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Butler Matrix
A Butler matrix is a beamforming network used to feed a phased array of driven element, antenna elements. Its purpose is to control the direction of a beam, or beams, of radio transmission. It consists of an n \times n matrix (n some power of two) with hybrid couplers and fixed-value phase shifters at the junctions. The device has n input Port (circuit theory), ports (the beam ports) to which power is applied, and n output ports (the element ports) to which n antenna elements are connected. The Butler matrix feeds power to the elements with a progressive phase difference between elements such that the beam of radio transmission is in the desired direction. The beam direction is controlled by switching power to the desired beam port. More than one beam, or even all n of them can be activated simultaneously. The concept was first proposed by Butler and Lowe in 1961. It is a development of the work of Blass in 1960. Its advantage over other methods of angular beamforming is the si ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beamforming
Beamforming or spatial filtering is a signal processing technique used in sensor arrays for directional signal transmission or reception. This is achieved by combining elements in an antenna array in such a way that signals at particular angles experience constructive interference while others experience destructive interference. Beamforming can be used at both the transmitting and receiving ends in order to achieve spatial selectivity. The improvement compared with omnidirectional reception/transmission is known as the directivity of the array. Beamforming can be used for radio or sound waves. It has found numerous applications in radar, sonar, seismology, wireless communications, radio astronomy, acoustics and biomedicine. Adaptive beamforming is used to detect and estimate the signal of interest at the output of a sensor array by means of optimal (e.g. least-squares) spatial filtering and interference rejection. Techniques To change the directionality of the array when transm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reciprocity Theorem (electrical Circuits)
Reciprocity in electrical networks is a property of a circuit that relates voltages and currents at two points. The reciprocity theorem states that the current at one point in a circuit due to a voltage at a second point is the same as the current at the second point due to the same voltage at the first. The reciprocity theorem is valid for almost all passive networks. The reciprocity theorem is a feature of a more general principle of reciprocity in electromagnetism. Description If a current, I_\text , injected into port A produces a voltage, V_\text , at port B and I_\text injected into port B produces V_\text at port A, then the network is said to be reciprocal. Equivalently, reciprocity can be defined by the dual situation; applying voltage, V_\text , at port A producing current I_\text at port B and V_\text at port B producing current I_\text at port A. In general, passive networks are reciprocal. Any network that consists entirely of ideal capacitances, inductance ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Direction Finding
Direction finding (DF), or radio direction finding (RDF), isin accordance with International Telecommunication Union (ITU)defined as radio location that uses the reception of radio waves to determine the direction in which a radio station or an object is located. This can refer to radio or other forms of wireless communication, including radar signals detection and monitoring (ELINT/ESM). By combining the direction information from two or more suitably spaced receivers (or a single mobile receiver), the source of a transmission may be located via triangulation. Radio direction finding is used in the navigation of ships and aircraft, to locate emergency transmitters for search and rescue, for tracking wildlife, and to locate illegal or interfering transmitters. RDF was important in combating German threats during both the World War II Battle of Britain and the long running Battle of the Atlantic. In the former, the Air Ministry also used RDF to locate its own fighter gr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mobile Network
A cellular network or mobile network is a communication network where the link to and from end nodes is wireless. The network is distributed over land areas called "cells", each served by at least one fixed-location transceiver (typically three cell sites or base transceiver stations). These base stations provide the cell with the network coverage which can be used for transmission of voice, data, and other types of content. A cell typically uses a different set of frequencies from neighboring cells, to avoid interference and provide guaranteed service quality within each cell. When joined together, these cells provide radio coverage over a wide geographic area. This enables numerous portable transceivers (e.g., mobile phones, tablets and laptops equipped with mobile broadband modems, pagers, etc.) to communicate with each other and with fixed transceivers and telephones anywhere in the network, via base stations, even if some of the transceivers are moving through more than ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Base Station
Base station (or base radio station) is – according to the International Telecommunication Union's (ITU) Radio Regulations (RR) – a "land station in the land mobile service." The term is used in the context of mobile telephony, wireless computer networking and other wireless communications and in land surveying. In surveying, it is a GPS receiver at a known position, while in wireless communications it is a transceiver connecting a number of other devices to one another and/or to a wider area. In mobile telephony, it provides the connection between mobile phones and the wider telephone network. In a computer network, it is a transceiver acting as a switch for computers in the network, possibly connecting them to a/another local area network and/or the Internet. In traditional wireless communications, it can refer to the hub of a dispatch fleet such as a taxi or delivery fleet, the base of a TETRA network as used by government and emergency services or a CB shack. Land s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Substrate-integrated Waveguide
