Whitepaper

VSWR and its Effects on Power Amplifiers

Exodus Advanced Communications

This application note from Exodus Advanced Communications details the impact of Voltage Standing Wave Ratio (VSWR) on RF/Microwave power amplifiers, particularly in test applications. The paper explains VSWR as a consequence of impedance mismatch – typically between 50Ω source and load – and how this leads to reflected power reducing system efficiency. A VSWR of 2:1 corresponds to approximately 10% reflected power, which can increase total power dissipation by up to 110%. The document outlines methods for mitigating VSWR issues, including the use of attenuators (3dB provides improvement but halves output) and matching networks, as well as amplifier protection techniques like shutdown and foldback mechanisms. It emphasizes that amplifiers rated to handle 2:1 VSWR are common, but sustained higher levels—especially above 6:1 resulting in >50% reflected power—can be detrimental even if not immediately damaging.