Communication Channel - Assignment Example

Q a) Block diagram of a communication channel b) the functions of the each systems are described here Transmitter: Transmitter is the first part in this piece outline. By utilizing the framework, messages can be created which is to be sent. 2. Encoder: Encoder comes second after the transmitter component in the correspondence framework. It performs the encoding of the given information, which implies that it changes the messages for transmission reason. In this framework, groupings of characters are made in an exceptional organization for a successful transmission. Encoding is utilized for security reason. 3. Noisy Channel: This is the third square in the piece chart of the floe diagram. Noisy channel is only the medium through which the message is transmitted. Messages are passed on through this channel. Distinctive channels have diverse qualities and shortcoming. 4. Decoder: Decoder translates the encoded message to recover the original message. This procedure has to be correct and accurate, or else the message is lost completely. This encoding and decoding will be exceptionally help full in military and versatile correspondences. 5. Receiver: it comes at the last part of the flow diagram. This could be said to mark the focus to which the data need to be conveyed (R.e). Q2 The electromagnetic spectrum The various wavelengths available in the electromagnetic spectrum are as follows: Radio Microwave Infrared Visible Ultraviolet X-rays Gamma rays 1) Radio Radio waves are electromagnetic spectra across a wide range of space. They can be categorized as follows; a) Super Low and Extra Low Frequency bands (SLF and ELF) normally occur natural. This can be very long antennae used by electricity authorities, called power lines radiating 50 or 60 Hz. The signal is experienced as hum. The largest natural source of this radio wave is the interaction between the solar wind and the ionosphere, which results in low frequency currents in the earth and oceans. They are usually studied by geophysicists to understand, inter alia, the availability of ore deposits whose electrical conductance is different from that of the surrounding crust. Like ULF (As illustrated in b) below), these bands achieve applications in communication with submarines, and uses very low information rates. b) 300 Hz - 3 kHz. Ultra Low Frequency (ULF). Water or the earth does not readily consume electromagnetic waves occurring in this range. As such, they might be utilized to communicate among or with submarines and with mines. One drawback is that, with such low frequencies, one can only be in a position to modulate the amplitude sufficiently so they cannot convey much data. This is not a disservice if the stage is needed, as is the situation for systems used for navigation. The wavelengths are long to the point that radio wires may be very long. c) 3 - 30 kHz. Very Low Frequency (VLF). They are similar to UHF in terms of capabilities to carry information and their application in navigation systems. d) 30 - 300 kHz. Low Frequency (LF). This band advantageous since waves can be propagated around the Earth, using refraction and reflections within the ionosphere or the earth surface. For this reason, these two wave channels form a waveguide for the radio waves in this range, which can hence be tapped for communication purposes across the oceans and around the world. e) 300 kHz - 3 MHz. Medium Frequency (MF).These waves are hindered by the fact that they are not so well reflected/refracted by the ionosphere, but during the night there is much reflection and ability to pick up radio stations hundreds or thousands of km away is achievable with ease. This is however not realizable when much shorter waves are put into perspective. They are very reliable for FM radio or television transmission for these one is required to have unobstructed path to the transmitter otherwise a relatively straight line. f) 3 - 30 MHz. High Frequency (HF). This is also referred to as the Short Wave band. It encompasses the CB band and the wave channels used for radio control. When the frequency of the carrier wave is increased, the possibilities to encode more information and to crowd channels are realized. g) 30 - 300 MHz. Very High Frequency (VHF). This wave range includes FM radio and television. Antennae are designed and constructed to about one quarter or one half wavelength long. h) 300 MHz - 3 GHz. Ultra High Frequency (UHF). (Note that GHz = 109 Hz). This includes some television and mobile phones because the band allows many channels to be utilized. i) 3 - 30 GHz. Super High Frequency (SHF). This range may be compared to microwave band, which is made use of in communication with satellites. j) 30 - 300 GHz. Extra High Frequency (EHF). This range has not had much use in the radio communication to this moment, for the reasons that the technology has complexity when it comes to encoding, decoding, amplitude modulation, and frequency modulation at such high frequencies. 2) Microwaves Microwaves are a type of electromagnetic radiation that has wavelength that ranges from as long as one meter to as short as one millimeter. They can be compared to frequencies between 300 MHz (0.3 GHz) and 300 GHz. Microwave sometimes includes the whole SHF band (3 to 30 GHz, or 10 to 1 cm) on the minimum. RF designs and implementation puts the lower boundary at 1 GHz (30 cm), and the upper boundary at around 100 GHz (3 mm). 3) Infrared These are wavelengths much longer than the visible wave and up to about 1 mm. the radio wave here as radiated can be felt as radiant heat. Most snakes have IR sensors for reading the environment. The band achieves military use in IR binoculars for the same reasons snakes use it for hunting and finding mammals, which are characterized by warmer bodies. 