Gain, Efficiency, Directivity — Antenna Testing Covers It All

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April 26, 2023

Large lawns next to buildings and sports fields need water to stay green and healthy. Sprinklers distribute water to the lawn, focusing on areas to receive water through the sprinkler’s design and by adjustment of its settings.

Antennas can be thought of like that. The difference is that instead of water, radiofrequency (RF) energy is distributed.  In either case, the idea is the same. Transmitting antennas are used to launch RF signals into the air. Their design is optimized to focus on areas intended to receive the signal. Similarly, receiving antennas are optimized to detect signals for processing by the receiver.

Typical antenna pattern measurement result

A well-designed transmitting antenna radiates nearly all the energy from the transmitter into free space as electromagnetic (EM) waves. To assure an antenna is performing as designed, testing is done to check efficiency, gain, directivity, and its associated patterns.

Antenna testing is especially important in cellular wireless devices. Small dimensions and low power levels make it critical to maximize antenna performance. Antennas are passive devices, not generating energy of their own. They are only useful when connected to an RF device that generates the energy for transmission or has the means to decode signals for reception. By virtue of their design, antenna characteristics can be measured.

Cutaway showing typical antenna locations in mobile device

Passive Antenna Testing

Testing under laboratory conditions requires isolating the antenna from its device for repeatability.

For passive testing in Elite’s lab, the device under test (DUT) antenna port is connected to a vector network analyzer (VNA) at a desired frequency and amplitude. The turntable-mounted DUT is rotated 360 degrees (the azimuth). A receiving antenna, typically a horn or patch-type with dual polarization, is placed on a boom moving from zero to 165 degrees (the elevation). Measurements are taken at several elevation and azimuth angles to provide 2-dimensional and 3-dimensional plots of the radiation pattern. Software algorithms use the data to calculate efficiency, gain, directivity, and equivalent isotropic radiated power (EIRP).

Active Antenna Testing

An active antenna test involves the overall system, meaning the antenna plus the RF front-end circuitry. Total radiated power (TRP) and total isotropic sensitivity (TIS) are measured as figures of merit to qualitatively evaluate the antenna system. These are measured in a fully anechoic antenna chamber for data-collection consistency. These numerical measurements can also be done in a reverberation chamber, though they are not useful for antenna pattern tests.

TRP is the power radiated by the antenna averaged over a 3-dimensional sphere. TIS applies to receiving antennas and is the average sensitivity over a 3-dimensional sphere. Cellular carriers pay close attention to these measurements, as they have specific TRP and TIS requirements for reliable performance in portable telecom devices.

Elite’s John Peters preparing an antenna test

Elite’s status as a CTIA Authorized Testing Lab (CATL) gives us insight into this industry’s requirements. Our wireless specialists actively participate in CTIA working groups advancing testing methods and support international standards aligning with the latest technology.

Contact the experts at Elite If you have questions about your wireless device’s antenna performance and how to measure its performance.

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