73 lines
3.1 KiB
Fortran
73 lines
3.1 KiB
Fortran
subroutine fil3c(c1,n1,c2,n2)
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! FIR complex-to-complex low-pass filter designed with ScopeFIR
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!
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!-----------------------------------------------
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! fsample (Hz) 12000 Input sample rate
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! Ntaps 113 Number of filter taps
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! fc (Hz) 500 Cutoff frequency
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! fstop (Hz) 750 Lower limit of stopband
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! Ripple (dB) 0.2 Ripple in passband
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! Stop Atten (dB) 50 Stopband attenuation
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! fout (Hz) 1500 Output sample rate
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! Suggest calling with n1 = 8*n2 + 105, where n2 is the desired number
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! of 1500 Hz output samples.
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parameter (NTAPS=113)
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parameter (NH=NTAPS/2)
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parameter (NDOWN=8) !Downsample ratio = 1/8
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complex c1(n1)
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complex c2(n1/NDOWN)
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complex z
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! Filter coefficients:
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real a(-NH:NH)
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data a/ &
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-0.001818142144,-0.000939132050,-0.001044063556,-0.001042685542, &
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-0.000908957610,-0.000628132309,-0.000202701465, 0.000346307629, &
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0.000978154552, 0.001634336295, 0.002243121592, 0.002726064379, &
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0.003006201675, 0.003018055983, 0.002717699575, 0.002091546534, &
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0.001162489032,-0.000007904811,-0.001321554806,-0.002649908053, &
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-0.003843608784,-0.004747338068,-0.005218967042,-0.005148229529, &
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-0.004470167307,-0.003177923811,-0.001335998901, 0.000915924193, &
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0.003386100636, 0.005818719744, 0.007939147967, 0.009465071347, &
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0.010145641899, 0.009787447819, 0.008285915754, 0.005645995244, &
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0.001995842303,-0.002410369720,-0.007202515555,-0.011916811719, &
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-0.016028350845,-0.018993391440,-0.020297455955,-0.019503792208, &
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-0.016298136197,-0.010526834635,-0.002223837363, 0.008378305829, &
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0.020854478160, 0.034608532659, 0.048909701463, 0.062944127288, &
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0.075874892030, 0.086903764340, 0.095332017649, 0.100619428175, &
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0.102420526192, 0.100619428175, 0.095332017649, 0.086903764340, &
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0.075874892030, 0.062944127288, 0.048909701463, 0.034608532659, &
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0.020854478160, 0.008378305829,-0.002223837363,-0.010526834635, &
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-0.016298136197,-0.019503792208,-0.020297455955,-0.018993391440, &
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-0.016028350845,-0.011916811719,-0.007202515555,-0.002410369720, &
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0.001995842303, 0.005645995244, 0.008285915754, 0.009787447819, &
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0.010145641899, 0.009465071347, 0.007939147967, 0.005818719744, &
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0.003386100636, 0.000915924193,-0.001335998901,-0.003177923811, &
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-0.004470167307,-0.005148229529,-0.005218967042,-0.004747338068, &
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-0.003843608784,-0.002649908053,-0.001321554806,-0.000007904811, &
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0.001162489032, 0.002091546534, 0.002717699575, 0.003018055983, &
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0.003006201675, 0.002726064379, 0.002243121592, 0.001634336295, &
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0.000978154552, 0.000346307629,-0.000202701465,-0.000628132309, &
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-0.000908957610,-0.001042685542,-0.001044063556,-0.000939132050, &
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-0.001818142144/
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save a
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n2=(n1-NTAPS+NDOWN)/NDOWN
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k0=NH-NDOWN+1
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! Loop over all output samples
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do i=1,n2
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z=0.
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k=k0 + NDOWN*i
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do j=-NH,NH
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z=z + c1(j+k)*a(j)
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enddo
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c2(i)=z
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enddo
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return
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end subroutine fil3c
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