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Loading Coil
A LOADING COIL or LOAD COIL is an inductor that is inserted into an electronic circuit to increase its inductance . A loading coil is not a transformer as it does not provide coupling to another circuit. The term originated in the 19th century for inductors used to prevent signal distortion in long-distance telegraph transmission cables. The term is also used for inductors in radio antennas , or between the antenna and its feedline , to make an electrically short antenna resonant at its operating frequency. The concept of loading coils was discovered by Oliver Heaviside
Oliver Heaviside
in studying the problem of slow signalling speed of the first transatlantic telegraph cable in the 1860s. He concluded additional inductance was required to prevent amplitude and time delay distortion of the transmitted signal
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Passband
A PASSBAND is the range of frequencies or wavelengths that can pass through a filter . For example, a radio receiver contains a bandpass filter to select the frequency of the desired radio signal out of all the radio waves picked up by its antenna. The passband of a receiver is the range of frequencies it can receive. A bandpass-filtered signal (that is, a signal with energy only in a passband), is known as a BANDPASS SIGNAL, in contrast to a baseband signal . CONTENTS * 1 Filters * 2 Digital transmission * 3 Details * 4 See also * 5 References FILTERS Unrestricted signal (upper diagram). Bandpass filter
Bandpass filter
applied to signal (middle diagram). Resulting passband signal (bottom diagram). A(f) is the frequency function of the signal or filter in arbitrary units
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Carrier System
A CARRIER SYSTEM is a telecommunications system that transmits information, such as the voice signals of a telephone call and the video signals of television , by modulation of one or multiple carrier signals above the principal voice frequency or data rate. Carrier systems typically transmit multiple channels of communication simultaneously over the shared medium using various forms of multiplexing . Prominent multiplexing methods of the carrier signal are time-division multiplexing (TDM) and frequency-division multiplexing (FDM). A cable television system is an example of frequency-division multiplexing. Many television programs are carried simultaneously on the same coaxial cable by sending each at a different frequency. Multiple layers of multiplexing may ultimately be performed upon a given input signal . For example, in the public switched telephone network , many telephone calls are sent over shared trunk lines by time-division multiplexing
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M-derived Filter
M-DERIVED FILTERS or M-TYPE FILTERS are a type of electronic filter designed using the image method. They were invented by Otto Zobel
Otto Zobel
in the early 1920s. This filter type was originally intended for use with telephone multiplexing and was an improvement on the existing constant k type filter . The main problem being addressed was the need to achieve a better match of the filter into the terminating impedances. In general, all filters designed by the image method fail to give an exact match, but the m-type filter is a big improvement with suitable choice of the parameter m. The m-type filter section has a further advantage in that there is a rapid transition from the cut-off frequency of the pass band to a pole of attenuation just inside the stop band . Despite these advantages, there is a drawback with m-type filters; at frequencies past the pole of attenuation, the response starts to rise again, and m-types have poor stop band rejection
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Audio Frequency
An AUDIO FREQUENCY (abbreviation: AF) or AUDIBLE FREQUENCY is characterized as a periodic vibration whose frequency is audible to the average human. The SI unit of audio frequency is the hertz (Hz). It is the property of sound that most determines pitch . The generally accepted standard range of audible frequencies is 20 to 20,000 Hz, although the range of frequencies individuals hear is greatly influenced by environmental factors. Frequencies below 20 Hz are generally felt rather than heard, assuming the amplitude of the vibration is great enough. Frequencies above 20,000 Hz can sometimes be sensed by young people. High frequencies are the first to be affected by hearing loss due to age and/or prolonged exposure to very loud noises
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Distributed Element Model
