Design a Repeater for Digital Rf Signal

Abstract Repeaters for digital TV broadcasting set up use all(prenominal) analogue or digital techniques. The purpose of utilise reversionist is to boost manoeuvres into beas of weak c everyplaceage in any radio communication system. However wave interference means the recidivist usu all(prenominal)y requires a frequency flip-flop for analogue modulated show. For digitally modulated point it whitethorn be mathematical to use same frequency. This paper investigated and designed a RF repeater which will improve the inter image interference by incorporating delay betwixt absorbd and transmit manoeuver.This jutting also reviewed the basics of current Digital moving video distri thateing-Terrestrial (DVB-T) techniques and selected it as a suitable choice for lab experiment. The practical stance of this count on is to design and skeletal system a repeater incorporating suitable electrical delay. Contents 1. 0 Introduction4 1. 1 Background4 1. 2Aim of this project6 1. 3Project objectives6 1. 3 Project deliverable7 2. 0 Problem analysis8 2. 1 Repeater8 2. 1. 1 Analogue repeaters9 2. 1. 2 Digital repeaters10 2. 2 Inter figure interference13 2. 3 Multipath propagation15 2. 3. 1 Multipath fading15 2. 4 The TV channels16 2. 5 transmitting business18 . 6 Signal Amplifiers20 2. 7 Transmission delay (Coaxial telephone circuit)21 3. 0 Possible solution24 3. 1 RF amplifier25 3. 1. 1 The Transistor Amplifier26 3. 1. 2 Ultra High oftenness Transistor Array (HFA)29 3. 1. 3 Surface mounts technology32 3. 1. 4 Surface Mount Monolithic Amplifier32 3. 1. 5 Loft box 8 way home scattering whole34 3. 2. 6 Maxview signal booster35 3. 2. 7 Antenna36 4. 0 Design37 4. 1 Circuit design37 4. 2 PCB design38 5. 0 instruction execution40 5. 1 Implementation with HFA312740 5. 2 Implementation with MAV-11SM amplifier41 6. 0 Test result42 6. 1 Laboratory test result42 6. 2 Field test result44 7. Result Discussion46 8. 0 Conclusion48 Future work49 Works Cited50 phase Li st visualize 1System block diagram6 regard 2 Passive and Active repeater block diagram7 Figure 3 Analog repeater8 Figure 4 Digital repeater9 Figure 5 Channel management for digital repeater10 Figure 6 Channel management for analogue repeater10 Figure 7 Broadcast in valley with digital repeaters11 Figure 8 101101 transmitted data12 Figure 9 Received data12 Figure 10 Transmitted data vs. Received data13 Figure 11 Multipath propagation14 Figure 12 Cable tone ending in dB (Antenna basics, 2008)18 Figure 13 Linear heighten phase vs frequency22Figure 14 The basic junction junction transistor amplifier26 Figure 15 HFA3127 transistor array30 Figure 16 MAV-11SM amplifier31 Figure 17 Suggested PCB lay appear with MAV-11SM33 Figure 18 Loft box home distri yetor33 Figure 19 Maxview signal booster35 Figure 20 Antenna used for this project35 Figure 21 Interference mingled with relay signal and chief(prenominal) transmitted signal36 Figure 22 ISIS established of circuit design37 Figure 2 3 PCB design according to the datasheet in ARES37 Figure 24 3D view for PCB38 Figure 25 Circuit with HFA3127 amplifier39 Figure 26 MAV-11SM amplifier circuit board40 Figure 27 HFA3127 gain with soldering error41Figure 28 HFA3127 amplifier gain41 Figure 29 One MAV-11SM amplifier gain42 Figure 30 Two MAV-11SM amplifier circuits give more gain42 Figure 31 Three amplifiers in concert was the maximum gain43 Figure 32 Low choice picture with normal antenna43 Figure 33 Picture with repeater connected antenna44 Figure 34 Rebroadcasting connection44 1. 0 Introduction 1. 1 Background Digital Video air (DVB) is be adopted as the stock(a) for digital tv set in many countries. The DVB standard offers many advantages over the previous analogue standards and has enabled television to make a major step forwards in impairment of its technology.Digital Video Broadcasting, DVB is now one of the success stories of modern broadcasting. The take up has been enormous and it is currently deployed in over 80 countries worldwide, including nigh of Europe and also within the USA. It offers advantages in terms of far greater efficiency in terms of spectrum usage and might utilisation as well as cosmos able to affect considerably more facilities, the prospect of more channels and the ability to work alongside existing analogue services. (Pool, 2002) In these days when in that location atomic number 18 many ways in hich television plunder be carried from the transmitter to the receiver no one standard can be optimised for all applications. As a result there ar many some(prenominal)(predicate) forms of the Digital Video Broadcasting, DVB, standards, each designed for a given application. The primary(prenominal) forms of DVB argon summarised be first DVB Standard Meaning Description DVB-C Cable The standard for delivery of video service via cable networks. DVB-H Handheld DVB services to handheld devices, e. g. mobile phones, and so forth DVB-RSC Return satellite chann el Satellite DVB services with a return channel for interactivity. DVB-S Satellite services DVB standard for delivery of television / video from a satellite. DVB-SH Satellite handheld Delivery of DVB services from a satellite to handheld devices DVB-S2 Satellite here and now gene ration The second generation of DVB satellite broadcasting. DVB-T Terrestrial The standard for Digital Terrestrial Television Broadcasting. Digital Video Broadcasting- Terrestrial (DVB-T) The common perception of digital television these days is of broadcasts emanating from