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Topic: Digital modulation

	Modulation - Wikipedia, the free encyclopedia
		A device that performs modulation is known as a modulator and a device that performs the inverse operation of demodulation is known as a demodulator.
		In digital modulation, the changes in the signal are chosen from a fixed list (the modulation alphabet) each entry of which conveys a different possible piece of information (a symbol).
		Digital modulation schemes are possible because the transmitter-receiver pair have prior knowledge of how data is encoded and represented in the communications system.
	en.wikipedia.org /wiki/Modulation (676 words)

	Quadrature amplitude modulation - Wikipedia, the free encyclopedia
		As with all modulation schemes, QAM conveys data by changing some aspect of a carrier signal, or the carrier wave, (usually a sinusoid) in response to a data signal.
		As for many digital modulation schemes, the constellation diagram is a useful representation and is relied upon in this article.
		Since in digital telecommunications the data is usually binary, the number of points in the grid is usually a power of 2 (2,4,8...).
	en.wikipedia.org /wiki/Quadrature_amplitude_modulation (1334 words)

	Digital Modulation
		The digital signal is converted into light pulses; the laser is on for a “1” and off for a “0.” Time-division multiplexing is used by digital systems to either combine multiple video signals on to one fiber or to create subchannels for digitized audio and/or data signals.
		Digital modulation does not require a linear light source, allowing the light source of a digital system to have a wide range of non-critical operating parameters.
		he accurate transmission of a digitally modulated signal ultimately relies on the optical receiver's ability to detect the transition between a “1” and a “0” in the data stream, a function called a decision circuit.
	www.fiber-optics.info /articles/digital-modulation.htm (757 words)

	Digital television - Wikipedia, the free encyclopedia
		Digital television (DTV) is a telecommunication system for broadcasting and receiving moving pictures and sound by means of digital signals, in contrast to analog signals in analog (traditional) TV.
		It uses digital modulation data, which is digitally compressed and requires decoding by a specially designed television set or a standard receiver with a set-top box.
		However, digital television picture technology is still in its early stages and there are many advances yet to be made in eliminating picture defects not present on analog television or motion picture cinema.
	en.wikipedia.org /wiki/Digital_tv (1389 words)

	Agilent Technologies \| Educator's Corner - Resource Guide for Engineering Educators \| IQ Modulation
		In part (a), since the plot of the modulated carrier is relative to the unmodulated carrier, an unmodulated carrier appears as a fixed vector along the positive I axis.
		Euler's identity is utilized to show that the modulating signal comprises both a positive and negative frequency component; otherwise the modulated carrier would not stay on the I axis.
		The spectrum of the modulated carrier, shown in the upper left corner of the simulation screen, is that of double-sideband, suppressed-carrier amplitude modulation.
	www.educatorscorner.com /index.cgi?CONTENT_ID=2478 (1096 words)

	Analog and Digital Modulation - Tutorial - Developer Zone - National Instruments
		Modulation is a process in which a modulator changes some attribute of a higher frequency carrier signal proportional to a lower frequency message signal.
		Digital modulation is similar to analog modulation, but rather than being able to continuously change the amplitude, frequency, or phase of the carrier, there are only discrete values of these attributes that correspond to digital codes.
		These digital sinusoids are of a lower frequency than the analog oscillators in the IQ modulation scheme, but still at a significantly higher frequency than the message signal.
	zone.ni.com /devzone/conceptd.nsf/webmain/3B9F48EACAAE3D95862570AB00668617?opendocument&node=dz00000_us (753 words)

	Privateline.com: Digital Wireless Basics: Modulation
		Amplitude modulation means a carrier wave is modulated in proportion to the strength of a signal.
		Phase modulation is strictly for digital working and is closely related to F.M. Phase in fact enjoys the same capture effect as F.M. First, a note.
		A digital signal means an ongoing stream of bits, 0s and 1s, on and off pulses of electrical energy.
	www.privateline.com /PCS/modulation.htm (2492 words)

