Digital Waveguide Filters

A Digital Waveguide Filter (DWF) can be defined as any digital filter built by stringing together digital waveguides.^C.7 In the case of a cascade combination of unit-length waveguide sections, they are essentially the same as microwave filters [372] and unit element filters [136] (Appendix F). This section shows how DWFs constructed as a cascade chain of waveguide sections, and reflectively terminated, can be transformed via elementary manipulations to well known ladder and lattice digital filters, such as those used in speech modeling [297,363].

DWFs may be derived conceptually by sampling the unidirectional traveling waves in a system of ideal, lossless waveguides. Sampling is across time and space. Thus, variables in a DWF structure are equal exactly (at the sampling times and positions, to within numerical precision) to variables propagating in the physical medium in an interconnection of uniform 1D waveguides.

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Subsections

• Ladder Waveguide Filters
• Reflectively Terminated Waveguide Filters
• Half-Rate Ladder Waveguide Filters
• Conventional Ladder Filters
• Power-Normalized Waveguide Filters

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About the Author: Julius Orion Smith III
Julius Smith's background is in electrical engineering (BS Rice 1975, PhD Stanford 1983). He is presently Professor of Music and Associate Professor (by courtesy) of Electrical Engineering at Stanford's Center for Computer Research in Music and Acoustics (CCRMA), teaching courses and pursuing research related to signal processing applied to music and audio systems. See http://ccrma.stanford.edu/~jos/ for details.