Initial Commit

lib/fsk4hf/getfc1.f90

@@ -0,0 +1,58 @@
+subroutine getfc1(c,fc1)
+
+  parameter (KK=84)                     !Information bits (72 + CRC12)
+  parameter (ND=168)                    !Data symbols: LDPC (168,84), r=1/2
+  parameter (NS=65)                     !Sync symbols (2 x 26 + Barker 13)
+  parameter (NR=3)                      !Ramp up/down
+  parameter (NN=NR+NS+ND)               !Total symbols (236)
+  parameter (NSPS=16)                   !Samples per MSK symbol (16)
+  parameter (N2=2*NSPS)                 !Samples per OQPSK symbol (32)
+  parameter (N13=13*N2)                 !Samples in central sync vector (416)
+  parameter (NZ=NSPS*NN)                !Samples in baseband waveform (3760)
+  parameter (NFFT1=4*NSPS,NH1=NFFT1/2)
+
+  complex c(0:NZ-1)                     !Complex waveform
+  complex c2(0:NFFT1-1)                 !Short spectra
+  real s(-NH1+1:NH1)                    !Coarse spectrum
+
+  nspec=NZ/NFFT1
+  fs=12000.0/72.0
+  df1=fs/NFFT1
+  s=0.
+  do k=1,nspec
+     ia=(k-1)*N2
+     ib=ia+N2-1
+     c2(0:N2-1)=c(ia:ib)
+     c2(N2:)=0.
+     call four2a(c2,NFFT1,1,-1,1)
+     do i=0,NFFT1-1
+        j=i
+        if(j.gt.NH1) j=j-NFFT1
+        s(j)=s(j) + real(c2(i))**2 + aimag(c2(i))**2
+     enddo
+  enddo
+!        call smo121(s,NFFT1)
+  smax=0.
+  ipk=0
+  fc1=0.
+  ia=nint(40.0/df1)
+  do i=-ia,ia
+     f=i*df1
+     if(s(i).gt.smax) then
+        smax=s(i)
+        ipk=i
+        fc1=f
+     endif
+!            write(51,3001) f,s(i),db(s(i))
+! 3001       format(f10.3,e12.3,f10.3)
+  enddo
+
+! The following is for testing SNR calibration:
+!        sp3n=(s(ipk-1)+s(ipk)+s(ipk+1))               !Sig + 3*noise
+!        base=(sum(s)-sp3n)/(NFFT1-3.0)                !Noise per bin
+!        psig=sp3n-3*base                              !Sig only
+!        pnoise=(2500.0/df1)*base                      !Noise in 2500 Hz
+!        xsnrdb=db(psig/pnoise)
+
+  return
+end subroutine getfc1