Digital Filter Design & Simulation
 

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DISPRO FEATURES

[Available as DISPRO_Features.pdf]

USER-INTERFACE FEATURES

  • Easy to use pull-down and pop-up menus speed and simplify the design process

  • Entry of specifications on graphics model of desired frequency response

  • User control of all tradeoffs between specifications and order / length

  • Independent entry of filter order / length and specifications

  • Full retention of parameter values during tradeoff analysis--no retyping

  • Hardcopy output of any screen plot on Epson or HP LaserJet compatible printer

  • Automatic naming of filter data files, with user override

FILTER DESIGN

IIR FILTERS DESIGNED VIA BILINEAR-Z TRANSFORMATION

  • Low Pass, High Pass, Band Pass, and Band Stop (Up to order 99)

  • Butterworth

  • Chebyshev I

  • Chebyshev II

  • Elliptic

  • User-controlled ordering of biquad sections

  • Scaling of biquad sections to combat overflow in fixed-point arithmetic

FIR LINEAR-PHASE FILTERS

Parks-McClellan-Remez

  • Up to length 2000

  • Low Pass, High Pass, Band Pass, and Band Stop

  • Multiband (up to 7 bands)

  • Approximate length computed from specifications--can be overridden

  • Compensation for zero-order hold distortion (sin x / x rolloff) of DAC

Arbitrary Magnitude Shape Specification:

  • Linear or dB amplitude scale

  • Piece-wise linear interpolation between specified points

  • Values input from file or keyboard

  • Built-in editor for specified point values

  • Keyboard input can be saved to disk file

Kaiser-Windowed

  • Up to length 8191

  • Low Pass, High Pass, Band Pass, and Band Stop

  • Approximate length computed from specifications--can be overridden

COEFFICIENT VALUES & WORDLENGTHS FOR ALL FILTERS

  • 32-bit Floating-Point

  • 4-bit to 24-bit Integer / Fixed-Point

  • Displayed on screen or printed: decimal, integer, 2's-complement hex values

POLE-ZERO VALUES FOR IIR FILTERS

  • For Floating-Point Coefficients

  • For 4 to 24 bit Integer / Fixed-Point

  • Table of Numerical Values (magnitude, angle in degrees and Hz)

  • Graphics plot in z-Plane

FREQUENCY RESPONSE COMPUTATION AND PLOTTING

  • Any coefficient wordlength

  • Linear or dB magnitude

  • Numeric values for any set of frequencies, displayed on screen or printed

FIR:

  • Full range plot: up to 4096 points using FFT

  • Any frequency range: up to 1000 points

  • Specified arbitrary-magnitude values can be plotted with actual response

IIR:

  • Any frequency range: up to 1000 points

  • Phase (degrees) and delay (samples)

FILTER PERFORMANCE EVALUATION

TEST SIGNAL GENERATION

  • Sum of sine waves:
        Specified by Fourier series coefficients
        Specified as arbitrary frequencies, amplitude, and phase

  • Special waveforms:
        Rectangular pulse (arbitrary starting point, amplitude, and length)
        Square wave (arbitrary period, amplitude, and number of periods)
        Sawtooth wave (arbitrary period, amplitude, and number of periods)
        Triangular wave (arbitrary period, amplitude, and number of periods)
        Chirp signal (arbitrary initial & final frequencies, and length)
        Gaussian white noise, arbitrary rms level (can be added to sum of sine waves)

IIR & FIR FILTER SIMULATION

 

  • Filter Topology:
    IIR Biquad: Canonic form and Merged-biquads
    FIR: Direct implementation of convolution sum

  • Arithmetic:
    Computation wordlength: 3 to 23 bits-plus-sign
    Accumulator: single / double length, saturating / 2's-complement arithmetic
    Truncation or rounding

  • Coefficients:
    Any wordlength less than or equal to computation wordlength
    Scaling by any power-of-two

  • Excitation:
    Test signal file
    User-created file in proper format
    Impulse
    Step
    Sine Wave

TIME-DOMAIN PLOTTING: IIR AND FIR FILTERS

Linear or log-of-absolute-magnitude amplitude scale
Decimal or integer values for linear amplitude scale
Continuous or discrete-line plots, with optional marking of data points

Forced-response
Impulse response
Step response
Sine Wave response
Excitation signal file
User-created file in proper format

SPECTRAL ANALYSIS
    Fourier series or Fourier transform
    Real-input FFT up to 8192 points
    Optional time sample windowing (Hann, Hamming, Blackman, Kaiser)

  • Data sources:
    Forced-, impulse-, step-response samples for IIR & FIR filters
    Any time sample file in proper format
    Keyboard input of sample values (which can be saved to a disk file)

  • Integrated plotting:
    Linear or dB magnitude
    Phase (degrees)
    Magnitude values: unnormalized; normalized to peak or specified component
    Continuous or discrete-line plots, with optional marking of data points

  • Tables of numeric values:
    Linear or dB magnitude
    Phase (degrees)
    Magnitude values: unnormalized; normalized to peak or specified component
    Show only values above / below a specified threshold
    Displayed on screen or printed

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