	Digital OSCAR Communications
		Digital communications have a significant and growing impact in the telecommunications industry, and the non-commercial world of amateur radio is no different.
		Either the amplitude of the RF carrier is modulated, or its frequency is modulated, or its instantaneous phase is modulated.
		BPSK is a very robust form of digital modulation and has been used to good advantage in copying extremely weak signals from several interplanetary deep space probes.
	www.amsat.org /amsat/articles/kd2bd/Digital (3463 words)

	Lesson 2 - Modulation Techniques (Site not responding. Last check: 2007-10-31)
		The modulation of digital signals with analogue carriers allows an improvement in signal to noise ratio as compared to analogue modulating schemes.
		Modulation of a carrier by a digital signal is denoted by shift keying because there is a discrete change in the carrier parameters.
		In this case the modulating signal is a binary bit train, which leads to a phase change of the carrier.
	users.deec.ist.utl.pt /~ineit/mt/chapter1/lesson3.htm (436 words)

	Fundamentals of Digital Quadrature Modulation \| RF Design - Digital Quadrature Modulation 101, digital cmos ...
		The concept of modulation is not at all new, it has been around since the early days of radio.
		Modulation, especially in the context of RF applications, refers to the mixing of two sinusoidal signals.
		In figure 1 the functional representation of a single and double sideband modulator are shown along with the associated frequency spectra.
	rfdesign.com /mag/radio_fundamentals_digital_quadrature/index.html (753 words)

	QPSK Modulation Demystified - Maxim/Dallas (Site not responding. Last check: 2007-10-31)
		Digital processing is used to remove phase and frequency errors.
		Frequency modulation and phase modulation presented a certain immunity to noise, whereas amplitude modulation was simpler to demodulate.
		With digital modulation techniques come all the advantages that traditional microprocessor circuits have over their analog counterparts.
	www.maxim-ic.com /tarticle/view_article.cfm/article_id/70 (1456 words)

	Pulse width modulation based digital incremental encoder patent invention (Site not responding. Last check: 2007-10-31)
		A digital incremental encoder for generating an output signal indicative of an angular position, a direction of rotation, and a speed of rotation of a shaft.
		The digital incremental encoder includes a counter for receiving a PWM signal indicative of the angular position of the shaft and a clock signal from an angular position sensor, and generates a multi-bit output.
		The digital incremental encoder system includes an angular position sensor for generating a PWM signal indicative of the angular position of the shaft and a clock signal.
	www.freshpatents.com /Pulse-width-modulation-based-digital-incremental-encoder-dt20051215ptan20050275568.php (1650 words)

	modulation - Glossary - CNET.com (Site not responding. Last check: 2007-10-31)
		Modulation refers to the process of encoding digital data into analog signals for transmission.
		When transferring data over phone lines, for example, a modem modulates the data into audible tones "carried" on frequencies between 0 Hz and 4 KHz.
		But instead of audible tones, cable has sophisticated digital modulation schemes to greatly increase the amount of data that can be sent.
	www.cnet.com /Resources/Info/Glossary/Terms/modulation.html (87 words)

	Tektronix MBD: Products > Digital Modulation Analyzers DMA120 * DMA121 : Intro
		It has been a performance measurement for digital communication systems in the past and provides a means of system comparability for some engineers.
		Digital Channel Average Power: RF signal level measurement is made by integrating all the channel power through a channel bandwidth IF filter.
		Digital transmission is new to most cable TV system technicians and so are measurements to verify performance.
	www.tek.com /Measurement/Products/catalog/dma120 (1403 words)

	Digital modulation method (EP0392506A2) (Site not responding. Last check: 2007-10-31)
		The number of consecutive identical bits in a series of 14-bit digital modulation codes is restricted to 2 - 7.
		The absolute value of DSV at the end of each 14-bit digital modulation code is restricted to 2 or less, and the absolute value of DSV at each bit of any 14-bit digital modulation codes is limited to 7 or less.
		step 4 for further selecting one 14-bit digital modulation code among the selected modulation codes at step 3 so that said one 14-bit digital modulation code satisfies the requirement that the absolute value of bit DSV (Digital Sum Value) for each bit in the modulation code is equal to or less than 7.
	www.delphion.com /details?pn=EP00392506A2 (340 words)

