SignalFlow

Signal flow refers to the path that an electrical or digital signal takes through a system from input to output, including the components, junctions, and transformations it experiences. It is a core concept in signal processing, control theory, and communications, used to model and analyze how signals are modified by networks of amplifiers, filters, delays, and nonlinear elements. Practitioners often represent signal flow with visual diagrams.

Common representations include block diagrams, which show components as blocks with arrows indicating signal direction; and signal-flow graphs, where signals are represented as nodes and system elements as directed edges. For linear time-invariant systems, the behavior is captured by transfer functions, impulse responses, or state-space models. Signal-flow graphs enable systematic analysis via Mason’s gain formula, especially for complex networks with multiple feedback paths. In digital domains, discrete-time equivalents use z-transforms and digital filters.

Applications span audio engineering, telecommunications, controls, and biomedical instrumentation. In practice, signal flow analysis helps derive overall transfer functions, assess stability, predict how cascading stages affect amplitude and phase, and guide design choices for filtering, amplification, and feedback.

History: Concepts of signal flow date to early control theory and electronic circuit analysis, with Mason’s signal-flow graphs introduced in the 1950s as a method to represent and analyze signal networks.

See also: block diagram, transfer function, signal-flow graph, Mason’s gain formula, state-space representation.