52 lines
1.7 KiB
Plaintext
52 lines
1.7 KiB
Plaintext
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subroutine genfsk4hf(msgbits,f0,id,c)
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parameter (KK=84) !Information bits (72 + CRC12)
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parameter (ND=84) !Data symbols: LDPC (168,84), r=1/2
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parameter (NS=12) !Sync symbols (3 @ 4x4 Costas arrays)
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parameter (NR=2) !Ramp up/down
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parameter (NN=NR+NS+ND) !Total symbols (98)
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parameter (NSPS=2688/84) !Samples per symbol (32)
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parameter (NZ=NSPS*NN) !Samples in baseband waveform (3136)
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complex c(0:NZ-1) !Complex waveform
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integer id0(NN) !2-bit data (values 0-3), all symbols
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integer id(ND) !2-bit data (values 0-3), data only
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integer*1 msgbits(KK),codeword(2*ND)
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integer icos4(4) !4x4 Costas array
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data icos4/0,1,3,2/
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twopi=8.0*atan(1.0)
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fs=12000.0/84.0
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dt=1.0/fs
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baud=1.0/(NSPS*dt)
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call encode168(msgbits,codeword) !Encode the test message
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id0(1)=0 !Ramp-up
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id0(2:5)=icos4 !First Costas array
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id0(48:51)=icos4 !Second
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id0(94:97)=icos4 !Third
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id0(98)=0 !Ramp down
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j=5
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do i=1,84 !Data symbols
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id(i)=2*codeword(2*i-1) + codeword(2*i)
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j=j+1
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if(i.eq.43) j=j+4
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id0(j)=id(i)
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enddo
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! Generate the 4-FSK waveform, low tone at f=0
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c=0.
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phi=0.d0
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k=-1
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do j=1,NN
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dphi=twopi*(f0+id0(j)*baud)*dt
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do i=1,NSPS
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k=k+1
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phi=phi+dphi
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if(phi.gt.twopi) phi=phi-twopi
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c(k)=cmplx(cos(phi),sin(phi))
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enddo
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enddo
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return
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end subroutine genfsk4hf
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