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65 lines
1.9 KiB
Fortran
65 lines
1.9 KiB
Fortran
subroutine ft2_iwave(msg37,f0,snrdb,iwave)
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! Generate waveform for experimental "FT2" mode
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use packjt77
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include 'ft2_params.f90' !Set various constants
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parameter (NWAVE=NN*NSPS)
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character msg37*37,msgsent37*37
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real wave(NWAVE),xnoise(NWAVE)
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integer itone(NN)
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integer*2 iwave(NWAVE) !Generated full-length waveform
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twopi=8.0*atan(1.0)
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fs=12000.0 !Sample rate (Hz)
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dt=1.0/fs !Sample interval (s)
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hmod=0.8 !Modulation index (MSK=0.5, FSK=1.0)
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tt=NSPS*dt !Duration of symbols (s)
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baud=1.0/tt !Keying rate (baud)
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bw=1.5*baud !Occupied bandwidth (Hz)
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txt=NZ*dt !Transmission length (s)
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bandwidth_ratio=2500.0/(fs/2.0)
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! sig=sqrt(2*bandwidth_ratio) * 10.0**(0.05*snrdb)
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! if(snrdb.gt.90.0) sig=1.0
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txt=NN*NSPS/12000.0
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! Source-encode, then get itone():
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itype=1
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call genft2(msg37,0,msgsent37,itone,itype)
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k=0
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phi=0.0
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sqsig=0.
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do j=1,NN !Generate real waveform
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dphi=twopi*(f0*dt+(hmod/2.0)*(2*itone(j)-1)/real(NSPS))
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do i=1,NSPS
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k=k+1
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wave(k)=sqrt(2.0)*sin(phi) !Signal has rms = 1.0
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sqsig=sqsig + wave(k)**2
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phi=mod(phi+dphi,twopi)
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enddo
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enddo
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if(snrdb.gt.90.0) then
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iwave=nint((32767.0/sqrt(2.0))*wave)
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return
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endif
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sqnoise=1.e-30
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if(snrdb.lt.90) then
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do i=1,NWAVE !Add gaussian noise at specified SNR
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xnoise(i)=gran() !Noise has rms = 1.0
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enddo
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endif
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xnoise=xnoise*sqrt(0.5*fs/2500.0)
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fac=30.0
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snr_amplitude=10.0**(0.05*snrdb)
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wave=fac*(snr_amplitude*wave + xnoise)
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datpk=maxval(abs(wave))
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print*,'A',snr_amplitude,datpk
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iwave=nint((30000.0/datpk)*wave)
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return
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end subroutine ft2_iwave
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