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Frequency Band
A frequency band is an interval in the frequency domain, delimited by a lower frequency and an upper frequency. The term may refer to a radio band or an interval of some other spectrum. The frequency range of a system is the range over which it is considered to provide satisfactory performance, such as a useful level of signal with acceptable distortion characteristics. A listing of the upper and lower limits of frequency limits for a system is not useful without a criterion for what the range represents. Many systems are characterized by the range of frequencies to which they respond. Musical instruments produce different ranges of notes within the hearing range. The electromagnetic spectrum can be divided into many different ranges such as visible light, infrared or ultraviolet radiation, radio waves, X-rays and so on, and each of these ranges can in turn be divided into smaller ranges. A radio communications signal must occupy a range of frequencies carrying most of its ener ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mains Hum Spectrum
Mains may refer to: * Mains electricity ("line power" in the United States) * Mains electricity by country * Electricity transmission * Public utility, "mains services", including electricity, natural gas, water, and sewage disposal * Main course, the primary dish of a meal, following a starter * Mains (Scotland), the main buildings of a farm * BMX racing * Water mains * Author abbreviation for Edwin Butterworth Mains See also * Main (other) Main may refer to: Geography *Main River (other) **Most commonly the Main (river) in Germany *Main, Iran, a village in Fars Province *" Spanish Main", the Caribbean coasts of mainland Spanish territories in the 16th and 17th centuries * ... * Mane (other) {{disambig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spectrum Allocation
Frequency allocation (or spectrum allocation or spectrum management) is the allocation and regulation of the electromagnetic spectrum into radio frequency bands, normally done by governments in most countries. Because radio propagation does not stop at national boundaries, governments have sought to harmonise the allocation of RF bands and their standardization. ITU definition The International Telecommunication Union defines frequency allocation as being of "a given frequency band for the purpose of its use by one or more terrestrial or space radiocommunication services or the radio astronomy service under specified conditions".ITU Radio Regulations, Section IV. Radio Stations and Systems – Article 1.16, definition: allocation (of a frequency band). ''Frequency allocation'' is also a special term, used in national frequency administration. Other terms are: Bodies Several bodies set standards for frequency allocation, including: * International Telecommunication Union (IT ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wideband Audio
Wideband audio, also known as wideband voice or HD voice, is high definition voice quality for telephony audio, contrasted with standard digital telephony "toll quality". It extends the frequency range of audio signals transmitted over telephone lines, resulting in higher quality speech. The range of the human voice extends from 100 Hz to 17 kHz but traditional, voiceband or narrowband telephone calls limit audio frequencies to the range of 300 Hz to 3.4 kHz. Wideband audio relaxes the bandwidth limitation and transmits in the audio frequency range of 50 Hz to 7 kHz. In addition, some wideband codecs may use a higher audio bit depth of 16 bits to encode samples, also resulting in much better voice quality. Wideband codecs have a typical sample rate of 16 kHz. For superwideband codecs the typical value is 32 kHz. History In 1987, the International Telecommunication Union (ITU) standardized a version of wideband audio known as G.722. Radio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transition Band
The transition band, also called the skirt, is a range of frequencies that allows a transition between a passband and a stopband of a signal processing filter. The transition band is defined by a passband and a stopband cutoff frequency or corner frequency. This is the area between where a filter "turns the corner" and where it "hits the bottom". An example of this can be taken from a low-pass filter, commonly used in audio systems to allow the bass signal to pass through to a subwoofer, and cut out all unwanted frequencies above a defined point. If the cutoff point for such a filter is defined as 200 Hz, then in a perfect system, all frequencies above 200 Hz will be stopped and all frequencies below 200 Hz will be allowed to pass through. The transition band can be implemented to allow for a smooth fall off to avoid introducing audible peaks in amplitude. If the transition band of the example 200 Hz filter is 20 Hz, then the signal should start attenuat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spectral Width
In telecommunications, spectral width is the wavelength interval over which the magnitude of all spectral components is equal to or greater than a specified fraction of the magnitude of the component having the maximum value. In optical communications applications, the usual method of specifying spectral width is the full width at half maximum. This is the same convention used in bandwidth, defined as the frequency range where power drops by less than half (at most −3 dB). The FWHM method may be difficult to apply when the spectrum has a complex shape. Another method of specifying spectral width is a special case of root-mean-square deviation where the independent variable is wavelength, λ, and ''f'' (λ) is a suitable radiometric quantity. The ''relative spectral width'', Δλ/λ, is frequently used where Δλ is obtained according to note 1, and λ is the center wavelength. See also *Spectral linewidth in optics Optics is the branch of physics that studies the beha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Range (music)