signal towers, bouncing off satellites, and being beamed to home receivers.This is the magic ofsatellite transmittal, and it is reliable as long as the view of those satellites is non obscured. However, this is not the solely way in which television signals are transmitted. Another popular method of transmitting signalsdigital video broadcastingterrestrial (DVB-T). When broadcasters employ this method, the digital signals do not l eave the earth. The signals transmitted useDVB-Tdo not travel via cable, though rather, they go fromantenna to aerial antenna, from signal blaster to home receiver. Digital signals are routinely transmitted using terrestrial methods.The transmission method has different names in different parts of the world. DVB-Tis the name used in Europe and Australia. North American customers receive these signals using a set of standards approved by the Advanced Television Systems Committee (ATSC). In Japan, it is known as Integrated Services Digital BroadcastingTerrestrial (IDSB-T). DVB-Tbroadcasters transmit data using a compressed digital audio-video stream, with the finished process standd on theMPEG-2 standard. These transmissions can include all kinds of digital broadcasting, includingHDTVand other eminent-intensity methods.This is a vast improvement over the old analog signals, which required separate streams of transmission. Oddly enough, someDVB-Ttransmissions take place over analog networks, with the antennas and receivers getting some helpful technological upgrades along the way. (Pool, 2002) 1. 2 Aim of this project The aim of this project is to investigate the design of a repeater for DVB-T system but incorporating a delay surrounded by receives and transmits signals to avoid Inter Symbol Interference (ISI). It is useful to use a repeater to boost the signal into areas of weak coverage in any radio wave communication system.However wave interference means the repeater usually requires a frequency shift for analogue modulated signals. For digitally modulated signals it may be possible to use the same frequency. The project will review the basics of current digital systems such as DVB (Broadcast TV) and WLAN and to identify a suitable choice for a lab experiment. The practical side will be to design and build a repeater incorporating suitable transmission delay. 1. 3 Project objectives 1. Investigate and find Inter Symbol Interference effect on real sign al. 2.Investigate and learn the delay effect on real signal and cause of the delay. 3. Investigate and learn Multipath propagation and Doppler shift of the frequencies. 4. Investigate and learn about Digital Video Broadcasting (DVB) techniques. 5. Investigate and learn about transmission delay of maunderial cable. 6. Investigate and learn about different symbol of Amplifier. 7. Designing repeater circuit. 8. Implementing circuit. 9. exam the circuit. Figure 1System block diagram 1. 3 Project deliverable * System design * Circuit design * Documentation 2. 0 Problem analysis . 1 Repeater Repeaters provide an efficient solution to increase the coverage of the broadcasting networks. In the broadcasting networks, the network operators usually first put high originator transmitters at the strategic points to quickly ensure an attractive coverage and then, in a second step, increase their coverage by placing low- designer repeaters in the dead secernate or shadow areas, such as a tun nel, valley or an indoor area. A repeater is simply a device that receives an analogue signal or a digital signal and regenerates the signal along the next leg of the medium.In DVB-T networks, there are two different kinds of repeaters. They are passive repeaters, which are also called as gap-fillers and active repeaters that are also called as regenerative repeaters. A passive repeater receives and retransmits a DVB-T signal without changing the signalling information bits. The signal is only boosted. An active repeater can demodulate the incoming signal, perform error recovery and then re-modulates the bit stream. The production of the error recovery can blush be connected to a local re-multiplexer to enable insertion of local programmes.This means that the entire signal is regenerated. The building blocks of the passive and active repeater configurations are shown in Figure 1. Figure 2 Passive and Active repeater block diagram In a first step, DVB-T broadcasters, as all broadca sters, engulf their networks with high power transmitters in strategic point in order to quickly insure an attractive coverage to TV operators and then, in a second step, increase their coverage by placing low power repeaters in shadow area. To repeat a DVB-T signal, two solutions can be used An analogue repeat in this case, repeaters use well-known techniques such as down conversion, filtering, up conversion and amplification. The signal is only boosted. * A digital repeat this new subject of repeater uses a professional DVB-T receiver to recover the programme stream (and correct all errors) carried in the RF channel, performs a new modulation followed by an up conversion and amplification. It means that the entire signal is regenerated. 2. 1. 