en>Spinningspark: Reverted good faith edits by 130.215.172.151 (talk): Rv gratuitous emphasis. We don't use bolding for that in any case. (TW)

2014-12-14T13:12:11Z

Reverted good faith edits by 130.215.172.151 (talk): Rv gratuitous emphasis. We don't use bolding for that in any case. (TW)

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96.224.66.100: ugh stop confusing these. it even explains this later in the article

2014-02-21T20:37:31Z

ugh stop confusing these. it even explains this later in the article

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en>Kvng: simplify

2014-01-26T14:38:28Z

simplify

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			{{refimprove\|date=February 2011}}
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			[[Image:bandlimited2.svg\|thumb\|Spectrum of a '''baseband signal''', energy as a function of frequency\|right\|300px]]
			In [[telecommunications]] and [[signal processing]], '''''baseband''''' is an adjective that describes signals and systems whose range of [[frequencies]] is measured from close to 0 hertz to a [[cut-off frequency]] (a maximum bandwidth or highest signal frequency); it is sometimes used as a noun for a band of frequencies starting close to zero. Baseband can often be considered a synonym to '''lowpass''' or '''non-modulated''', and antonym to [[passband]], [[bandpass]], [[modulation\|carrier-modulated]], [[intermediate frequency]], or [[RF signal\|radio frequency (RF)]]. The term is often used in contrast to ''[[passband]]'', which refers to a signal which has been translated to a higher frequency, often for transmission by [[frequency division multiplexing]].

			==Various uses==

			===Baseband bandwidth===
			A ''baseband [[bandwidth (signal processing)\|bandwidth]]'' is equal to the highest frequency of a signal or system, or an upper bound on such frequencies,<ref>{{cite book \| title = Information, Transmission, Modulation and Noise: A Unified Approach to Communication Systems \| author = Mischa Schwartz \| publisher = McGraw-Hill \| year = 1970\| url = http://books.google.com/books?id=-gkjAAAAMAAJ&q=baseband-bandwidth&dq=baseband-bandwidth&pgis=1 }}</ref> for example the upper [[cut-off frequency]] of a passband filter. By contrast, passband bandwidth is the difference between a highest frequency and a nonzero lowest frequency.

			===Baseband channel===
			A ''baseband channel'' or ''lowpass channel'' (or ''system'', or ''network'') is a [[communication channel]] that can transfer frequencies that are very near zero.<ref>{{cite book \| title = Digital Signal Transmission \| author = Chris C. Bissell and David A. Chapman \| publisher = Cambridge University Press \| year = 1992 \| isbn = 0-521-42557-3 \| url = http://books.google.com/books?id=cj12nN2uW0AC&pg=PA149&dq=called-baseband-channels}}</ref> Examples are serial cables and [[local area network]]s (LANs), as opposed to [[passband]] channels such as radio frequency channels and passband filtered wires of the analog telephone network. [[Frequency division multiplexing]] (FDM) allows an analog telephone wire to carry a baseband telephone call, concurrently as one or several carrier-modulated telephone calls.

			===Digital baseband transmission===
			{{Main\|Line code}}
			Digital baseband transmission, also known as [[line coding]],<ref>{{cite book \| title = CMOS Data Converters for Communications \| author = Mikael Gustavsson and J. Jacob Wikner \| publisher = Springer \| year = 2000 \| isbn = 0-7923-7780-X \| url = http://books.google.com/books?id=D_I2XvNOc4wC&pg=PA28&dq=passband+baseband}}</ref> aims at transferring a digital bit stream over baseband channel, typically an unfiltered wire, contrary to [[passband]] transmission, also known as ''carrier-modulated'' transmission.<ref>{{cite book \| title = Digital Baseband Transmission and Recording \| author = Jan W. M. Bergmans \| publisher = Springer \| isbn = 0-7923-9775-4 \| year = 1996 \| url =http://books.google.com/books?id=TN-sTybrCLsC&pg=PR11&dq=baseband+carrier-modulated}}</ref> Passband transmission makes communication possible over a bandpass filtered channel, such as the telephone network local-loop or a band-limited wireless channel.

