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Return Loss
In telecommunications, return loss is a measure in relative terms of the power of the signal reflected by a discontinuity in a transmission line or optical fiber. This discontinuity can be caused by a mismatch between the termination or load connected to the line and the characteristic impedance of the line. It is usually expressed as a ratio in decibels (dB); :RL(\mathrm) = 10 \log_ :where ''RL''(dB) is the return loss in dB, ''P''i is the incident power and ''P''r is the reflected power. Return loss is related to both standing wave ratio (SWR) and reflection coefficient (Γ). Increasing return loss corresponds to lower SWR. Return loss is a measure of how well devices or lines are matched. A match is good if the return loss is high. A high return loss is desirable and results in a lower insertion loss. From a certain perspective 'Return Loss' is a misnomer. The usual function of a transmission line is to convey power from a source to a load with minimal loss. If a tran ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telecommunications
Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that feasible with the human voice, but with a similar scale of expediency; thus, slow systems (such as postal mail) are excluded from the field. The transmission media in telecommunication have evolved through numerous stages of technology, from beacons and other visual signals (such as smoke signals, semaphore telegraphs, signal flags, and optical heliographs), to electrical cable and electromagnetic radiation, including light. Such transmission paths are often divided into communication channels, which afford the advantages of multiplexing multiple concurrent communication sessions. ''Telecommunication'' is often used in its plural form. Other examples of pre-modern long-distance communication included audio messages, such as coded drumb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fresnel Reflection
The Fresnel equations (or Fresnel coefficients) describe the reflection and transmission of light (or electromagnetic radiation in general) when incident on an interface between different optical media. They were deduced by Augustin-Jean Fresnel () who was the first to understand that light is a transverse wave, even though no one realized that the "vibrations" of the wave were electric and magnetic fields. For the first time, polarization could be understood quantitatively, as Fresnel's equations correctly predicted the differing behaviour of waves of the ''s'' and ''p'' polarizations incident upon a material interface. Overview When light strikes the interface between a medium with refractive index ''n''1 and a second medium with refractive index ''n''2, both reflection and refraction of the light may occur. The Fresnel equations give the ratio of the ''reflected'' wave's electric field to the incident wave's electric field, and the ratio of the ''transmitted'' wave's electri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrical Parameters
Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by Maxwell's equations. Various common phenomena are related to electricity, including lightning, static electricity, electric heating, electric discharges and many others. The presence of an electric charge, which can be either positive or negative, produces an electric field. The movement of electric charges is an electric current and produces a magnetic field. When a charge is placed in a location with a non-zero electric field, a force will act on it. The magnitude of this force is given by Coulomb's law. If the charge moves, the electric field would be doing work on the electric charge. Thus we can speak of electric potential at a certain point in space, which is equal to the work done by an external agent in carrying a unit of positiv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Engineering Ratios
Engineering is the use of scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline of engineering encompasses a broad range of more specialized fields of engineering, each with a more specific emphasis on particular areas of applied mathematics, applied science, and types of application. See glossary of engineering. The term ''engineering'' is derived from the Latin ''ingenium'', meaning "cleverness" and ''ingeniare'', meaning "to contrive, devise". Definition The American Engineers' Council for Professional Development (ECPD, the predecessor of ABET) has defined "engineering" as: The creative application of scientific principles to design or develop structures, machines, apparatus, or manufacturing processes, or works utilizing them singly or in combination; or to construct or operate the same with full cognizance of their design; or to forecast their behavior under specifi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Electronics
Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates the waves, and received by another antenna connected to a radio receiver. Radio is very widely used in modern technology, in radio communication, radar, radio navigation, remote control, remote sensing, and other applications. In radio communication, used in radio and television broadcasting, cell phones, two-way radios, wireless networking, and satellite communication, among numerous other uses, radio waves are used to carry information across space from a transmitter to a receiver, by modulating the radio signal (impressing an information signal on the radio wave by varying some aspect of the wave) in the transmitter. In radar, used to locate and track objects like aircraft, ships, spacecraft a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wave Mechanics
Wave mechanics may refer to: * the mechanics of waves * the ''wave equation'' in quantum physics, see Schrödinger equation See also * Quantum mechanics * Wave equation The (two-way) wave equation is a second-order linear partial differential equation for the description of waves or standing wave fields — as they occur in classical physics — such as mechanical waves (e.g. water waves, sound waves and s ... {{Disambiguation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MIL-STD-188
