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51 lines
2.0 KiB
Fortran
51 lines
2.0 KiB
Fortran
subroutine fil658(c1,n1,c2,n2)
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C FIR lowpass filter designed using ScopeFIR
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C Pass #1 Pass #2 Pass #3
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C-----------------------------------------------
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C fsample (Hz) 96000.0 24000 6000 Input sample rate
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C Ntaps 47 47 47 Number of filter taps
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C fc (Hz) 6000 1500 375 Cutoff frequency (-3 dB)
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C fstop (Hz) 11025.0 2756.25 689.0625 Lower limit of stopband
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C Ripple (dB) 0.06 0.06 0.06 Ripple in passband
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C Stop Atten (dB) 41 41 41 Stopband attenuation
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C fout (Hz) 24000.0 6000 1500 Output sample rate
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parameter (NTAPS=47)
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parameter (NH=NTAPS/2)
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parameter (NDOWN=4) !Downsample ratio = 1/4
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complex c1(n1)
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complex c2(n1/NDOWN)
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C Filter coefficients:
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real a(-NH:NH)
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data a/
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+ 0.004066057444,-0.000483030239,-0.002085155775,-0.004036668720,
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+ -0.005338083014,-0.004952374329,-0.002267639582, 0.002499787691,
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+ 0.008113543743, 0.012522509052, 0.013441779030, 0.009233544068,
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+ -0.000256999594,-0.013156485907,-0.025660797518,-0.032755808092,
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+ -0.029602578877,-0.013013352845, 0.017249853203, 0.057885304099,
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+ 0.102497204557, 0.142897857652, 0.171067807479, 0.181167084990,
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+ 0.171067807479, 0.142897857652, 0.102497204557, 0.057885304099,
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+ 0.017249853203,-0.013013352845,-0.029602578877,-0.032755808092,
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+ -0.025660797518,-0.013156485907,-0.000256999594, 0.009233544068,
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+ 0.013441779030, 0.012522509052, 0.008113543743, 0.002499787691,
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+ -0.002267639582,-0.004952374329,-0.005338083014,-0.004036668720,
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+ -0.002085155775,-0.000483030239, 0.004066057444/
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n2=(n1-NTAPS+NDOWN)/NDOWN
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k0=NH-NDOWN+1
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C Loop over all output samples
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do i=1,n2
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c2(i)=0.
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k=k0 + NDOWN*i
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do j=-NH,NH
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c2(i)=c2(i) + c1(j+k)*a(j)
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enddo
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enddo
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return
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end
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