Summary

This blog excerpt from Rick Lyons' Understanding DSP explains the design, analysis, and implementation of a simple IIR "DC removal" (DC-blocking) filter. Readers will learn the filter's transfer function and difference equation, how the pole radius controls settling time and low-frequency attenuation, and practical implementation notes for audio and communications systems.

Key Takeaways

• Derive the first-order IIR DC-blocking transfer function and corresponding difference equation for implementation.
• Compute and choose the pole radius (r) to meet desired settling time or low-frequency attenuation requirements.
• Implement the filter in direct-form with guidance on numerical (fixed- or floating-point) considerations and stability.
• Analyze transient and steady-state behavior to balance DC rejection against response speed in audio and communications use cases.

Who Should Read This

Intermediate DSP engineers, audio/communications system designers, and students who need a practical, implementation-focused guide to IIR DC-blocking filters and their trade-offs.

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