111 lines
2.6 KiB
Fortran
111 lines
2.6 KiB
Fortran
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program wsprlf
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parameter (NN=121) !Total symbols
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parameter (NSPS=28800) !Samples per symbol @ fs=12000 Hz
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parameter (NZ=NSPS*NN) !Samples in waveform
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character*8 arg
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complex c(0:NZ-1)
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real*8 twopi,fs,f0,dt,phi,dphi
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real x(0:NZ-1)
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real p(0:NZ/2)
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real h0(0:NSPS/2) !Pulse shape, rising edge
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real h1(0:NSPS/2) !Pulse shape, trailing edge
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real tmp(NN)
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integer id(NN) !Generated data
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integer ie(NN) !Differentially encoded data
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data fs/12000.d0/
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nargs=iargc()
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if(nargs.ne.3) then
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print*,'Usage: wsprlf f0 t1 snr'
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goto 999
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endif
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call getarg(1,arg)
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read(arg,*) f0
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call getarg(2,arg)
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read(arg,*) t1
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call getarg(3,arg)
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read(arg,*) snrdb
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call random_number(tmp) !Generate random bipolar data
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id=1
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where(tmp.lt.0.5) id=-1
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ie(1)=1
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do i=2,NN !Differentially encode
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ie(i)=id(i)*ie(i-1)
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enddo
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n1=nint(t1*NSPS)
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twopi=8.d0*atan(1.d0)
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do i=0,2*n1-1 !Define the shape functions
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if(i.le.n1-1) then
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h0(i)=0.5*(1.0-cos(0.5*i*twopi/n1))
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else
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h1(i-n1)=0.5*(1.0-cos(0.5*i*twopi/n1))
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endif
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enddo
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if(t1.eq.0.0) h0=1
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if(t1.eq.0.0) h1=1
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! Shape the channel pulses
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x=1.
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x(0:n1-1)=h0(0:n1-1) !Leading edge of 1st pulse
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do j=2,NN !Leading edges
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if(ie(j).ne.ie(j-1)) then
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ia=(j-1)*NSPS + 1
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ib=ia+n1-1
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x(ia:ib)=h0(0:n1-1)
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endif
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enddo
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do j=1,NN-1 !Trailing edges
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if(ie(j+1).ne.ie(j)) then
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ib=j*NSPS
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ia=ib-n1+1
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x(ia:ib)=h1(0:n1-1)
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endif
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enddo
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ib=NN*NSPS-1
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ia=ib-n1+1
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x(ia:ib)=h1(0:n1-1) !Trailing edge of last pulse
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dt=1.d0/fs
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ts=dt*NSPS
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baud=fs/NSPS
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write(*,1000) baud,ts
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1000 format('Baud:',f6.3,' Tsym:',f6.3)
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dphi=twopi*f0*dt
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phi=0.d0
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i=-1
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do j=1,NN !Generate the baseband waveform
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a=ie(j)
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do k=1,NSPS
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i=i+1
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x(i)=a*x(i)
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phi=phi+dphi
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if(phi.gt.twopi) phi=phi-twopi
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xphi=phi
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c(i)=x(i)*cmplx(cos(xphi),sin(xphi))
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sym=i*dt/ts
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if(j.le.20) write(13,1010) sym,x(i),c(i)
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1010 format(4f12.6)
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enddo
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enddo
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call four2a(c,NZ,1,-1,1) !To freq domain
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df=fs/NZ
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nh=NZ/2
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do i=0,nh
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f=i*df
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p(i)=real(c(i))**2 + aimag(c(i))**2
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enddo
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p=p/maxval(p)
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do i=0,nh !Save spectrum for plotting
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write(14,1020) i*df,p(i),10.0*log10(p(i)+1.e-8)
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1020 format(f10.3,2e12.3)
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enddo
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999 end program wsprlf
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