FIR filtering

John Hunter jdhunter at ace.bsd.uchicago.edu
Wed Mar 15 16:24:04 CET 2006


>>>>> "LabWINC" == LabWINC  <vincenzo.cacciatore at gmail.com> writes:

    LabWINC> Hi all, i'm looking for a module to implement a digital
    LabWINC> FIR filter!  Can anyone help me?

scipy.org

Between scipy and matplotlib, you'll feel quite comfortable with
python as a former matlab user

help scipy.filter (see FIR filter design below)

DESCRIPTION
    Signal Processing Tools
    =======================

     Convolution:

        convolve      --  N-dimensional convolution.
        correlate     --  N-dimensional correlation.
        fftconvolve   --  N-dimensional convolution using the FFT.
        convolve2d    --  2-dimensional convolution (more options).
        correlate2d   --  2-dimensional correlation (more options).
        sepfir2d      --  Convolve with a 2-D separable FIR filter.


     B-splines:

        bspline       --  B-spline basis function of order n.
        gauss_spline  --  Gaussian approximation to the B-spline basis
        function.
        cspline1d     --  Coefficients for 1-D cubic (3rd order)
        B-spline.
        qspline1d     --  Coefficients for 1-D quadratic (2nd order)
        B-spline.
        cspline2d     --  Coefficients for 2-D cubic (3rd order)
        B-spline.
        qspline2d     --  Coefficients for 2-D quadratic (2nd order)
        B-spline.

     Filtering:

        order_filter  --  N-dimensional order filter.
        medfilt       --  N-dimensional median filter.
        medfilt2      --  2-dimensional median filter (faster).
        wiener        --  N-dimensional wiener filter.

        symiirorder1  --  2nd-order IIR filter (cascade of first-order
        systems).
        symiirorder2  --  4th-order IIR filter (cascade of
        second-order systems).
        lfilter       --  1-dimensional FIR and IIR digital linear
        filtering.

        deconvolve    --  1-d deconvolution using lfilter.

        hilbert       --- Compute the analytic signal of a 1-d signal.
        get_window    --- Create FIR window.

        detrend       --- Remove linear and/or constant trends from
        data.


     Filter design:

        remez         --  Optimal FIR filter design.
        firwin        --- Windowed FIR filter design.
        iirdesign     --- IIR filter design given bands and gains
        iirfilter     --- IIR filter design given order and critical
        frequencies
        freqs         --- Analog filter frequency response
        freqz         --- Digital filter frequency response

    Matlab-style IIR filter design:

        butter (buttord)  -- Butterworth
        cheby1 (cheb1ord) -- Chebyshev Type I
        cheby2 (cheb2ord) -- Chebyshev Type II
        ellip (ellipord)  -- Elliptic (Cauer)
        bessel            -- Bessel (no order selection available --
        try butterod)

     Linear Systems:

        lti -- linear time invariant system object.
        lsim -- continuous-time simulation of output to linear system.
        impulse -- impulse response of linear, time-invariant (LTI)
        system.
        step -- step response of continous-time LTI system.

     LTI Reresentations:

        tf2zpk -- transfer function to zero-pole-gain.
        zpk2tf -- zero-pole-gain to transfer function.
        tf2ss -- transfer function to state-space.
        ss2tf -- state-pace to transfer function.
        zpk2ss -- zero-pole-gain to state-space.
        ss2zpk -- state-space to pole-zero-gain.

     Waveforms:

        sawtooth -- Periodic sawtooth
        square -- Square wave
        gausspulse -- Gaussian modulated sinusoid
        chirp -- Frequency swept cosine signal

     Wavelets:

        daub -- return low-pass filter for daubechies wavelets
        qmf  -- return quadrature mirror filter from low-pass
        cascade -- compute scaling function and wavelet from
        coefficients



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