mirror of https://github.com/pavel-demin/ft8d.git
80 lines
2.5 KiB
Fortran
80 lines
2.5 KiB
Fortran
subroutine gen_ft8wave(itone,nsym,nsps,bt,fsample,f0,cwave,wave,icmplx,nwave)
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!
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! generate ft8 waveform using Gaussian-filtered frequency pulses.
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!
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parameter(MAX_SECONDS=20,NTAB=65536)
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real wave(nwave)
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complex cwave(nwave),ctab(0:NTAB-1)
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real pulse(23040)
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real dphi(0:(nsym+2)*nsps-1)
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integer itone(nsym)
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data ibt0/0/
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save pulse,twopi,dt,hmod,ibt0,ctab
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ibt=nint(10*bt)
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if(ibt0.ne.ibt) then
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twopi=8.0*atan(1.0)
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dt=1.0/fsample
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hmod=1.0
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! Compute the frequency-smoothing pulse
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do i=1,3*nsps
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tt=(i-1.5*nsps)/real(nsps)
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pulse(i)=gfsk_pulse(bt,tt)
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enddo
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ibt0=nint(10*bt)
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do i=0,NTAB-1
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phi=i*twopi/NTAB
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ctab(i)=cmplx(cos(phi),sin(phi))
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enddo
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endif
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! Compute the smoothed frequency waveform.
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! Length = (nsym+2)*nsps samples, first and last symbols extended
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dphi_peak=twopi*hmod/real(nsps)
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dphi=0.0
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do j=1,nsym
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ib=(j-1)*nsps
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ie=ib+3*nsps-1
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dphi(ib:ie) = dphi(ib:ie) + dphi_peak*pulse(1:3*nsps)*itone(j)
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enddo
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! Add dummy symbols at beginning and end with tone values equal to 1st and last symbol, respectively
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dphi(0:2*nsps-1)=dphi(0:2*nsps-1)+dphi_peak*itone(1)*pulse(nsps+1:3*nsps)
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dphi(nsym*nsps:(nsym+2)*nsps-1)=dphi(nsym*nsps:(nsym+2)*nsps-1)+dphi_peak*itone(nsym)*pulse(1:2*nsps)
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! Calculate and insert the audio waveform
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phi=0.0
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dphi = dphi + twopi*f0*dt !Shift frequency up by f0
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if(icmplx .eq. 0) wave=0.
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if(icmplx .ne. 0) cwave=0. !Avoid writing to memory we may not have access to
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k=0
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do j=nsps,nsps+nwave-1 !Don't include dummy symbols
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k=k+1
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if(icmplx.eq.0) then
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wave(k)=sin(phi)
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else
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i=phi*float(NTAB)/twopi
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cwave(k)=ctab(i)
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endif
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phi=mod(phi+dphi(j),twopi)
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enddo
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! Apply envelope shaping to the first and last symbols
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nramp=nint(nsps/8.0)
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if(icmplx.eq.0) then
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wave(1:nramp)=wave(1:nramp) * &
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(1.0-cos(twopi*(/(i,i=0,nramp-1)/)/(2.0*nramp)))/2.0
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k1=nsym*nsps-nramp+1
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wave(k1:k1+nramp-1)=wave(k1:k1+nramp-1) * &
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(1.0+cos(twopi*(/(i,i=0,nramp-1)/)/(2.0*nramp)))/2.0
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else
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cwave(1:nramp)=cwave(1:nramp) * &
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(1.0-cos(twopi*(/(i,i=0,nramp-1)/)/(2.0*nramp)))/2.0
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k1=nsym*nsps-nramp+1
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cwave(k1:k1+nramp-1)=cwave(k1:k1+nramp-1) * &
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(1.0+cos(twopi*(/(i,i=0,nramp-1)/)/(2.0*nramp)))/2.0
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endif
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return
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end subroutine gen_ft8wave
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