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Total Active Reflection Coefficient
The total active reflection coefficient (TARC) within mathematics and physics scattering theory, relates the total incident power to the total outgoing power in an N-port microwave component. The TARC is mainly used for multiple-input multiple-output (MIMO) antenna systems and array antennas, where the outgoing power is unwanted reflected power. The name shows the similarities with the active reflection coefficient, which is used for single elements. The TARC is the square root of the sum of all outgoing powers at the ports, divided by the sum of all incident powers at the ports of an N-port antenna. Similarly to the active reflection coefficient, the TARC is a function of frequency, and it also depends on scan angle and tapering. With this definition we can characterize the multi-port antenna’s frequency bandwidth and radiation performance. When the antennas are made of lossless materials, TARC can be computed directly from the scattering matrix by : \Gamma^t_a = \frac, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mathematics
Mathematics is an area of knowledge that includes the topics of numbers, formulas and related structures, shapes and the spaces in which they are contained, and quantities and their changes. These topics are represented in modern mathematics with the major subdisciplines of number theory, algebra, geometry, and analysis, respectively. There is no general consensus among mathematicians about a common definition for their academic discipline. Most mathematical activity involves the discovery of properties of abstract objects and the use of pure reason to prove them. These objects consist of either abstractions from nature orin modern mathematicsentities that are stipulated to have certain properties, called axioms. A ''proof'' consists of a succession of applications of deductive rules to already established results. These results include previously proved theorems, axioms, andin case of abstraction from naturesome basic properties that are considered true starting points of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Euclidean Vector
In mathematics, physics, and engineering, a Euclidean vector or simply a vector (sometimes called a geometric vector or spatial vector) is a geometric object that has magnitude (or length) and direction. Vectors can be added to other vectors according to vector algebra. A Euclidean vector is frequently represented by a '' directed line segment'', or graphically as an arrow connecting an ''initial point'' ''A'' with a ''terminal point'' ''B'', and denoted by \overrightarrow . A vector is what is needed to "carry" the point ''A'' to the point ''B''; the Latin word ''vector'' means "carrier". It was first used by 18th century astronomers investigating planetary revolution around the Sun. The magnitude of the vector is the distance between the two points, and the direction refers to the direction of displacement from ''A'' to ''B''. Many algebraic operations on real numbers such as addition, subtraction, multiplication, and negation have close analogues for vectors, operations whic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scattering Theory
In mathematics and physics, scattering theory is a framework for studying and understanding the scattering of waves and particles. Wave scattering corresponds to the collision and scattering of a wave with some material object, for instance sunlight scattered by rain drops to form a rainbow. Scattering also includes the interaction of billiard balls on a table, the Rutherford scattering (or angle change) of alpha particles by gold nuclei, the Bragg scattering (or diffraction) of electrons and X-rays by a cluster of atoms, and the inelastic scattering of a fission fragment as it traverses a thin foil. More precisely, scattering consists of the study of how solutions of partial differential equations, propagating freely "in the distant past", come together and interact with one another or with a boundary condition, and then propagate away "to the distant future". The direct scattering problem is the problem of determining the distribution of scattered radiation/particle flux basing ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yahya Rahmat-Samii
Yahya Rahmat-Samii ( fa, یحیی رحمت-سمیعی; born August 20, 1948) is the Northrop Grumman Chair Professor in Electromagnetics at the Electrical Engineering Department at the University of California, Los Angeles, where he teaches and conducts research on microwave transmission and radio antennas. Professor Rahmat-Samii received his Bachelor of Science degree in Electrical Engineering in 1970 from the University of Tehran, Iran, and the Master of Science in 1972 and the Doctor of Philosophy degrees in Electrical Engineering in 1975 from the University of Illinois at Urbana-Champaign. Before joining UCLA in 1989, he was a Senior Research Scientist at the NASA Jet Propulsion Laboratory. He has made innovations in satellite communications antennas, personal communication antennas, wearable and implanted antennas for communications and biotelemetry, and antennas for remote sensing and radio astronomy applications. He is the Director of the UCLA Antenna Research, Analysis and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Majid Manteghi , a family of crabs
{{Disambiguation ...
