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Use a table lookup for exp(i*phi) in gen_ft8wave.f90.

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This commit is contained in:
Joe Taylor 2020-03-03 12:40:27 -05:00
parent 761ee1cd85
commit 02eb4fe90b
1 changed files with 16 additions and 8 deletions
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20
lib/ft8/gen_ft8wave.f90
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@ -2,15 +2,15 @@ subroutine gen_ft8wave(itone,nsym,nsps,bt,fsample,f0,cwave,wave,icmplx,nwave)
!
! generate ft8 waveform using Gaussian-filtered frequency pulses.
!
parameter(MAX_SECONDS=20)
use timer_module, only: timer
parameter(MAX_SECONDS=20,NTAB=65536)
real wave(nwave)
complex cwave(nwave)
complex cwave(nwave),ctab(0:NTAB-1)
real pulse(23040)
real dphi(0:(nsym+2)*nsps-1)
integer itone(nsym)
data ibt0/0/
save pulse,twopi,dt,hmod,ibt0
save pulse,twopi,dt,hmod,ibt0,ctab
ibt=nint(10*bt)
if(ibt0.ne.ibt) then
@ -23,6 +23,10 @@ subroutine gen_ft8wave(itone,nsym,nsps,bt,fsample,f0,cwave,wave,icmplx,nwave)
pulse(i)=gfsk_pulse(bt,tt)
enddo
ibt0=nint(10*bt)
do i=0,NTAB-1
phi=i*twopi/NTAB
ctab(i)=cmplx(cos(phi),sin(phi))
enddo
endif
! Compute the smoothed frequency waveform.
@ -42,17 +46,21 @@ subroutine gen_ft8wave(itone,nsym,nsps,bt,fsample,f0,cwave,wave,icmplx,nwave)
phi=0.0
dphi = dphi + twopi*f0*dt !Shift frequency up by f0
wave=0.
if (icmplx .ne. 0) cwave=0. ! avoid writing to memory we may not have access to
if(icmplx .ne. 0) cwave=0. !Avoid writing to memory we may not have access to
call timer('gen_loop',0)
k=0
do j=nsps,nsps+nwave-1 !Don't include dummy symbols
k=k+1
if(icmplx.eq.0) then
wave(k)=sin(phi)
else
cwave(k)=cmplx(cos(phi),sin(phi))
i=phi*float(NTAB)/twopi
cwave(k)=ctab(i)
endif
phi=mod(phi+dphi(j),twopi)
enddo
call timer('gen_loop',1)
! Apply envelope shaping to the first and last symbols
nramp=nint(nsps/8.0)