What are antennas?

Some articles on antennas, antenna:

Sector Antenna - Use
... area, and thus the number of served clients, several sector antennas are installed on the same supporting structure, e.g ... construction is often called a sectorized antenna, though sometimes for brevity "sector antenna" is used as well ... It has several angularly-separated sector antennas as shown on the figures at right ...
Panorama Antennas
... Panorama Antennas Ltd is a British based company that designs and manufactures communications antennas and closely related diplexer products ...
Signals Intelligence Operational Platforms By Nation - Ground Platforms - Australia: Ground Platforms
... It is reported to have four satellite antennas...trained on satellites above the Indian Ocean and the Pacific ... It has 18 antennas, and has been considered first a receiving station for SIGINT satellites, but the size of some of its antennas are more associated with a requirement to ... Of the satellite antennas visible on photographs, the five larger ones have a maximum diameter of 8 m, and the sixth antenna visible is smaller still ...
Many Antennas
... Many antennas is a smart antenna technique which overcomes the performance limitation of single user multiple-input multiple-output (MIMO) techniques ... In cellular communication, the maximum number of considered antennas for downlink is 2 and 4 to support 3GPP Long Term Evolution (LTE) and IMT Advanced ... highly probable that the number of transmit antennas at the base station must be increased to 8–64 or more ...
Spatial Correlation
... systems can be improved by having multiple antennas at the transmitter and the receiver ... channels between each pair of transmit and receive antennas are statistically independent and identically distributed, then multiple independent channels with ... In practice, the channels between different antennas are often correlated and therefore the potential multi antenna gains may not always be obtainable ...