Array gain

Lore & Background

Array gain is distinct from terms such as 'gain,' 'power gain,' 'directive gain,' or 'directivity.' However, if the noise environment around the array is isotropic and the array input signal is from an isotropic radiator, then array gain equals gain as defined from the array beam pattern. The terms 'power gain' and 'directive gain' are deprecated by IEEE. In practice, array gain is realized by using multiple antenna elements; for a uniformly weighted array (un-tapered, with all elements contributing equally), the array gain equals the number of elements N.

Reader's Guide

Array gain is significant in applications where signal-to-noise ratio is inherently low. In radio astronomy, background noise from modern communications makes it difficult to achieve good SNR; even strong astronomical radio emissions typically have SNR levels below 0 decibels. To counter this, exposure of the antenna to the source over large periods of time is needed, and array gain is achieved by using multiple—even dozens—of radio receivers to collect as much signal as possible. Robots equipped with antenna arrays also benefit from array gain, using it to eradicate dead spots and reduce interferences, thereby improving communication reliability.

Did You Know?

• Array gain is calculated as the SNR of the array output divided by the SNR of the array input.
• For a uniformly weighted array, array gain equals the number of array elements N.
• If noise is uncorrelated, array gain is ≤ N, the number of array elements.
• In radio astronomy, typical SNR levels for strong astronomical emissions are below 0 decibels.