mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2025-06-26 15:05:21 -04:00
30 lines
727 B
Fortran
30 lines
727 B
Fortran
|
subroutine wspr_fsk8_downsample(iwave,c)
|
||
|
|
|
||
|
|
! Input: i*2 data in iwave() at sample rate 12000 Hz
|
||
|
|
! Output: Complex data in c(), sampled at 4=500 Hz
|
||
|
|
|
||
|
|
include 'wspr_fsk8_params.f90'
|
||
|
|
parameter (NMAX=240*12000,NFFTD=NMAX/24)
|
||
|
|
integer*2 iwave(NMAX)
|
||
|
|
complex c(0:NZ-1)
|
||
|
|
complex c1(0:NFFTD-1)
|
||
|
|
complex cx(0:NMAX/2)
|
||
|
|
real x(NMAX)
|
||
|
|
equivalence (x,cx)
|
||
|
|
|
||
|
|
df=12000.0/NMAX
|
||
|
|
x=iwave
|
||
|
|
call four2a(x,NMAX,1,-1,0) !r2c FFT to freq domain
|
||
|
|
i0=nint(1500.0/df)
|
||
|
|
c1(0)=cx(i0)
|
||
|
|
do i=1,NFFTD/2
|
||
|
|
c1(i)=cx(i0+i)
|
||
|
|
c1(NFFTD-i)=cx(i0-i)
|
||
|
|
enddo
|
||
|
|
c1=c1/NFFTD
|
||
|
|
call four2a(c1,NFFTD,1,1,1) !c2c FFT back to time domain
|
||
|
|
c=c1(0:NZ-1)
|
||
|
|
|
||
|
|
return
|
||
|
|
end subroutine wspr_fsk8_downsample
|