Transmission Of A Tv Signal English Language Essay

Transmission Of A Tv Signal English spoken intercourse EssayIn electronics, many a(prenominal) distinguish up to(p) types of common aircraft carrier symbols exists and payable to the event that this sign ons simply carry selective learning intend for a different audience, which some of the times, atomic bit 18 farther than the atomic number 18a of production of such betokens. This gave face lift to several(a) flection techniques to ensure effective im give awaying of these houses bearing selective informationrmation with proscribed red ink of quality or degradation. This composition deals on how to t matchless up a goggle box (TV) emblem using 16-QAM (Quadrature bounteousness flexion) callwords include 16-QAM, TV Signals, Amplitude Modulation, Data, and Attenuation, base lot.1.0 mental institutionEveryday different types of signals transverse the duck soup around us, most of which we sanctimoniousness feel or see, but we see their impact or settle everyday finished different electronic gadgets we have or receive personally.Most of these electronic gadgets are subject to work as a result of them existence able to receive a signal and they able to right interpret that signal and we in turn appreciate the devices.For the devices to mightily interpret these signals a kind of technique was use and this is known as De intonation, this being that the devices are designed to receive this type of signals. The executees that led to being able to demodulate is what my focus is on the process is known as transition.Why modulation? This is due to the detail that not all intended users of a particular device or service reside clam up to the production station and in any case production signals called baseband signals orduret travel practically and would wishing a lot of power to intercommunicate them over the air long suit and this adds to the operating cost of the station and this is not acceptable.2.0 Transmission medium for TV signalAs with any kind of signal, the most grave of that signal is to be received and decoded correctly, so that information encoded enkindle be seen or viewed. The medium of passage of such signals is of con successiveness, because these helps to know the appropriate modulation to use and what, this information is tied to the channel coding, the advantages of the channel and the noise judge of that channel in consideration.For example, the contagion medium for healthful received by the ears is usually air, sound dismiss also travel through solids, liquids and blood plasma Electromagnetic waves have no need of any material stub for it to propagate but can be bear on by the transmission media they pass through at the boundary between the media by absorption, reflexion or refraction.Therefore, TV signals are like communicating data move from one location to another which requires a pathway or medium. These pathways, called communication channels two types of preferr ed media are (a) Cable (twisted-pair melodic line, cable, and fibre-optic cable) and (b) pervade (microwave, satellite, radio, and infrared). Note- Cable media use physical wires of cables to transmit data and information, plot of ground Twisted-pair wire and coaxial cables are make of copper, and fibre-optic cable is made of glass.2.1 BASEBAND SIGNALThe definition of a baseband signal is a signal that contains information, which may vary from audio signals, video signals, speech signal, image signal and many different other types depending on application and use. These signals cant move to a greater extent than a few metres after production for example, a speech signal two persons can perk themselves all the way in close proximity to to each one other, as the distance between them increase, they start essaying eliminateible messages or signals from each other and at a phase, they cant hear each other again. Therefore for them to be heard no proceeds the distance bet ween them on that sign is need to modulate the speech signal gene wanderd by each person, so that each person can hear what the other person has verbalise or is saying.A signal can be said to be an analogue data bombard with which it varies with follow to space and time with this property, each signal can be sampled, quantized, and change into digital data streams or packets. These processes it goes from being analogue to digital data streams or packet is called modulation. There are different modulation techniques utilize to carry different signals depending on the transmission medium and the condition inborn in that medium.2.2 ModulationWhat is modulation? According to Margaret Rouse, modulation is the conspiracy of signal to an electronic signal carrier, modulation is useful in direct locate of flow by turning it on and off to alternating current.Literally, modulation can be said to be a way of quicken the transfer of data or information through a medium. Transmission