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8-VSB
8VSB is the modulation method used for broadcast in the ATSC digital television standard. ATSC and 8VSB modulation is used primarily in North America; in contrast, the DVB-T standard uses COFDM. A modulation method specifies how the radio signal fluctuates to convey information. ATSC and DVB-T specify the modulation used for over-the-air digital television; by comparison, QAM is the modulation method used for cable. The specifications for a cable-ready television, then, might state that it supports 8VSB (for broadcast TV) and QAM (for cable TV). 8VSB is an 8-level vestigial sideband modulation. In essence, it converts a binary stream into an octal representation by amplitude-shift keying a sinusoidal carrier to one of eight levels. 8VSB is capable of transmitting three bits (23=8) per symbol; in ATSC, each symbol includes two bits from the MPEG transport stream which are trellis modulated to produce a three-bit figure. The resulting signal is then band-pass filtered with a N ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
COFDM
In telecommunications, orthogonal frequency-division multiplexing (OFDM) is a type of digital transmission and a method of encoding digital data on multiple carrier frequencies. OFDM has developed into a popular scheme for wideband digital communication, used in applications such as digital television and audio broadcasting, DSL internet access, wireless networks, power line networks, and 4G/ 5G mobile communications. OFDM is a frequency-division multiplexing (FDM) scheme that was introduced by Robert W. Chang of Bell Labs in 1966. In OFDM, multiple closely spaced orthogonal subcarrier signals with overlapping spectra are transmitted to carry data in parallel.webe.org - 2GHz BAS Relocation Tech-Fair, COFDM Technology Basics 2007-03-02 Demodula ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orthogonal Frequency-division Multiplexing
In telecommunications, orthogonal frequency-division multiplexing (OFDM) is a type of digital transmission and a method of encoding digital data on multiple carrier frequencies. OFDM has developed into a popular scheme for wideband digital communication, used in applications such as digital television and audio broadcasting, DSL internet access, wireless networks, power line networks, and 4G/ 5G mobile communications. OFDM is a frequency-division multiplexing (FDM) scheme that was introduced by Robert W. Chang of Bell Labs in 1966. In OFDM, multiple closely spaced orthogonal subcarrier signals with overlapping spectra are transmitted to carry data in parallel.webe.org - 2GHz BAS Relocation Tech-Fair, COFDM Technology Basics 2007-03-02 Demodula ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Digital Cable
Digital cable is the distribution of cable television using digital data and video compression. The technology was first developed by General Instrument. By 2000, most cable companies offered digital features, eventually replacing their previous analog-based cable by the mid 2010s. During the late 2000s, broadcast television converted to the digital HDTV standard, which was incompatible with existing analog cable systems. In addition to providing high-definition video, digital cable systems provide more services such as pay-per-view programming, cable internet access and cable telephone services. Most digital cable signals are encrypted, which reduced the incidence of cable television piracy which occurred in analog systems. History In 1990, General Instrument (acquired by Motorola and now owned by ARRIS Group) demonstrated that it was possible to use digital compression to deliver high quality HDTV in a standard 6 MHz television channel. Using the same technology General ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pulse-amplitude Modulation
Pulse-amplitude modulation (PAM) is a form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses. It is an analog pulse modulation scheme in which the amplitudes of a train of carrier pulses are varied according to the sample value of the message signal. Demodulation is performed by detecting the amplitude level of the carrier at every single period. Types There are two types of pulse amplitude modulation: * In ''single polarity PAM'', a suitable fixed DC bias is added to the signal to ensure that all the pulses are positive. * In ''double polarity PAM'', the pulses are both positive and negative. Pulse-amplitude modulation is widely used in modulating signal transmission of digital data, with non-baseband applications having been largely replaced by pulse-code modulation, and, more recently, by pulse-position modulation. The number of possible pulse amplitudes in analog PAM is theoretically infinite. Digital PAM reduces ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Modulation
In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the ''carrier signal'', with a separate signal called the ''modulation signal'' that typically contains information to be transmitted. For example, the modulation signal might be an audio signal representing sound from a microphone, a video signal representing moving images from a video camera, or a digital signal representing a sequence of binary digits, a bitstream from a computer. The carrier is higher in frequency than the modulation signal. In radio communication the modulated carrier is transmitted through space as a radio wave to a radio receiver. Another purpose is to transmit multiple channels of information through a single communication medium, using frequency-division multiplexing (FDM). For example in cable television which uses FDM, many carrier signals, each modulated with a different television channel, are transported through a sing ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gross Bit Rate
