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An antenna array (or array antenna) is a set of multiple connected antennas which work together as a single antenna, to transmit or receive radio waves. [1]: p.149 [2] The individual antennas (called elements) are usually connected to a single receiver or transmitter by feedlines that feed the power to the elements in a specific phase relationship.
Since directional antennas must be pointed at the transmitting antenna, this is a problem when the television stations to be received are located in different directions. In this case, two or more directional rooftop antennas, each pointed at a different transmitter, are often mounted on the same mast and connected to one receiver for best ...
Mobile phone towers also often take advantage of diversity - each face (sector) of a tower will often have two antennas; one is transmitting and receiving, while the other is a receive only antenna. Two receivers are used to perform diversity reception. Cell antennas on an electricity pylon showing two antennas per sector
[12] [13] For example, the "receiving pattern" (sensitivity to incoming signals as a function of direction) of an antenna when used for reception is identical to the radiation pattern of the antenna when it is driven and functions as a radiator, even though the current and voltage distributions on the antenna itself are different for receiving ...
Antennas can be classified in various ways, and various writers organize the different aspects of antennas with different priorities, depending on whether their text is most focused on specific frequency bands; or antenna size, construction, and placement feasibility; or explicating principles of radio theory and engineering that underlie ...
Patch antenna gain pattern. A directional antenna or beam antenna is an antenna which radiates or receives greater radio wave power in specific directions. Directional antennas can radiate radio waves in beams, when greater concentration of radiation in a certain direction is desired, or in receiving antennas receive radio waves from one specific direction only.
A dual-polarized signal thus carries two independent data streams to a receiving antenna, which can itself be a single-polarized one, for receiving only one of the two streams at a time, or a dual-polarized model, again relaying its received signal to two single-polarization output connectors (via an OMT if in waveguide).
It is a fundamental property of antennas that the receiving pattern (sensitivity as a function of direction) of an antenna when used for receiving is identical to the far-field radiation pattern of the antenna when used for transmitting. This is a consequence of the reciprocity theorem of electromagnetics and is proved below. Therefore, in ...