In electrical engineering , the DISTRIBUTED ELEMENT MODEL or TRANSMISSION LINE MODEL of electrical circuits assumes that the attributes of the circuit (resistance , capacitance , and inductance ) are distributed continuously throughout the material of the circuit. This is in contrast to the more common lumped element model , which assumes that these values are lumped into electrical components that are joined by perfectly conducting wires. In the distributed element model, each circuit element is infinitesimally small, and the wires connecting elements are not assumed to be perfect conductors ; that is, they have impedance. Unlike the lumped element model, it assumes non-uniform current along each branch and non-uniform voltage along each node. The distributed model is used at high frequencies where the wavelength becomes comparable to the physical dimensions of the circuit, making the lumped model inaccurate
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Cutoff Frequency
In physics and electrical engineering , a CUTOFF FREQUENCY, CORNER FREQUENCY, or BREAK FREQUENCY is a boundary in a system's frequency response at which energy flowing through the system begins to be reduced (attenuated or reflected) rather than passing through. Typically in electronic systems such as filters and communication channels , cutoff frequency applies to an edge in a lowpass , highpass , bandpass , or band-stop characteristic – a frequency characterizing a boundary between a passband and a stopband. It is sometimes taken to be the point in the filter response where a transition band and passband meet, for example, as defined by a 3 dB corner (a frequency for which the output of the circuit is −3 dB of the nominal passband value)
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Low-pass Filter
A LOW-PASS FILTER is a filter that passes signals with a frequency lower than a certain cutoff frequency and attenuates signals with frequencies higher than the cutoff frequency. The exact frequency response of the filter depends on the filter design . The filter is sometimes called a HIGH-CUT FILTER, or TREBLE CUT FILTER in audio applications. A low-pass filter is the complement of a high-pass filter . Low-pass filters exist in many different forms, including electronic circuits such as a HISS FILTER used in audio , anti-aliasing filters for conditioning signals prior to analog-to-digital conversion , digital filters for smoothing sets of data, acoustic barriers, blurring of images, and so on. The moving average operation used in fields such as finance is a particular kind of low-pass filter, and can be analyzed with the same signal processing techniques as are used for other low-pass filters
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Lumped Element Model
The LUMPED ELEMENT MODEL (also called LUMPED PARAMETER MODEL, or LUMPED COMPONENT MODEL) simplifies the description of the behaviour of spatially distributed physical systems into a topology consisting of discrete entities that approximate the behaviour of the distributed system under certain assumptions. It is useful in electrical systems (including electronics ), mechanical multibody systems , heat transfer , acoustics , etc. Mathematically speaking, the simplification reduces the state space of the system to a finite dimension , and the partial differential equations (PDEs) of the continuous (infinite-dimensional) time and space model of the physical system into ordinary differential equations (ODEs) with a finite number of parameters
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Longwave
In radio, LONGWAVE, LONG WAVE or LONG-WAVE, and commonly abbreviated LW, refers to parts of the radio spectrum with wavelengths longer than what was originally called the medium wave broadcasting band. The term is historic, dating from the early 20th century, when the radio spectrum was considered to consist of longwave (LW), medium wave (MW), and short wave (SW) radio bands. Most modern radio systems and devices use wavelengths which would then have been considered 'ultra-short'. In contemporary usage, the term longwave is not defined precisely, and its precise meaning varies. It may be used for radio wavelengths longer than 1,000 metres, i.e. frequencies up to 300 kilohertz (kHz) including the International Telecommunications Union\'s (ITU's) low frequency (LF) (30–300 kHz) and very low frequency (VLF) (3–30 kHz) bands. Sometimes the upper limit is taken to be higher than 300 kHz, but not above the start of the medium wave band at 520 kHz
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Monopole Antenna
A MONOPOLE ANTENNA is a class of radio antenna consisting of a straight rod -shaped conductor, often mounted perpendicularly over some type of conductive surface, called a ground plane . The driving signal from the transmitter is applied, or for receiving antennas the output signal to the receiver is taken, between the lower end of the monopole and the ground plane. One side of the antenna feedline is attached to the lower end of the monopole, and the other side is attached to the ground plane, which is often the Earth. This contrasts with a dipole antenna which consists of two identical rod conductors, with the signal from the transmitter applied between the two halves of the antenna. The monopole is a resonant antenna; the rod functions as an open resonator for radio waves, oscillating with standing waves of voltage and current along its length. Therefore, the length of the antenna is determined by the wavelength of the radio waves it is used with