In music, the range, or chromatic range, of a musical instrument is the distance from the lowest to the highest pitch it can play. For a singing voice, the equivalent is vocal range. The range of a musical part is the distance between its lowest and highest note. Compass Among British English speakers, and perhaps others, compass means the same thing as chromatic range—the interval between the lowest and highest note attainable by a voice or musical instrument. Other ranges The terms sounding range, written range, designated range, duration range and dynamic range have specific meanings. The sounding range"Music theory online : musical instrument ranges & names", Brian Blood, Dolmetsch.com, 2009, webpage: Dolmetsch-M29 refers to the pitches produced by an instrument, while the written range refers to the compass (span) of notes written in the sheet music, where the part is sometimes transposed for convenience. A piccolo, for example, typically has a sounding range one o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Window
The radio window is a range of frequencies of electromagnetic radiation that penetrate the earth's atmosphere. It plays an important role in astronomy; up until World War II, astronomers could only use the visible and near infrared portions of the optical window for their measurements. With the development of radio telescopes however, the radio window became more and more utilizable, leading to the development of radio astronomy that provided astrophysicists with valuable observational data. Range Typically, the lower limit of the radio window's range has a value of about 15 MHz (λ ≈ 20 m); the best upper limit achievable from optimal terrestrial observation sites is equal to approximately 1 THz (λ ≈ 0.3 mm). Factors affecting lower and upper limits The lower and upper limits of the radio window's range of frequencies are not fixed; they depend on a variety of factors. Absorption of mid-IR The upper limit is affected by the vibrational transitions of atmospheric mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Band
The radio spectrum is the part of the electromagnetic spectrum with frequencies from 0 Hz to 3,000 GHz (3 THz). Electromagnetic waves in this frequency range, called radio waves, are widely used in modern technology, particularly in telecommunication. To prevent interference between different users, the generation and transmission of radio waves is strictly regulated by national laws, coordinated by an international body, the International Telecommunication Union (ITU). Different parts of the radio spectrum are allocated by the ITU for different radio transmission technologies and applications; some 40 radiocommunication services are defined in the ITU's Radio Regulations (RR). In some cases, parts of the radio spectrum are sold or licensed to operators of private radio transmission services (for example, cellular telephone operators or broadcast television stations). Ranges of allocated frequencies are often referred to by their provisioned use (for example, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 when it is tuned into the desired frequency (channel). 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. Filters In telecommunications, optics, and acoustics, a passband (a band-pass filtered signal) is the portion of the frequency spectrum that is transmitted (with minimum relative loss or maximum relative gain) by some filtering device. In other words, it is a ''band'' of frequencies which ''pass''es through some filter or a set of filters. The accompanying figure shows a schematic of a waveform being filtered by a bandpass filter consisting of a highpass and a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frequency Deviation
Frequency deviation (f_) is used in FM radio to describe the difference between the minimum or maximum extent of a frequency modulated signal, and the nominal center or carrier frequency. The term is sometimes mistakenly used as synonymous with frequency drift, which is an unintended offset of an oscillator from its nominal frequency. The frequency deviation of a radio is of particular importance in relation to bandwidth, because less deviation means that more channels can fit into the same amount of frequency spectrum. The FM broadcasting range between 87.5 and 108 MHz uses a typical channel spacing of 100 or 200 kHz, with a maximum frequency deviation of +/-75 kHz, in some cases leaving a buffer above the highest and below the lowest frequency to reduce interaction with other channels. The most common FM transmitting applications use peak deviations of +/-75 kHz (100 or 200 kHz spacing), +/-5 kHz (15–25 kHz spacing), +/-2.5 kHz (3.75-12 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frequency Allocation
Frequency allocation (or spectrum allocation or spectrum management) is the allocation and regulation of the electromagnetic spectrum into radio frequency bands, normally done by governments in most countries. Because radio propagation does not stop at national boundaries, governments have sought to harmonise the allocation of RF bands and their standardization. ITU definition The International Telecommunication Union defines frequency allocation as being of "a given frequency band for the purpose of its use by one or more terrestrial or space radiocommunication services or the radio astronomy service under specified conditions".ITU Radio Regulations, Section IV. Radio Stations and Systems – Article 1.16, definition: allocation (of a frequency band). ''Frequency allocation'' is also a special term, used in national frequency administration. Other terms are: Bodies Several bodies set standards for frequency allocation, including: * International Telecommunication U ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Free Spectral Range
Free spectral range (FSR) is the spacing in optical frequency or wavelength between two successive reflected or transmitted optical intensity maxima or minima of an interferometer or diffractive optical element. The FSR is not always represented by \Delta\nu or \Delta\lambda, but instead is sometimes represented by just the letters FSR. The reason is that these different terms often refer to the bandwidth or linewidth of an emitted source respectively. In general The free spectral range (FSR) of a cavity in general is given by :\left, \Delta\lambda_\text\ = \frac\left, \left(\frac\right)^ \ or, equivalently, :\left, \Delta\nu_\text\ = \frac\left, \left(\frac\right)^\ These expressions can be derived from the resonance condition \Delta \beta L = 2\pi by expanding \Delta \beta in Taylor series. Here, \beta = k_0 n(\lambda) = \fracn(\lambda) is the wavevector of the light inside the cavity, k_0 and \lambda are the wavevector and wavelength in vacuum, n is the refractive index o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
