Frequencyselectief

Frequencyselectief, or frequency-selective, describes the property of a system that responds differently to inputs depending on frequency. A frequency-selective device passes energy in some parts of the spectrum while attenuating others. In signal processing, the frequency response H(f) characterizes how each frequency component is scaled and phase-shifted by the system. For a linear, time-invariant system, the output spectrum is the product of the input spectrum and the system’s frequency response, Y(f) = H(f)X(f). The magnitude |H(f)| indicates how strongly each frequency is transmitted, while the phase tells the shift introduced.

Common types of frequency-selective behavior include low-pass, high-pass, band-pass, and notch filters. The sharpness of the pass/stop transitions, often quantified by the quality factor Q, determines the selectivity. Idealized filters with infinitely sharp transitions are non-causal or require infinite impulse responses; practical designs trade off selectivity against delay and computational resources.

Implementation is achieved in analog and digital forms. Analog filters use passive or active components (resistors, capacitors, inductors); digital filters use finite impulse response (FIR) or infinite impulse response (IIR) structures. Design methods aim to meet a target H(f) while keeping stability and linear phase where needed.

Applications span telecommunications (channel equalization, spectrum shaping), audio processing (equalizers, tone controls), radar and sensing (frequency discrimination), and imaging. The human auditory system is itself highly frequency-selective, with the cochlea acting as a bank of frequency-dependent filters that help separate sounds by pitch.