of sound through air has restricted score of power generated by the lungs, to sire the extent at which the voice can reach thither is need to transmit it through a medium such as retrieve line, radio etc. in that locationfore, the successful conversion of information in this typeface voice, to pass through a medium such as wire or radio waves is known as Modulation (www.complextoreal.com ).2.3 TYPES OF MODULATIONModulation helps in many ways and it can be referred to as the process of transposing a signal wave onto a carrier wave in put together to carry information. There are 3 three spot properties of this carrier wave, which is a sinusoid wave with an bountifulness, a phase and a frequence, these properties can be exploited to generate another kind of wave shape to carry the intended information which is known referred to as a modulate signal. (www.encyclopediapro.com/mw/modulation)In most part of the world, frequence spectrum is expensive to waste and often its a nati onal property, which means, to use it, the intending user has to be licensed and must follow a protocol process to have that frequency band delegate to him solely and given the channels parameters he can use. This is because, there are many different users competing for the same frequency band, due to the fact that the lower the frequency given, the lower the operating cost of using that frequency band.There are 2 broad class of modulation they are the analogue modulation and the digital modulation.In analogue modulation, there is a continuous change in response to the signal to be play this can be seen in Phase Modulation, Frequency Modulation, Amplitude Modulation, Single-Sideband Modulation, and Vestigial-sideband Modulation.In digital Modulation, there are changes in the signal position with honour to a starting position, while each position corresponds to a number of information or symbol and can be playacted on a conformation plat. Examples include Phase- huckster Key (PS K), Frequency- bring up Key (FSK), Amplitude- careen Key ( wait), Minimum- transmutation Key (MSK), Gaussian minimum-shift Key (GMSK), Very minimum-shift Key (VMSK), Quadrature Amplitude Modulation (QAM), this a combination of PSK and ASK. Continuous phase modulation(CPM) and Trellis coded modulation(TCM). (www.encyclopediapro.com/mw/modulation)For each of these types of modulation techniques, their phases, frequencies and amplitude are assigned a unique sequence of whiles which corresponds to an equal number of bits and make up a symbol that see that particular phase or code.3.0 QAMThe modulation of interest for the purpose of his paper is the QAM, or Quadrature Amplitude Modulation, from research it was noticed that QAM has both an analogue and digital modulation properties depending on how its to be applied.QAM is made up of two modulation synopsis, namely the Amplitude-shift Keying which is achieved by modulating or changing the state of the amplitude of two carrier waves to carry two analogue message signal or two digital data streams. The other is the Phase-shift Keying, in which the sinusoidal waves are usually out of phase to each other and apart by 90o. When these two waveforms are combined, it results to Quadrature Amplitude Modulation (two different amplitudes two out of phase signals).QAM, this modulation technique is utilize to encode and transmit digital cable channels, while the simplest of the QAM techniques is the 16-QAM i.e. 24 phase points, this is able to carry 6MHz bandwidth modulate by the authoritys policy. The type of signal interested in is the signal generated from a video source, this type of signal consumes more than the set frequency of 6MHz, a typical video source signal is huge, so using 16- QAM techniques, it is practicable to encode the signal onto the QAM carrier wave to carry it and pass through the 6MHz bandwidth limit and still be able to carry supernumerary signals such as the voice signal component of the video s ignal. However there are different video formats such as the NTSC, PAL, MPEG this video formats also help in reducing the size of video signal, hereby assisting the 16-QAM to efficaciously encode the signal without loss of quality and making it noise proof. other(a) variants of QAM includes 64, 256 phase variants, but as this phases size increase, so do they mix noise and mismatching often affect the performance of the receiver to be correctly tuned in to receive the sequence of bits sent over the medium.One of the uses of QAM is in the modulation of digital television systems, due to its high spectral efficiencies and the urgency of a cleaner path, and such hybrid fibre coaxial cables are use to deliver digital television signals to homes. (http//en.wikipedia.org/wiki/QAM_tuner, 2012) In the United Kingdom, 2 variants of the QAM are being used, this are the 16 and 64 variants and they are used for digital terrestrial TV like Freeview by British Telecoms Top-Up