Majid or majeed may refer to: * , ''majīd'' 'majestic', and , ''mājid'' 'magnificent', two names of God in Islam Arts and entertainment * ''Majid'' (film), a 2010 Moroccan film *Majid (rapper) (born 1975), a Danish rapper of Moroccan-Berber origin *Majid Jordan, a Canadian R&B duo *Majid (comics), a pan-Arab comic book anthology and children's magazine Other uses *Majid (name), or variant spellings, including a list of people with the given name or family name *Majid, Iran (other), a number of places in Iran *Majeed syndrome, an inherited skin disorder See also * * * * *Majd (other) *Majidae Majidae is a family of crabs, comprising around 200 marine species inside 52 genera, with a carapace that is longer than it is broad, and which forms a point at the front. The legs can be very long in some species, leading to the name "spider cra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antenna Array
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. 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. The radio waves radiated by each individual antenna combine and superpose, adding together ( interfering constructively) to enhance the power radiated in desired directions, and cancelling ( interfering destructively) to reduce the power radiated in other directions. Similarly, when used for receiving, the separate radio frequency currents from the individual antennas combine in the receiver with the correct phase relationship to enhance signals received from the desired directions and cancel signals from undesired directions. More sophisticated array antennas may have multiple transmitter or receiver modules, each connected to a separate a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Active Reflection Coefficient
The active reflection coefficient (ARC) is the reflection coefficient for a single antenna element in an array antenna, in the presence of mutual coupling. The active reflection coefficient is a function of frequency in addition to the excitation of the neighboring cells. In computational electromagnetics, the active reflection coefficient is usually determined from unit cell analysis in the frequency domain, where the phase shift over the unit cell (progressive phase shift used to steer the beam) is applied as a boundary condition. It has been suggested that the name "scan reflection coefficient" is more appropriate than "active reflection coefficient", however the latter remains the most commonly used name. Mathematical description General case The ARC for antenna element m in an array of N elements is calculated by: \Gamma_S = \sum_^N S_ \frac, where a_n are the excitation coefficients and S_ are the coupling coefficients. Linear array with specified scan ang ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Realized Gain
Realization or realisation may refer to: * ''Realization'' (album), a 1973 album by Eddie Henderson * ''Realization'' (climb), a sport climbing route in Ceüse, France * Realization (figured bass), the creating of a musical accompaniment from a figured bass * Realization (finance), the pricing of security at market value * Realization (linguistics), the production of an actual form in a human language from an abstract representation * Realization (metrology), a physical form of a measurement standard * Realization (probability), an actually observed value of random variable * Realization (systems), a state space model implementing a given input-output behavior * Realization (tax), one of the principles for defining income for tax purposes in the U.S. * Realization of an apeirogon, a mapping of an abstract apeirogon See also * Realize (other) * Self-realization Self-realization is an expression used in Western psychology, philosophy, and spirituality; and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Directivity
In electromagnetics, directivity is a parameter of an antenna or optical system which measures the degree to which the radiation emitted is concentrated in a single direction. It is the ratio of the radiation intensity in a given direction from the antenna to the radiation intensity averaged over all directions.IEEE Std 145-2013, IEEE Standard for Definitions of Terms for Antennas, IEEE Therefore, the directivity of a hypothetical isotropic radiator is 1, or 0 dBi. An antenna's directivity is greater than its gain by an efficiency factor, radiation efficiency. Directivity is an important measure because many antennas and optical systems are designed to radiate electromagnetic waves in a single direction or over a narrow-angle. By the principle of reciprocity, the directivity of an antenna when receiving is equal to its directivity when transmitting. The directivity of an actual antenna can vary from 1.76 dBi for a short dipole to as much as 50 dBi for a large dish antenna. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Decibel Scale
The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a power or root-power quantity on a logarithmic scale. Two signals whose levels differ by one decibel have a power ratio of 101/10 (approximately ) or root-power ratio of 10 (approximately ). The unit expresses a relative change or an absolute value. In the latter case, the numeric value expresses the ratio of a value to a fixed reference value; when used in this way, the unit symbol is often suffixed with letter codes that indicate the reference value. For example, for the reference value of 1 volt, a common suffix is " V" (e.g., "20 dBV"). Two principal types of scaling of the decibel are in common use. When expressing a power ratio, it is defined as ten times the logarithm in base 10. That is, a change in ''power'' by a factor of 10 corresponds to a 10 dB change in level. When expressing root-power quantities, a change in ''amp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Real Number
In mathematics, a real number is a number that can be used to measure a ''continuous'' one-dimensional quantity such as a distance, duration or temperature. Here, ''continuous'' means that values can have arbitrarily small variations. Every real number can be almost uniquely represented by an infinite decimal expansion. The real numbers are fundamental in calculus (and more generally in all mathematics), in particular by their role in the classical definitions of limits, continuity and derivatives. The set of real numbers is denoted or \mathbb and is sometimes called "the reals". The adjective ''real'' in this context was introduced in the 17th century by René Descartes to distinguish real numbers, associated with physical reality, from imaginary numbers (such as the square roots of ), which seemed like a theoretical contrivance unrelated to physical reality. The real numbers include the rational numbers, such as the integer and the fraction . The rest of the real number ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scattering Matrix
In physics, the ''S''-matrix or scattering matrix relates the initial state and the final state of a physical system undergoing a scattering process. It is used in quantum mechanics, scattering theory and quantum field theory (QFT). More formally, in the context of QFT, the ''S''-matrix is defined as the unitary matrix connecting sets of asymptotically free particle states (the ''in-states'' and the ''out-states'') in the Hilbert space of physical states. A multi-particle state is said to be ''free'' (non-interacting) if it transforms under Lorentz transformations as a tensor product, or ''direct product'' in physics parlance, of ''one-particle states'' as prescribed by equation below. ''Asymptotically free'' then means that the state has this appearance in either the distant past or the distant future. While the ''S''-matrix may be defined for any background (spacetime) that is asymptotically solvable and has no event horizons, it has a simple form in the case of the Minkowski ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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