Array processing
Encyclopedia
Array processing is signal processing of the outputs of an array of sensor
s to:
Array processing is used in radar
, sonar
, seismic exploration, anti-jamming and wireless
communications. One of the main advantages of using array processing along with an array of sensors is a smaller foot-print. The problems associated with array processing include the number of sources used, their direction of arrivals
, and their signal waveforms.
There are four assumptions in array processing. The first assumption is that there is uniform propagation in all directions of isotropic and nondispersive medium. The second assumption is that for far field array processing, the radius of propagation is much greater than size of the array and that there is plane wave propagation. The third assumption is that there is a zero mean white noise and signal, which shows uncorrelation. Finally, the last assumption is that there is no coupling and the calibration is perfect.
NORSAR is an independent geo-scientific research facility that was founded in Norway in 1968. NORSAR has been working with array processing ever since to measure seismic activity around the globe. They are currently working on an International Monitoring System which will comprise 50 primary and 120 auxiliary seismic stations around the world. NORSAR has ongoing work to improve array processing to improve monitoring of seismic activity not only in Norway but around the globe.
Sensor
A sensor is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument. For example, a mercury-in-glass thermometer converts the measured temperature into expansion and contraction of a liquid which can be read on a calibrated...
s to:
- Enhance the signal-to-interference-plus-noise ratio (SINR)SINRSINR is Signal to Interference plus Noise Ratio that is calculated as SINR = P / I + N where P is signal power, I is interference power and N is noise power....
compared to that of a single sensorSensorA sensor is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument. For example, a mercury-in-glass thermometer converts the measured temperature into expansion and contraction of a liquid which can be read on a calibrated...
using conventional or adaptive beamformingBeamformingBeamforming is a signal processing technique used in sensor arrays for directional signal transmission or reception. This is achieved by combining elements in the array in a way where signals at particular angles experience constructive interference and while others experience destructive...
. - Determine the number of emitting sources, the locations of these sources, their waveforms, and other signal parameters.
- Track multiple moving sources.
Array processing is used in radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
, sonar
Sonar
Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...
, seismic exploration, anti-jamming and wireless
Wireless
Wireless telecommunications is the transfer of information between two or more points that are not physically connected. Distances can be short, such as a few meters for television remote control, or as far as thousands or even millions of kilometers for deep-space radio communications...
communications. One of the main advantages of using array processing along with an array of sensors is a smaller foot-print. The problems associated with array processing include the number of sources used, their direction of arrivals
Direction of arrival
In signal processing literature, direction of arrival denotes the direction from which usually a propagating wave arrives at a point, where usually a set of sensors are located. This set of sensors forms what is called a sensor array. Often there is the associated technique of beamforming which...
, and their signal waveforms.
There are four assumptions in array processing. The first assumption is that there is uniform propagation in all directions of isotropic and nondispersive medium. The second assumption is that for far field array processing, the radius of propagation is much greater than size of the array and that there is plane wave propagation. The third assumption is that there is a zero mean white noise and signal, which shows uncorrelation. Finally, the last assumption is that there is no coupling and the calibration is perfect.
Applications
In radio astronomy because of background noise from modern communications it is difficult to achieve a good signal to noise ratio. Even for strong astronomical radio emission it is typical for SNR levels to be below 0 decibel. 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.NORSAR is an independent geo-scientific research facility that was founded in Norway in 1968. NORSAR has been working with array processing ever since to measure seismic activity around the globe. They are currently working on an International Monitoring System which will comprise 50 primary and 120 auxiliary seismic stations around the world. NORSAR has ongoing work to improve array processing to improve monitoring of seismic activity not only in Norway but around the globe.