The information contained herein incorporates public domain material from the Avionics Department of the Naval Air Warfare Center Weapons Division document "Electronic Warfare and Radar Systems Engineering Handbook (report number TS 92-78)" (retrieved on 9 June 2006) (pp. 6-4.1 to 6-4.5 Power Dividers and Directional Couplers).
Retrieved from "http://en.wikipedia.org/wiki/Power_dividers_and_directional_couplers"
Wilkinson Power Divider
A specific class of power divider circuit that can achieve isolation between the output ports while maintaining a matched condition on all ports. The Wilkinson design can also be used as a power combiner because it is made up of passive components and hence reciprocal. First published by Ernest J. Wilkinson in 1960, this circuit finds wide use in radio frequency (RF) communication systems utilizing multiple channels since the high degree of isolation between the output ports prevents crosstalk between the individual channels. [Wik1114] ^ E.J. Wilkinson, "An N-way Power Divider", IRE Trans. on Microwave Theory and Techniques, vol. 8, p. 116-118, Jan. 1960
Wilkinson Power Divider Diagram courtesy of Stündle, http://de.wikipedia.org/wiki/Benutzer:St%C3%BCndle
Worldwide Interoperability for Microwave Access; a wireless industry coalition dedicated to the advancement of IEEE 802.16 standards for broadband wireless access (BWA) networks.
WiMAX supports mobile, nomadic and fixed wireless applications. A mobile user, in this context, is someone in transit, such as a commuter on a train. A nomadic user is one that connects on a portable device but does so only while stationary -- for example, connecting to an office network from a hotel room and then again from a coffee shop. Fixed wireless typically refers to wireless connectivity among non-mobile devices in homes or businesses. According to the WiMAX forum, the group's aim is to promote and certify compatibility and interoperability of devices based on the IEEE 802.16 specifications, and to develop such devices for the marketplace. WiMAX is expected to provide about 10 megabits per second of upload and download, at a distance of 10 kilometers from a base station. The Forum says that over 455 WiMAX networks have been deployed in over 135 countries (as of May 2008). In May of 2008, Sprint and Clearwire announced that they would be combining their WiMAX businesses. Intel, Google, Comcast, Time Warner Cable and Bright House Networks combined to invest $3.2 billion US in Clearwire. The company has begun deployment of a planned nationwide 4G network in the United States as Clear WiMax wireless broadband services. Comcast and Time Warner Cable have announced that they will resell the service in areas where they have cable coverage. WiMAX is competing with the 3rd Generation Partnership Project (3GPP)'s Long-Term Evolution (LTE) in the 4G market. [Sea08] Windload
The amount of wind pressure a satellite antenna or off-air antenna can sustain. [Arr11] Windows Media Digital Rights Management (WMDRM)
Microsoft's DRM solution. Windshield Wiper Effect
Onset of overload in multichannel cable television systems caused by cross-modulation, where the horizontal sync pulses of one or more TV channels are superimposed on the desired channel carrier. Both black and white windshield wiping are observed and are caused by different mechanisms.
The concept of television and other communications data, educational material, instructional television and information retrieval service that wired services can provide. Broadcast services must, of necessity, be limited by scarce spectrum space; wired services have theoretically unlimited channel capacity.
A network or terminal that uses electromagnetic waves, such as RF, infrared, laser, visible light and acoustic energy, not wires, for telecommunications. [Fib111] Wireless Cable
Uses microwaves frequencies to transmit programming to a small antenna at a subscriber's home. WirelessHD (WiHD)
WIRELESS High Definition (WiHD); a short-range wireless technology from the WirelessHD Consortium. It provides up to 4 Gbps of data transmission in the unlicensed 60 GHz band over a distance of approximately 10 meters. The first 60 GHz wireless standard, WirelessHD (WiHD) was designed to transmit uncompressed HD video and other media between TVs and A/V equipment. Consortium founders include SiBEAM, LG, NEC, Panasonic, Sony, Toshiba and Samsung. At 60 GHz, the wavelength is only five millimeters and highly directional; however, in 2007, SiBEAM demonstrated its OmniLink60 CMOS chips which steer the signal to take advantage of surface areas such as walls and objects in the room using an array of up to 36 antennas on a 1" square surface. [PCm111] Wireless Local Area Network (WLAN)
A wireless networking architecture based on IEEE 802.11a/b/g/n standards. Also referred to as Wi-Fi, the association tasked to certify WLAN capable devices for interoperability. Wi-Fi certified devices have successfully passed interoperability test by an authorized third party. Wireless Local Loop
In conventional wired systems, the local loop refers to the connection that runs from the subscriber's telephone set, PBX or telephone system to the telephone company's central office (CO). As the name implies, a WLL connects potential users to the CO by substituting a wireless base station for the local-loop connection. WLL service is the most advantageous alternative for parts of the world that can leapfrog expensive and time-consuming wire installations in establishing modern telecommunications systems.
