Introduction to Communication Systems and Noise Analysis Part 1 PDF

INTRODUCTION TO COMMUNICATION SYSTEMS AND NOISE ANALYSIS PART1 Communication Systems Types of Electronic Communication Modulation and Multiplexing Electromagnetic Spectrum Danniver R. Guzman, ECE, MIT COMMUNICATION SYSTE...

INTRODUCTION TO COMMUNICATION SYSTEMS AND NOISE ANALYSIS PART1 Communication Systems Types of Electronic Communication Modulation and Multiplexing Electromagnetic Spectrum Danniver R. Guzman, ECE, MIT COMMUNICATION SYSTEMS COMPONENTS OF COMMUNICATION SYSTEM TRANSMITTER – a collection of electronic components and circuit designed to convert the electrical signal to a signal suitable for transmission over a given communication medium. It is made up of oscillators, amplifiers, tuned circuits and filters, modulators, frequency mixers, frequency synthesizers and other circuits. COMMUNICATION CHANNEL – the medium by which the electronic signal is sent from one place to another. This include wire conductors, fiber optic cables, free space, sonar, carrier current transmission. COMPONENTS OF COMMUNICATION SYSTEM RECEIVERS – a collection of electronic components and circuits that accepts the transmitted message from the channel and convert it back to a form understandable by humans. It contains amplifiers, oscillators, mixers, tuned circuits and filters and a demodulator or detector that recovers the original intelligence signal from the modulated carrier. TRANSCEIVERS – it can be both transmitter and receiver so that it can both send and receive. The transmitter and receiver circuits are packaged in a single housing and usually share same circuits such as power supply. COMPONENTS OF COMMUNICATION SYSTEM ATTENUATION – inevitable no matter what medium of transmission. It is proportional to the square of the distance between the transmitter and receiver. NOISE – it is the bane of all electronic communications, its effect is mostly experienced on the receiver part of any electronic communications. The measure of noise is usually expressed in terms of the signal-to-noise ratio (SNR), which is the signal power divided by the noise power and can be stated numerically in terms of Decibels (dB) TYPES OF ELECTRONIC COMMUNICATIONS SIMPLEX – Communication is conducted in ONE WAY COMMUNICATION. TYPES OF ELECTRONIC COMMUNICATIONS DUPLEX – Communication is TWO-WAY but not at the same time. TYPES OF ELECTRONIC COMMUNICATIONS FULL-DUPLEX – Communication is TWO-WAY and simultaneous. TYPES OF ELECTRONIC COMMUNICATIONS ANALOG SIGNAL a smoothly and continuously varying voltage or current. Voice and video voltages are analog signals that vary in accordance with the sound or light variations that are analogous to the information being transmitted. TYPES OF ELECTRONIC COMMUNICATIONS DIGITAL SIGNAL contrast to analog signals, do not vary continuously, but change in steps or in discrete increments. Most digital signals use binary or two-state codes. MODULATION AND MULTIPLEXING Modulation and multiplexing are electronic techniques for transmitting information efficiently from one place to another. Modulation makes the information signal more compatible with the medium, and multiplexing allows more than one signal to be transmitted concurrently over a single medium. Modulation and multiplexing techniques are basic to electronic communication. Once you have mastered the fundamentals of these techniques, you will easily understand how most modern communication systems work. MODULATION AND MULTIPLEXING BASEBAND TRANSMISSION – putting the original voice, video, or digital signals directly into the medium. For example, telephone and intercom systems, it is the voice itself that is placed in the wires and transmitted over some distance to the receiver. In most computer networks, the digital signals are applied directly to coaxial or twisted-pair cables for transmission to another computer. BROADBAND TRANSMISSION – when a baseband voice, video or digital signal modify another, high frequency signal called carrier. The intelligence signal changes the