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首頁 ＞ DSP應用 ＞ 音效處理 ＞ QEDesign Lite
QEDesign Lite 
簡介：

        在QEDesign系列中QEDesign List是具基本功能，這可以分別支援128個係數以下和6條命令的FIR和IIR濾波器設計。只包含C語言產生器。QEDesign Lite只支援低通、高通、帶通和帶拒濾波器，適合學生和初學者使用。

Features：
  1. Recycling of input for comparative analysis - input for a filter is retained until a new specification is called for. This allows various IIR designs to be compared with FIR window designs as well as FIR equiripple designs.
  2. Use of 64-bit floating point for all design calculations ensures that maximum accuracy is maintained for the design calculations.
  3. Specification file which allows the retention and retrieval of filter specifications.
  4. Help screens for all data entry fields.
  5. Cursor tracking on all frequency domain plots. X and Y coordinates read out automatically as the cursor is tracked on the function by holding the mousebutton down and dragging across the window as desired.
  6. Graphical Zooming is available.
Design Methods：
For the IIR design, a normalized Lowpass Analog Transfer Function is generated based on the given filter specifications. This normalized analog transfer function is transformed via the analog transform formulas with the values suitably chosen for prewarping. The unnormalized transfer functions for Lowpass, Highpass, Bandpass and Bandstop Filters are then transformed to the digital domain via the bilinear transformation. Details of the transformations are printed in the output file SFIL.OUT Output for each design will be accumulated in this file until it is printed.

The filter characteristics including the impulse response are simulated via cascaded second order sections with the poles and zeros grouped using the L. B. Jackson algorithm to minimize stability problems. For the FIR design with windows, the number of taps in the filter are determined using the Kaiser window calculation again based on input specifications.

The coefficients for the taps are then determined by using Fourier series design techniques for computing the impulse response and the window coefficients. The Equiripple FIR design uses the Remez exchange algorithm to determine an optimal solution. It should be noted that this algorithm can give erroneous results if the filter specifications are too tight.
產品應用：

Infinite Impulse Response Filter Design:

  • Lowpass, Highpass, Bandpass and Bandstop Filters
  • Filter orders up to 6 for Lowpass and Highpass Filters
  • Filter orders up to 12 for Bandpass and Bandstop Filters
  • Five Analog Type Filters are available:
    –Butterworth
    –Tschebyscheff
    –Inverse Tschebyscheff
    –Elliptic
    –Bessel
  • Digital Transformation can be performed by the following method:
    –Bilinear Transformation Method
  • Reports show design details such as all transformations from normalized
    lowpass filter to desired filter

Finite Impulse Response Filter Design:

  • Design Method Selection:
    –FIR Windows Design
    –FIR Equiripple Design (Parks-McClellan)
  • Lowpass, Highpass, Bandpass and Bandstop Filters
  • A filter can have up to 128 taps
  • Following window functions are supported:
    –Rectangular
    –Hanning (Hann)
    –Hamming
    –Triangular
    –Blackman
    –Exact Blackman
    –3 Term Cosine
    –3 Term Cosine with continuous 3rd Derivative
    –Minimum 3 Term Cosine
    –4 Term Cosine
    –4 Term Cosine with continuous 5th Derivative
    –Minimum 4 Term Cosine
    –Good 4 Term Blackman Harris
    –Harris Flat Top
    –Kaiser
    –Dolph-Tschebyscheff
    –Taylor
    –Gaussian
  • Reports show design details such as window coefficients and Impulse
    Response prior to multiplying by the window function
  • Filters can be designed for a maximum gain of 1
Other General Features
  • Graphical Output includes:
    –Magnitude Response vs. Frequency
    –Log Magnitude vs. Frequency
    –Phase Response vs. Frequency
    –Group Delay vs. Frequency
    –Impulse Response vs. Time (per sample)
    –Step Response vs. Time (per sample)
    –Pole and Zero Locations