MIL-STD-188 is a series of U.S. military standards relating to telecommunications. Purpose Faced with "past technical deficiencies in telecommunications systems and equipment and software…that were traced to basic inadequacies in the application of telecommunication standards and to the lack of a well defined…program for their review, control and implementation", the U.S. Department of Defense looked to develop a series of standards that would alleviate the problem. By 1988, the U.S. Department of Defense (DoD) issued Instruction 4630.8 (reissued in 1992, 2002, 2004) stating its policy that "all forces for joint and combined operations be supported through compatible, interoperable, and integrated Command, Control, Communications, and Intelligence systems. … nd that all suchsystems developed for use by U.S. forces are considered to be for joint use." To achieve this the director of the Defense Information Systems Agency (DISA) is charged with "developing information techn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Federal Standard 1037C
Federal Standard 1037C, titled Telecommunications: Glossary of Telecommunication Terms, is a United States Federal Standard issued by the General Services Administration pursuant to the Federal Property and Administrative Services Act of 1949, as amended. This document provides federal departments and agencies a comprehensive source of definitions of terms used in telecommunications and directly related fields by international and U.S. government telecommunications specialists. As a publication of the U.S. government, prepared by an agency of the U.S. government, it appears to be mostly available as a public domain resource, but a few items are derived from copyrighted sources: where this is the case, there is an attribution to the source. This standard was superseded in 2001 by American National Standard T1.523-2001, Telecom Glossary 2000, which is published by ATIS. The old standard is still frequently used, because the new standard is protected by copyright, as usual for A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Time Domain Reflectometer
An optical time-domain reflectometer (OTDR) is an optoelectronic instrument used to characterize an optical fiber. It is the optical equivalent of an electronic time domain reflectometer which measures the impedance of the cable or transmission line under test. An OTDR injects a series of optical pulses into the fiber under test and extracts, from the same end of the fiber, light that is scattered ( Rayleigh backscatter) or reflected back from points along the fiber. The scattered or reflected light that is gathered back is used to characterize the optical fiber. The strength of the return pulses is measured and integrated as a function of time, and plotted as a function of length of the fiber. Reliability and quality of OTDR equipment The reliability and quality of an OTDR is based on its accuracy, measurement range, ability to resolve and measure closely spaced events, measurement speed, and ability to perform satisfactorily under various environmental extremes and after var ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Time-domain Reflectometer
A time-domain reflectometer (TDR) is an electronic instrument used to determine the characteristics of electrical lines by observing reflected waveforms. It can be used to characterize and locate faults in metallic cables (for example, twisted pair wire or coaxial cable). It can also be used to locate discontinuities in a connector, printed circuit board, or any other electrical path. Description A TDR measures reflections along a conductor. In order to measure those reflections, the TDR will transmit an incident signal onto the conductor and listen for its reflections. If the conductor is of a uniform impedance and is properly terminated, then there will be no reflections and the remaining incident signal will be absorbed at the far-end by the termination. Instead, if there are impedance variations, then some of the incident signal will be reflected back to the source. A TDR is similar in principle to radar. The impedance of the discontinuity can be determined from the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Signal Reflection
In telecommunications, signal reflection occurs when a signal is transmitted along a transmission medium, such as a copper cable or an optical fiber. Some of the signal power may be reflected back to its origin rather than being carried all the way along the cable to the far end. This happens because imperfections in the cable cause impedance mismatches and non-linear changes in the cable characteristics. These abrupt changes in characteristics cause some of the transmitted signal to be reflected. In radio frequency (RF) practice this is often measured in a dimensionless ratio known as voltage standing wave ratio (VSWR) with a VSWR bridge. The ratio of energy bounced back depends on the impedance mismatch. Mathematically, it is defined using the reflection coefficient. Because the principles are the same, this concept is perhaps easiest to understand when considering an optical fiber. Imperfections in the glass create mirrors that reflect the light back along the fiber. Impe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mismatch Loss
Mismatch loss in transmission line theory is the amount of power expressed in decibels that will not be available on the output due to impedance mismatches and signal reflections. A transmission line that is properly terminated, that is, terminated with the same impedance as that of the characteristic impedance of the transmission line, will have no reflections and therefore no mismatch loss. Mismatch loss represents the amount of power wasted in the system. It can also be thought of as the amount of power gained if the system was perfectly matched. Impedance matching is an important part of RF system design; however, in practice there will likely be some degree of mismatch loss. In real systems, relatively little loss is due to mismatch loss and is often on the order of 1dB. Calculation Mismatch loss (ML) is the ratio of incident power to the difference between incident and reflected power: : ML_\mathrm = 10 \log_ \bigg(\frac\bigg) \, : P_r=P_i - P_d\, where P_i = inc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
