HOME TheInfoList.com
Providing Lists of Related Topics to Help You Find Great Stuff
[::MainTopicLength::#1500] [::ListTopicLength::#1000] [::ListLength::#15] [::ListAdRepeat::#3]

picture info

Amplitude Modulation
AMPLITUDE MODULATION (AM) is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave . In amplitude modulation, the amplitude (signal strength) of the carrier wave is varied in proportion to the waveform being transmitted. That waveform may, for instance, correspond to the sounds to be reproduced by a loudspeaker , or the light intensity of television pixels. This technique contrasts with frequency modulation , in which the frequency of the carrier signal is varied, and phase modulation , in which its phase is varied. AM was the earliest modulation method used to transmit voice by radio. It was developed during the first two decades of the 20th century beginning with Landell de Moura and Reginald Fessenden
Reginald Fessenden
's radiotelephone experiments in 1900
[...More...]

"Amplitude Modulation" on:
Wikipedia
Google
Yahoo

picture info

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 pulse. 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
[...More...]

"Pulse-amplitude Modulation" on:
Wikipedia
Google
Yahoo

picture info

Two-way Radio
A TWO-WAY RADIO is a radio that can do both transmit and receive a signal (a transceiver ), unlike a broadcast receiver which only receives content. A two-way radio (transceiver) allows the operator to have a conversation with other similar radios operating on the same radio frequency (channel). Two-way radios are available in mobile , stationary base and hand-held portable configurations. Hand-held radios are often called walkie-talkies , handie-talkies, or just hand-helds. Two-way radio
Two-way radio
systems usually operate in a half-duplex mode; that is, the operator can talk, or he can listen, but not at the same time. A push-to-talk or Press To Transmit button activates the transmitter; when it is released the receiver is active. A mobile phone or cellular telephone is an example of a two-way radio that can transmit and receive at the same time, i.e., in full-duplex mode
[...More...]

"Two-way Radio" on:
Wikipedia
Google
Yahoo

picture info

Pulse-code Modulation
PULSE-CODE MODULATION (PCM) is a method used to digitally represent sampled analog signals . It is the standard form of digital audio in computers, compact discs , digital telephony and other digital audio applications. In a PCM stream , the amplitude of the analog signal is sampled regularly at uniform intervals, and each sample is quantized to the nearest value within a range of digital steps. LINEAR PULSE-CODE MODULATION (LPCM) is a specific type of PCM where the quantization levels are linearly uniform. This is in contrast to PCM encodings where quantization levels vary as a function of amplitude (as with the A-law algorithm or the μ-law algorithm ). Though PCM is a more general term, it is often used to describe data encoded as LPCM
[...More...]

"Pulse-code Modulation" on:
Wikipedia
Google
Yahoo

picture info

Pulse-width Modulation
PULSE-WIDTH MODULATION (PWM), or PULSE-DURATION MODULATION (PDM), is a modulation technique used to encode a message into a pulsing signal . Although this modulation technique can be used to encode information for transmission, its main use is to allow the control of the power supplied to electrical devices, especially to inertial loads such as motors. In addition, PWM is one of the two principal algorithms used in photovoltaic solar battery chargers, the other being maximum power point tracking . The average value of voltage (and current ) fed to the load is controlled by turning the switch between supply and load on and off at a fast rate. The longer the switch is on compared to the off periods, the higher the total power supplied to the load. The PWM switching frequency has to be much higher than what would affect the load (the device that uses the power), which is to say that the resultant waveform perceived by the load must be as smooth as possible
[...More...]

"Pulse-width Modulation" on:
Wikipedia
Google
Yahoo

picture info

Delta-sigma Modulation
DELTA-SIGMA (ΔΣ; or SIGMA-DELTA, ΣΔ) modulation is a method for encoding analog signals into digital signals as found in an analog-to-digital converter (ADC). It is also used to transfer high bit-count low frequency digital signals into lower bit-count higher frequency digital signals as part of the process to convert digital signals into analog as part of a digital-to-analog converter (DAC). In a conventional ADC, an analog signal is integrated, or sampled, with a sampling frequency and subsequently quantized in a multi-level quantizer into a digital signal. This process introduces quantization error noise. The first step in a delta-sigma modulation is delta modulation. In delta modulation the change in the signal (its delta) is encoded, rather than the absolute value. The result is a stream of pulses, as opposed to a stream of numbers as is the case with PCM
[...More...]

