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Isolator (microwave)
An isolator is a Two-port network, two-port device that transmits microwave or radio frequency power in one direction only. The non-reciprocity observed in these devices usually comes from the interaction between the propagating wave and the material, which can be different with respect to the direction of propagation. It is used to shield equipment on its input side, from the effects of conditions on its output side; for example, to prevent a microwave source being detuned by a mismatched load. Non-reciprocity An isolator is a non-Reciprocity (electrical networks), reciprocal device, with a non-Symmetric matrix, symmetric Scattering parameters, scattering matrix. An ideal isolator transmits all the power entering Port (circuit theory), port 1 to port 2, while absorbing all the power entering port 2, so that to within a phase-factor its S-matrix is :S = \begin 0 & 0 \\ 1 & 0 \end To achieve non-reciprocity, an isolator must necessarily incorporate a non-reciprocal material. A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dielectric
In electromagnetism, a dielectric (or dielectric medium) is an Insulator (electricity), electrical insulator that can be Polarisability, polarised by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the material as they do in an electrical conductor, because they have no loosely bound, or free, electrons that may drift through the material, but instead they shift, only slightly, from their average equilibrium positions, causing dielectric polarisation. Because of Polarisation density, dielectric polarisation, positive charges are displaced in the direction of the field and negative charges shift in the direction opposite to the field. This creates an internal electric field that reduces the overall field within the dielectric itself. If a dielectric is composed of weakly Chemical bond, bonded molecules, those molecules not only become polarised, but also reorient so that their Symmetry axis, symmetry axes a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bell System Technical Journal
The ''Bell Labs Technical Journal'' was the in-house scientific journal for scientists of Bell Labs, published yearly by the IEEE society. The journal was originally established as ''The Bell System Technical Journal'' (BSTJ) in New York by the American Telephone and Telegraph Company (AT&T) in 1922. It was published under this name until 1983, when the breakup of the Bell System placed various parts of the companies in the system into independent corporate entities. The journal was devoted to the scientific fields and engineering disciplines practiced in the Bell System for improvements in the wide field of electrical communication. After the restructuring of Bell Labs in 1984, the journal was renamed to ''AT&T Bell Laboratories Technical Journal''. In 1985, it was published as the ''AT&T Technical Journal'' until 1996, when it was renamed to ''Bell Labs Technical Journal''. The journal was discontinued in 2020. The last managing editor was Charles Bahr. History The Bell System ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gyrator
A gyrator is a passivity (engineering), passive, Linear circuit, linear, lossless, two-port network, two-port electrical lumped-element model, network element proposed in 1948 by Bernard D. H. Tellegen as a hypothetical fifth linear element after the resistor, capacitor, inductor and transformer#Ideal transformer, ideal transformer. Unlike the four conventional elements, the gyrator is Reciprocity (electrical networks), non-reciprocal. Gyrators permit network synthesis filters, network realizations of two-(or-more)-Port (circuit theory), port devices which cannot be realized with just the four conventional elements. In particular, gyrators make possible network realizations of isolator (microwave), isolators and circulators. Gyrators do not however change the range of one-port devices that can be realized. Although the gyrator was conceived as a fifth linear element, its adoption makes both the ideal transformer and either the capacitor or inductor redundant. Thus the number of neces ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Circulator
In electrical engineering, a circulator is a passivity (engineering), passive, non-Reciprocity (electrical networks), reciprocal three- or four-port (circuit theory), port device that only allows a microwave or radio frequency, radio-frequency (RF) signal to exit through the port directly after the one it entered. Optical circulators have similar behavior. Ports are where an external waveguide (electromagnetism), waveguide or transmission line, such as a microstrip line or a coaxial cable, connects to the device. For a three-port circulator, a signal applied to port 1 only comes out of port 2; a signal applied to port 2 only comes out of port 3; a signal applied to port 3 only comes out of port 1. An ideal three-port circulator thus has the following scattering parameters, scattering matrix: :S = \begin 0 & 0 & 1\\ 1 & 0 & 0 \\ 0 & 1 & 0 \end Theory of operation Microwave circulators rely on the anisotropic and ''non-Reciprocity (electrical networks), reciprocal'' proper ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Power Dividers And Directional Couplers
Power dividers (also power splitters and, when used in reverse, power combiners) and directional couplers are Passivity (engineering), 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 (circuit theory), 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, lumpe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X Band
