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Halo Antenna
A halo antenna, or halo, is a center-fed dipole antenna, which has been bent into a circle, with a break directly opposite the feed point. The dipole ends are close, but do not touch, and may be widened to form an air capacitor, whose spacing is used to adjust the antenna's resonant frequency. Most often mounted horizontally, this antenna's radiation is then approximately omnidirectional and horizontally polarized. Halo antennas vs. loop antennas This section contrasts halo antennas with loop antennas which are electrically dissimilar, but can be confused as they all share the same circular shape. Halo vs. large loops Although also a resonant antenna, the halo antenna is distinct from the full-wave loop antenna, which is approximately double its size for the same operating frequency. In the case of the halo antenna, each half is about a quarter wavelength long and ends with a current node (zero current and peak voltage) at the break. On the other hand, the two semi-circles of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Halo Antenna
A halo antenna, or halo, is a center-fed dipole antenna, which has been bent into a circle, with a break directly opposite the feed point. The dipole ends are close, but do not touch, and may be widened to form an air capacitor, whose spacing is used to adjust the antenna's resonant frequency. Most often mounted horizontally, this antenna's radiation is then approximately omnidirectional and horizontally polarized. Halo antennas vs. loop antennas This section contrasts halo antennas with loop antennas which are electrically dissimilar, but can be confused as they all share the same circular shape. Halo vs. large loops Although also a resonant antenna, the halo antenna is distinct from the full-wave loop antenna, which is approximately double its size for the same operating frequency. In the case of the halo antenna, each half is about a quarter wavelength long and ends with a current node (zero current and peak voltage) at the break. On the other hand, the two semi-circles of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dipole Antenna
In radio and telecommunications a dipole antenna or doublet is the simplest and most widely used class of antenna. The dipole is any one of a class of antennas producing a radiation pattern approximating that of an elementary electric dipole with a radiating structure supporting a line current so energized that the current has only one node at each end. A dipole antenna commonly consists of two identical conductive elements such as metal wires or rods. The driving current from the transmitter is applied, or for receiving antennas the output signal to the receiver is taken, between the two halves of the antenna. Each side of the feedline to the transmitter or receiver is connected to one of the conductors. This contrasts with a monopole antenna, which consists of a single rod or conductor with one side of the feedline connected to it, and the other side connected to some type of ground. A common example of a dipole is the "rabbit ears" television antenna found on broadcast telev ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ground (electricity)
In electrical engineering, ground or earth is a reference point in an electrical circuit from which voltages are measured, a common return path for electric current, or a direct physical connection to the Earth. Electrical circuits may be connected to ground for several reasons. Exposed conductive parts of electrical equipment are connected to ground, to protect users from electrical shock hazard. If internal insulation fails, dangerous voltages may appear on the exposed conductive parts. Connecting exposed parts to ground will allow circuit breakers (or RCDs) to interrupt power supply in the event of a fault. In electric power distribution systems, a protective earth (PE) conductor is an essential part of the safety provided by the earthing system. Connection to ground also limits the build-up of static electricity when handling flammable products or electrostatic-sensitive devices. In some telegraph and power transmission circuits, the ground itself can be used as one condu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Balun
A balun (from "balanced to unbalanced", originally, but now dated from "balancing unit") is an electrical device that allows balanced and unbalanced lines to be interfaced without disturbing the impedance arrangement of either line. A balun can take many forms and may include devices that also transform impedances but need not do so. Sometimes, in the case of transformer baluns, they use magnetic coupling but need not do so. Common-mode chokes are also used as baluns and work by eliminating, rather than rejecting, common mode signals. Types of balun Classical transformer type In classical transformers, there are two electrically separate windings of wire coils around the transformer's core. The advantage of transformer-type over other types of balun is that the electrically separate windings for input and output allow these baluns to connect circuits whose ground-level voltages are subject to ground loops or are otherwise electrically incompatible; for that reason they ... [...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 example, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antenna Feed
