WSJT-X/lib/degrade_snr.f90

subroutine degrade_snr(d2,npts,db,bw)

  integer*2 d2(npts)
  real dat(60*12000)

  dat(1:npts)=d2
  p0=dot_product(dat(1:npts),dat(1:npts))/npts
  if(bw.gt.0.0) p0=p0*6000.0/bw
  s=sqrt(p0*(10.0**(0.1*db) - 1.0))
  fac=sqrt(p0/(p0+s*s))
  do i=1,npts
     d2(i)=nint(fac*(dat(i) + s*gran()))
  enddo

  return
end subroutine degrade_snr
Calibration of the "Degrade S/N of .wav file" requires knowledge of receiver bandwidth. git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6491 ab8295b8-cf94-4d9e-aec4-7959e3be5d79 2016-02-23 19:37:38 +00:00			`subroutine degrade_snr(d2,npts,db,bw)`
Add degrade_snr.f90 git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6167 ab8295b8-cf94-4d9e-aec4-7959e3be5d79 2015-11-23 18:20:55 +00:00
			`integer*2 d2(npts)`
			`real dat(60*12000)`

			`dat(1:npts)=d2`
			`p0=dot_product(dat(1:npts),dat(1:npts))/npts`
Calibration of the "Degrade S/N of .wav file" requires knowledge of receiver bandwidth. git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6491 ab8295b8-cf94-4d9e-aec4-7959e3be5d79 2016-02-23 19:37:38 +00:00			`if(bw.gt.0.0) p0=p0*6000.0/bw`
Add degrade_snr.f90 git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6167 ab8295b8-cf94-4d9e-aec4-7959e3be5d79 2015-11-23 18:20:55 +00:00			`s=sqrt(p0(10.0(0.1db) - 1.0))`
Maintain approximately constant baseline level when degrading S/N for tests. git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7158 ab8295b8-cf94-4d9e-aec4-7959e3be5d79 2016-10-07 15:34:55 +00:00			`fac=sqrt(p0/(p0+s*s))`
Add degrade_snr.f90 git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6167 ab8295b8-cf94-4d9e-aec4-7959e3be5d79 2015-11-23 18:20:55 +00:00			`do i=1,npts`
Maintain approximately constant baseline level when degrading S/N for tests. git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7158 ab8295b8-cf94-4d9e-aec4-7959e3be5d79 2016-10-07 15:34:55 +00:00			`d2(i)=nint(fac(dat(i) + sgran()))`
Add degrade_snr.f90 git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6167 ab8295b8-cf94-4d9e-aec4-7959e3be5d79 2015-11-23 18:20:55 +00:00			`enddo`

			`return`
			`end subroutine degrade_snr`