1 Analogue repeaters In case of analogue repetition, the output signal property cannot exceed the quality of the received signal because the signal is not regenerated.Figure 3 Analog repeater Furthermore, being a passive process, it degrad es the signal the phase hinderance of the local oscillator involves a degradation of the phase noise of the received signal and creates an inter-modulation. The local oscillator phase noise adds to the phase noise of the received signal. In these conditions, what are the performances of analogue repetition for Modulation Error Ratio (MER) and Carrier to kerfuffle ratio (C/N)? Of course, performances are linked to the technology but analogue repetition cannot be insured ad infinitum. And, if one link in the analogue repetition chain is weak, all the system is deficient. Trolet, 2002) 2. 1. 2 Digital repeaters In case of a digital repetition, the entire signal is regenerated it means that repeaters, as transmitters, insure the quality of the broadcasted signal as long as it is able to demodulate it. Figure 4 Digital repeater The output signal quality is independent of the infix signal quality * Phase noise is linked to the local oscillator only, * A weak link, in a digital repetiti on chain, is erased by the following repeater, * Several digital repeaters can be cascaded without any cumulative degradation.Drawback of Digital repeater The delay in spite of appearance a digital repeater is taller than the guard interval. So, the signal cannot be repeated on the frequency of the main transmitter main transmitters and repeaters cannot operate in a iodin frequency Network (SFN) even with 8K carriers and a guard interval of 1/4. (Trolet, 2002) Figure 5 Channel management for digital repeater The delay inside an analogue repeater is lower than the guard interval and allows main transmitters and repeaters to operate in SFN mode. Figure 6 Channel management for analogue repeaterBut, with such technique, converging between repeater cells and transmitter cell cannot be optimised/adjusted. Analogue repeaters have not the possibility to buffer the signal they cannot add delay to move the circle zone. To optimise single frequency network with this technique, two solutio ns * Move the repeater that means you have to find new broadcasting site. * Reduce the output power of your repeaters and forbid overlap. So, to build an efficient Single Frequency Network (SFN), Broadcasters have benefits in using transmitters * government agency more freedom for defining the size of the cells Means more freedom for defining the repeater locations Benefits of Digital Repeater * As long as the repeater is able to demodulate the RF channels, signal quality is independent of excitant signal quality. * Output MER 33 dB (Trolet, 2002) * In theory, thanks to the forward error correction (FEC) and the output signal quality, digital repeaters can be cascaded ad infinitum. It is an efficient solution to broadcast in valleys. TV viewers and distant repeaters share the broadcasted signal. Figure 7 Broadcast in valley with digital repeaters The demodulation process, down to the programme stream, allows broadcasters to insert a local multiplexor in order to customize the con tent for a local broadcasting. More and more, local communities aim their local programmes. Digital repeaters offer a flexible solution to the network. * Shadow area can be covered by several repeaters. Repeaters operate together in SFN mode without any external references (10 MHz and 1 PPS) (Trolet, 2002). In their inbred memory, digital repeaters can buffer the signal so as to optimise overlaps. 2. 2 Inter symbol interferenceInter-symbol interference (ISI) is an unavoidable consequence of some(prenominal) wired and wireless communication systems. Morse first noticed it on the transatlantic telegraph cables transmitting messages using dots and dashes and it has not gone way since. He handled it by just slowing down the transmission. Amplitude period Figure 8 101101 transmitted data Figure 8 shows a data sequence, 1,0,1,1,0, which wish to be sent. This sequence is in form of square pulses. Square pulses are tenuous as an abstraction but in practice they are hard to create and a lso require far too much bandwidth. Amplitude TimeFigure 9 Received data Figure 9 shows each symbol as it is received. It also shows what the transmission medium creates a tail of capacity that lasts much long-acting than intended. The energy from symbols 1and 2 goes all the way into symbol 3. each symbol interferes with one or more of the subsequent symbols. The circled areas show areas of big(a) interference. Amplitude Time Figure 10 Transmitted data vs. Received data Fig. 3 shows the actual signal seen by the receiver. It is the sum of all these distorted symbols. Compared to the transmitted signal, the received signal looks quite indistinct.The receiver does not actually this signal it sees only the little dots, the value of the amplitude at the timing instant. Symbol 3, this value is some half of the transmitted value, which makes this particular symbol is more susceptible to noise and incorrect interpretation and this phenomena is the result of this symbol delay and smeari ng. This spreading and smearing of symbols such that the energy from one symbol effects the next ones in such a way that the received signal has a higher probability of being interpret incorrectly is called Inter Symbol Interference or ISI.ISI can be caused by many different reasons. It can be caused by filtering effects from computer hardware or frequency selective fading, from non- line of descentarity and from charging effects. Very few systems are immune from it and it is nearly always present in wireless communications. Communication system designs for both wired and wireless nearly always need to incorporate some way of controlling it. The main problem is that energy, which is been wishing to confine to one symbol, leaks into others. So one of the simplest things can be done to reduce ISI is to just slowing down the signal.Transmitting the next pulse of information only after allowing the received signal has damped down. The time it takes for the signal to die down is called delay spread, whereas the original time of the pulse is called the symbol time. If delay spread is less than or correspond to the symbol time then no ISI will result, otherwise yes. (Charan, 2002) Slowing down the bit rate was the main way ISI was controlled on those initial transmission lines. then(prenominal) faster chips came and allowed to do signal processing controlling ISI and transmission hotfoots increased accordingly. . 