Separate generation of SuperFox sync LO, and rationalize frequencies used in gen_sfox.f90 and hard_symbols.f90.

CMakeLists.txt

@@ -590,6 +590,7 @@ set (wsjt_FSRCS
   lib/superfox/gen_sfox.f90
   lib/superfox/sync_sf.f90
   lib/superfox/hard_symbols.f90
+  lib/superfox/gen_sf_clo.f90
   lib/superfox/ran1.f90
   )
 

lib/superfox/gen_sf_clo.f90

@@ -0,0 +1,26 @@
+subroutine gen_sf_clo(fsample,syncwidth,clo)
+
+! Generate complex LO for the SuperFox sync signal
+  
+  use sfox_mod
+  complex clo(NMAX)                      !Complex Local Oscillator
+  complex w,wstep
+
+  twopi=8.0*atan(1.0)
+  tsync=NS*NSPS/fsample
+  w=1.0
+  a0=1500.0+ syncwidth/2.0          !Frequency at midpoint of LO waveform
+  a2=2.0*syncwidth/tsync            !Frequency drift rate
+  x0=0.5*(nsync+1)
+  s=2.0/nsync
+  do i=1,nsync
+     if(i.eq.nsync/2+1) a2=-a2       !Reverse sign of drift at midpoint
+     x=s*(i-x0)
+     dphi=(a0 + x*a2)*(twopi/fsample)
+     wstep=cmplx(cos(dphi),sin(dphi))
+     w=w*wstep
+     clo(i)=conjg(w)
+  enddo
+
+  return
+end subroutine gen_sf_clo

lib/superfox/gen_sfox.f90

@@ -1,39 +1,22 @@
-subroutine gen_sfox(idat,f0,fsample,syncwidth,cdat,clo)
+subroutine gen_sfox(idat,f0,fsample,syncwidth,cdat)
 
   use sfox_mod
 !  include "sfox_params.f90"
   complex cdat(NMAX)                     !Generated complex waveform
-  complex clo(NMAX)                      !Complex Local Oscillator
   complex w,wstep
   integer idat(ND)
 
   twopi=8.0*atan(1.0)
   tsync=NS*NSPS/fsample
-
-! Generate complex LO for SuperFox sync
-  w=1.0
-  a0=1500.0+ syncwidth/2.0          !Frequency at midpoint of LO waveform
-  a2=2.0*syncwidth/tsync            !Frequency drift rate
-  x0=0.5*(nsync+1)
-  s=2.0/nsync
-  do i=1,nsync
-     if(i.eq.nsync/2+1) a2=-a2       !Reverse sign of drift at midpoint
-     x=s*(i-x0)
-     dphi=(a0 + x*a2)*(twopi/fsample)
-     wstep=cmplx(cos(dphi),sin(dphi))
-     w=w*wstep
-     clo(i)=conjg(w)
-  enddo
-
-! Generate complex SuperFox waveform
-
   df=fsample/NSPS
+  w=1.0
   j=0
   k=0
+  i0=NQ/2
 ! First group of data symbols:
   do n=1,ND1
      k=k+1
-     dphi=(f0 + (idat(k)-65)*df)*(twopi/fsample)
+     dphi=(f0 + (idat(k)-i0)*df)*(twopi/fsample)
      wstep=cmplx(cos(dphi),sin(dphi))
      do i=1,NSPS
         j=j+1
@@ -45,6 +28,8 @@ subroutine gen_sfox(idat,f0,fsample,syncwidth,cdat,clo)
 ! Sync waveform
   a1=f0 + syncwidth/2.0             !Frequency at midpoint of sync waveform
   a2=2.0*syncwidth/tsync            !Frequency drift rate
+  x0=0.5*(nsync+1)
+  s=2.0/nsync
   do i=1,nsync
      j=j+1
      if(i.eq.nsync/2+1) a2=-a2       !Reverse sign of drift at midpoint
@@ -58,7 +43,7 @@ subroutine gen_sfox(idat,f0,fsample,syncwidth,cdat,clo)
 ! Final group of data symbols:
   do n=1,ND2
      k=k+1
-     dphi=(f0 + (idat(k)-65)*df)*(twopi/fsample)
+     dphi=(f0 + (idat(k)-i0)*df)*(twopi/fsample)
      wstep=cmplx(cos(dphi),sin(dphi))
      do i=1,NSPS
         j=j+1

