Initial Commit

lib/wspr_downsample.f90

@@ -0,0 +1,76 @@
+subroutine wspr_downsample(id2,k)
+
+! Input:
+!  id2       raw 16-bit integer data, 12000 Hz sample rate
+!  k         pointer to the most recent new data
+
+! Output (in common/c0com)
+!  c0        complex data downsampled to 1500 Hz
+
+  parameter (NMAX=120*12000)         !Total sample intervals per 30 minutes
+  parameter (NDMAX=120*1500)         !Sample intervals at 1500 Hz rate
+  parameter (NSMAX=1366)             !Max length of saved spectra
+  parameter (NFFT1=1024)
+  parameter (MAXFFT3=32768)
+  real*4 w3(MAXFFT3)
+  real*4 x0(NFFT1)
+  real*4 x2(NFFT1+105)
+  real*4 ssum(NSMAX)
+  integer*2 id2(NMAX)
+  complex c0
+  common/c0com/c0(NDMAX)
+  data rms/999.0/,k0/99999999/,nfft3z/0/,nsps/8192/,nbfo/1500/
+  save
+
+  nfft3=nsps/4
+  jstep=nsps/16
+  if(k.gt.NMAX) go to 999
+  if(k.lt.nfft3) go to 999                   !Wait for enough samples to start
+  if(nfft3.ne.nfft3z) then
+     pi=4.0*atan(1.0)
+     do i=1,nfft3
+        w3(i)=2.0*(sin(i*pi/nfft3))**2             !Window for nfft3
+     enddo
+     nfft3z=nfft3
+  endif
+
+  if(k.lt.k0) then
+     ja=0
+     ssum=0.
+     k1=0
+     k8=0
+     x2=0.
+!     if(ndiskdat.eq.0) then
+!        id2(k+1:)=0
+!        c0=0.          !This is necessary to prevent "ghosts".  Not sure why.
+!     endif
+  endif
+  k0=k
+ 
+  nzap=0
+  nbslider=0
+  sigmas=1.0*(10.0**(0.01*nbslider)) + 0.7
+  peaklimit=sigmas*max(10.0,rms)
+  px=0.
+
+  nwindow=2
+  kstep1=NFFT1
+  if(nwindow.ne.0) kstep1=NFFT1/2
+  fac=2.0/NFFT1
+  nblks=(k-k1)/kstep1
+  gain=1.0
+  nb=0
+  do nblk=1,nblks
+     do i=1,NFFT1
+        x0(i)=gain*id2(k1+i)
+     enddo
+!     call timf2(x0,k,NFFT1,nwindow,nb,peaklimit,x1,   &
+!          slimit,lstrong,px,nzap)
+! Mix at nbfo Hz, lowpass at +/-750 Hz, and downsample to 1500 Hz complex.
+     call mixlpf(x0,nbfo,c0(k8+1))
+     k1=k1+kstep1
+     k8=k8+kstep1/8
+  enddo
+
+999 return
+end subroutine wspr_downsample