A radio transmitter or receiver is connected to an antenna which emits or receives the radio waves. The antenna feed system or antenna feed is the cable or conductor, and other associated equipment, which connects the transmitter or receiver with the antenna and makes the two devices compatible. In a radio transmitter, the transmitter generates an alternating current of radio frequency, and the feed system feeds the current to the antenna, which converts the power in the current to radio waves. In a radio receiver, the incoming radio waves excite tiny alternating currents in the antenna, and the feed system delivers this current to the receiver, which processes the signal. To transfer radio frequency current efficiently, the ''feedline'' connecting the transmitter or receiver to the antenna must be a special type of cable called transmission line. At microwave frequencies, waveguide is often used, which is a hollow metal pipe carrying radio waves. In a parabolic (dish) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antenna Efficiency
Antenna ''apertureillumination efficiency is a measure of the extent to which an antenna or array is uniformly excited or illuminated. It is typical for an antenna pertureor array to be intentionally under-illuminated or under-excited in order to mitigate sidelobes and reduce antenna temperature. It is not to be confused with radiation efficiency or antenna efficiency. Definition Antenna pertureillumination efficiency is defined as "The ratio, usually expressed in percent, of the maximum directivity of an antenna pertureto its standard directivity." It is synonymous with normalized directivity. Standard eferencedirectivity is defined as "The maximum directivity from a planar aperture of area A, or from a line source of length L, when excited with a uniform-amplitude, equiphase distribution." Key to understanding these definitions is that "maximum" directivity refers to the direction of maximum radiation intensity, i.e., the main lobe. Therefore, illumination effici ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Series And Parallel Circuits
Two-terminal components and electrical networks can be connected in series or parallel. The resulting electrical network will have two terminals, and itself can participate in a series or parallel topology. Whether a two-terminal "object" is an electrical component (e.g. a resistor) or an electrical network (e.g. resistors in series) is a matter of perspective. This article will use "component" to refer to a two-terminal "object" that participate in the series/parallel networks. Components connected in series are connected along a single "electrical path", and each component has the same current through it, equal to the current through the network. The voltage across the network is equal to the sum of the voltages across each component. Components connected in parallel are connected along multiple paths, and each component has the same voltage across it, equal to the voltage across the network. The current through the network is equal to the sum of the currents through each com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Halo Geometry
Halo, halos or haloes usually refer to: * Halo (optical phenomenon) * Halo (religious iconography), a ring of light around the image of a head HALO, halo, halos or haloes may also refer to: Arts and entertainment Video games * ''Halo'' (franchise), a video game franchise ** '' Halo: Combat Evolved'', the first game in the series ** Halo Array, fictional megastructures and superweapons in the franchise Film and television * ''Halo'' (1996 film), a drama film made in India * ''Halo'' (2007 cancelled film), a cancelled movie based on ''Halo'' video game franchise * ''Halo'' (TV series), a 2022 TV series based on the ''Halo'' video game franchise * Nickelodeon HALO Awards, annual American television special (2008–2018) Comics * Comics in the ''Halo'' franchise * Halo (DC Comics), a fictional superheroine * the title character of ''The Ballad of Halo Jones'', a science-fiction comic strip Music * Halo Records Bands and musicians * Halo (Christian rock band), an American ban ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parasitic Capacitance
Parasitic capacitance is an unavoidable and usually unwanted capacitance that exists between the parts of an electronic component or circuit simply because of their proximity to each other. When two electrical conductors at different voltages are close together, the electric field between them causes electric charge to be stored on them; this effect is capacitance. All practical circuit elements such as inductors, diodes, and transistors have internal capacitance, which can cause their behavior to depart from that of ideal circuit elements. Additionally, there is always non-zero capacitance between any two conductors; this can be significant with closely spaced conductors, such as wires or printed circuit board traces. The parasitic capacitance between the turns of an inductor or other wound component is often described as ''self-capacitance''. However, in electromagnetics, the term self-capacitance more correctly refers to a different phenomenon: the capacitance of a condu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Displacement Current
In electromagnetism, displacement current density is the quantity appearing in Maxwell's equations that is defined in terms of the rate of change of , the electric displacement field. Displacement current density has the same units as electric current density, and it is a source of the magnetic field just as actual current is. However it is not an electric current of moving charges, but a time-varying electric field. In physical materials (as opposed to vacuum), there is also a contribution from the slight motion of charges bound in atoms, called dielectric polarization. The idea was conceived by James Clerk Maxwell in his 1861 paper On Physical Lines of Force, Part III' in connection with the displacement of electric particles in a dielectric medium. Maxwell added displacement current to the electric current term in Ampère's Circuital Law. In his 1865 paper A Dynamical Theory of the Electromagnetic Field Maxwell used this amended version of Ampère's Circuital Law to de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
