What is VSWR?
VSWR (Voltage Standing Wave Ratio) is the ratio of the maximum to minimum voltage amplitude in a standing wave pattern on a transmission line, caused by impedance mismatch between the transmission line and the load (typically an antenna). A VSWR of 1:1 indicates perfect matching (no reflections), while higher ratios indicate increasing mismatch and reflected power. VSWR is a critical parameter in 5G base station installation, as poor VSWR from damaged cables or connectors causes power loss, increased interference, and potential PA damage.
How Does VSWR Work?
When the impedance of an antenna or other load does not match the characteristic impedance of the transmission line (typically 50 ohms in telecom), a portion of the transmitted power is reflected back toward the transmitter. The forward and reflected waves combine to create a standing wave pattern with voltage maxima and minima. VSWR = V_max/V_min = (1+|Γ|)/(1-|Γ|), where Γ is the reflection coefficient. Common VSWR requirements: antennas typically specify VSWR < 1.5:1 (return loss > 14 dB) across the operating band. During installation, VSWR is measured using a cable and antenna analyser swept across the frequency band. Degraded VSWR (e.g., > 2:1) indicates connector problems, cable damage, water ingress, or antenna faults.
Use Cases
5G base station antenna system installation and commissioning, transmission line and connector fault detection, antenna performance verification, RF system return loss measurement, and preventive maintenance of cell site RF infrastructure.
3GPP / Standards Reference
3GPP TS 38.104 (NR BS radio — antenna port return loss), IEC/IEEE antenna measurement standards
Related Terms
EIRP | Antenna reciprocity | Cell Tower | Tx | Rx
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This glossary entry is part of the 5GWorldPro Complete 5G Glossary. To go deeper into 5G architecture and technology, explore our 5G Training courses.