The X band is the designation for a band of frequencies in the microwave radio region of the electromagnetic spectrum. In some cases, such as in communication engineering, the frequency range of the X band is set at approximately 7.0–11.2 GHz. In radar engineering, the frequency range is specified by the Institute of Electrical and Electronics Engineers (IEEE) as 8.0–12.0 GHz. The X band is used for radar, satellite communication, and wireless computer networks. Radar X band is used in radar applications, including continuous-wave, pulsed, single- polarization, dual-polarization, synthetic aperture radar, and phased arrays. X-band radar frequency sub-bands are used in civil, military, and government institutions for weather monitoring, air traffic control, maritime vessel traffic control, defense tracking, and vehicle speed detection for law enforcement. X band is often used in modern radars. The shorter wavelengths of the X band provide higher-r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Faraday Effect
The Faraday effect or Faraday rotation, sometimes referred to as the magneto-optic Faraday effect (MOFE), is a physical magneto-optical phenomenon. The Faraday effect causes a polarization rotation which is proportional to the projection of the magnetic field along the direction of the light propagation. Formally, it is a special case of gyroelectromagnetism obtained when the dielectric permittivity tensor is diagonal. This effect occurs in most optically transparent dielectric materials (including liquids) under the influence of magnetic fields. Discovered by Michael Faraday in 1845, the Faraday effect was the first experimental evidence that light and electromagnetism are related. The theoretical basis of electromagnetic radiation (which includes visible light) was completed by James Clerk Maxwell in the 1860s. Maxwell's equations were rewritten in their current form in the 1870s by Oliver Heaviside. The Faraday effect is caused by left and right circularly polarized wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transmission Line
In electrical engineering, a transmission line is a specialized cable or other structure designed to conduct electromagnetic waves in a contained manner. The term applies when the conductors are long enough that the wave nature of the transmission must be taken into account. This applies especially to radio-frequency engineering because the short wavelengths mean that wave phenomena arise over very short distances (this can be as short as millimetres depending on frequency). However, the Telegrapher's equations, theory of transmission lines was historically developed to explain phenomena on very long electrical telegraph, telegraph lines, especially submarine telegraph cables. Transmission lines are used for purposes such as connecting Transmitter, radio transmitters and Radio receiver, receivers with their antenna (radio), antennas (they are then called feed lines or feeders), distributing cable television signals, trunking, trunklines routing calls between telephone switchi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Circulator
In electrical engineering, a circulator is a passivity (engineering), passive, non-Reciprocity (electrical networks), reciprocal three- or four-port (circuit theory), port device that only allows a microwave or radio frequency, radio-frequency (RF) signal to exit through the port directly after the one it entered. Optical circulators have similar behavior. Ports are where an external waveguide (electromagnetism), waveguide or transmission line, such as a microstrip line or a coaxial cable, connects to the device. For a three-port circulator, a signal applied to port 1 only comes out of port 2; a signal applied to port 2 only comes out of port 3; a signal applied to port 3 only comes out of port 1. An ideal three-port circulator thus has the following scattering parameters, scattering matrix: :S = \begin 0 & 0 & 1\\ 1 & 0 & 0 \\ 0 & 1 & 0 \end Theory of operation Microwave circulators rely on the anisotropic and ''non-Reciprocity (electrical networks), reciprocal'' proper ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electric Field
An electric field (sometimes called E-field) is a field (physics), physical field that surrounds electrically charged particles such as electrons. In classical electromagnetism, the electric field of a single charge (or group of charges) describes their capacity to exert attractive or repulsive forces on another charged object. Charged particles exert attractive forces on each other when the sign of their charges are opposite, one being positive while the other is negative, and repel each other when the signs of the charges are the same. Because these forces are exerted mutually, two charges must be present for the forces to take place. These forces are described by Coulomb's law, which says that the greater the magnitude of the charges, the greater the force, and the greater the distance between them, the weaker the force. Informally, the greater the charge of an object, the stronger its electric field. Similarly, an electric field is stronger nearer charged objects and weaker f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wave Impedance
The wave impedance of an electromagnetic wave is the ratio of the transverse components of the electric and magnetic fields (the transverse components being those at right angles to the direction of propagation). For a transverse-electric-magnetic ( TEM) plane wave traveling through a homogeneous medium, the wave impedance is everywhere equal to the intrinsic impedance of the medium. In particular, for a plane wave travelling through empty space, the wave impedance is equal to the impedance of free space. The symbol ''Z'' is used to represent it and it is expressed in units of ohms. The symbol ''η'' (eta) may be used instead of ''Z'' for wave impedance to avoid confusion with electrical impedance. Definition The wave impedance is given by : Z = where E_0^-(x) is the electric field and H_0^-(x) is the magnetic field, in phasor representation. The impedance is, in general, a complex number. In terms of the parameters of an electromagnetic wave and the medium it travels through ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
