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Transmitarray Antenna
A transmitarray antenna (or just transmitarray or called as layered lens antenna) is a phase-shifting surface (PSS), a structure capable of focusing electromagnetic radiation from a source antenna to produce a high-Antenna gain, gain Directional antenna, beam. Transmitarrays consist of an array of unit cells placed above a source (feeding) Antenna (radio), antenna. Phase shifts are applied to the unit cells, between elements on the receive and transmit surfaces, to focus the incident wavefronts from the feeding antenna. These thin surfaces can be used instead of a Luneburg lens, dielectric lens. Unlike phased arrays, transmitarrays do not require a feed network, so losses can be greatly reduced. Similarly, they have an advantage over Reflectarray antenna, reflectarrays in that feed blockage is avoided. It is worth clarifying that transmitarrays can be used in both transmit and receive modes: the waves are transmitted through the structure in either direction. An important paramete ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Di Palma Txarray
Di or DI may refer to: Arts and media Music * Di, a tone in the solfège ascending chromatic scale existing between Do and Re * dizi (instrument) or di, a Chinese transverse flute * D.I. (band), ''D.I.'' (band), a punk band from Southern California ** D.I. (EP), ''D.I.'' (EP), a 1983 EP by the same band above Other media * ''The D.I.'', 1957 military film by Jack Webb * ''Dagens Industri'', a Swedish financial newspaper * DI.FM, an internet radio service Businesses and organisations * Defence Intelligence, a UK military intelligence agency * Defensa Interior, an anti-Franco militant anarchist group in 1960s Spain * Deseret Industries, an LDS thrift store * Desert Inn, a former casino in Las Vegas * Direction Italy, a liberal-conservative political party in Italy * Dirgantara Indonesia, an Indonesian aircraft company * Discovery Institute, an intelligent design advocacy group * Norwegian Air UK, a UK based airline (IATA designator) * DynCorp International, a major United States d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aperture Efficiency
In electromagnetics and antenna theory, the aperture of an antenna is defined as "A surface, near or on an antenna, on which it is convenient to make assumptions regarding the field values for the purpose of computing fields at external points. The aperture is often taken as that portion of a plane surface near the antenna, perpendicular to the direction of maximum radiation, through which the major part of the radiation passes." Effective area The effective area of an antenna is defined as "In a given direction, the ratio of the available power at the terminals of a receiving antenna to the power flux density of a plane wave incident on the antenna from that direction, the wave being polarization matched to the antenna." Of particular note in this definition is that both effective area and power flux density are functions of incident angle of a plane wave. Assume a plane wave from a particular direction (\theta, \phi), which are the azimuth and elevation angles relative to the ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PIN Diode
A pin is a device used for fastening objects or material together. Pin or PIN may also refer to: Computers and technology * Personal identification number (PIN), to access a secured system ** PIN pad, a PIN entry device * PIN, a former Dutch debit card system * An image on Pinterest * PIN diode, a semiconductor diode * Pin, a short lead in electronics * Pinning, the act of attaching a social media post to the top of a page to signify importance * To pin an object to another object in interface, such as pinning an application to the taskbar * Pin (computer program), a platform for creating analysis tools Awards, brooches, or fasteners * Award pin, recognising an achievement * Bobby pin or kirby grip or hair grip, a hairpin * Clevis pin, a three-piece fastener system * Collar pin, for a shirt collar * Drawing pin or thumbtack * Lapel pin, a small pin worn on clothing * Pin-back button, a badge fastened to garments with a safety pin. * Safety pin, pin which includes a s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Di Palma Txarray Rad Patterns
Di or DI may refer to: Arts and media Music * Di, a tone in the solfège ascending chromatic scale existing between Do and Re * dizi (instrument) or di, a Chinese transverse flute * ''D.I.'' (band), a punk band from Southern California ** ''D.I.'' (EP), a 1983 EP by the same band above Other media * ''The D.I.'', 1957 military film by Jack Webb * '' Dagens Industri'', a Swedish financial newspaper * DI.FM, an internet radio service Businesses and organisations * Defence Intelligence, a UK military intelligence agency * Defensa Interior, an anti-Franco militant anarchist group in 1960s Spain * Deseret Industries, an LDS thrift store * Desert Inn, a former casino in Las Vegas * Direction Italy, a liberal-conservative political party in Italy * Dirgantara Indonesia, an Indonesian aircraft company * Discovery Institute, an intelligent design advocacy group * Norwegian Air UK, a UK based airline (IATA designator) * DynCorp International, a major United States defense contractor E ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mobile Telephony
Mobile telephony is the provision of telephone services to phones which may move around freely rather than stay fixed in one location. Telephony is supposed to specifically point to a voice-only service or connection, though sometimes the line may blur. Mobile phones connect to a terrestrial cellular network of base stations ( cell sites), whereas satellite phones connect to orbiting satellites. Both networks are interconnected to the public switched telephone network (PSTN) to allow any phone in the world to be dialed. In 2010 there were estimated to be five billion mobile cellular subscriptions in the world. History According to internal memos, American Telephone & Telegraph discussed developing a wireless phone in 1915, but were afraid that deployment of the technology could undermine its monopoly on wired service in the U.S. Public mobile phone systems were first introduced in the years after the Second World War and made use of technology developed before a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Floquet Theory
