Array gain

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Characteristics Array gain Directivity Efficiency Electrical length Equivalent radius Factor Friis transmission equation Gain Height Radiation pattern Radiation resistance Radio propagation Radio spectrum Signal-to-noise ratio Spurious emission
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In array antenna systems, array gain is the measure of the improvement in signal-to-noise ratio (SNR) achieved by the array. It is calculated as the SNR of the array output signal divided by the SNR of the array input signal. Intuitively, the array gain is realized by the fact that the signal is coherently added from N array elements, while the noise is incoherently added from those same elements. The noise is presumed to be spatially isotropic and uncorrelated. The array gain is always ≤ N, the number of array elements. For any arbitrary array, the array gain is the inverse of the square of the 2-norm of the array weight vector, under the assumption that the weight vector is normalized such that its sum is unity. For a uniformly weighted array (un-tapered such that all elements contribute equally), the array gain is equal to N.^[1]

${\displaystyle A={1 \over {\vec {w}}^{H}{\vec {w}}}}$

Array gain is not the same thing as "gain," "power gain," "directive gain," or "directivity." The terms "power gain" and "directive gain" are deprecated by IEEE.^[2]

Applications[]

In radio astronomy it is difficult to achieve a good signal-to-noise ratio because of background noise from modern communications. Even for strong astronomical radio emission it is typical for SNR levels to be below 0 decibels. To counter this problem exposure of the antenna to the source over large periods of time are needed just as in visible sky viewing. Array gain is done by using multiple, even dozens of radio receivers to collect as much signal as possible.

Robots equipped with antenna arrays have better communication using array gain to eradicate dead spots and reduce interferences.^[3]

See also[]

• Diversity gain

References[]

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