Directional Couplers

A directional coupler is used to sample RF energy traveling in a transmission line while minimizing disruption to the main signal path. It allows engineers to measure forward and reflected power, monitor signals, or feed test equipment safely. Directional couplers are commonly used in RF testing, broadcast systems, and communication networks.

For example, a coupler with 30 dB coupling may sample 1 watt from a 1,000-watt transmission line.

A directional coupler works by coupling a small portion of RF energy from a transmission line to a secondary port for measurement or monitoring. The device separates forward and reflected signals, enabling accurate analysis of power flow and system performance. Its design allows measurements without significantly affecting the main transmission signal.

For example, a coupler may measure forward power at 500 watts while detecting 15 watts of reflected power.

Directivity is a measure of how well a directional coupler isolates forward and reflected RF signals from each other. Higher directivity results in more accurate reflected power and VSWR measurements because unwanted signal leakage is minimized. Directivity is typically expressed in decibels (dB), with higher values indicating better performance.

For example, a coupler with 35 dB directivity provides more accurate reflected power readings than one rated at 20 dB.