WSJT-X/lib/ft8/gen_ft8wave.f90

83 lines
2.6 KiB
Fortran

subroutine gen_ft8wave(itone,nsym,nsps,bt,fsample,f0,cwave,wave,icmplx,nwave)
!
! generate ft8 waveform using Gaussian-filtered frequency pulses.
!
use timer_module, only: timer
parameter(MAX_SECONDS=20,NTAB=65536)
real wave(nwave)
complex cwave(nwave),ctab(0:NTAB-1)
real pulse(23040)
real dphi(0:(nsym+2)*nsps-1)
integer itone(nsym)
data ibt0/0/
save pulse,twopi,dt,hmod,ibt0,ctab
ibt=nint(10*bt)
if(ibt0.ne.ibt) then
twopi=8.0*atan(1.0)
dt=1.0/fsample
hmod=1.0
! Compute the frequency-smoothing pulse
do i=1,3*nsps
tt=(i-1.5*nsps)/real(nsps)
pulse(i)=gfsk_pulse(bt,tt)
enddo
ibt0=nint(10*bt)
do i=0,NTAB-1
phi=i*twopi/NTAB
ctab(i)=cmplx(cos(phi),sin(phi))
enddo
endif
! Compute the smoothed frequency waveform.
! Length = (nsym+2)*nsps samples, first and last symbols extended
dphi_peak=twopi*hmod/real(nsps)
dphi=0.0
do j=1,nsym
ib=(j-1)*nsps
ie=ib+3*nsps-1
dphi(ib:ie) = dphi(ib:ie) + dphi_peak*pulse(1:3*nsps)*itone(j)
enddo
! Add dummy symbols at beginning and end with tone values equal to 1st and last symbol, respectively
dphi(0:2*nsps-1)=dphi(0:2*nsps-1)+dphi_peak*itone(1)*pulse(nsps+1:3*nsps)
dphi(nsym*nsps:(nsym+2)*nsps-1)=dphi(nsym*nsps:(nsym+2)*nsps-1)+dphi_peak*itone(nsym)*pulse(1:2*nsps)
! Calculate and insert the audio waveform
phi=0.0
dphi = dphi + twopi*f0*dt !Shift frequency up by f0
if(icmplx .eq. 0) wave=0.
if(icmplx .ne. 0) cwave=0. !Avoid writing to memory we may not have access to
call timer('gen_loop',0)
k=0
do j=nsps,nsps+nwave-1 !Don't include dummy symbols
k=k+1
if(icmplx.eq.0) then
wave(k)=sin(phi)
else
i=phi*float(NTAB)/twopi
cwave(k)=ctab(i)
endif
phi=mod(phi+dphi(j),twopi)
enddo
call timer('gen_loop',1)
! Apply envelope shaping to the first and last symbols
nramp=nint(nsps/8.0)
if(icmplx.eq.0) then
wave(1:nramp)=wave(1:nramp) * &
(1.0-cos(twopi*(/(i,i=0,nramp-1)/)/(2.0*nramp)))/2.0
k1=nsym*nsps-nramp+1
wave(k1:k1+nramp-1)=wave(k1:k1+nramp-1) * &
(1.0+cos(twopi*(/(i,i=0,nramp-1)/)/(2.0*nramp)))/2.0
else
cwave(1:nramp)=cwave(1:nramp) * &
(1.0-cos(twopi*(/(i,i=0,nramp-1)/)/(2.0*nramp)))/2.0
k1=nsym*nsps-nramp+1
cwave(k1:k1+nramp-1)=cwave(k1:k1+nramp-1) * &
(1.0+cos(twopi*(/(i,i=0,nramp-1)/)/(2.0*nramp)))/2.0
endif
return
end subroutine gen_ft8wave