4) Visible They are wavelengths of about 400 nm which is violet light to 700 nm normally red light. (Note that nanometer = 10-9 m). This is the range that the sun radiates most strongly, and is not usually absorbed by the atmosphere. This range of visible light causes chemical reactions like experienced for vision and photosynthesis in plants. More artificially, they are made use of in diodes used in solar cells. 5) Ultraviolet They are wavelengths shorter than visible and across to about 10 nanometres. Chemistry employs the UV more, because individual photon is characterized by energy similar to that of a chemical reaction. When objects become hotter than the sun, they radiate in the UV. 6) X rays They are characterized by wavelengths that span over from several nm to 10 pm (Note that a picometre = 10-12 m). For those X-rays, which have wavelengths similar to atom, dimensions are used in determining the structure of crystals. X rays can be subdivided informally into soft X rays with longer wavelengths and hard X rays which are shorter in wavelengths and have higher energies. These energies however are enough to undertake an atom through ionization, which are capable of destroying chemical bonds. Naturally, some radioactive sources, or very hot parts like neutron stars can produce them. 7) Gamma rays Gamma rays have wavelengths that are less than about 10 pm. These rays posses high energies, and are often experienced at deep space. A 10 GeV cosmic ray contains a similar energy to an electron when accelerated through 10 billion volts. This energy causes a chain reaction of ionization that leads to showers of charged particles (Dodd). Q3 Signal spectra There are two signal spectra from the waveform illustrated above. One spectra is of T = 0.005 and the other of T = 0.001 W1 = 2π/T = 2*3.142/0.005 = 1256 rads = 200Hz W2 =2π/T = 2*3.142/0.001 = 6284 rads = 1Khz Q4 Calculations a) Power gain or loses at each stage RF amp stage Gain =output/input Gain = (1*10-3)/ (10*10-6) Gain = 100 Mixer stage Gain = output/input Gain = (0.5 * 10-3)/ (1 * 10-3) Gain = 0.5 Hence loss IF filter stage Gain = output/input Gain = (0.316 * 10-3)/ (0.5 * 10-3) Gain = 0.632 Hence loss IF amp stage Gain = output/input Gain = (0.314 * 10-3)/ (0.316 * 10-3) Gain = 0.9937 Hence loss b) Overall power gain Overall power Gain = Gain at RF amp stage * Gain at Mixer stage * Gain at IF filter * Gain at IF amp = (100 * 0.5 * 0.632 * 0.9937) = 31.4 c) power into the detector if the power into the first stage from the antenna is 2pW Pout = Pin * gain = (2 * 31.4) = 62.8pW d) Diagram Data Lengths of Cable 1 0.1 m Length of Cable 2 0.4 m Length of Cable 3 2.0 m Pin is -5 dB Insertion loss for the line is 1 dB per meter Calculation for Pout is as follows Loss due to Cable 1 = (0.1*1) = 0.1 dB Loss due to cable 2 = (0.4*1) = 0.4 dB Loss due to cable 3 = (2.0*1) = 2 dB Total loss due to cable insertion = (0.1 + 0.4 + 2) = 2.5 dB Pout = Pin + G1 + G2 + G3 – (Total loss due to cable insertion) Pout = (-5 + 20 + 15 + 10 – 2.5) dB Pout = 37.5 dB Q5 a) Operational Amplifier Noise i) Sources of noise and explanations Operational amplifiers have internal and external sources of noise. External noise are picked up from the environment while internal noise is associated with circuitry. The op-amp has three major noise sources that is a voltage noise (Vn) and a current noise (In). Voltage noise occurs differentially across the two inputs while the current noise occurs in both the inputs (The inverting and non-inverting inputs). Bias-compensated op-amps are likely to have some correlation between current noise in both their inverting and non-inverting inputs, and at very high frequencies, noise that is available within the tail currents of a long-tailed pair of FETs may couple to both gates through the gate-channel capacitance to experience correlated input noise currents at High Frequency. In addition to the two noises is the thermal or Johnson 1 noise. All resistors have thermal or Johnson1 noise intrinsically. When these elements heat up during operation, they deliver the noise into the system. ii) Types of noise The types of noise available in operational amplifiers are is white and popcorn noise, pink noise, shot noise, avalanche noise, and thermal noise. b) Factors for cumulative Effect of noise Sources. More than one noise source are involved for the cumulative effect to occur. Two noise sources, which produce same dB ratings, will result in a composite noise level 3 dB greater than individual noise considered alone. On the other hand, when the sources of noise differ by 10 dB, the resultant noise level is 0.4 dB higher than the loudest source considered alone. Q6) Calculations a) Data Noise figure of 13 dB Bandwidth of 1MHz Calculations for equivalent amplifier input noise power Conversion of frequency into gain dB From the conversion table of frequency to gain and vice versa 1Mhz = 60 dB Hence equivalent noise input power (60 – 13) = 47 dB They subtract each other b) Data Noise figure of 20db Power gain of 15 dB and Noise figure of 9dB Calculation of the overall noise figure referred to the input The resultant noise gain will be 0.4 dB greater than the highest noise level In this case 20 dB Resultant noise = 20 + 0.4 = 20.4 dB The overall gain referred to the input = (15 + 20.4) = 35.4 dB References Dodd, Annabel Z. The Essential Guide to Telecommunications. illnois: Prentice Hal, 2012. R.e, Blahut. Digital transmission of information. Ed. none. 3. Vol. 4. new york: addison-wesley, 1990. valder, Andy. Understanding telecommunication. Chicago: Institution of Engineering and Technology, 2006. Read More