"Delta-sigma Modulation" on:
Wikipedia
Google
Yahoo

picture info

Modem
A MODEM (MOdulator-DEModulator) is a network hardware device that modulates one or more carrier wave signals to encode digital information for transmission and demodulates signals to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data. Modems can be used with any means of transmitting analog signals, from light emitting diodes to radio . A common type of modem is one that turns the digital data of a computer into modulated electrical signal for transmission over telephone lines and demodulated by another modem at the receiver side to recover the digital data. Modems are generally classified by the maximum amount of data they can send in a given unit of time , usually expressed in bits per second (symbol BIT/S, sometimes abbreviated "bps"), or bytes per second (symbol B/S). Modems can also be classified by their symbol rate , measured in baud
[...More...]

"Modem" on:
Wikipedia
Google
Yahoo

picture info

Line Code
In telecommunication , a LINE CODE is a code chosen for use within a communications system for transmitting a digital signal down a line. Line coding is often used for digital data transport. Some line codes are DIGITAL BASEBAND MODULATION or DIGITAL BASEBAND TRANSMISSION methods, and these are baseband line codes that are used when the line can carry DC components. Line coding consists of representing the digital signal to be transported, by a waveform that is appropriate for the specific properties of the physical channel (and of the receiving equipment). The pattern of voltage, current or photons used to represent the digital data on a transmission link is called line encoding. The common types of line encoding are unipolar , polar , bipolar , and Manchester encoding
[...More...]

"Line Code" on:
Wikipedia
Google
Yahoo

picture info

Landell De Moura
FATHER ROBERTO LANDELL DE MOURA (January 21, 1861 – June 30, 1928) was a Brazilian Roman Catholic
Roman Catholic
priest and inventor who publicly demonstrated a radio broadcast of the human voice on June 3, 1900. Landell de Moura
Landell de Moura
was ordained to the priesthood in 1886 in Rome
Rome
. He also studied the physical sciences, and following his radio broadcast over 8 km in São Paulo
São Paulo
, he was granted a Brazilian patent on March 9, 1901. Landell de Moura
Landell de Moura
then travelled to the United States
United States
and secured three patents there, for a Wave Transmitter on October 11, 1904, a Wireless Telephone, and a Wireless Telegraph, both dated November 22, 1904. His subsequent requests to the Brazilian government for assistance in developing his invention were denied, and his efforts then languished
[...More...]

"Landell De Moura" on:
Wikipedia
Google
Yahoo

picture info

Frequency
FREQUENCY is the number of occurrences of a repeating event per unit of time . It is also referred to as TEMPORAL FREQUENCY, which emphasizes the contrast to spatial frequency and angular frequency . The PERIOD is the duration of time of one cycle in a repeating event, so the period is the reciprocal of the frequency. For example, if a newborn baby's heart beats at a frequency of 120 times a minute, its period—the time interval between beats—is half a second (that is, 60 seconds divided by 120 beats ). Frequency
Frequency
is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio (sound ) signals, radio waves , and light
[...More...]

"Frequency" on:
Wikipedia
Google
Yahoo

picture info

Phase (waves)
PHASE is the position of a point in time (an instant) on a waveform cycle. A complete cycle is defined as the interval required for the waveform to return to its arbitrary initial value. The graphic to the right shows how one cycle constitutes 360° of phase. The graphic also shows how phase is sometimes expressed in radians , where one radian of phase equals approximately 57.3°. Phase can also be an expression of relative displacement between two corresponding features (for example, peaks or zero crossings) of two waveforms having the same frequency . In sinusoidal functions or in waves "PHASE" has two different, but closely related, meanings. One is the initial angle of a sinusoidal function at its origin and is sometimes called PHASE OFFSET or PHASE DIFFERENCE. Another usage is the fraction of the wave cycle that has elapsed relative to the origin
[...More...]