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Standing Wave Ratio
In radio engineering and telecommunications , STANDING WAVE RATIO (SWR) is a measure of impedance matching of loads to the characteristic impedance of a transmission line or waveguide . Impedance mismatches result in standing waves along the transmission line, and SWR is defined as the ratio of the partial standing wave 's amplitude at an antinode (maximum) to the amplitude at a node (minimum) along the line. The SWR is usually thought of in terms of the maximum and minimum AC voltages along the transmission line, thus called the VOLTAGE STANDING WAVE RATIO or VSWR (sometimes pronounced "vizwar" ). For example, the VSWR value 1.2:1 denotes an AC voltage due to standing waves along the transmission line reaching a peak value 1.2 times that of the minimum AC voltage along that line. The SWR can as well be defined as the ratio of the maximum amplitude to minimum amplitude of the transmission line's currents , electric field strength , or the magnetic field strength
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Inductive Reactance
In electrical and electronic systems, REACTANCE is the opposition of a circuit element to a change in current or voltage , due to that element's inductance or capacitance . The notion of reactance is similar to electrical resistance , but it differs in several respects. In phasor analysis, reactance is used to compute amplitude and phase changes of sinusoidal alternating current going through a circuit element. It is denoted by the symbol X {displaystyle scriptstyle {X}} . An ideal resistor has zero reactance, whereas ideal inductors and capacitors have zero resistance – that is, respond to current only by reactance. The magnitude of the reactance of an inductor rises in proportion to a rise in frequency, while the magnitude of the reactance of a capacitor decreases in proportion to a rise in frequency. As frequency goes up, inductive reactance goes up and capacitive reactance goes down
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Constant K Filter
CONSTANT K FILTERS, also K-TYPE FILTERS, are a type of electronic filter designed using the image method. They are the original and simplest filters produced by this methodology and consist of a ladder network of identical sections of passive components. Historically, they are the first filters that could approach the ideal filter frequency response to within any prescribed limit with the addition of a sufficient number of sections. However, they are rarely considered for a modern design, the principles behind them having been superseded by other methodologies which are more accurate in their prediction of filter response. CONTENTS * 1 History * 2 Terminology * 3 Derivation * 3.1 Image impedance * 3.2 Transmission parameters * 3.3 Prototype transformations * 4 Cascading sections * 5 See also * 6 Notes * 7 References * 8 Further reading HISTORYConstant k filters were invented by George Campbell
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Capacitive Reactance
In electrical and electronic systems, REACTANCE is the opposition of a circuit element to a change in current or voltage , due to that element's inductance or capacitance . The notion of reactance is similar to electrical resistance , but it differs in several respects. In phasor analysis, reactance is used to compute amplitude and phase changes of sinusoidal alternating current going through a circuit element. It is denoted by the symbol X {displaystyle scriptstyle {X}} . An ideal resistor has zero reactance, whereas ideal inductors and capacitors have zero resistance – that is, respond to current only by reactance. The magnitude of the reactance of an inductor rises in proportion to a rise in frequency, while the magnitude of the reactance of a capacitor decreases in proportion to a rise in frequency. As frequency goes up, inductive reactance goes up and capacitive reactance goes down
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Electrical Resistance
The ELECTRICAL RESISTANCE of an electrical conductor is a measure of the difficulty to pass an electric current through that conductor. The inverse quantity is ELECTRICAL CONDUCTANCE, and is the ease with which an electric current passes. Electrical resistance shares some conceptual parallels with the notion of mechanical friction . The SI unit of electrical resistance is the ohm (Ω ), while electrical conductance is measured in siemens (S). An object of uniform cross section has a resistance proportional to its resistivity and length and inversely proportional to its cross-sectional area. All materials show some resistance, except for superconductors , which have a resistance of zero
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