In telecommunications and computing, bit rate (bitrate or as a variable ''R'') is the number of bits that are conveyed or processed per unit of time. The bit rate is expressed in the unit bit per second (symbol: bit/s), often in conjunction with an SI prefix such as kilo (1 kbit/s = 1,000 bit/s), mega (1 Mbit/s = 1,000 kbit/s), giga (1 Gbit/s = 1,000 Mbit/s) or tera (1 Tbit/s = 1,000 Gbit/s). The non-standard abbreviation bps is often used to replace the standard symbol bit/s, so that, for example, 1 Mbps is used to mean one million bits per second. In most computing and digital communication environments, one byte per second (symbol: B/s) corresponds to 8 bit/s. Prefixes When quantifying large or small bit rates, SI prefixes (also known as metric prefixes or decimal prefixes) are used, thus: Binary prefixes are sometimes used for bit rates. The International Standard ( IEC 80000-13) specifies different a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Low-pass Filter
A low-pass filter is a filter that passes signals with a frequency lower than a selected 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. In optics, high-pass and low-pass may have different meanings, depending on whether referring to frequency or wavelength of light, since these variables are inversely related. High-pass frequency filters would act as low-pass wavelength filters, and vice versa. For this reason it is a good practice to refer to wavelength filters as ''short-pass'' and ''long-pass'' to avoid confusion, which would correspond to ''high-pass'' and ''low-pass'' frequencies. Low-pass filters exist in many different forms, including electronic circuits such as a hiss filter used in audio, anti-aliasing fil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Effective Radiated Power
Effective radiated power (ERP), synonymous with equivalent radiated power, is an IEEE standardized definition of directional radio frequency (RF) power, such as that emitted by a radio transmitter. It is the total power in watts that would have to be radiated by a half-wave dipole antenna to give the same radiation intensity (signal strength or power flux density in watts per square meter) as the actual source antenna at a distant receiver located in the direction of the antenna's strongest beam (main lobe). ERP measures the combination of the power emitted by the transmitter and the ability of the antenna to direct that power in a given direction. It is equal to the input power to the antenna multiplied by the gain of the antenna. It is used in electronics and telecommunications, particularly in broadcasting to quantify the apparent power of a broadcasting station experienced by listeners in its reception area. An alternate parameter that measures the same thing is effec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NTSC
The first American standard for analog television broadcast was developed by National Television System Committee (NTSC)National Television System Committee (1951–1953), Report and Reports of Panel No. 11, 11-A, 12–19, with Some supplementary references cited in the Reports, and the Petition for adoption of transmission standards for color television before the Federal Communications Commission, n.p., 1953], 17 v. illus., diagrs., tables. 28 cm. LC Control No.:5402138Library of Congress Online Catalog/ref> in 1941. In 1961, it was assigned the designation CCIR System M, System M. In 1953, a second NTSC standard was adopted, which allowed for color television broadcast compatible with the existing stock of black-and-white receivers. It is one of three major color formats for analog television, the others being PAL and SECAM. NTSC color is usually associated with the System M. The only other broadcast television system to use NTSC color was the System J. Since the introdu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quadrature Amplitude Modulation
Quadrature amplitude modulation (QAM) is the name of a family of digital modulation methods and a related family of analog modulation methods widely used in modern telecommunications to transmit information. It conveys two analog message signals, or two digital bit streams, by changing (''modulating'') the amplitudes of two carrier waves, using the amplitude-shift keying (ASK) digital modulation scheme or amplitude modulation (AM) analog modulation scheme. The two carrier waves are of the same frequency and are out of phase with each other by 90°, a condition known as orthogonality or quadrature. The transmitted signal is created by adding the two carrier waves together. At the receiver, the two waves can be coherently separated (demodulated) because of their orthogonality property. Another key property is that the modulations are low-frequency/low-bandwidth waveforms compared to the carrier frequency, which is known as the narrowband assumption. Phase modulation (analog PM) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
4VSB
4VSB is an abbreviation for 4-level vestigial sideband modulation, a type of radio transmission capable of transmitting two bits of information (22=4) at a time. Other faster but less rugged forms include 8VSB 8VSB is the modulation method used for broadcast in the ATSC standards, ATSC digital television standard. ATSC and 8VSB modulation is used primarily in North America; in contrast, the COFDM#DVB-T, DVB-T standard uses COFDM. A modulation method ... and 16VSB. While 2VSB is more rugged, it is also slower. References {{radio-comm-stub Radio modulation modes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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