RF directional couplers are passive microwave components designed to sample and measure the power of RF signals flowing through transmission lines or RF circuits while minimizing signal disruption. They consist of coupled transmission lines or waveguides that allow a portion of the RF power to be extracted and redirected to a measurement port while maintaining signal integrity and impedance matching. RF directional couplers are used in RF and microwave systems for applications such as power monitoring, signal distribution, feedback control, and signal analysis. They are commonly found in RF test equipment, RF power amplifiers, RF filters, and RF communication systems where accurate power measurement and signal monitoring are essential for system performance and optimization.