WSJT-X/lib/t1.f90

141 lines
2.8 KiB
Fortran
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program t1
parameter (NSPM=1404)
complex csig(0:NSPM-1)
complex c(0:NSPM-1)
complex cnoise(0:NSPM-1)
complex cd(0:11,0:3)
complex z,zmax
integer itone(234)
real r(234)
real ss(0:3)
character*12 arg
nargs=iargc()
if(nargs.ne.3) then
print*,'Usage: t1 nsymtest snrdb iters'
go to 999
endif
call getarg(1,arg)
read(arg,*) nsymtest
call getarg(2,arg)
read(arg,*) snrdb
call getarg(3,arg)
read(arg,*) iters
call init_random_seed() ! seed Fortran RANDOM_NUMBER generator
call sgran() ! see C rand generator (used in gran)
call random_number(r)
itone=0
where(r.gt.0.5) itone=1
twopi=8.0*atan(1.0)
fmid=1500.0
f0=fmid-500.
f1=fmid+500.
dt=1.0/12000.0
phi=0.
do n=0,3
k=-1
dphi=twopi*f0*dt
if(n.ge.2) dphi=twopi*f1*dt
do i=0,5
k=k+1
phi=phi+dphi
if(phi.gt.twopi) phi=phi-twopi
cd(k,n)=cmplx(cos(phi),sin(phi))
enddo
dphi=twopi*f0*dt
if(mod(n,2).eq.1) dphi=twopi*f1*dt
do i=6,11
k=k+1
phi=phi+dphi
if(phi.gt.twopi) phi=phi-twopi
cd(k,n)=cmplx(cos(phi),sin(phi))
enddo
enddo
! do k=0,11
! write(13,1000) k,cd(k,0:3)
!1000 format(i4,8f9.3)
!enddo
! Generate signal waveform
k=-1
phi=0.
do j=1,234
dphi=twopi*f0*dt
if(itone(j).eq.1) dphi=twopi*f1*dt
do i=1,6
k=k+1
phi=phi+dphi
if(phi.gt.twopi) phi=phi-twopi
csig(k)=cmplx(cos(phi),sin(phi))
! write(14,1000) k,csig(k)
enddo
enddo
write(*,1010)
1010 format(' S/N (S+N)/N BER'/'----------------------')
isnra=10
isnrb=-3
nsyms=234
do isnr=isnra,isnrb,-1
snr=10.0**(0.1*isnr)
if(snrdb.ne.0.0) snr=10.0**(0.1*snrdb)
fac=1.0/sqrt(snr)
nsumerr=0
do iter=1,iters
do i=0,NSPM-1
x=gran()
y=gran()
cnoise(i)=cmplx(x,y)
enddo
c=csig + fac*cnoise
nerr=0
n1=2
nstep=2
iz=5
if(nsymtest.eq.2) then
n1=3
nstep=1
iz=11
endif
do j=1,nsyms
smax=0.
do n=0,n1,nstep
s=0.
k=6*(j-1)
do i=0,iz
s=s + aimag(c(k+i))*aimag(cd(i,n))
enddo
ss(n)=s
if(abs(s).gt.abs(smax)) then
smax=s
npk=n
endif
enddo
sym=max(abs(ss(2)),abs(ss(3))) - max(abs(ss(0)),abs(ss(1)))
! ibit=npk/2
ibit=0
if(sym.ge.0.0) ibit=1
if(ibit.ne.itone(j)) nerr=nerr+1
enddo
nsumerr=nsumerr+nerr
enddo
write(*,1020) 10.0*log10(snr),10.0*log10(snr+1.0), &
float(nsumerr)/(nsyms*iters)
1020 format(f5.1,f7.1,f9.3)
if(snrdb.ne.0.0) exit
enddo
999 end program t1