May 1 · 5 min read · Transfer Function The State Variable Filter (SVF) implements three simultaneous outputs — lowpass (LP), highpass (HP), and bandpass (BP) — from a single shared pole structure. All three biquads share
Join discussionApr 26 · 6 min read · A 2nd-order Butterworth gives you 40 dB/decade. Double the order to fourth and you get 80 dB/decade — the same maximally flat passband, twice the stopband suppression. At fc = 1000 Hz with fs = 44100
Join discussionApr 26 · 7 min read · Every IIR lowpass filter we have covered — Butterworth, Chebyshev, Elliptic — achieves steep rolloff at the cost of nonlinear phase, meaning different frequency components are delayed by different amo
Join discussionApr 26 · 7 min read · Every sensor signal chain has a frequency-dependent noise floor. Below the shelf frequency the signal is clean; above it, quantization noise, switching harmonics, or electromagnetic interference domin
Join discussionApr 22 · 6 min read · A pure integrator (pole at z = 1) delivers infinite DC gain and infinite wind-up risk. A low shelf biquad gives you the same low-frequency gain boost with a defined upper limit, no saturation algebra
Join discussionApr 22 · 6 min read · Every filter you've used so far in this series attenuates some frequencies. The allpass filter does something different: it leaves the magnitude spectrum completely untouched — 0 dB gain at every freq
Join discussionApr 18 · 5 min read · Elliptic (Cauer) filters achieve the steepest possible transition from passband to stopband for a given filter order. They pay for this with equiripple in both passband and stopband — but when embedde
Join discussionApr 17 · 5 min read · Every PID loop has a dirty secret: the derivative term amplifies noise. A step change or a noisy measurement causes the D-term to spike — saturating the actuator, stressing the plant, and sometimes de
Join discussionApr 17 · 5 min read · Every control engineer eventually asks: why does my filtered signal ring, overshoot, or arrive late? Butterworth gives you a flat magnitude response, but its non-linear phase smears signals in time. T
Join discussionApr 17 · 6 min read · The moving average is the most-deployed FIR filter in embedded control systems — one accumulator, one subtraction, zero multiply overhead on a power-of-2 window. But "simplest" does not mean "unintell
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