carrier in a unique way. The modulated carrier is amplified and sent to the antenna for transmission. MODULATION AND MULTIPLEXING MODULATION AND MULTIPLEXING Two most common method of modulation is Amplitude Modulation(AM) and Frequency Modulation(FM) MODULATION AND MULTIPLEXING MODULATION – The process of varying the characteristics or properties of a higher frequency carrier signal AmplitudeModulation(AM) – baseband information signal called the modulating signal varies the amplitude of the higher- frequency carrier signal, FrequencyModulation(FM) - baseband information signal called the modulating signal varies the FREQUENCY of the higher- frequency carrier signal, PhaseModulation(PM) - baseband information signal called the modulating signal varies the PHASE ANGLE of the higher- frequency carrier signal, It has the same appearance as FM. MODULATION AND MULTIPLEXING FREQUENCY SHIFT KEYING - data is converted into frequency varying tones. PHASE SHIFT KEYING – data introduces a 180o phase shift MODEM – an electronic device used to convert digital to analog and vice versa. MODULATION AND MULTIPLEXING MULTIPLEXING – the process of allowing two or more signals to share the same medium or channel MULTIPLEXER – converts the individual baseband signal into a composite signal that is used to modulate a carrier in the transmitter. DEMULTIPLEXER – converts the composite signal into baseband signal 3 TYPES OF MULTIPLEXING: Frequency Division Multiplexing – the intelligence signals modulate subcarriers on different frequencies that are then added together Time Division Multiplexing – multiple intelligence signal are sequentially sampled and a small piece of each is used to modulate a carrier Code Division Multiplexing – the signals to be transmitted are converted to digital data that is then uniquely coded with a faster binary code. MODULATION AND MULTIPLEXING Multiplexing at the Transmitter Demultiplexing at the Receiver THE ELECTROMAGNETIC SPECTRUM Electromagnetic waves are signals that oscillate; i.e., the amplitudes of the electric and magnetic fields vary at a specific rate. The field intensities fluctuate up and down, and the polarity reverses a given number of times per second. The electromagnetic waves vary sinusoidally. These oscillations may occur at a very low frequency or at an extremely high frequency. The range of electromagnetic signals encompassing all frequencies is referred to as the electromagnetic spectrum. THE ELECTROMAGNETIC SPECTRUM All electrical and electronic signals that radiate into free space fall into the electromagnetic spectrum. Not included are signals carried by cables. Signals carried by cable may share the same frequencies of similar signals in the spectrum, but they are not radio signals. Within the Electromagnetic spectrum, the middle ranges are located the most commonly used radio frequencies for two-way communication, TV, cell phones, wireless LANs, radar, and other applications. At the upper end of the spectrum are infrared and visible light. THE ELECTROMAGNETIC SPECTRUM THE ELECTROMAGNETIC SPECTRUM FREQUENCY is the number of times a phenomenon occurs at a given period of time. The number of cycles of a repetitive wave that occurs in a given period of time. Measured in cycles per second (cps) and Hertz (Hz), named for the German physicist Heinrich Hertz, who was a pioneer in the field of electromagnetics. One cycle per second is equal to one hertz, abbreviated (Hz). Therefore, 440 cps=440 Hz THE ELECTROMAGNETIC SPECTRUM WAVELENGTH The distance occupied by one cycle of a wave, and it is usually expressed in meters. measured between identical points on succeeding cycles of a wave also the distance traveled by an electromagnetic wave during the time of one cycle THE ELECTROMAGNETIC SPECTRUM WAVELENGTH Electromagnetic waves travel at the speed of light, or 299,792,800 m/s. The speed of light and radio waves in a vacuum or in air is usually rounded off to 300,000,000 m/s (3x108 m/s), or 186,000 mi/s. The speed of transmission in media such as a cable is less. The wavelength of a signal, which is represented by the Greek letter λ (lambda), is computed by dividing the speed of light by the frequency f of the wave in hertz: λ 5 300,000,000/f. For example, the wavelength of a 4,000,000- Hz signal is λ = 300,000,000/4,000,000 = 75 m THE ELECTROMAGNETIC SPECTRUM EXAMPLE: THE ELECTROMAGNETIC SPECTRUM EXAMPLE: 1. A signal with a wavelength of 1.5m has a frequency of _________. 