Floquet theory is a branch of the theory of ordinary differential equations relating to the class of solutions to periodic linear differential equations of the form :\dot = A(t) x, with \displaystyle A(t) a piecewise continuous periodic function with period T and defines the state of the stability of solutions. The main theorem of Floquet theory, Floquet's theorem, due to , gives a canonical form for each fundamental matrix solution of this common linear system. It gives a coordinate change \displaystyle y=Q^(t)x with \displaystyle Q(t+2T)=Q(t) that transforms the periodic system to a traditional linear system with constant, real coefficients. When applied to physical systems with periodic potentials, such as crystals in condensed matter physics, the result is known as Bloch's theorem. Note that the solutions of the linear differential equation form a vector space. A matrix \phi\,(t) is called a '' fundamental matrix solution'' if all columns are linearly independent solution ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Side Lobe
In antenna engineering, sidelobes are the lobes (local maxima) of the far field radiation pattern of an antenna or other radiation source, that are not the '' main lobe''. The radiation pattern of most antennas shows a pattern of "''lobes''" at various angles, directions where the radiated signal strength reaches a maximum, separated by "'' nulls''", angles at which the radiated signal strength falls to zero. This can be viewed as the diffraction pattern of the antenna. In a directional antenna in which the objective is to emit the radio waves in one direction, the lobe in that direction is designed to have a larger field strength than the others; this is the "'' main lobe''". The other lobes are called "''sidelobes''", and usually represent unwanted radiation in undesired directions. The sidelobe directly behind the main lobe is called the back lobe. The longer the antenna relative to the radio wavelength, the more lobes its radiation pattern has. In transmitting a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Via (electronics)
A via (Latin for ''path'' or ''way'') is an electrical connection between copper layers in a printed circuit board. Essentially a via is a small drilled hole that goes through two or more adjacent layers; the hole is plated with copper that forms electrical connection through the insulation that separates the copper layers. Vias are important for PCB manufacturing. This is because the vias are drilled with certain tolerances and may be fabricated off their designated locations, so some allowance for errors in drill position must be made prior to manufacturing or else the manufacturing yield can decrease due to non-conforming boards (according to some reference standard) or even due to failing boards. In addition, regular through hole vias are considered fragile structures as they are long and narrow; the manufacturer must ensure that the vias are plated properly throughout the barrel and this in turn causes several processing steps. In printed circuit boards In printed ci ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Post-wall Waveguide
A substrate-integrated waveguide (SIW) (also known as post-wall waveguide or laminated waveguide) is a synthetic rectangular electromagnetic waveguide formed in a dielectric substrate by densely arraying metallized posts or 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 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 lines technologies cannot be used because they have high insertion and radiation losses at these frequenc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Horn Antenna
A horn antenna or microwave horn is an antenna that consists of a flaring metal waveguide shaped like a horn to direct radio waves in a beam. Horns are widely used as antennas at UHF and microwave frequencies, above 300 MHz. They are used as feed antennas (called feed horns) for larger antenna structures such as parabolic antennas, as standard calibration antennas to measure the gain of other antennas, and as directive antennas for such devices as radar guns, automatic door openers, and microwave radiometers. Their advantages are moderate directivity, low standing wave ratio (SWR), broad bandwidth, and simple construction and adjustment. One of the first horn antennas was constructed in 1897 by Bengali-Indian radio researcher Jagadish Chandra Bose in his pioneering experiments with microwaves. reprinted in The modern horn antenna was invented independently in 1938 by Wilmer Barrow and G. C. Southworth The development of radar in World War 2 stimul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polarization (waves)
Polarization ( also polarisation) is a property applying to transverse waves that specifies the geometrical orientation of the oscillations. In a transverse wave, the direction of the oscillation is perpendicular to the direction of motion of the wave. A simple example of a polarized transverse wave is vibrations traveling along a taut string ''(see image)''; for example, in a musical instrument like a guitar string. Depending on how the string is plucked, the vibrations can be in a vertical direction, horizontal direction, or at any angle perpendicular to the string. In contrast, in longitudinal waves, such as sound waves in a liquid or gas, the displacement of the particles in the oscillation is always in the direction of propagation, so these waves do not exhibit polarization. Transverse waves that exhibit polarization include electromagnetic waves such as light and radio waves, gravitational waves, and transverse sound waves ( shear waves) in solids. An electromagneti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bandwidth (signal Processing)
Bandwidth is the difference between the upper and lower frequencies in a continuous band of frequencies. It is typically measured in hertz, and depending on context, may specifically refer to '' passband bandwidth'' or '' baseband bandwidth''. Passband bandwidth is the difference between the upper and lower cutoff frequencies of, for example, a band-pass filter, a communication channel, or a signal spectrum. Baseband bandwidth applies to a low-pass filter or baseband signal; the bandwidth is equal to its upper cutoff frequency. Bandwidth in hertz is a central concept in many fields, including electronics, information theory, digital communications, radio communications, signal processing, and spectroscopy and is one of the determinants of the capacity of a given communication channel. A key characteristic of bandwidth is that any band of a given width can carry the same amount of information, regardless of where that band is located in the frequency spectrum. For exam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