A substrate-integrated waveguide (SIW) (also known as post-wall waveguide or laminated waveguide) is a synthetic Waveguide (radio frequency), rectangular electromagnetic waveguide formed in a dielectric substrate by densely arraying metallized posts or Via (electronics), via holes that connect the upper and lower metal plates of the substrate. The waveguide can be easily fabricated with low-cost mass-production using Through-hole technology, through-hole techniques, where the post walls consists of via fences. SIW is known to have similar guided wave and mode characteristics to conventional rectangular waveguide with equivalent guide wavelength. Since the emergence of new communication technologies in the 1990s, there has been an increasing need for high-performance millimeter-wave systems. These need to be reliable, low-cost, compact, and compatible with high-frequencies. Unfortunately, above 10 GHz, the well known microstrip and coplanar waveguide, coplanar lines technolog ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Waveguide (electromagnetism)
In radio-frequency engineering and communications engineering, waveguide is a hollow metal pipe used to carry radio waves. This type of waveguide is used as a transmission line mostly at microwave frequencies, for such purposes as connecting microwave transmitters and receivers to their antennas, in equipment such as microwave ovens, radar sets, satellite communications, and microwave radio links. The electromagnetic waves in a (metal-pipe) waveguide may be imagined as travelling down the guide in a zig-zag path, being repeatedly reflected between opposite walls of the guide. For the particular case of rectangular waveguide, it is possible to base an exact analysis on this view. Propagation in a dielectric waveguide may be viewed in the same way, with the waves confined to the dielectric by total internal reflection at its surface. Some structures, such as non-radiative dielectric waveguides and the Goubau line, use both metal walls and dielectric surfaces to confine the wave ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Insertion Loss
In telecommunications, insertion loss is the loss of signal power resulting from the insertion of a device in a transmission line or optical fiber and is usually expressed in decibels (dB). If the power transmitted to the load before insertion is ''P''T and the power received by the load after insertion is ''P''R, then the insertion loss in decibels is given by, :IL(\mathrm) = 10 \log_ Electronic filters Insertion loss is a figure of merit for an electronic filter and this data is generally specified with a filter. Insertion loss is defined as a ratio of the signal level in a test configuration without the filter installed (\left\vert V_1 \right\vert) to the signal level with the filter installed (\left\vert V_2 \right\vert). This ratio is described in decibels by the following equation: :\mbox = 10 \log_ = 20 \log_ For passive filters, \left\vert V_2 \right\vert will be smaller than \left\vert V_1 \right\vert. In this case, the insertion loss is positive and measures ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Analog Delay Line
An analog delay line is a network of electrical components connected in cascade, where each individual element creates a time difference between its input and output. It operates on analog signals whose amplitude varies continuously. In the case of a periodic signal, the time difference can be described in terms of a change in the phase of the signal. One example of an analog delay line is a bucket-brigade device. Other types of delay line include acoustic (usually ultrasonic), magnetostrictive, and surface acoustic wave devices. A series of resistor–capacitor circuits (RC circuits) can be cascaded to form a delay. A long transmission line can also provide a delay element. The delay time of an analog delay line may be only a few nanoseconds or several milliseconds, limited by the practical size of the physical medium used to delay the signal and the propagation speed of impulses in the medium. Analog delay lines are applied in many types of signal processing circuits; for ex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cascade Connection
A two-port network (a kind of four-terminal network or quadripole) is an electrical network ( circuit) or device with two ''pairs'' of terminals to connect to external circuits. Two terminals constitute a port if the currents applied to them satisfy the essential requirement known as the port condition: the electric current entering one terminal must equal the current emerging from the other terminal on the same port.Gray, §3.2, p. 172Jaeger, §10.5 §13.5 §13.8 The ports constitute interfaces where the network connects to other networks, the points where signals are applied or outputs are taken. In a two-port network, often port 1 is considered the input port and port 2 is considered the output port. It's used in mathematical circuit analysis. Application The two-port network model is used in mathematical circuit analysis techniques to isolate portions of larger circuits. A two-port network is regarded as a "black box" with its properties specified by a matrix of num ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Branch-line Coupler
Power dividers (also power splitters and, when used in reverse, power combiners) and directional couplers are passive devices used mostly in the field of radio technology. They couple a defined amount of the electromagnetic power in a transmission line to a port enabling the signal to be used in another circuit. An essential feature of directional couplers is that they only couple power flowing in one direction. Power entering the output port is coupled to the isolated port but not to the coupled port. A directional coupler designed to split power equally between two ports is called a hybrid coupler. Directional couplers are most frequently constructed from two coupled transmission lines set close enough together such that energy passing through one is coupled to the other. This technique is favoured at the microwave frequencies where transmission line designs are commonly used to implement many circuit elements. However, lumped component devices are also possible at lower ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Airbridge
Airbridge or air bridge may refer to: *AirBridge (alliance) or AiRUnion, a defunct Russian-backed consortium *Airbridge (band), an early-1980s British progressive-rock band *Airbridge (logistics), the route and means of delivering material from one place to another by an airlift *Airbridge (ultralight aircraft manufacturer), a Russian manufacturer of ultralights *Jet bridge or airbridge, a passenger boarding bridge used at large airports *An electronic component used to allow two traces to cross in, for instance, planar transmission line circuits See also *AirBridgeCargo Airlines, LLC, a subsidiary of Volga-Dnepr Airlines based in Moscow, Russia *Oriental Air Bridge is an airline headquartered on the grounds of Nagasaki Airport and in Ōmura, Nagasaki Prefecture, Japan. It operates in southern Japan, offering charter services and a scheduled service between Nagasaki and Fukuoka. Its main base is Nagasaki Airp ... Co., Ltd., a Japanese charter airline based at Nagasaki Airport * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
