56 lines
1.5 KiB
Plaintext
56 lines
1.5 KiB
Plaintext
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subroutine geniscat(msg,msgsent,itone)
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! Generate an ISCAT waveform.
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parameter (NSZ=1291)
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character msg*28,msgsent*28 !Message to be transmitted
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integer imsg(30)
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integer itone(NSZ)
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real*8 sps
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character c*42
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integer icos(4) !Costas array
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data icos/0,1,3,2/
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data nsync/4/,nlen/2/,ndat/18/
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data c/'0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ /.?@-'/
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sps=256.d0*12000.d0/11025.d0
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nsym=int(30*12000.d0/sps)
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nblk=nsync+nlen+ndat
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do i=22,1,-1
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if(msg(i:i).ne.' ' .and. msg(i:i).ne.char(0)) exit
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enddo
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nmsg=i
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msglen=nmsg+1
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k=0
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kk=1
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imsg(1)=40 !Always start with BOM char: '@'
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do i=1,nmsg !Define the tone sequence
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imsg(i+1)=36 !Illegal char set to blank
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do j=1,42
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if(msg(i:i).eq.c(j:j)) imsg(i+1)=j-1
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enddo
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enddo
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do i=1,nsym !Total symbols in 30 s
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j=mod(i-1,nblk)+1
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if(j.le.nsync) then
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itone(i)=icos(j) !Insert 4x4 Costas array
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else if(j.gt.nsync .and. j.le.nsync+nlen) then
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itone(i)=msglen !Insert message-length indicator
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if(j.ge.nsync+2) then
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n=msglen + 5*(j-nsync-1)
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if(n.gt.41) n=n-42
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itone(i)=n
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endif
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else
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k=k+1
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kk=mod(k-1,msglen)+1
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itone(i)=imsg(kk)
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endif
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enddo
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msgsent=msg
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return
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end subroutine geniscat
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