3 Multipath propagation Multipath propagation is caused by multipath receptions of the same signal. in city surround or indoors signal travels along different path from transmitter (Tx) to receiver (Rx). * Signal components received at some different times (delay) * These components are combined at Rx * Results as a signal that varies widely in amplitude, phase or polarization 2. 3. 1 Multipath fading When the components add destructively repayable to phase differences amplitude of the received signal is very small.At the other times the components add constructively the amplitude of received signal is large. This amplitude variations in the received signal called signal fading, are due to the time-variant characteristics of the channel. Relative motion between Tx and Rx (or surrounding objects causing e. g. reflection) causes random frequency modulation. Figure 11 Multipath propagation Each multipath component has different Doppler shift. The Doppler shift can be calculated by using fd=V? cos? V is the velocity of the terminal ? is the spatial weight down between the direction of motion and the wave ? is the wavelengthThe three most important effects of multipath fading and moving scatters are * Rapid changes in signal posture over a small travelled distance or time interval * Random frequency modulation due to vary Doppler shifts on different multipath signals. * Time dispersion (echoes) caused by multipath propagation 2. 4 The TV channels Hertz(Hz) meanscycles per second. (Heinrich Hertz was the first to build a radio transm itter and receiver while under stand up what he was doing. )KHz means 1000 Hertz, MHz means 1,000,000 Hertz, and gigahertz means 1,000,000,000 Hertz The radio frequency spectrum is separate into major bandsFrequencyWavelength(in meters) VLFvery low frequency3 KHz 30 KHz 100 Km 10 Km LFlow frequency 30 KHz 300 KHz 10 Km 1 Km MFmedium frequency300 KHz 3 MHz 1 Km 100 m HFhigh frequency 3 MHz 30 MHz 100 m 10 m VHFvery high frequency30 MHz 300 MHz 10 m 1 m UHF immoderate high frequency300 MHz 3 GHz 1 m 100 mm SHFsuper high frequency 3 GHz 30 GHz 100 mm 10 mm EHFextremely high frequency 30 GHz 300 GHz 10 mm 1 mm (Antenna basics, 2008) The UK uses UHF for terrestrial television transmissions, with both PAL-I analogue broadcasts and DVB-T digital broadcasts sharing the band. The following table is a proficient channel/frequency conversion table showing the E channel number, PAL-I vision and sound carrier frequencies, and the centre frequency for digital tuning. The frequ ency image for the UK involves each channel having an 8MHz bandwidth the space in the spectrum that each channel is allotted. The PAL-I standard specifies a video bandwidth of 5. 0 MHz and an audio carrier at 6 MHz.The DVB-T transmissions must fall within this channel plan, resulting in each digital channel also having a bandwidth of 8 MHz. Unlike PAL-I, the digital channel (carrying a multiplexed signal) utilises the entire bandwidth available to it simultaneously, transmitting 2048 carriers (in 2k mode). For tuning purposes, a centre frequency is used (Table is included in appendices). (digital spy, 2009) Decibels Decibels (dB) are commonly used to bring up gain or loss in circuits. The number of decibels is found from Gain in dB = 10*log(gain factor)or (Antenna basics, 2008) In some situations this is more involved than using gain or loss factors. But in many situations, decibels are simpler.For example, suppose 10 feet of cable loses 1 dB of signal. To figure the loss in a interminable cable, just add 1 dB for every 10 feet. In general, decibels let add or subtract kinda of multiply or divide. Noise Whether a signal is receivable is determined by thesignal to noise ratio(S/N). For TVs there are two main sources of noise 1. Atmosphere noise. There are many types of sources for this noise. A light switch creates a radio wave every time it opens or closes. Motors in some appliances produce nastyRF(radio frequency) noise. 2. Receiver noise. Most of this noise comes from the first transistor the antenna is attached to. about receivers are quieter than others. 2. Transmission cable Twin lead (ribbon cable) used to be common for TV antennas. It has its advantages. But due to its unpredictability when positioned near metal or dielectric objects, it has fallen out of favour. Coaxial cable is recommended. It is fully shielded and not affected by nearby objects. Transmission cable has a feature called itscharacteristic impedance, which for TV coax should alway s be 75 ohms. Although rated in ohms, this has nothing to do with resistance. A resistor converts electric energy into heat. The 75 ohms of a coaxial cable does not cause heat. Where it comes from is mathematically complicated and beyond our scope here.But coax also has ordinary resistance (mostly in the center conductor) and thus loses some of the signal, converting it into heat. The amount of this dissolution (loss) depends on the frequency as well as the cable length. TypeCentre conductorCable diameter RG-5920-23 gauge0. 