TV, while for th e 256-QAM, is being considered for the HD version of freeview which is delivered over high speed fibre optics golf links to homes across the country.Therefore, the makeup of QAM is shown via the figure on a lower floor and the different modulation techniques it uses to modulate and encode its own signal and how it lead to the development of QAM.3.0.1 Amplitude permutation Keying (Ask)According to N.Vlajic (2010), Ask is the modulation of digital data with changes in the amplitude of a carrier while both frequencies an d phase stay on constant carrier signal is varied by representing the binary star with 0 and 1.Also in ASK, the mode of operation is to vary the amplitude of the carrier wave to carry a baseband signal, while the frequency and phase inhabit constant.Ask has two levels called binary bits of implementing its modulation process and it is often referred to as Binary Amplitude shift keying or on-off keying (B-ASK or OOK). Each binary bit corresponds to a symbol that re presents an amplitude level.According to (Glover and Grant, 2004, chapter 11, page 391), they said that in B-ASK, the two digital levels can be one and cypher, to represent the pulse of a sinusoidal carrier wave, although any one of the changing amplitude can be inferred to be one and the other zero and from this result, it describes why it also referred to as on-off keying sequence. This method of digital sequence of one and zero can be referred to a switch and was used to transmit Morse codes (Wikipedia) in the early 20th century.In recent times, additional amplitude levels has been developed for enhanced encoding schemes such as a 4 quartet level encoding scheme to take on two bits or 22with corresponding shift in amplitude, also there is an eight level scheme to represent 3 three bits or 23, and so on. This gives a reduced power required to transmit and therefore advantageous to use. (Wikipedia-http//en.wikipedia.org/wiki/Amplitude-shift_keying)A binary amplitude-shift keying (BASK) signal can be specify byS (t) = A m (t) cos 2pfct. For (0 Implementation of ASK is relatively cheap and simple but its amplitude is usually affected by noise, distortion s and the propagation conditions on different roadway which makes the process more difficult. In ASK digital data is patrimonial over an optical fiber.Figure 1. ASK signal representation.3.0.2 Phase shift keying (PSK)Phase-shift keying (PSK) refers to a modulation scheme that is used to carry information by changing, or modulating, the phase of the carrier wave.PSK can still be specify as the modulation of digital data with amplitude at peak, frequency remain constant and phase with carrier signal varied to envision binary 0 or 1, with binary 0 = 180 degree phase and binary 1 = 0 degree.PSK is not sensitive to demerit and productively make use of bandwidth, so high data rate is possible but has more complex signal detection (N. Vlajic, 2010).This modulation scheme like the Amplitude shift Keying (or AS K) also uses a limited number of distinct signals to represent digital data. Each of the finite phases, is assigned a unique pattern of binary digits that forms a symbol. Phase shift keying comes in two forms, which are binary PSK (this uses two phases which are 180o apart) and Quadrature PSK (this uses four phases and the phases are 45o, -45o 135o and -135o). (Forouzan, 2013 pg 144)3.0.2.1 Binary PSKIn Binary PSK, it has only two signal element said suggested by Forouzan, 2013, pg 142 with each phase set at 0o and the other at 180o. The general form for BPSK follows this equation Sn (t). (wikipedia- H. blue S. Mahmoud, Communications Systems, Pearson Prentice Hall, 2004, p283)s_n(t) = sqrtfrac2E_bT_b cos(2 pi f_c t + pi(1-n )), n = 0,1.This yields two phases, 0 and . In the specific form, binary data is often conveyed with the following signalss_0(t) = sqrtfrac2E_bT_b cos(2 pi f_c t + pi ) = sqrtfrac2E_bT_b cos(2 pi f_c t)For binary 0s_1(t) = sqrtfrac2E_bT_b cos(2 pi f_c t)For binary 1where fc is frequency of the carrier-wave.Also, the BER of a two signal BPSK in AWGN can be calculated as followsP_b = Qleft(sqrtfrac2E_bN_0right)P_b = frac12 operatornameerfc left( sqrtfracE_bN_0right)3.0.2.2 Quadrature PSKThis sub part of psk is such that it uses two separate BPSK modulations to generate a QPSK modulation scheme this is able to work due to each BPSK band as an in-phase carrier and the other out of phase carrier. The phases are different and the first point is located at 45o, then 135o, then -135o and lastly -45o, the amplitude cincture constant at 2. The bit stream is then cashier into two bit streams I (in-phase) and Q (Quadrature) .The bit stream in-phase (I) is called the even stream and quadrature(Q) is called Odd stream. (http//turboblogsite.com/quadrature-phase-shift-keying-qpsk-modulation.html)QPSK is used mostly to transfer digital data by varying the phases of the carrier signal, the 4 phase points tally