05.04.22 -- Guidelines For Antenna Testing

Antenna factor (AF) is a comparison between the field level presented to the antenna and the actual voltage produced by the antenna at its connector. AF varies with frequency; that is, for the same presented field strength, but at a different frequency, the voltage produced at the connector is not constant.

There are four common methods of determining definitions for the near-field and far-field regions of an antenna and their boundaries. The definitions generally depend on use cases and the acceptable amount of error in calculating this definition and any conversions that may need to be performed.

VSWR, or the voltage standing wave ratio, is used in EMC to specify the effect of a mismatch presented to a test system signal. This article offers a brief overview of the history of VSWR, as well an introduction on short-circuit and open-circuit termination and the creation of standing waves.

Connectors will influence RF test results in various and sometimes unpredictable ways. Test equipment can compensate for some of these influences but often with detrimental effects. This article discusses how connections will affect test results and why it is important to create a valid test environment.

The strength of the magnetic component of the electromagnetic field is typically measured with loop antennas. The design of loops varies with the application and frequency range. In most cases, the loops are electrostatically shielded by enclosing the wire turns inside a tubular conducting shield, which is broken at some point around the periphery to prevent the shield acting as a shorting turn.