242 inches RG-618 gauge0. 265 inches RG-1114 gauge0. 405 inches Figure 12 Cable loss in dB (Antenna basics, 2008) The above chart is only approximate. There are many cable manufacturers for each type and there is no enforcement of standards. If the mast-mount amplifier gain exceeds the cable loss then it shouldnt matter what cable you use.But there are two problems with this * Some cable has in come shielding. This is most common for RG-59, some other reason to avoid it. * When the cable run is longer than 200 feet, the low-numbered channels can become too soaked relative to the high-numbered channels. In this case, RG-11 or an ultra-low-loss RG-6 is recommended. (These alternatives are expensive. )Alternatively, frequency compensated amplifiers will work. 2. 6 Signal Amplifiers There are two types of signal amplifiers Preamplifiers(Mast-mounted amplifiers)These should be mounted as close to the antenna as possible. Usually the amplifier comes in two parts 1. The amplifier.This is an outdoor unit that is normally bolted to the antenna mast. It must have a very low noise figure, and enough gain to overcome the cable loss and the receivers noise figure. 2. The power module (power injector). This is an indoor unit that commonly lies on the floor behind the TV. It is inserted into the antenna cable between the amplifier and the TV. This module injects some power, usually DC, into the coaxial cable where the amplifier can use it. The power in jector is the amplifiers power supply. Distribution amplifiersThese are simple signal boosters. They are often necessary when an antenna drives multiple TVs or when the antenna cable is longer than 150 feet.Distribution amplifiers dont need to have a low noise figure, but they need to be able to handle large signals without over adulterateing. Commonly, distribution amplifiers have multiple outputs. (Unused outputs usually do not need to be terminated. ) Never feed an amplifier output directly into another amplifier. There should always be a long cable between the preamplifier and the distribution amplifier. Placing the two amplifiers close together can cause overload and/or oscillation. A mast-mounted amplifiers most important characteristic is its noise level, usually specified by thenoise figure. But many manufacturers dont take this number seriously. If it is given at all, it is often wrong. If all makers dont do them right then comparison-shopping is not possible.The author is inclined to rate amplifiers for their noise figures as follows 0. 5 dBsuperb (anything better runs into thermic atmospheric noise) 2. 0 dBexcellent 4. 0 dBfair 6. 0 dBpoor 10 dBawful 2. 7 Transmission delay (Coaxial cable) Transmission lines are described by their two most important characteristics the characteristic impedance Zo and the delay. For instance, a go almost (say 0. 01 wavelength) piece of coaxial cable such RG-58U has been taken and measured its capacitance with the other end open. A one foot length yields more or less 31. 2 pF. The inductance also has been measured with the other end shorted. It yields 76. 8 nH. The impedance may now be computed as Zo=LC Zo=76. ? 10-931. 2? 10-12=49. 6 ohms Here L and C are measured for the same length. The delay may also be computed Delay= L? C Delay= 76. 8? 10-9? 31. 2? 10-12=1. 55 nSec For an ideal line, the delay increases linearly with its length, while its impedance remains constant. After that it has been computed the velocity in foot per second V=lendelay V=11. 55? 10-9=6. 46? 108 foot per second or meters/second 8 10*966. 1 This is less than the speed of light. The ratio of the above speed to the speed of light gives the velocity factor Vf Vf=1. 966? 1082. 998? 108=0. 666 or 66. % of the speed of light As mentioned earlier, the delay increases linearly with the line length. For a given length, the phase difference between the input and output will increase with the frequency ? =2? f? delay Here the phase ? is in radians and the frequency f is Hertz. Converting the phase from radians to degrees requires multiplying by 3602? In this case if frequency is 900 MHz so phase delay will be ?deg=f? 360? delay=900? 106? 360? 1. 55? 10-9? 502. 2 This length that gives 90 degrees of phase shift is also known as a quarter wavelength. Figure 13 Linear change phase vs frequency Figure-13 An ideal transmission line gives a linear change of phase versus frequency.The distributed inductance and capacitance are the basic transmission line parameters. From these, it can be calculated the line impedance, the delay in terms of time and phase, the speed of propagation and the velocity factor. The inductive component has an additional component at the lower frequencies which slows the signal somewhat. This occurs nigh 100 KHz for small coax and lower for larger cables. For frequencies above 1 MHz, the dielectric constant of the cable is probably responsible for the decrease in the delay. Measuring the delay of cables can reveal some hidden properties that could make it unsuitable for some applications, such as carrying wideband data. (Audet, 2001) 3. 