85 lines
2.0 KiB
Plaintext
85 lines
2.0 KiB
Plaintext
subroutine freqcal(id2,k,nkhz,noffset,ntol,line)
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parameter (NZ=30*12000,NFFT=55296,NH=NFFT/2)
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integer*2 id2(0:NZ-1)
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complex sp,sn
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real x(0:NFFT-1)
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real xi(0:NFFT-1)
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real w(0:NFFT-1) !Window function
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real s(0:NH)
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character line*80,cflag*1
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logical first
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complex cx(0:NH)
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equivalence (x,cx)
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data n/0/,k0/9999999/,first/.true./
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save n,k0,w,first,pi,fs,xi
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if(first) then
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pi=4.0*atan(1.0)
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fs=12000.0
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do i=0,NFFT-1
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ww=sin(i*pi/NFFT)
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w(i)=ww*ww/NFFT
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xi(i)=2.0*pi*i
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enddo
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first=.false.
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endif
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if(k.lt.NFFT) go to 900
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if(k.lt.k0) n=0
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k0=k
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x=w*id2(k-NFFT:k-1) !Apply window
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call four2a(x,NFFT,1,-1,0) !Compute spectrum, r2c
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df=fs/NFFT
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if (ntol.gt.noffset) then
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ia=0
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ib=nint((noffset*2)/df)
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else
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ia=nint((noffset-ntol)/df)
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ib=nint((noffset+ntol)/df)
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endif
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smax=0.
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s=0.
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do i=ia,ib
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s(i)=real(cx(i))**2 + aimag(cx(i))**2
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if(s(i).gt.smax) then
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smax=s(i)
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ipk=i
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endif
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enddo
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call peakup(s(ipk-1),s(ipk),s(ipk+1),dx)
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fpeak=df * (ipk+dx)
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ap=(fpeak/fs+1.0/(2.0*NFFT))
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an=(fpeak/fs-1.0/(2.0*NFFT))
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sp=sum(id2((k-NFFT):k-1)*cmplx(cos(xi*ap),-sin(xi*ap)))
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sn=sum(id2((k-NFFT):k-1)*cmplx(cos(xi*an),-sin(xi*an)))
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fpeak=fpeak+fs*(abs(sp)-abs(sn))/(abs(sp)+abs(sn))/(2*NFFT)
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xsum=0.
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nsum=0
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do i=ia,ib
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if(abs(i-ipk).gt.10) then
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xsum=xsum+s(i)
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nsum=nsum+1
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endif
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enddo
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ave=xsum/nsum
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snr=db(smax/ave)
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pave=db(ave) + 8.0
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cflag=' '
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if(snr.lt.20.0) cflag='*'
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n=n+1
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nsec=mod(time(),86400)
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nhr=nsec/3600
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nmin=mod(nsec/60,60)
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nsec=mod(nsec,60)
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ncal=1
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ferr=fpeak-noffset
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write(line,1100) nhr,nmin,nsec,nkhz,ncal,noffset,fpeak,ferr,pave, &
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snr,cflag,char(0)
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1100 format(i2.2,':',i2.2,':',i2.2,i7,i3,i6,2f10.3,2f7.1,2x,a1,a1)
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900 return
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end subroutine freqcal
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