mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2025-10-31 13:10:19 -04:00
d788ca7b44
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7626 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
63 lines
1.5 KiB
Fortran
63 lines
1.5 KiB
Fortran
subroutine dopspread(c,fspread)
|
|
|
|
parameter (NFFT=268800,NH=NFFT/2)
|
|
complex c(0:NFFT-1)
|
|
complex cspread(0:NFFT-1)
|
|
|
|
df=12000.0/nfft
|
|
twopi=8*atan(1.0)
|
|
cspread(0)=1.0
|
|
cspread(NH)=0.
|
|
b=6.0 !Lorenzian 3/28 onward
|
|
do i=1,NH
|
|
f=i*df
|
|
x=b*f/fspread
|
|
z=0.
|
|
a=0.
|
|
if(x.lt.3.0) then !Cutoff beyond x=3
|
|
a=sqrt(1.111/(1.0+x*x)-0.1) !Lorentzian
|
|
call random_number(r1)
|
|
phi1=twopi*r1
|
|
z=a*cmplx(cos(phi1),sin(phi1))
|
|
endif
|
|
cspread(i)=z
|
|
z=0.
|
|
if(x.lt.50.0) then
|
|
call random_number(r2)
|
|
phi2=twopi*r2
|
|
z=a*cmplx(cos(phi2),sin(phi2))
|
|
endif
|
|
cspread(NFFT-i)=z
|
|
enddo
|
|
|
|
izh=fspread/df
|
|
do i=-izh,izh
|
|
f=i*df
|
|
j=i
|
|
if(j.lt.0) j=j+nfft
|
|
s=real(cspread(j))**2 + aimag(cspread(j))**2
|
|
! write(23,3000) f,s,cspread(j)
|
|
!3000 format(f10.3,3f12.6)
|
|
enddo
|
|
|
|
call four2a(cspread,NFFT,1,1,1) !Transform to time domain
|
|
|
|
sum=0.
|
|
do i=0,NFFT-1
|
|
p=real(cspread(i))**2 + aimag(cspread(i))**2
|
|
sum=sum+p
|
|
enddo
|
|
avep=sum/NFFT
|
|
fac=sqrt(1.0/avep)
|
|
cspread=fac*cspread !Normalize to constant avg power
|
|
c=cspread*c !Apply Rayleigh fading to c()
|
|
|
|
do i=0,NFFT-1
|
|
p=real(cspread(i))**2 + aimag(cspread(i))**2
|
|
! write(24,3010) i,p,cspread(i)
|
|
!3010 format(i8,3f12.6)
|
|
enddo
|
|
|
|
return
|
|
end subroutine dopspread
|