0 Possible solutionThe main component of a repeater is amplifier. There are many types of amplifier can be used for this job. RF amplifiers are electronic devices that accept a varying input signal and produce an output signal that varies in the same way as the input, but that has larger amplitude. RF amplifiers generate a all in all new output signal base d on the input, which may be emf, current, or another type of signal. Usually, the input and output signals are of the same type however, separate circuits are used. The input circuit applies varying resistance to an output circuit generated by the power supply, which smoothes the current to generate an even, uninterrupted signal.Depending on load of the output circuit, one or more RF pre-amplifiers may boost the signal and send the stronger output to a RFpower amplifier(PA). Other types of RF amplifiers include low noise, pulse, bi-directional, multi-carrier, buffer, and limiting amplifiers. Detector log video amplifiers (DLVAs) are used to amplify or measuresignals witha wide dynamic chemical chain and wide broadband. Successive detection logvideo amplifiers (SDLVAs)are log amplifiers that can operate over a wider dynamic range than DLVAs, while elongate range detector log video amplifiers (ERDLVAs)areDLVAs that can operate with a wider operating frequency. (Global Spec, 2008) * Military / Defense * Mobile / WirelessSystems * Plasma / electron Laser * RF Induction Heating * Radar SystemsAmplifier Type Applications * Low Noise Amplifier * Power Amplifier * Bi-directional Amplifier * Multi-carrier Amplifier * Multiplier (RF amplifier, 2008) 3. 1 RF amplifier Selecting RF amplifiers requires an analysis of several performance specifications. Operating frequency is the frequency range for which RF amplifiers meet all guaranteed specifications. Design gain, the ratio of the output to the input power, is normally expressed in decibels (dB), or Gdb= 10 * log (Po/Pi) Output power isthe signal power at the output of the amplifier under specified conditions such as temperature, load, potentiality standing wave ratio (VSWR), and supply voltage.Gain flatness indicates the degree of the gain variation over its range of operating wavelengths. Secondary performance specifications to consider include noise figure (NF), input VSWR, output VSWR, and monolithic microwave i ntegrated circuit (MMIC) technology. The noise figure, a measure of the amount of noise added to the signal during normal operation, is the ratio of the signal-to-noise ratio at the input of the component and the signal-to-noise ratio measured at the output. The NF value sets the lower limit of the dynamic range of the amplifier. enter VSWR and output VSWR are unit-less ratios ranging from1 to infinity that express the amount of reflected energy. Global Spec, 2008) There are several physical and electrical specifications to consider when selecting RF amplifiers. bodily specifications include package type and connector type. Package types includesurface mount technology (SMT),flat pack, and by hole technology (THT). RF amplifiers may also beconnector zedor use waveguide assemblies. Connector types include BNC, MCX, Mini UHF, MMCX, SMA, SMB, SMP, TNC, Type F, Type N, UHF, 1. 6 / 5. 6, and 7/16. definitive electrical characteristics include nominal operating voltage and nominal impe dance. Operating temperature is an important environmental parameter to consider. (Global Spec, 2008) 3. 1. 1 The Transistor AmplifierIn the preceding section explains the internal workings of the transistor and will introduce new terms, such as emitter, base, and gatherer. Here it discusses the overall operation of transistor amplifier. To understand the overall operation of the transistor amplifier, it must have to only consider the current in and out of the transistor and through the various components in the circuit. Therefore, from this point on, only the schematic symbol for the transistor will be used in the illustrations, and rather than thinking about majority and minority carriers that mean it will be only emitter, base and collector current. Before going into the basic transistor amplifier, there are two terms it should be familiar with AMPLIFICATION and AMPLIFIER.Amplification is the process of increasing the strength of a SIGNAL. A signal is just a general term used t o refer to any particular current, voltage, or power in a circuit. An amplifier is thedevicethat provides amplification (the increase in current, voltage, or power of a signal) without appreciably altering the original signal. Transistors are frequently used as amplifiers. Some transistor circuits are CURRENT amplifiers, with a small load resistance other circuits are designed for VOLTAGE amplification and have a high load resistance others amplify POWER. By inserting one or more resistors in a circuit, different methods of biasing may be achieved and the emitter-base battery eliminated.In addition to eliminating the battery, some of these biasing methods compensate for slight variations in transistor characteristics and changes in transistor conduction resulting from temperature irregularities. Notice in figure 2-12 that the emitter-base battery has been eliminated and the bias resistor RBhas been inserted between the collector and the base. electrical resistance RBprovides the nec essary forward bias for the emitter-base junction. Current flows in the emitter-base bias circuit from ground to the emitter, out the base lead, and through RBto VCC. Since the current in the base circuit is very small (a few hundred microamperes) and the forward resistance of the transistor is low, only a few