lib/superfox/hard_symbols.f90

@@ -1,16 +1,16 @@
-subroutine hard_symbols(crcvd,f,t,jdat)
+subroutine hard_symbols(crcvd,f,t,chansym)
 
   use sfox_mod
 !  include "sfox_params.f90"
   complex crcvd(NMAX)                    !Signal as received
   complex c(0:NSPS-1)                    !Work array, one symbol long
-  real s(0:NSPS-1)                       !Power spectrum
+  real s(0:NQ-1)                         !Power spectrum
-  integer jdat(NN)                       !Recovered hard-decision symbols
+  integer chansym(NN)                    !Recovered hard-decision symbols
   integer ipk(1)
 
   i0=nint(12000.0*t)
   df=12000.0/NSPS
-  j0=nint(f/df)-128
+  j0=nint(f/df)-NQ/2
   do n=1,ND                             !Loop over all symbols
      ib=n*NSPS + i0
      if(n.gt.ND1) ib=(NS+n)*NSPS + i0
@@ -18,8 +18,8 @@ subroutine hard_symbols(crcvd,f,t,jdat)
      if(ia.lt.1 .or. ib.gt.NMAX) cycle
      c=crcvd(ia:ib)
      call four2a(c,NSPS,1,-1,1)          !Compute symbol spectrum
-     do i=0,NSPS-1
+     do j=0,NQ-1
-        s(i)=real(c(i))**2 + aimag(c(i))**2
+        s(j)=real(c(j0+j))**2 + aimag(c(j0+j))**2
      enddo
 
 ! Could we measure fspread, perhaps in the sync routine, and use that to
@@ -27,13 +27,8 @@ subroutine hard_symbols(crcvd,f,t,jdat)
 !     call smo121(s,NSPS)                !Helps for LD, HM propagation...
 !     call smo121(s,NSPS)
 
-     ipk=maxloc(s)
+     ipk=maxloc(s(0:NQ-1))
-     ipk(1)=ipk(1)-j0
+     chansym(n)=ipk(1) - 1
-     if(ipk(1).ge.64) then
-        jdat(n)=ipk(1)-64
-     else
-        jdat(n)=ipk(1)+256-64
-     endif
   enddo
 
   return

lib/superfox/sfoxtest.f90

@@ -80,11 +80,15 @@ program sfoxtest
   h=default_header(12000,NMAX)
   idummy=0
   bandwidth_ratio=2500.0/6000.0
+  fgood0=1.0
 
 ! Generate a message
   msg0=0
   do i=1,KK-2
-     msg0(i)=i
+!     msg0(i)=i-1
+     msg0(i)=int(NQ*ran1(idummy))
+!     msg0(i)=0
+!     if(i.gt.ND1) msg0(i)=NQ-1
   enddo
 ! Append a CRC here ...
 
@@ -92,10 +96,12 @@ program sfoxtest
   call rs_encode_sf(msg0,parsym)            !Compute parity symbols
   chansym0(1:kk)=msg0(1:kk)
   chansym0(kk+1:nn)=parsym(1:nn-kk)
-  fgood0=1.0
 
-! Generate cdat (SuperFox waveform) and clo (LO for sync detection)
+! Generate clo, the LO for sync detection
-  call gen_sfox(chansym0,f0,fsample,syncwidth,cdat,clo)
+  call gen_sf_clo(fsample,syncwidth,clo)
+  
+! Generate cdat, the SuperFox waveform
+  call gen_sfox(chansym0,f0,fsample,syncwidth,cdat)
 
   do isnr=0,-20,-1
      snr=isnr
@@ -154,6 +160,7 @@ program sfoxtest
         call twkfreq(crcvd,crcvd,NMAX,12000.0,a)
         f=1500.0
         call hard_symbols(crcvd,f,t,chansym)           !Get hard symbol values
+
         nera=0
         chansym=mod(chansym,nq)                        !Enforce 0 to nq-1
         nharderr=count(chansym.ne.chansym0)            !Count hard errors