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d2(i)=nint(fac*(d2(i) + s*gran()))
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2015-11-23 13:20:55 -05:00
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enddo
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return
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end subroutine degrade_snr
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