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Beamforming

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Beamforming is a signal processing technique used on an array of sensors in order control the directionality of the radiation pattern. When receiving a signal, beamforming can increase the gain in the direction of wanted signals and decrease the gain in the direction of interference and noise. When transmitting a signal, beamforming can increase the gain in the direction the signal is to be sent. This is done by creating a beams and nulls in the radiation pattern. Beamforming can be thought of as spatial filtering.

Beamforming uses the principle of interference to change the directionality of the sensor array. While transmiting, a beamformer controls the amplitude and phase of the signal transmitted on each sensor. This creates constructive and destructive interference in the signals.

For the full mathematics on directing beams using see the math section in phased array.

Beamforming techniques can be broadly divided into two categories:

  • conventional (fixed) beamformers
  • adaptive beamformers

Conventional beamformers use a fixed set of weightings and time-delays to combine the signals from the sensors in the array, primarily using only information about the location of the sensors in space and the wave directions of interest. In contrast, adaptive beamforming techniques, generally combine this information with properties of the signals actually received by the array, typically to improve rejection of unwanted signals from other directions. As the name indicates, an adaptive beamformer is able to automatically adapt its response to different situations.

This term has been frequently used in sensor networks.

Sonar beamforming

Sonar implementation is comparatively easy compared to electromagnetic implementation because of the relatively slow speed of sound in relation to the speed of the controlling hardware. Sonar arrays are used both actively and passively in 1, 2, and 3 dimensional arrays.

  • 1 dimensional arrays are usually towed behind ships.
  • 2 dimensional arrays are common in side-scan sonar.
  • 3 dimensional arrays are used in 'sonar domes' in the modern submarine.

Sonar also differs from radar in that all directions can be listened to and, in theory, broadcast to, simultaneously, and the phases can be manipulated entirely by signal processing software, as compared to present radar systems that use hardware to 'listen' in a single direction at a time. At a certain level the human brain does the same thing, using signal processing on its 2 dimensional array (ears) to figure out where sound comes from.

See also

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