A Butterworth filter is a human-made analog or digital filter design characterized by maximally flat frequency response in the passband, with no ripples. Parameters: (1) filter order N (determines rolloff steepness of 20·N dB/decade), (2) cutoff frequency fc (3 dB point where response drops), (3) passband ripple (zero by design), (4) stopband attenuation profile. A Butterworth filter of order N has all poles placed on a semicircle in the left half of the s-plane at equal angular intervals, yielding the flat magnitude response |H(f)|² = 1/(1+(f/fc)^(2N)). Persistence mechanism: persists through filter design textbooks (Sedra/Smith, Oppenheim), standard electronic component catalogs, SPICE model libraries, DSP implementation toolkits (MATLAB's filter design, SciPy's scipy.signal.butter), and analog circuit design handbooks. [formal: butterworth | substrate: matter | horizon: generations | explicit: yes | epoch: 0.02]
Accepted ontology entry
butterworth-filter
A Butterworth filter is a human-made analog or digital filter design characterized by maximally flat frequency response in the passband, with no ripples. Parameters: (1) filter order N (determines rolloff steepness of 20·N dB/decade), (2)…
Definition
Why it is in scope
A human-made filter design standard — the classic maximally-flat magnitude-response prototype — built to persist as the reference filter family in signal-processing textbooks and design toolkits, from which analog and digital IIR filters are derived.
Names and aliases
- butterworth-filteren · CANONICAL
Relations from this entry
- cmsps9i0v06eejlssqrjcqyviSERVES →
The Butterworth filter is a signal filter specifically designed for signal processing applications — its purpose is to provide a maximally flat frequency response in the passband for signal processing tasks. Servant (butterworth-filter) points at master (signal-processing).
- iir-filterINSTANCE_OF →
Pinned sense (Law 11d): the classic Butterworth design as realized recursively — the maximally-flat prototype |H(jw)|=1/sqrt(1+(w/wc)^(2N)) carried to the digital domain by bilinear transform, with poles inside the unit circle and feedback in the difference equation. That realization is a specific member of the recursive filter class: a competent speaker calls a Butterworth IIR section an IIR filter. Nearest kind (Law 11e): iir-filter — no nearer recursive-kind rung exists in the web. FIR approximations of the Butterworth magnitude are a secondary sense, not the pinned one.
- cmsps9i0v06eejlssqrjcqyviDEPENDS_ON →
Butterworth filter operates as a digital/analog signal processing filter; removing signal processing capability stops it from operating. The filter's computation (frequency response evaluation, pole placement) requires signal processing operations.
Relations to this entry
No accepted relations in this direction.
Record identity
- Created
- Sep 2, 2026, 12:18 AM UTC
- Content hash
- c3ba9c917666a2bf8fedcb7330565561440c440137a3d497efc59a687019b22a