mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2024-11-22 20:28:42 -05:00
65 lines
1.9 KiB
Fortran
65 lines
1.9 KiB
Fortran
subroutine ft2_iwave(msg37,f0,snrdb,iwave)
|
|
|
|
! Generate waveform for experimental "FT2" mode
|
|
|
|
use packjt77
|
|
include 'ft2_params.f90' !Set various constants
|
|
parameter (NWAVE=NN*NSPS)
|
|
character msg37*37,msgsent37*37
|
|
real wave(NWAVE),xnoise(NWAVE)
|
|
integer itone(NN)
|
|
integer*2 iwave(NWAVE) !Generated full-length waveform
|
|
|
|
twopi=8.0*atan(1.0)
|
|
fs=12000.0 !Sample rate (Hz)
|
|
dt=1.0/fs !Sample interval (s)
|
|
hmod=0.8 !Modulation index (MSK=0.5, FSK=1.0)
|
|
tt=NSPS*dt !Duration of symbols (s)
|
|
baud=1.0/tt !Keying rate (baud)
|
|
bw=1.5*baud !Occupied bandwidth (Hz)
|
|
txt=NZ*dt !Transmission length (s)
|
|
bandwidth_ratio=2500.0/(fs/2.0)
|
|
! sig=sqrt(2*bandwidth_ratio) * 10.0**(0.05*snrdb)
|
|
! if(snrdb.gt.90.0) sig=1.0
|
|
txt=NN*NSPS/12000.0
|
|
|
|
! Source-encode, then get itone():
|
|
itype=1
|
|
call genft2(msg37,0,msgsent37,itone,itype)
|
|
|
|
k=0
|
|
phi=0.0
|
|
sqsig=0.
|
|
do j=1,NN !Generate real waveform
|
|
dphi=twopi*(f0*dt+(hmod/2.0)*(2*itone(j)-1)/real(NSPS))
|
|
do i=1,NSPS
|
|
k=k+1
|
|
wave(k)=sqrt(2.0)*sin(phi) !Signal has rms = 1.0
|
|
sqsig=sqsig + wave(k)**2
|
|
phi=mod(phi+dphi,twopi)
|
|
enddo
|
|
enddo
|
|
|
|
if(snrdb.gt.90.0) then
|
|
iwave=nint((32767.0/sqrt(2.0))*wave)
|
|
return
|
|
endif
|
|
|
|
sqnoise=1.e-30
|
|
if(snrdb.lt.90) then
|
|
do i=1,NWAVE !Add gaussian noise at specified SNR
|
|
xnoise(i)=gran() !Noise has rms = 1.0
|
|
enddo
|
|
endif
|
|
xnoise=xnoise*sqrt(0.5*fs/2500.0)
|
|
fac=30.0
|
|
snr_amplitude=10.0**(0.05*snrdb)
|
|
wave=fac*(snr_amplitude*wave + xnoise)
|
|
datpk=maxval(abs(wave))
|
|
print*,'A',snr_amplitude,datpk
|
|
|
|
iwave=nint((30000.0/datpk)*wave)
|
|
|
|
return
|
|
end subroutine ft2_iwave
|