By Eamon Nash, applications engineering director, and Eberhard Brunner, senior design engineer, Analog Devices

Directional couplers are used in many applications to sense RF power and may appear at multiple points in a signal chain. Inline RF power and return loss measurements are typically implemented using directional couplers and RF power detectors.

In Figure 1, a bidirectional coupler is used in a radio or test and measurement application to monitor transmitted and reflected RF power. It’s also sometimes desirable to have RF power monitoring embedded in a circuit, with a good example being when two or more sources are being switched into the transmission path, either using an RF switch or with external cables…