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Educational Software for Electronic Filter Design

MAKERS: Michael Ellis

This is an educational homw program that is meant to teach electronic filter design as well as provide useful designs for active, passive, and digital (IIR and FIR) filters. In the project image, the Electronic Filter Design software has generated a high order elliptic filter to block certain parts of the audio spectrum. I wanted to explore what music would sound like if certain frequency ranges were eliminated, plus also explore the difference between FIR and IIR filter with regard to the group delay audio effects of IIR filters. The programs displays all design equations for active, passive, and switched capacitor filters, including analytic inverse Laplace transform equations, design equations for MFB, VCVS, and state variable active filters, the input impedance formulation of unevenly terminated elliptic passive filters, and more. The are 20 mini tutorials written into the program. In order to make this program as useful as possible, the following features have been included. Features include: Active filters include Butterworth, Tchebyscheff, inverse Tchebyscheff, elliptic designs. Filter orders to degree 40 (20 for elliptic). Lowpass, bandpass, bandstop,and highpass variations Provides a utility to estimate the filter order for analog (active and passive) and FIR digital filters, based on design requirements. Active filters include multiple feedback, voltage controlled voltage source, and state-variable implementations. Passive elliptic filters with arbitrary source and load resistances (up to order 9) for lowpass, bandpass, bandstop, and highpass configurations Allows canonical transforms on various passive filter sections. Includes image parameter passive filter design utility. Includes Butterworth and Tchebyscheff passive filters. Generates PSPICE file for independent verification of all active and passive filters. Generates source code for MC56F84789 DSP for FIR and IIR filters. Limit is order 20 for IIR and length 512 for FIR filters. A/D sampling rates from 1 to 100K. 32 bit arithmetic allows for ultra high Q audio filters with less than 1Hz bandpass to stopband transition. Proprietary algorithm allows for IIR bandpass and bandstop filters with no anomolies. Provides for real time implementation of FIR and IIR digital filters on MC56F8400 development board. . Various window design of FIR filters including rectangular, triangular, Hamming, Hanning, generalized Hamming, and Kaiser Remez exchange algorithm for FIR equiripple filters to length 512 Numerous equations are shown analytically for educational purposes including: Displays the input impedance equation set for unevenly terminated elliptic filters lowpass prototypes. Displays the magnitude squared function for the lowpass prototype filters. Shows the transfer functions for analog filters. Displays poles and zeros for all analog and IIR filters. Shows the DSP assembly code for and FIR and IIR filters. Provides the step and impulse response equations from the inverse Laplace transform utility. Shows the equations for the canonical transform of passive filter sections. Lowpass to bandpass, bandstop, and highpass transforms equations for analog filters are displayed. Generates Martin & Sedra switched capacitor biquads based on the bi-linear transform. Utilities include PLL analysis, RF directional coupler design, L-C matching, resistive pad design, and more.

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