Directional Coupler

Coupling Structure Operation

Coupled transmission lines exploit electromagnetic field interactions to transfer energy from a main line to an auxiliary port. Within adaptive RF front-ends, a directional coupler routes forward power to a detector for output power regulation while routing reverse power to monitor antenna mismatch. The orientation of coupled lines determines signal selectivity, allowing precise differentiation between incident and reflected signal waves.

Balanced microstrip, stripline, or lumped-element structures implement this coupling functionality within compact integrated circuit packages.

Directivity Performance Boundary

Directivity quantifies the ratio of power coupled in the intended direction to power coupled in the reverse direction. Low directivity degrades reflection measurement accuracy, introducing standing wave calculation errors into closed-loop antenna tuning circuits.

Front End Signal Loss

Main-line insertion loss directly reduces transmitter RF output power and receiver noise figure performance. Minimizing main line losses prevents thermal dissipation issues and preserves receiver sensitivity in battery-powered wireless systems.