2. A signal travels a distance of 75ft. In the time it takes to complete 1 cycle. What is its frequency? 3. The maximum peaks of an e-wave are separated by a distance of 8in. What is the frequency in Megahertz? In Gigahertz? THE ELECTROMAGNETIC SPECTRUM EXTREMELY LOW FREQUENCIES (ELF)-30 to 300 Hz This include AC power lines as well as those in the low end of human audio range. VOICE FREQUENCIES (VF) – 300 to 3000Hz Normal range of human speech VERY LOW FREQUENCIES (VLF) – 9KHz to 30KHz Includes the higher end of the human hearing range up to about 15 to 20 KHz. Musical instruments make sounds in this range as well as in the ELF and VF. Also for government and military communication – VLF radio transmission is used by navy to communicate with submarines. LOW FREQUENCIES (LF) – 30KHz to 300KHz Aeronautical and marine navigation communication. Used as SUBCARRIERS for baseband modulation. THE ELECTROMAGNETIC SPECTRUM MEDIUM FREQUENCIES (MF)-300KHz to 3000KHz AM radio broadcasting (535 to 1605 KHz) Other Applications are various marine and amateur radio communication HIGH FREQUENCIES (HF)-3MHz to 30MHz Known as short waves All kinds of simplex broadcasting and half-duplex two-way radio communication Voice of America and British Broadcasting Company Government and military communication Amateur radio and CB communication VERY HIGH FREQEUNCIES (VHF)-30 to 300MHz Mobile radio, marine and aeronautical communication FM Broadcasting (88 to 108MHz) and TV Broadcasting channels 2 through 13 Radio Amateurs THE ELECTROMAGNETIC SPECTRUM ULTRA HIGH FREQUNECIES(ULF)-300 to 3000MHz Includes the UHF TV channels 14 through 51. Land mobile communication and services e.g. Cellular telephones and military communications radar and navigation services and also radio amateurs SUPER HIGH FREQUENCIES(SHF)-1000MHz to 30GHz Aka microwaves; microwave ovens operate at 2.45GHz Widely used by satellite communication and radar. Wireless local area network(WLAN) and cellular telephone system EXTREMELY HIGH FREQUENCIES (EHF)-30 to 300GHz Used in satellite communication telephony, computer data, short-haul cellular networks and specialized radar. THE ELECTROMAGNETIC SPECTRUM OPTICAL SPECTRUM – this is the region occupied by light waves (0.1mm to 700nm) INFRARED – sandwiched between the highest radio frequencies and the visible portion of the electromagnetic spectrum. Generally associated with heat which is produced by light-bulbs, our bodies and any physical equipment that generates heat. It can also be generated by special type of light emitting diodes (LED) and lasers. Used in various very special kind of communication. Used in astronomy to detect stars and other physical bodies in the Universe and guidance for weapon systems. Used as detectors when heat radiate from aircrafts and missiles and also guide missiles to target. Used as remote control for TV units where coded signals are send to the TV from the remote control for different functions. It also the basis for fiber optic communication. VISIBLE SPECTRUM – Light is a especial type of electromagnetic radiation that has a wavelength of THE ELECTROMAGNETIC SPECTRUM OPTICAL SPECTRUM VISIBLE SPECTRUM – Light is a especial type of electromagnetic radiation that has a wavelength of 400 to 800 nm. Red is low-frequency or long- wavelength light, whereas violet is high-frequency or short-wavelength light. Light is used for various kinds of communication, light waves can be modulated and transmitted through glass fiber, and they can also be transmitted through free space. ULTRAVIOLET - covers the range from about 4 to 400 nm. Ultraviolet is not used for communication; its primary use is medical.