subroutine analytic(d,npts,nfft,c) ! Convert real data to analytic signal parameter (NFFTMAX=1024*1024) real d(npts) real h(NFFTMAX/2) complex c(NFFTMAX) data nfft0/0/ save nfft0,h df=12000.0/nfft nh=nfft/2 if(nfft.ne.nfft0) then t=1.0/2000.0 beta=0.1 pi=4.0*atan(1.0) do i=1,nh+1 ff=(i-1)*df f=ff-1500.0 h(i)=0. if(abs(f).le.(1-beta)/(2*t)) h(i)=1.0 if(abs(f).gt.(1-beta)/(2*t) .and. abs(f).le.(1+beta)/(2*t)) then h(i)=0.5*(1+cos((pi*t/beta )*(abs(f)-(1-beta)/(2*t)))) endif ! h(i)=sqrt(h(i)) enddo nfft0=nfft 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 ! do i=1,nh ! f=(i-1)*df ! s(i)=real(c(i))**2 + aimag(c(i))**2 ! write(12,3001) f,s(i),db(s(i)) !3001 format(3f12.3) ! enddo ! ia=700.0/df ! c(1:ia)=0. ! ib=2300.0/df ! c(ib:nfft)=0. c(1:nh+1)=h(1:nh+1)*c(1:nh+1) 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