How do you measure an antenna with a VNA?

A vector network analyzer (VNA) measures an antenna’s complex reflection coefficient S₁₁ (impedance, return loss, VSWR) and, with two ports, coupling S₂₁ between antennas. Accurate results require calibration (e.g., SOLT) at the cable end, port extension or de-embedding to the antenna feed point, chokes against common-mode currents, and an environment free of nearby reflectors.^[1][2]

What calibration should be used?

A full one-port calibration (open, short, load) at the end of the test cable removes systematic directivity, source-match and reflection-tracking errors; two-port SOLT or TRL is used for isolation measurements. Then extend the reference plane through the pigtail to the antenna terminals using electrical delay or a de-embedding file.^[2]

What pitfalls are common?

• Measuring a small antenna with a cable that radiates; add ferrites near the DUT and check sensitivity to cable movement.
• Reflective surroundings (benches, monitors, people) within a few wavelengths.
• Uncompensated pigtail length rotating the Smith-chart locus.
• Too few points to resolve high-Q resonances.^[1][3]

What is time gating?

Transforming S₁₁ to the time domain separates the antenna’s reflection from reflections at connectors and nearby objects; gating out the unwanted responses and transforming back improves results, within resolution limits set by the measurement bandwidth.^[1]

Frequently asked questions

See also

• Input impedance
• VSWR and return loss
• Smith chart
• Common-mode currents

References

Online sources accessed October 21, 2026; printed works cited by edition. See all sources.

1. “Understanding the Fundamental Principles of Vector Network Analysis (Application Note 1287-1)”. Keysight Technologies. application note.
2. “Applying Error Correction to Network Analyzer Measurements (Application Note 1287-3)”. Keysight Technologies. application note.
3. “IEEE Recommended Practice for Antenna Measurements (IEEE Std 149-2021)”. IEEE Antennas and Propagation Society. 2022.