Match-n-Freq 6.11 ... Problem-Solving Application
Match n Freq (tm): Finds optimal pole-zero locations to minimize intersymbol interference
Match n Freq (tm): Pulse shaping filter program that finds the pole-zero locations of a transfer function H(s) for a matched filter. H(s) equals a -desired- signal (Yout) divided by a given input signal (Yin). Both Yout and Yin are functions of frequency (not time). This is an example of how Automatic Differentiation does simpify problem solving.
Group delay may also be calculated to
compliment a given data set, thus, providing a flat group delay.
Minimizing Intersymbol Interference in a
read/write channel for disc drives by shaping and slimming an isolated readback pulse was the main objective for writing this matched filter program. For more info, see Kost, R. and P. Brubaker; 'Arbitrary equalization with simple LC structures';IEEE Transactions on Magnetics, Nov. 1981, pp 3346-3348.
The original matched filter problem was 'solved' in hours! Years of testing hardware designs and modifying design requirements/goals finally produced present program logic. All those minus signs in the transfer function gave me many white hairs! User input and objectives are from or in the frequency domain. Someday a time domain version of this matched filter program will be developed with a better objective function.
For a technical write-up on Match-n-Freq see Pulse Slimming / InterSymbol Interference. Other associated articles include Optimum Matched Filter (Transfer Function) and Magnetic Recording.
Match-n-Freq was made possible due to the
FortranCalculus compiler. The source code is relatively short (7 pages
+ 11 input/output pages) showing the FortranCalculus programming simplicity. Sometimes Match-n-Freq has three nested solvers in execution at once. Match-n-Freq is a free (4.5 MB) download.