Directional Couplers

Directional couplers are passive four-port RF and microwave components that sample a portion of a signal traveling in a specific direction along a transmission line. They allow engineers to monitor forward and reflected power simultaneously without interrupting the main signal path. With typical coupling values of 6 dB to 30 dB, directional couplers enable power measurement, signal monitoring, and reflected power detection across frequencies from a few MHz to tens of GHz. RF directional bridges extend this capability to broadband impedance measurement applications.

Coaxial directional couplers are essential tools in vector network analyzer (VNA) front ends, transmitter testing, antenna feed systems, and signal distribution networks. They are widely applied in telecommunications base station testing, aerospace & defense radar systems, power amplifier characterization, and production RF verification. Models such as the Keysight 87300B coaxial coupler and Bird 4801-100 line section represent the precision passive components used in professional RF test environments across a broad range of industries.

Typical Applications

Forward and reflected power monitoring in transmitter and amplifier test setups
Signal sampling for spectrum analysis without breaking the main transmission path
Return loss and VSWR measurement in antenna and transmission line testing
VNA front-end signal separation for accurate S-parameter measurements
Power leveling and automatic gain control loops in RF signal generators

Popular Brands

Keysight Technologies offers a range of coaxial directional couplers and RF directional bridges, including the 86205A/B series and 87300B, covering frequencies from DC through microwave bands with high directivity and low insertion loss. Bird Technologies specializes in high-power directional couplers such as the 4801-100 series, widely used in transmitter test and broadcast verification. Both companies provide components suited for laboratory measurement and production line RF testing.