with 4 points on a circle and can be so r epresented. The figure below shows the mapping of the 4 phase points.QPSK diagram present how four different binary codes can be transmittedFig QPSK diagram showing how four different binary codes can be transmittedThe name below gives some of the other commonly used forms of phase shift keying, PSK, they are O-QPSK Offset Quadrature Phase Shift Keying, 8 PSK 8 quest Phase Shift Keying, 16 PSK 16 Point Phase Shift Keying, QAM Quadrature Amplitude Modulation, 16 QAM 16 Point Quadrature Amplitude Modulation and 64 QAM 64 Point Quadrature Amplitude Modulation (http//www.radio-electronics.com/info/rf-technology-design/pm-phase-modulation/what-is-psk-phase-shift-keying-tutorial.php)Figure 2. PSK signal diagram representation3.1 QAM bits per symbolThe advantage of using QAM is that it is a higher(prenominal) order form of modulation and as a result it is able to carry more bits of information per symbol. By selecting a higher order format of QAM, the data rate of a link can be in creased. (http//www.radio-electronics.com/info/rf-technology-design/pm-phase-modulation/8qam-16qam-32qam-64qam-128qam-256qam.php)The table below gives a summary of the bit order of different forms of QAM and PSK.ModulationBits per symbolSymbol RateBPSK11 x bit rateQPSK21/2 bit rate8PSK31/3 bit rate16QAM41/4 bit rate32QAM51/5 bit rate64QAM61/6 bit rate3.1.1 Quantized QAM using constellation diagramIn QAM, the constellation diagram plots are usually arranged in square formation with different spacing and this spacing point represent binary bits per symbol, this spacing point is in the power of 2s. The more the bits per symbol, the more it is to transfer more information over a given channel or medium. But as the bits increase, the points move closer and make the system susceptible to noise corruption, and this gives rise to a high BER ratio, making useless the information sent due to its high noise component.There are different bit positions for the constellation diagram, this diagra ms show the different position of each symbol and the states of QAM, and the constellation diagrams for BSPK, 16 QAM. 32 QAM, 64 QAM. Therefore, the figures below show various constellation diagramshttp//www.radio-electronics.com/info/rf-technology-design/pm-phase-modulation/modulation-constellation-bpsk.gifhttp//www.radio-electronics.com/info/rf-technology-design/pm-phase-modulation/modulation-constellation-16qam.gifhttp//www.radio-electronics.com/info/rf-technology-design/pm-phase-modulation/modulation-constellation-32qam.gifhttp//www.radio-electronics.com/info/rf-technology-design/pm-phase-modulation/modulation-constellation-64qam.gif3.1.2 QAM applicationsQAM is in many radio communications and data delivery applications. However some specific variants of QAM are used in some specific applications and standards.For domestic broadcast applications for example, 64 QAM and 256 QAM are often used in digital cable television and cable modem applications. In the UK, 16 QAM and 64 QAM a re currently used for digital terrestrial television using DVB Digital Video Broadcasting. In the US, 64 QAM and 256 QAM are the mandated modulation schemes for digital cable as standardised by the SCTE in the standard ANSI/SCTE 07 2000.In addition to this, variants of QAM are also used for many wireless and cellular technology applications.4.0 ConclusionIn this review, it is clearly shown that Amplitude Shift Keying (ASK) and Phase Shift Keying (PSK) modulation techniques that form Quadrature Amplitude Modulation (QAM) ensures effective transfer of TV signals In QAM different combination of amplitude and phase are used to achieve higher digital data rate, the number of bit transmitted per time T (sec) separation can be further increased by increasing the number of levels usedReferencesBehrouz A. Forouzan , Data communications and NetworkingH. Stern S. Mahmoud, Communications Systems, Pearson Prentice Hall, 2004, p283)http//engineering.mq.edu.au/cl/files_pdf/elec321/lect_mask.pdf http//en.wikipedia.org/wiki/Amplitude-shift_keying (Accessed 06 December 2012)http//en.wikipedia.org/wiki/QAM_tuner, 2012 (Accessed 28 November 2012)http//turboblogsite.com/quadrature-phase-shift-keying-qpsk-modulation.htmlhttp//www.radio-electronics.com/info/rf-technology-design/pm-phase-modulation/8qam-16qam-32qam-64qam-128qam-256qam.php (Accessed 06 December 2012)http//www.radio-electronics.com/info/rf-technology-design/pm-phase-modulation/what-is-psk-phase-shift-keying-tutorial.php (Accessed 06 December 2012)Ian A. Glover and gibe M. Grant, Digital communications, second editionIntuitive Guide to Principle of Communication, www.complextoreal.comMargaret Rouse, July 2005Merriam WebsterN.Vlajic, Instructor, CSC 3213, fall 2010. Analog transmission of digital data (ASK, FSK, PSK, QAM)Wikipedia, the free encyclopaedia (Accessed 28 December 2012)www.encyclopediapro.com/mw/modulation (Accessed 28 November 2012)