Wireshark is a network protocol analyzer for Unix and Windows. www.wireshark.org WiWiWiWi (Wi4)
When I Want It Where I Want It WLAN
Wireless LAN; a wireless local area network, which is the linking of two or more computers without using wires. WLAN utilizes spread-spectrum technology based on radio waves to enable communication between devices in a limited area, also known as the basic service set. This gives users the mobility to move around within a broad coverage area and still be connected to the network. For the home user, wireless has become popular due to ease of installation, and location freedom with the gaining popularity of laptops. For the business, public businesses such as coffee shops or malls have begun to offer wireless access to their customers; some are even provided as a free service. Large wireless network projects are being put up in many major cities. Google is providing a free service to Mountain View, California and has entered a bid to do the same for San Francisco. New York City has also begun a pilot program to cover all five boroughs of the city with wireless Internet access. IEEE 802.11, also known by the brand Wi-Fi, denotes a set of Wireless LAN (WLAN) standards developed by working group 11 of the IEEE LAN/MAN Standards Committee (IEEE 802). The term 802.11x is also used to denote this set of standards and is not to be mistaken for any one of its elements. There is no single 802.11x standard. The term IEEE 802.11 is also used to refer to the original 802.11, which is now sometimes called "802.11 legacy". The 802.11 family currently includes six over-the-air modulation techniques that all use the same protocol. The most popular techniques are those defined by the b, a, and g amendments to the original standard; security was originally included and was later enhanced via the 802.11i amendment. 802.11n is another modulation technique that has recently been developed. Other standards in the family (c-f, h, j) are service enhancements and extensions or corrections to previous specifications. 802.11b was the first widely accepted wireless networking standard, followed (somewhat counterintuitively) by 802.11a and 802.11g. 802.11b and 802.11g standards use the 2.40 GHz (gigahertz) band, operating (in the United States) under Part 15 of the FCC Rules and Regulations. Because of this choice of frequency band, 802.11b and 802.11g equipment can incur interference from microwave ovens, cordless telephones, Bluetooth devices, and other appliances using this same band. The 802.11a standard uses the 5 GHz band, and is therefore not affected by products operating on the 2.4 GHz band. The segment of the radio frequency spectrum used varies between countries, with the strictest limitations in the United States. While it is true that in the U.S. 802.11a and g devices may be legally operated without a license, it is not true that 802.11a and g operate in an unlicensed portion of the radio frequency spectrum. Unlicensed (legal) operation of 802.11 a & g is covered under Part 15 of the FCC Rules and Regulations. Frequencies used by channels one (1) through six (6) (802.11b) fall within the range of the 2.4 gigahertz amateur radio band. Licensed amateur radio operators may operate 802.11b/g devices under Part 97 of the FCC Rules and Regulations, allowing increased power output but not allowing any commercial content. [Wir111] World Wide Web (www)
The name given to all HTML documents which exist on all of the interconnected HTTP servers around the world. Originally developed in 1989 for the European Laboratory for Particle Physics to enable its users to share documents in a more graphical fashion. WWW World Wide Web
X.509 An International Telecommunication Union recommendation for form of Public Key Infrastructure digital certificate
A public key certificate specification developed as part of the ITU-T X.500 standards directory.
Extended Application Information Table. Used for launching and managing the lifecycle of unbound applications.
The frequency range between 8.0 and 8.4 GHz. [Fib111] XC
See cross-connect. xDSL
The general term applied to a whole family of high-speed digital data products. The letters DSL stand for Digital Subscriber Line. The x is a place keeper for the term describing the type of DSL connection: A for Asymmetric, H for High Speed, I for ISDN, S for Symmetric. These technologies, ADSL, HDSL, IDSL, and SDSL are expected to be the next-generation high-speed data products that will someday replace existing technologies like ISDN and Fractional T-1 lines. XGM
See cross-gain modulation.
XHTML Extensible Hypertext Mark-up Language
Xlet is the interface used for execution engine application lifecycle control.
XRML Extensible Rights Markup Language X-Series Recommendations
Sets of data telecommunications protocols and interfaces defined by the ITU. [Fib111]
A variation on the tee coupler in which input light is split between two channels (typically planar waveguide) that branch out like a Y from the input. [Fib111]
Y Coupler Diagram courtesy of Fiber Optics Info, http://www.fiber-optics.info/fiber_optic_glossary/y
The term YAG laser is usually used for solid-state lasers based on neodymium-doped YAG (Nd:YAG, more precisely Nd3+:YAG), although there are other rare-earth-doped YAG crystals, e.g. with ytterbium, erbium, thulium or holmium doping (see below). YAG is the acronym for yttrium aluminum garnet (Y3Al5O12), a synthetic crystal material which became popular in the form of laser crystals in the 1960s. Yttrium ions in YAG can be replaced with laser-active rare earth ions without strongly affecting the lattice structure, because these ions have a similar size. YAG is a host medium with favorable properties, particularly for high-power lasers and Q-switched lasers emitting at 1064 nm. YAG lasers are in many cases bulk lasers made from discrete optical elements. However, there are also monolithic YAG lasers, e.g. microchip lasers and nonplanar ring oscillators. The most popular alternatives to Nd:YAG among the neodymium-doped gain media are Nd:YVO4 and Nd:YLF. Nd:YAG lasers nowadays also have to compete with Yb:YAG lasers (see below).