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Wireless & Mobility · Intermediate

Phase

The position of a point in a wave's cycle, measured in degrees, relative to another wave or reference.

Definition

Phase describes the timing offset between two waves of the same frequency. Signals arriving in phase add together (upfade), while signals 180 degrees out of phase cancel (nulling). Phase shifts are used to encode data in PSK and QAM modulation and to steer energy in beamforming.

Example

Two multipath copies arriving 180 degrees out of phase can nearly cancel each other.

Exam tip

Know how in-phase and out-of-phase multipath arrivals cause upfade, downfade, and nulling.

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