WSJT-X/lib/analytic.f90

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subroutine analytic(d,npts,nfft,c,pc,beq)
! Convert real data to analytic signal
parameter (NFFTMAX=1024*1024)
real d(npts) ! passband signal
real h(NFFTMAX/2) ! real BPF magnitude
real*8 pc(5),pclast(5) ! static phase coeffs
real*8 ac(5),aclast(5) ! amp coeffs
real*8 fp
complex corr(NFFTMAX/2) ! complex frequency-dependent correction
complex c(NFFTMAX) ! analytic signal
logical*1 beq ! boolean static equalizer flag
data nfft0/0/
data aclast/1.0,0.0,0.0,0.0,0.0/
data ac/1.0,0.05532,0.11438,0.12918,0.09274/ ! amp coeffs for TS2000
save corr,nfft0,h,ac,aclast,pclast,pi,t,beta
df=12000.0/nfft
nh=nfft/2
if( nfft.ne.nfft0 ) then
pi=4.0*atan(1.0)
t=1.0/2000.0
beta=0.1
do i=1,nh+1
ff=(i-1)*df
f=ff-1500.0
h(i)=1.0
if(abs(f).gt.(1-beta)/(2*t) .and. abs(f).le.(1+beta)/(2*t)) then
h(i)=h(i)*0.5*(1+cos((pi*t/beta )*(abs(f)-(1-beta)/(2*t))))
elseif( abs(f) .gt. (1+beta)/(2*t) ) then
h(i)=0.0
endif
enddo
nfft0=nfft
endif
if( any(aclast .ne. ac) .or. any(pclast .ne. pc) ) then
aclast=ac
pclast=pc
write(*,3001) pc
3001 format('Phase coeffs:',5f12.6)
do i=1,nh+1
ff=(i-1)*df
f=ff-1500.0
fp=f/1000.0
corr(i)=ac(1)+fp*(ac(2)+fp*(ac(3)+fp*(ac(4)+fp*ac(5))))
pd=fp*fp*(pc(3)+fp*(pc(4)+fp*pc(5))) ! ignore 1st two terms
corr(i)=corr(i)*cmplx(cos(pd),sin(pd))
enddo
endif
fac=2.0/nfft
c(1:npts)=fac*d(1:npts)
c(npts+1:nfft)=0.
call four2a(c,nfft,1,-1,1) !Forward c2c FFT
if( beq ) then
c(1:nh+1)=h(1:nh+1)*corr(1:nh+1)*c(1:nh+1)
else
c(1:nh+1)=h(1:nh+1)*c(1:nh+1)
endif
c(1)=0.5*c(1) !Half of DC term
c(nh+2:nfft)=0. !Zero the negative frequencies
call four2a(c,nfft,1,1,1) !Inverse c2c FFT
return
end subroutine analytic