			An unfiltered wire is intrinsically a low-pass transmission channel, while a line code is intrinsically a pulse wave signal that occupies a frequency [[Fourier series\|spectrum]] of infinite bandwidth. According to the [[Nyquist rate\|Nyquist theorem]], error-free detection of the line code requires a channel bandwidth of at least the [[Nyquist rate]], which is half the line code [[pulse rate]].

			====Baseband transmission in Ethernet {{anchor\|Baseband_Ethernet}}====
			The word "BASE" in [[Ethernet physical layer]] standards, for example [[10BASE5]], [[100BASE-T]] and [[1000BASE-SX]], implies baseband digital transmission, i.e. that a [[line code]] and an unfiltered wire are used.

			This is contrary to [[10PASS-TS]] Ethernet, where "PASS" implies passband transmission. Passband digital transmission requires a [[digital modulation]] scheme, often provided by [[modem]] equipment. In the 10PASS-TS case the [[VDSL]] standard is utilized, which is based on the [[Discrete multi-tone modulation]] (DMT) scheme. Other examples of passband network access technologies are wireless networks and [[cable modem]]s.

			===Baseband processor===
			A [[baseband processor]] is a chip in wireless transmission devices such as mobile phones, that performs signal processing and implements the device's realtime radio transmission operations.

			===Baseband signal===
			A ''baseband [[Signal (electronics)\|signal]]'' or ''lowpass signal'' is a signal that can include frequencies that are very near zero, by comparison with its highest frequency (for example, a sound waveform can be considered as a baseband signal, whereas a radio signal or any other modulated signal is not).<ref>{{cite book \| title = Communication System Design Using Dsp Algorithms: With Laboratory Experiments for the TMS320C30 \| author = Steven Alan Tretter \| publisher = Springer \| year = 1995 \| isbn = 0-306-45032-1 \| url = http://books.google.com/books?id=deHQeNxHhyEC&pg=PA65&dq=baseband-signal+lowpass-signal#PPA66,M1 }}</ref>

			A signal '''"at baseband"''' is usually considered to include frequencies from near 0 [[Hertz\|Hz]] up to the highest frequency in the signal with significant power.

			In general, [[signal (information theory)\|signals]] can be described as including a whole range of different [[frequencies]] [[spectral density\|added together]]. In [[telecommunication]]s in particular, it is often the case that those parts of the signal which are at low frequencies are "copied" up to higher frequencies for [[transmission (telecommunications)\|transmission]] purposes, since there are few communications media that will pass low frequencies without distortion. Then, the original, low frequency components are referred to as the '''baseband''' signal. Typically, the new, high-frequency copy is referred to as the "RF" ([[radio frequency\|radio-frequency]]) signal. A baseband signal is a low frequency signal which when modulated is transmitted on various channels.

			===Equivalent baseband signal===
			An ''equivalent baseband signal'' or ''equivalent lowpass signal'' is – in analog and digital modulation methods with constant carrier frequency (for example [[Amplitude-shift keying\|ASK]], [[Phase-shift keying\|PSK]] and [[Quadrature amplitude modulation\|QAM]], but not [[Frequency-shift keying\|FSK]]) – a complex valued representation of the modulated physical signal (the so-called [[passband]] signal or [[radio frequency\|RF]] signal). The equivalent baseband signal is <math>Z(t)=I(t)+jQ(t)\,</math> where <math>I(t)</math> is the inphase signal, <math>Q(t)</math> the quadrature phase signal, and <math>j</math> the imaginary unit. In a digital modulation method, the <math>I(t)</math> and <math>Q(t)</math> signals of each modulation symbol are evident from the [[constellation diagram]]. The frequency spectrum of this signal includes negative as well as positive frequencies. The physical passband signal corresponds to
			:<math>I(t)\cos(\omega t) - Q(t)\sin(\omega t) = \mathrm{Re}\{Z(t)e^{j\omega t}\}\,</math> <br> where <math>\omega</math> is the carrier angular frequency in rad/s.

