Motfaser

Motfaser is a term used to describe a counter phase relationship between two periodic signals or motions. It denotes when they are approximately 180 degrees out of phase, meaning peaks of one align with troughs of the other. The term is used in Swedish and other Nordic languages; in English the related concept is antiphase or opposite phase.

In physics and engineering, motfaser means that two waves, signals, or mechanical vibrations are out of phase by about half a cycle. When combined, this phase relation often produces destructive interference, reducing the resulting amplitude. This principle is exploited in noise cancellation, vibration damping, and certain audio crossover designs.

In electronics and signal processing, motfaser configurations can be used to suppress common-mode components, improve signal-to-noise ratio, or implement differential signaling, where opposing phases help cancel unwanted noise.

In mechanical systems, two opposite-phase excitations can cancel net motion, lowering transmitted vibrations or loads.

Etymology: motfaser comes from mot- meaning "against" and fas/faser meaning "phase" or "phase relations" in Swedish. It is closely related to terms in other languages such as antiphase or counterphase.

See also antiphase, destructive interference, phase difference, common-mode rejection.