tenths of a volt of positive bias will be felt on the base of the transistor.However, this is enough voltage on the base, along with ground on the emitter and the large positive voltage on the collector, to properly bias the transistor. (Intregrated Publishing, 2002) Figure 14 The basic transistor amplifier With Q1 properly biased, direct current flows continuously, with or without an input signal, passim the entire circuit. The direct current flowing through the circuit develops more than just base bias it also develops the collector voltage (VC) as it flows through Q1 and RL. Notice the collector voltage on the output graph. Since it is present in the circuit without an inp ut signal, the output signal starts at the VClevel and either increases or decreases.These dc voltages and currents that exist in the circuit before the application of a signal are known as quiescent voltages and currents (the quiescent state of the circuit). Resistor RL, the collector load resistor, is placed in the circuit to keep the full effect of the collector supply voltage off the collector. This permits the collector voltage (VC) to change with an input signal, which in turn allows the transistor to amplify voltage. Without RLin the circuit, the voltage on the collector would always be equal to VCC. The coupling capacitor (CC) is another new addition to the transistor circuit. It is used to pass the ac input signal and block the dc voltage from the preceding circuit. This prevents dc in the circuitry on the left of the coupling capacitor from affecting the bias on Q1.The coupling capacitor also blocks the bias of Q1 from reaching the input signal source. The input to the amp lifier is a sine wave that varies a few millivolts above and below zero. It is introduced into the circuit by the coupling capacitor and is applied between the base and emitter. As the input signal goes positive, the voltage across the emitter-base junction becomes more positive. This in effect increases forward bias, which causes base current to increase at the same rate as that of the input sine wave. Emitter and collector currents also increase but much more than the base current. With an increase in collector current, more voltage is unquestionable across RL.Since the voltage across RLand the voltage across Q1 (collector to emitter) must add up to VCC, an increase in voltage across RLresults in an equal decrease in voltage across Q1. Therefore, the output voltage from the amplifier, taken at the collector of Q1 with respect to the emitter, is anegativealternation of voltage that islargerthan the input, but has the same sine wave characteristics. During the negative alternation of the input, the input signal opposes the forward bias. This action decreases base current, which results in a decrease in both emitter and collector currents. The decrease in current through RLdecreases its voltage drop and causes the voltage across the transistor to rise along with the output voltage.Therefore, the output for the negative alternation of the input is apositivealternation of voltage that islargerthan the input but has the same sine wave characteristics. By examining both input and output signals for one complete alternation of the input, we can see that the output of the amplifier is an exact reproduction of the input except for thereversal in polarityand theincreased amplitude(a few millivolts as compared to a few volts). The PNP version of this amplifier is shown in the upper part of the figure. The primary difference between the NPN and PNP amplifier is the polarity of the source voltage. With a negative VCC, the PNP base voltage is slightly negative with respec t to ground, which provides the necessary forward bias condition between the emitter and base.When the PNP input signal goes positive, it opposes the forward bias of the transistor. This action cancels some of the negative voltage across the emitter-base junction, which reduces the current through the transistor. Therefore, the voltage across the load resistor decreases, and the voltage across the transistor increases. Since VCCis negative, the voltage on the collector (VC) goes in a negative direction (as shown on the output graph) toward -VCC(for example, from -5 volts to -7 volts). Thus, the output is a negative alternation of voltage that varies at the same rate as the sine wave input, but it is opposite in polarity and has a much larger amplitude.During the negative alternation of the input signal, the transistor current increases because the input voltage aids the forward bias. Therefore, the voltage across RLincreases, and consequently, the voltage across the transistor decre ases or goes in a positive direction (for example from -5 volts to -3 volts). This action results in a positive output voltage, which has the same characteristics as the input except that it has been amplified and the polarity is reversed. (Intregrated Publishing, 2002) 3. 1. 2 Ultra High Frequency Transistor Array (HFA) The HFA3046, HFA3096, HFA3127 and the HFA3128 are Ultra High Frequency Transistor Arrays that are fabricated from Intersil Corporations complementary bipolar UHF-1 process.Each array consists of five dielectrically isolated transistors on a common monolithic substrate. The NPN transistors face a fT of 8GHz while the PNP transistors provide a fT of 5. 5GHz. Both types exhibit low noise (3. 