mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2024-11-25 05:38:46 -05:00
89 lines
2.4 KiB
Fortran
89 lines
2.4 KiB
Fortran
subroutine ft2_gfsk_iwave(msg37,f0,snrdb,iwave)
|
|
|
|
! Generate waveform for experimental "FT2" mode
|
|
|
|
use packjt77
|
|
include 'ft2_params.f90' !Set various constants
|
|
parameter (NWAVE=(NN+2)*NSPS)
|
|
character msg37*37,msgsent37*37
|
|
real wave(NWAVE),xnoise(NWAVE)
|
|
real dphi(NWAVE)
|
|
real pulse(480)
|
|
|
|
integer itone(NN)
|
|
integer*2 iwave(NWAVE) !Generated full-length waveform
|
|
logical first
|
|
data first/.true./
|
|
save pulse
|
|
|
|
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
|
|
|
|
if(first) then
|
|
! The filtered frequency pulse
|
|
do i=1,480
|
|
tt=(i-240.5)/160.0
|
|
pulse(i)=gfsk_pulse(1.0,tt)
|
|
enddo
|
|
dphi_peak=twopi*(hmod/2.0)/real(NSPS)
|
|
first=.false.
|
|
endif
|
|
|
|
! Source-encode, then get itone():
|
|
itype=1
|
|
call genft2(msg37,0,msgsent37,itone,itype)
|
|
|
|
! Create the instantaneous frequency waveform
|
|
dphi=0.0
|
|
do j=1,NN
|
|
ib=(j-1)*160+1
|
|
ie=ib+480-1
|
|
dphi(ib:ie)=dphi(ib:ie)+dphi_peak*pulse*(2*itone(j)-1)
|
|
enddo
|
|
|
|
phi=0.0
|
|
wave=0.0
|
|
sqrt2=sqrt(2.)
|
|
dphi=dphi+twopi*f0*dt
|
|
do j=1,NWAVE
|
|
wave(j)=sqrt2*sin(phi)
|
|
sqsig=sqsig + wave(j)**2
|
|
phi=mod(phi+dphi(j),twopi)
|
|
enddo
|
|
wave(1:160)=wave(1:160)*(1.0-cos(twopi*(/(i,i=0,159)/)/320.0) )/2.0
|
|
wave(145*160+1:146*160)=wave(145*160+1:146*160)*(1.0+cos(twopi*(/(i,i=0,159)/)/320.0 ))/2.0
|
|
wave(146*160+1:)=0.
|
|
|
|
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_gfsk_iwave
|