mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2024-11-23 20:58:55 -05:00
d24537420f
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@4966 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
51 lines
1.3 KiB
Fortran
51 lines
1.3 KiB
Fortran
subroutine flat4(s,npts,nflatten)
|
|
|
|
! Flatten a spectrum for optimum display
|
|
! Input: s(npts) Linear scale in power
|
|
! nflatten If nflatten=0, convert to dB but do not flatten
|
|
! Output: s(npts) Flattened, with dB scale
|
|
|
|
|
|
implicit real*8 (a-h,o-z)
|
|
real*4 s(6827)
|
|
real*4 base
|
|
real*8 x(1000),y(1000),a(5)
|
|
data nseg/10/,npct/10/
|
|
|
|
if(s(1).gt.1.e29) go to 900 !Boundary between Rx intervals: do nothing
|
|
do i=1,npts
|
|
s(i)=10.0*log10(s(i)) !Convert to dB scale
|
|
enddo
|
|
if(nflatten.eq.0) go to 900
|
|
|
|
nlen=npts/nseg !Length of test segment
|
|
i0=npts/2 !Midpoint
|
|
k=0
|
|
do n=2,nseg !Skip first segment, likely rolloff here
|
|
ib=n*nlen
|
|
ia=ib-nlen+1
|
|
if(n.eq.nseg) ib=npts
|
|
call pctile(s(ia),ib-ia+1,npct,base) !Find lowest npct of points in segment
|
|
do i=ia,ib
|
|
if(s(i).le.base) then
|
|
if (k.lt.1000) k=k+1 !Save these "lower envelope" points
|
|
x(k)=i-i0
|
|
y(k)=s(i)
|
|
endif
|
|
enddo
|
|
enddo
|
|
kz=k
|
|
a=0.
|
|
nterms=3
|
|
|
|
call polfit(x,y,y,kz,nterms,0,a,chisqr) !Fit a low-order polynomial
|
|
|
|
do i=1,npts
|
|
t=i-i0
|
|
yfit=a(1)+t*(a(2)+t*(a(3)+t*(a(4)+t*(a(5)))))
|
|
s(i)=s(i)-yfit !Subtract the fitted baseline
|
|
enddo
|
|
|
|
900 return
|
|
end subroutine flat4
|