5dB), making them ideal for high frequency amplifier and sociable applications. (HFA3127, 2003) The HFA3046 and HFA3127 are all NPN arrays while the HFA3128 has all PNP transistors. The HFA3096 is an NPN-PNP combination. Access is provided to each of the terminals for the individu al transistors for maximum application flexibility. Monolithic construction of these transistor arrays provides close electrical and thermal matching of the five transistors. Features * NPN Transistor (fT) . . . . . . . . . . . . . . . . . . . . . . . . 8GHz * NPN Current Gain (hFE). . . . . . . . . . . . . . . . . . . . . . . . 130 * NPN Early Voltage (VA) . . . . . . . . . . . . . . . . . . . . . . . 50V * PNP Transistor (fT). . . . . . . . . . . . . . . . . . . . . . . . . 5. 5GHz * PNP Current Gain (hFE). . . . . . . . . . . . . . . . . . . . . . . . . 60 * PNP Early Voltage (VA) . . . . . . . . . . . . . . . . . . . . . . . .20V * Noise Figure (50? ) at 1. 0GHz . . . . . . . . . . . . . . . . . 3. 5dB * Collector to Collector Leakage . . . . . . . . . . . . . . . . . .30 dB) and this transistor amplifier gain was not enough for rebroadcasting signal, this project select another amplifier MAV-11SM from supervisor suggestion. One MAV-11SM amplifier gives around 10dB gain what has been shown in testing section. At last two MAV-11SM amplifiers and one HFA3127 has been used to get more than 30dB gain. It has been tested in network scalar analyzer. For battlefield test, a TV card, three TV aerials have been used. The amplifier circuit has been connected with one aerial. It was working very well when it was directly connected with TV card. That it can be said that the repeater was amplifying signal.But when another aerial with long transmission line was connected with amplifier and tried to rebroadcast the signal with 5v 1A power supply, TV picture quality was not improving expectedly. Digital repetition is an innovative concept, which helps to increase the DVB-T coverage while maintaining the highest quality and providing a greater flexibility. In spite of failure, this project was a high level platform to learn about signal and signalling. Future work As this project is unsuccessful at that certain point, this project will try to solve the rebroadcasting prob lem. And the transistor array will be a great option to amplify signal if all five transistors are been used. From HFA3127, it is possible to get min of 120 dB gain if it is soldered perfectly. Works CitedAntenna basics. (2008, October 12). Retrieved May 5, 2011, from http//www. hdtvprimer. com/ANTENNAS/basics. html. Audet, J. (2001). Coaxial Cable Delay. Charan, L. (2002). Inter symbos Interferance (ISI) and Raised Cosine filters. Retrieved celestial latitude 5, 2010, from http//www. complextoreal. com/chapters/isi. pdf. Datasheet. (2005, December 21). Retrieved February 20, 2011, from http//www. intersil. com/data/fn/fn3076. pdf. digital spy. (2009). Retrieved April 10, 2011, from http//www. digitalspy. co. uk/digitaltv/information/a12613/uhf-channel-and-frequency-guide. html. Global Spec. (2008). Retrieved April 10, 2011, from http//www. globalspec. om/learnmore/telecommunications_networking/rf_microwave_wireless_components/rf_amplifiers. HFA3127. (2003). Retrieved January 18, 20 11, from http//www. intersil. com/products/deviceinfo. asp? pn=HFA3127. Intregrated Publishing. (n. d. ). Retrieved April 4, 2011, from http//www. tpub. com/neets/book7/25c. htm. Monolithic Amplifier. (2002). Retrieved January 14, 2011, from http//www. minicircuits. com/pdfs/MAV-11SM+. pdf. Pool, I. (2002). Digital Video Broadcasting. Retrieved April 13, 2011, from http//www. radio-electronics. com/info/broadcast/digital-video-broadcasting/what-is-dvb-tutorial. php. Power Amplifier design. (1998). RF transmitting transistor and power ampli? er fundamentals . RF amplifier. (2008).Retrieved April 10, 2011, from http//www. globalspec. com/learnmore/telecommunications_networking/rf_microwave_wireless_components/rf_amplifiers. sub-TV. (2006, October 13). Retrieved April 20, 2011, from http//www. sub-tv. co. uk/antennatheory. asp. Trolet, C. (2002). SPOT filling gaps in DVB-T networks with digital repeaters. Presented by Gerard Faria, Scientific Director, Harris Broadcast Europe at Broadc astAsia2002 International Conference, Available at http//www. broadcast. harris. com. Gantt chart APPENDICES Frequency Allocation for DVB-T in UK Band IV Channel PAL-I Vision (MHz) PAL-I Sound (MHz) Centre (MHz) 21 471. 25 477. 25 474 22 479. 25 485. 25 482 3 487. 25 493. 25 490 24 495. 25 501. 25 498 25 503. 25 509. 25 506 26 511. 25 517. 25 514 27 519. 25 525. 25 522 28 527. 25 533. 25 530 29 535. 25 541. 25 538 30 543. 25 549. 25 546 31 551. 25 557. 25 554 32 559. 25 565. 25 562 33 567. 25 573. 25 570 34 575. 25 581. 25 578 35 583. 25 589. 25 586 36 591. 25 597. 25 594 37 599. 25 605. 25 602 38 607. 25 613. 25 610 Band V Channel PAL-I Vision (MHz) PAL-I Sound (MHz) Centre (MHz) 39 615. 25 621. 25 618 40 623. 25 629. 25 626 41 631. 25 637. 25 634 42 639. 25 645. 25 642 43 647. 25 653. 25 650 44 655. 25 661. 5 658 45 663. 25 669. 25 666 46 671. 25 677. 25 674 47 679. 25 685. 25 682 48 687. 25 693. 25 690 49 695. 25 701. 25 698 50 703. 25 709. 25 706 51 711. 25 717. 25 714 52 719. 2 5 725. 25 722 53 727. 25 733. 25 730 54 735. 25 741. 25 738 55 743. 25 749. 25 746 56 751. 25 757. 25 754 57 759. 25 765. 25 762 58 767. 25 773. 25 770 59 775. 25 781. 25 778 60 783. 25 789. 25 786 61 791. 25 797. 25 794 62 799. 25 805. 25 802 63 807. 25 813. 25 810 64 815. 25 821. 25 818 65 823. 25 829. 25 826 66 831. 25 837. 25 834 67 839. 25 845. 25 842 68 847. 25 853. 25 850