WSJT-X/lib/ft4/gen_ft4wave.f90

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subroutine gen_ft4wave(itone,nsym,nsps,fsample,f0,cwave,wave,icmplx,nwave)
real wave(nwave)
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complex cwave(nwave)
real pulse(6912) !576*4*3
real dphi(0:250000-1)
integer itone(nsym)
logical first
data first/.true./
save pulse,first,twopi,dt,hmod
if(first) then
twopi=8.0*atan(1.0)
dt=1.0/fsample
hmod=1.0
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! Compute the smoothed frequency-deviation pulse
do i=1,3*nsps
tt=(i-1.5*nsps)/real(nsps)
pulse(i)=gfsk_pulse(1.0,tt)
enddo
first=.false.
endif
! Compute the smoothed frequency waveform.
! Length = (nsym+2)*nsps samples, zero-padded
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
! Calculate and insert the audio waveform
phi=0.0
dphi = dphi + twopi*f0*dt !Shift frequency up by f0
wave=0.
if(icmplx.eq.1) cwave=0.
k=0
do j=0,(nsym+2)*nsps-1
k=k+1
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if(icmplx.eq.0) then
wave(k)=sin(phi)
else
cwave(k)=cmplx(cos(phi),sin(phi))
endif
phi=mod(phi+dphi(j),twopi)
enddo
! Compute the ramp-up and ramp-down symbols
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if(icmplx.eq.0) then
wave(1:nsps)=wave(1:nsps) * &
(1.0-cos(twopi*(/(i,i=0,nsps-1)/)/(2.0*nsps)))/2.0
k1=(nsym+1)*nsps+1
wave(k1:k1+nsps-1)=wave(k1:k1+nsps-1) * &
(1.0+cos(twopi*(/(i,i=0,nsps-1)/)/(2.0*nsps)))/2.0
else
cwave(1:nsps)=cwave(1:nsps) * &
(1.0-cos(twopi*(/(i,i=0,nsps-1)/)/(2.0*nsps)))/2.0
k1=(nsym+1)*nsps+1
cwave(k1:k1+nsps-1)=cwave(k1:k1+nsps-1) * &
(1.0+cos(twopi*(/(i,i=0,nsps-1)/)/(2.0*nsps)))/2.0
endif
return
end subroutine gen_ft4wave