"Phase (waves)" on:
Wikipedia
Google
Yahoo

picture info

Loudspeaker
A LOUDSPEAKER (or LOUD-SPEAKER or SPEAKER) is an electroacoustic transducer ; which converts an electrical audio signal into a corresponding sound . The most widely used type of speaker in the 2010s is the DYNAMIC SPEAKER, invented in 1925 by Edward W. Kellogg and Chester W. Rice . The dynamic speaker operates on the same basic principle as a dynamic microphone , but in reverse, to produce sound from an electrical signal. When an alternating current electrical audio signal is applied to its voice coil , a coil of wire suspended in a circular gap between the poles of a permanent magnet , the coil is forced to move rapidly back and forth due to Faraday\'s law of induction , which causes a diaphragm (usually conically shaped) attached to the coil to move back and forth, pushing on the air to create sound waves . Besides this most common method, there are several alternative technologies that can be used to convert an electrical signal into sound
[...More...]

"Loudspeaker" on:
Wikipedia
Google
Yahoo

Hierarchical Modulation
HIERARCHICAL MODULATION, also called LAYERED MODULATION, is one of the signal processing techniques for multiplexing and modulating multiple data streams into one single symbol stream, where base-layer symbols and enhancement-layer symbols are synchronously overplayed before transmission. Hierarchical modulation is particularly used to mitigate the cliff effect in digital television broadcast, particularly mobile TV , by providing a (lower quality) fallback signal in case of weak signals, allowing graceful degradation instead of complete signal loss. It has been widely proven and included in various standards, such as DVB-T
DVB-T
, MediaFLO
MediaFLO
, UMB ( Ultra Mobile Broadband , a new 3.5th generation mobile network standard developed by 3GPP2), and is under study for DVB-H
DVB-H

[...More...]

"Hierarchical Modulation" on:
Wikipedia
Google
Yahoo

Wavelet Modulation
WAVELET MODULATION, also known as FRACTAL MODULATION, is a modulation technique that makes use of wavelet transformations to represent the data being transmitted. One of the objectives of this type of modulation is to send data at multiple rates over a channel that is unknown. If the channel is not clear for one specific bit rate , meaning that the signal will not be received, the signal can be sent at a different bit rate where the signal to noise ratio is higher. SEE ALSO * Wavelet
Wavelet
REFERENCES * ^ Wavelet
Wavelet
Modulation
Modulation
in Gaussian and Rayleigh Fading Channels, Manish J. Manglani, (Masters thesis) This article related to telecommunications is a stub . You can help by expanding it
[...More...]

"Wavelet Modulation" on:
Wikipedia
Google
Yahoo

picture info

Carrier Signal
In telecommunications , a CARRIER WAVE, CARRIER SIGNAL, or just CARRIER, is a waveform (usually sinusoidal ) that is modulated (modified) with an input signal for the purpose of conveying information. This carrier wave usually has a much higher frequency than the input signal does. The purpose of the carrier is usually either to transmit the information through space as an electromagnetic wave (as in radio communication), or to allow several carriers at different frequencies to share a common physical transmission medium by frequency division multiplexing (as, for example, a cable television system). The term is also used for an unmodulated emission in the absence of any modulating signal. Most radio systems in the 20th century used frequency modulation (FM) or amplitude modulation (AM) to make the carrier carry information. The frequency of a radio or television station is actually the carrier wave's frequency
[...More...]

"Carrier Signal" on:
Wikipedia
Google
Yahoo

picture info

Trellis Modulation
In telecommunication , TRELLIS MODULATION (also known as TRELLIS CODED MODULATION, or simply TCM) is a modulation scheme that transmits information with high efficiency over band-limited channels such as telephone lines . Gottfried Ungerboeck invented trellis modulation while working for IBM in the 1970s, and first described it in a conference paper in 1976. It went largely unnoticed, however, until he published a new, detailed exposition in 1982 that achieved sudden and widespread recognition. In the late 1980s, modems operating over plain old telephone service (POTS) typically achieved 9.6 kbit/s by employing four bits per symbol QAM modulation at 2,400 baud (symbols/second)
[...More...]

"Trellis Modulation" on:
Wikipedia
Google
Yahoo
.