Transmission Of A Tv Signal English Language Essay

Transmission Of A Tv Signal English Language try onIn electronics, many antithetic types of newsboy emblems exists and due to the fact that this manoeuvers simply restrain selective in dression intended for a different audience, which most of the times, ar far than the ara of production of such prognostics. This gave splay to various chanting techniques to ensure effective transfer of these houses bearing entropyrmation without loss of quality or degradation. This write up deals on how to modulate a Television (TV) target using 16-QAM (Quadrature Amplitude inflexion) placewords include 16-QAM, TV Signals, Amplitude intonation, Data, and Attenuation, baseband.1.0 IntroductionEveryday different types of signals transverse the nervous strain around us, most of which we monger feel or see, but we see their impact or influence everyday finished different electronic gadgets we energize or own personally.Most of these electronic gadgets are able to work as a result of them being able to receive a signal and they able to correctly interpret that signal and we in turn appreciate the devices.For the devices to correctly interpret these signals a kind of technique was used and this is cognise as De intonation, this being that the devices are designed to receive this type of signals. The processes that led to being able to demodulate is what my focus is on the process is known as flexion.why modulation? This is due to the fact that not all intended users of a particular device or service reside close to the production plaza and also production signals called baseband signals earth-closett travel much and would need a lot of power to transmit them over the air medium and this adds to the operating be of the station and this is not acceptable.2.0 Transmission medium for TV signalAs with any kind of signal, the most important of that signal is to be received and decoded correctly, so that information encoded backnister be seen or viewed. The mediu m of passage of such signals is of consequence, because these helps to know the appropriate modulation to use and what, this information is tied to the channelise coding, the advantages of the channel and the interference rate of that channel in consideration.For example, the transmittal medium for sound received by the ears is usually air, sound send packing also travel through solids, liquids and plasma Electromagnetic waves have no need of any material substance for it to propagate but can be affected by the transmission media they pass through at the boundary between the media by absorption, reflection or refraction.Therefore, TV signals are identical communicating selective information sent from iodin location to another which requires a path agency or medium. These pathways, called communication channels ii types of preferred media are (a) origin (twisted-pair wire, cable, and fibre-optic cable) and (b) broadcast (microwave, satellite, radio, and infrared). Note- Cabl e media use physical wires of cables to transmit data and information, while Twisted-pair wire and coaxial cables are made 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 covering and use. These signals cant move to a greater extent(prenominal) than a few metres after production for example, a speech signal ii persons can hear themselves clearly in close proximity to each other, as the distance between them increase, they start hearing faint messages or signals from each other and at a full point, they cant hear each other again. Therefore for them to be heard no matter the distance between them there is need to modulate the speech signal generated by each person, so that each person can hear what the other person has said or is saying.A signal can be said to be a n analogue data stream with which it varies with respect to space and time with this property, each signal can be sampled, quantized, and transformed 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 used to carry different signals depending on the transmission medium and the condition inherent in that medium.2.2 ModulationWhat is modulation? According to Margaret Rouse, modulation is the gang of signal to an electronic signal carrier, modulation is efficacious in direct current 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 degree of power generated by the lungs, to give the extent at which the voice can reach there is need to transmit it through a medium such as recall line, radio etc. theref ore, the successful conversion of information in this case 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 order to carry information. There are 3 three key properties of this carrier wave, which is a sinusoid wave with an amplitude, a shape and a oftenness, these properties can be exploited to generate another kind of waveform to carry the intended information which is known referred to as a modulated signal. (www.encyclopediapro.com/mw/modulation)In most part of the world, frequency spectrum is expensive to waste and often its a national property, which means, to use it, the intending user has to be licensed and must follow a protocol process to have that frequency band assigned to him solely and given the channels parameters he can use. This is because, there are many differ ent 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 continual change in response to the signal to be modulated 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 respect to a starting position, while each position corresponds to a piece of information or attribute and can be represented on a constellation diagram. Examples include Phase-Shift Key (PSK), Frequency-shift Key (FSK), Amplitude-shift Key (ASK), Minimum-shift 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 m odulation(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 bits which corresponds to an equal number of bits and make up a symbol that represent that particular phase or code.3.0 QAMThe modulation of interest for the offer 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 scheme, 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 curving waves are usually out of phase to each other and apart by 90o. When these two waveforms are combined, it results to Quadrature Amplitude M odulation (two different amplitudes two out of phase signals).QAM, this modulation technique is used 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 regulated 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 possible 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 additional signals such as the voice signal component of the video signal. besides 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 in effect encode the signal without loss of quality and making it noise proof. Other variants of QA M includes 64, 256 phase variants, but as this phases size increase, so do they incorporate 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 requirement of a cleaner path, and such hybrid fibre coaxial cables are used 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 the 256-QAM, is being considered for the HD version of freeview which is delivered over high speed fibre optics links to homes across the country.Therefore, the makeup of QAM is set upn via the figure below and the different modulation techniques it uses to modulate and en code its own signal and how it lead to the development of QAM.3.0.1 Amplitude Shift Keying ( communicate)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 remain constant carrier signal is varied by representing the binary 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 remain constant.Ask has two levels called binary bits of implementing its modulation process and it is often referred to as binary program Amplitude shift keying or on-off keying (B-ASK or OOK). Each binary bit corresponds to a symbol that represents 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 zero, to represent the pulse of a sinusoidal carrier wave, although any one of the changing amplitude can be inferred to be one and t he other zero and from this result, it describes why it also referred to as on-off keying sequence. This mode 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 four level encoding scheme to watch 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 hence advantageous to use. (Wikipedia-http//en.wikipedia.org/wiki/Amplitude-shift_keying)A binary amplitude-shift keying (BASK) signal can be defined 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, spin s and the propagation conditions on different route which makes the process more difficult. In ASK digital data is transmit ted over an optical fiber. code 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 defined as the modulation of digital data with amplitude at peak, frequency remain constant and phase with carrier signal varied to depict binary 0 or 1, with binary 0 = 180 degree phase and binary 1 = 0 degree.PSK is not radiosensitive to error 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 ASK) also uses a finite 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 familiar form for BPSK follows this equation Sn (t). (wikipedia- H. Stern 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 particular 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 t o 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 stays constant at 2. The bit stream is then split 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 represented. The figure below shows the mapping of the 4 phase points.QPSK diagram showing how four different binary codes can be transmittedFig QPSK diagram showing how four different binary codes can be transmittedThe list 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 Point 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 high 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 increased. (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 rates of different forms of QAM and PSK.ModulationBits per symbolSymbol RateBPSK11 x bit rateQPSK21/2 bit rate8PSK31/3 bit rate16QAM41/4 bit rate32QAM51/5 b it rate64QAM61/6 bit rate3.1.1 Quantized QAM using constellation diagramIn QAM, the constellation diagram plots are usually arranged in square(a) 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 diagrams 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 are 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 techn ology 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) interval 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.pdfhttp//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-128q am-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 Peter 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)