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

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This commit is contained in:
Joe Taylor 2024-02-10 13:35:06 -05:00
parent 6310419a4d
commit c24a0d3c72
5 changed files with 53 additions and 39 deletions
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1
CMakeLists.txt
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@ -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
)

26
lib/superfox/gen_sf_clo.f90 Normal file
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@ -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

29
lib/superfox/gen_sfox.f90
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@ -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

21
lib/superfox/hard_symbols.f90
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@ -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
integer jdat(NN) !Recovered hard-decision symbols
real s(0:NQ-1) !Power spectrum
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
s(i)=real(c(i))**2 + aimag(c(i))**2
do j=0,NQ-1
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(1)=ipk(1)-j0
if(ipk(1).ge.64) then
jdat(n)=ipk(1)-64
else
jdat(n)=ipk(1)+256-64
endif
ipk=maxloc(s(0:NQ-1))
chansym(n)=ipk(1) - 1
enddo
return

15
lib/superfox/sfoxtest.f90
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@ -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)
call gen_sfox(chansym0,f0,fsample,syncwidth,cdat,clo)
! Generate clo, the LO for sync detection
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