	Digital TV.com.au :: How it Works
		As a modulation scheme, it has to be considered as an additional tool given to RF network planners, to introduce new possibilities in the use of the scarce radio frequency spectrum.
		As shown in figure 7, hierarchical modulation can be viewed as a separation of the RF channel in two virtual circuits, each having a specific bitrate capacity, a specific roughness and accordingly, covering two slightly different areas.
		One primary usage of the hierarchical modulation is to slightly modify the modulation parameters to facilitate the indoor reception for portable receivers.
	www.digital-tv.com.au /howitworks.html (5791 words)

	ELEN E6768: Topics in Telecom: Modern Digital Modulation Technologies (Site not responding. Last check: 2007-10-31)
		The goal of this course is to acquaint the student with modern digital modulations and with their applications in present and future wireless, satellite and wireline systems.
		He is currently working on digital modulation techniques and multiple access techniques for both terrestrial and satellite mobile wireless communications systems.
		CPM modulations are constant-envelope modulations which allow the use of non-linear power-efficient transmitter amplifiers in cellular and space communications.
	www.cvn.columbia.edu /courses/Spring2004/ELENE6768.html (998 words)

	Digital Modulation Test Tools: Instruments With Attitude
		The separation of I/Q pair generation and RF modulation is shown in Figure 2.
		Besides the complexity of the modulation formats, it is important that the I and Q data words change simultaneously even at the generator’s top data rate.
		Maximum modulation bandwidth is 40 MHz for the baseband Model 89610A, 36 MHz for the DC to 2.7-GHz Model 89640A, and 36 MHz for the 6.0-GHz Model 89641.
	www.evaluationengineering.com /archive/articles/0203wire.htm (2018 words)

	DIGITAL MODULATION: REVEALED (Site not responding. Last check: 2007-10-31)
		This is not a digital modulation scheme and class C amplification is used.
		It only takes the analog signal and "modulates" it into a serial data stream.) PCM takes the sampled analog levels and assigns them to one of 256 steps (which can be represented by 8 bits of data).
		As I defined previously, modulation is just frequency shifting and the simplest thing we can do is multiply the baseband signal we just created by a high frequency carrier and end up with "radio".
	www.qsl.net /k9so/DIGITALMODULATION.htm (2624 words)

	Digital Cable Quadrature Amplitude Modulation (QAM) (Site not responding. Last check: 2007-10-31)
		Trellis Coded Modulation (TCM) is an encoder that selects an optimal sequence from the data stream and a map of the QAM constellation.
		The constellation in TCM is usually larger than required for the data stream, and the encoder generates a sequence of wider words mapped such that the transition distances in the constellation are maximized.
		The mapped data pairs are upconverted to an intermediate frequency before transmitting.The digital upconverter (DUC) translates signals from a baseband frequency to the intermediate frequency and the numerically controlled oscillator (NCO) is the key component for the DUC.
	www.altera.com /end-markets/broadcast/delivery/qam/bro-qam.html?f=syshp&k=g2 (617 words)

	SCM analog modulation for 21st century digital content
		The D symbols are transmitted as digital QAM symbols, and the A symbols are combined in pairs and transmitted as analog QAM.
		The analog samples are converted to digital with a resolution of M bits per symbol.
		SCM is a versatile, hybrid analog-digital modulation scheme for transmitting analog signals to provide a repeater function for digital signals.
	rfdesign.com /mag/radio_scm_analog_modulation (2656 words)

