Array. - is the form an assembly of radiation elements in an electrical and geometrical configuration. This antenna that contain multi-elements is referred as Array.

Array. - is the form an assembly of radiation elements in an electrical and geometrical configuration. This antenna that contain multi-elements is referred as Array.

Very directive patterns. - It’s necessary that the fields from the elements of the array interference constructively (add) in the desired directions and cancel each other in the remaining space.

Five controls that can be used to shape the overall pattern of the antenna:

• The geometrical configuration of the overall array (linear, circular, rectangular, spherical)
• The relative displacement between the elements
• The excitation amplitude of the individual elements
• The excitation phase of the individual elements
• The Relative pattern of the individual elements

The Array factor. – is a function of the geometry of the array and the excitation phase.

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• DOA. – Directional of Arrival
• SOI.- Signal of interest
• SNOI.- Signal not of interest

Spatial processing. – is the central idea of adaptive antennas or smart-antenna system.

Cellular radio systems evolution:

Omnidirectional Antenna: Has several directional antennas

Sectorized:  Divide the cell in three sectors of 120°. Capacity is improve, frequency reuse, and reduce the relative interference.

Smart-antennas system. – are an extension of cell sectoring in which the sector coverage is composed of multiple beams. Can focus their radiation pattern toward the desired users while rejecting unwanted interference. They can provide greater coverage area for each base station, have higher rejection interference, and lower bit error rate. Are classified as:

• Switched- Beam: Can choose from one of many predefined patterns and increase the gain according to the location of the user. Main goal is increase the gain according to the location of the user. Predefined beam pattern
• Adaptive Array: Have ability to adapt on real time radiation pattern to the RF signal environment.  They can direct the main beam to the tower or (SOI or SNOIs), can customize an appropriate radiation pattern for each individual user, and increase the capacity.
• Spatial Division Multiple Access (SDMA): Locate many users, creating different beam for each user. Use the DOA algorithm.

Planar Array.- Is the configuration that is well suited for mobile communication.

Linear Array. - Is not has attractive because of its inability to scan in 3D space.

Beam-Forming: Is the process that adapts the beam by adjusting the magnitude and phase of each antenna element such that a desirable pattern is formed.

Digital Signal Processor (DSP) as two objectives the direction of arrival for all impinging signals and the appropriate weights to ideally steer the maximum radiation of the antenna pattern towar the SOI and to place nulls toward the SNOI.

After the antenna array receives the incoming signals from all directions the DOA algorithm determines the direction of all incoming signals based on the time delays.

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The ideal condition for measuring far-field radiation characteristics is the illumination of the test antenna by plane waves: uniform amplitude and phase.

Parameters than describe an antenna array are: pattern, gain, directivity, efficiency, impedance, current distribution, and polarization.

The testing and evaluation of antenna arrays have two ways outdoor and indoor ranges. Limitation of outdoor ranges are not protected from environmental conditions whereas indoor facilities are limited by space restrictions.

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