			In an ''equivalent baseband model'' of a communication system, the modulated signal is replaced by a complex valued equivalent baseband signal with carrier frequency of 0 hertz, and the [[radio frequency\|RF]] channel is replaced by an equivalent baseband channel model where the frequency response is transferred to baseband frequencies.

			==Modulation==

			A signal '''at baseband''' is often used to [[modulation\|modulate]] a higher frequency [[carrier wave]] in order that it may be transmitted via radio. Modulation results in shifting the signal up to much higher frequencies (radio frequencies, or RF) than it originally spanned. A key consequence of the usual [[double sideband\|double-sideband]] [[amplitude modulation]] (AM) is that the range of frequencies the signal spans (its spectral [[Bandwidth (signal processing)\|bandwidth]]) is doubled. Thus, the RF bandwidth of a signal (measured from the lowest frequency as opposed to 0 Hz) is twice its baseband bandwidth. Steps may be taken to reduce this effect, such as [[single-sideband modulation]]. Some transmission schemes such as [[frequency modulation]] use even more bandwidth.

			The figure shows what happens with AM modulation:

			[[Image:Baseband to RF.svg\|center\|frame\|Comparison of the equivalent baseband version of a signal and its AM-modulated (double-[[sideband]]) RF version, showing the typical doubling of the occupied bandwidth.]]

			Some signals can be treated as baseband or not, depending on the situation. For example, a switched analog connection in the telephone network has energy below 300 Hz and above 3400 Hz removed by [[bandpass filter]]ing; since the signal has no energy very close to zero frequency, it may not be considered a baseband signal, but in the telephone system's [[frequency-division multiplexing]] hierarchy, it is usually treated as a baseband signal, by comparison with the modulated signals used for long-distance transmission. The 300 Hz lower band edge in this case is treated as "near zero", being a small fraction of the upper band edge.

			The simplest definition is that a signal's baseband bandwidth is its bandwidth before [[modulation]] and [[multiplexing]], or after [[demultiplexing]] and [[demodulation]].

			The [[composite video]] signal created by devices such as most newer [[VCR]]s, [[game console]]s and [[DVD]] players is a commonly used baseband signal.

			==See also==
			*[[Broadband]] – generally refers to transmission of data over numerous frequencies
			*[[Wideband]] – a communications medium or signal that spans a large (continuous) range of frequencies, or is wide compared to something else
			*[[Narrowband]] – the opposite of wideband

			==References==
			{{Reflist\|30em}}

			[[Category:Signal processing]]

en>Spinningspark: WP:ENGVAR - see User Talk:Spinningspark#Sensory appendages. Undid revision 498288263 by C6H3N3O3 (talk)

2012-06-19T08:44:03Z

WP:ENGVAR - see User Talk:Spinningspark#Sensory appendages. Undid revision 498288263 by C6H3N3O3 (talk)

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Not a great deal to share really, ordinary web chap, participate in online blogging, walking and sports. Enthusiastic interest in house hold enhancements and body building science. Live in the UK in a little town in the middle of obscurity with literally almost nothing to do<br><br>my homepage; steam showers ([http://www.youtube.com/watch?v=DnPzDZaU-vc this contact form])

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en>Spinningspark: Reverted good faith edits by 130.215.172.151 (talk): Rv gratuitous emphasis. We don't use bolding for that in any case. (TW)

96.224.66.100: ugh stop confusing these. it even explains this later in the article

en>Kvng: simplify

en>Spinningspark: WP:ENGVAR - see User Talk:Spinningspark#Sensory appendages. Undid revision 498288263 by C6H3N3O3 (talk)