	Press Release - Intersil Unveils New Wideband Programmable Modulator for Digital Modulation in Wireless Systems ... (Site not responding. Last check: 2007-10-31)
		PALM BAY, FL, March 17, 2000 — Designers of wideband digital modulation systems looking for higher levels of integration can now incorporate a single signal processing solution into their design for the shaping, upconversion and modulation of quadrature (I/Q) data.
		The data is then shaped with an interpolation filter (24-symbol span) and modulated with programmable sine and cosine carriers from an on-chip carrier NCO.
		The HSP50415 is capable of digital output spectral purity that exceeds 50dB at the maximum output sample rate.
	www.intersil.com /pr/shell/0,1091,109,00.html (711 words)

	Examples of Digital Modulation (Using the Communications Blockset)
		DQPSK Modulator Baseband, in the PM sublibrary of the Digital Baseband sublibrary of Modulation
		The modulated signal's sampling rate of 3000 exceeds the sum of twice the carrier frequency and twice the input sampling rate.
		M-PSK Modulator Passband, in the PM sublibrary of the Digital Passband sublibrary of Modulation
	www.phys.ufl.edu /docs/matlab/toolbox/commblks/usersguide/tutor218.html (942 words)

	Amazon.com: Digital Modulation Techniques: Books: Fuqin Xiong (Site not responding. Last check: 2007-10-31)
		...covers the complete range of digital modulation methods, from traditional techniques to state-of-the-art developments...includes block diagrams and circuits of modulators, clock and carrier recovery, and comparisons with other schemes.
		Explains the full range of today's digital modulation techniques and their practical application to conventional, fixed microwave terrestrial communications, satellite communications, mobile wireless, mobile satellite, and fiber-optic communications.
		Multi-h modulation schemes: This is an important new topic that can't be found in many digital communications books.
	www.amazon.com /Digital-Modulation-Techniques-Fuqin-Xiong/dp/0890069700 (804 words)

	Digital Modulation Techniques (Site not responding. Last check: 2007-10-31)
		The techniques used to transmit analogue signals are used to transmit digital signals.
		The problem is to convert the digital signals to a form that can be treated as an analogue signal that is then in the appropriate form to either be transmitted down a twisted cable pair or applied to the RF stage where is modulated to a frequency that can be transmitted via microwave or satellite.
		There are many different modulation techniques that can be utilised in a modem.
	cbdd.wsu.edu /kewlcontent/cdoutput/TR502/page46.htm (156 words)

	Digital Modulation Schemes (Site not responding. Last check: 2007-10-31)
		In these schemes one is interested in preparing a digital signal of 1s and 0s for transmission.
		The simplest digital modulation scheme is called On Off Keying (OOK): here a signal is turned on in response to a 1 and off in response to a 0.
		Fancier schemes involve modulation in addition to turning a signal on and off.
	robotics.eecs.berkeley.edu /~sastry/ee20/modulation/node5.html (95 words)

	Zaxcom - Digital Wireless (Site not responding. Last check: 2007-10-31)
		Advances in digital modulation, battery technology and electronics miniaturization have allowed an entire rack of equipment to fit into a miniature sized transmitter.
		Digital RF modulation allows us to provide up to 117 dB of dynamic range.
		In the Digital domain it is possible to detect any loss or corruption of audio data.
	www.zaxcom.com /audio/wireless.shtml (1267 words)

	Digital Modulation Overview (Communications Toolbox) (Site not responding. Last check: 2007-10-31)
		Modulating a digital signal can be interpreted as a combination of two steps: mapping the digital signal to an analog signal and modulating the analog signal.
		Except for FSK and MSK methods, when the receiver tries to recover a digital message from the analog signal that it receives, it performs two steps: demodulating the analog signal and demapping the demodulated analog signal to produce a digital message.
		The functions are described in more detail in the sections that follow.
	www-rohan.sdsu.edu /doc/matlab/toolbox/comm/tutor28.html (141 words)

	Frequency Modulation
		FM is a so called angle modulation scheme, it was inspired by phase modulation but has proved to be more useful partly for its ease of generation and decoding.
		is called the frequency deviation of the modulation scheme.
		The index of modulation of an FM signal of the form
	robotics.eecs.berkeley.edu /~sastry/ee20/modulation/node4.html (327 words)

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