Dr. M. Venu Gopala Rao, Professor, Dept. of ECE, KL University KL University, Vaddeswaram, Dept. of ECE, II B. Tech ECE: Analog Communications 13-EC207 Lecture Notes-1 Fundamentals of Electronics Communications System 1.0 Introduction. 1.1 Important events in development of communications systems 1.2 Electronic Communications Systems Transmitter Communication Channel Receiver Noise 1.3 Modulation and Demodulation Need for Modulation Analog electronic communications system Types of Communications Systems 1.4 Propagation of electromagnetic waves 1.5 The Electromagnetic Frequency Spectrum 1.6 Objectives of Communications System Design OBJECTIVES Define the fundamental purpose of an electronic communications system. Illustrate a basic electronic communication system and their elements. Explain the terms modulation and demodulation and why they are needed in an electronic communications system. Describe the electromagnetic frequency spectrum and their propagation. 1 Dr. M. Venu Gopala Rao, Professor, Dept. of ECE, KL University 1.0 Introduction: The fundamental purpose of an electronic communications system is to transfer information from one place to another. Thus, electronic communication can be summarized as the transmission, reception and processing of information between two or more locations using electronic circuits. The original source information can be in analog form, such as human voice or music, or in digital form, such as binary coded numbers or alphanumeric codes. Analog signals are time varying voltages or currents that are continuously changing, such as sine and cosine waves. An analog signal contains an infinite number of values. Digital signals are voltages or currents that change in discrete steps or levels. The most common form of digital signal is binary, which has two levels. All forms of information however must be converted to electromagnetic energy before being propagated through an electronic communication system. There are numerous forms of communication. We have wired communication, wherein examples are telephone, broadband internet at home, local area networks at office, just to name a few. We also have wireless communication such as mobile, WiFi, Bluetooth, radio broadcast, TV broadcast, and many others. It seems that our lives could not function properly without communication. 1.1: Important events in development of communication systems 1838: Telegraph (Cooke and Wheatstone) 1871: Telephone “Caveat” Some believe Antonio Meucci (not A.G. Bell) was the inventor of the talking telegraph or telephone. 1900: Marconi sends wireless signal across Atlantic. 1920: Beginning of radio broadcasting. 1936: First public B/W TV broadcast. 1951: First public color TV broadcast. 1957: First earth satellite, Sputnik I. 1962: First communication satellite, Telstar I. 1966: Principles of fibre optic communications published (Kao and Hockham). 1973: Birth of Internet. 2 Dr. M. Venu Gopala Rao, Professor, Dept. of ECE, KL University 1979: First-generation cellular phone service. 1985: Fax machines gain popularity. 1990’s: HDTV, second-generation cellular systems. 2000’s: Third-generation cellular systems, satellite radio, “anytime, anywhere, multimedia communications”. 2010’s: Online social networks, smart phones, LTE, wireless sensor networks (WSNs) A Chronology of Electrical Communication Preliminary Developments: Volta discovers the battery; the mathematical treatises by Fourier, Cauchy, and 1800-1837 Laplace; experiments on electrical and magnetism by Oersted, Ampere, Faraday, and Henry; Ohm’s Law (1826); early telegraph systems by Gauss, Weber, and Wheatstone Telegraphy: Morse perfects his system; Steinhill finds that the earth can be used for a current path; commercial service initiated (1844); multiplexing techniques 1838-1866 devised; William Thomson (Lord Kelvin) calculates the pulse response of a telegraph line (1855); transatlantic cables installed by Cyrus Field and associates 1845 Kirchhoff’s circuit laws enunciated 1864 Maxwell’s equation predicts electromagnetic radiation Telephony Acoustic transducer perfected by Alexander Graham Bell, after earlier attempts by Reis; first telephone exchange, in New Haven, with eight lines (1878); 1876-1899 Edison’s carbon-button transducer; cable circuits introduced; Strowger devises automatic step-by-step switching (1887); the theory of cable loading by Heaviside, Pupin, and Campbell Wireless telegraphy Heinrich Hertz verifies Maxwell’s theory; demonstrations by Marconi and 1887-1907 Popov; Marconi patents a complete wireless telegraph system (1897); the theory of tuning circuits developed by Sir Oliver Lodge; commercial service begins, including ship-to-shore and transatlantic systems 1894 Marconi Radio broadcasting Oliver Heaviside’s publication on operational calculus, circuits, and 1892-1899 electromagnetics Communication electronics Lee De Forrest invents the Audion (triode) based on Fleming’s diode; basic filter types devised by G. A. Campbell and others; experiments with AM radio 1904-1920 broadcasting; transcontinental telephone line with electronic repeaters completed by the Bell System (1915); multiplexed carrier telephony introduced; E. H. Armstrong perfects the superheterodyne radio receiver (1918); first 3 Dr. M. Venu Gopala Rao, Professor, Dept. of ECE, KL University commercial broadcasting station, KDKA, Pittsburgh Transmission theory 1920-1928 Landmark papers on the theory of signal transmission and noise by J. R. Carson, H. Nyquist, J. B. Johnson, and R. V. L. Hartley Television Mechanical image-formation system demonstrated by Baird and Jenkins; 1923-1938 theoretical analysis of bandwidth requirements; Farnsworth and Zworykin propose electronic systems; vacuum cathode-ray tubes perfected by DuMont and others; field tests and experimental broadcast begin 1931 Teletypewriter service initiated 1934 H. S. Black develops the negative-feedback amplifier 1936 Armstrong’s paper states the case for FM radio 1936 First public B/W TV broadcast 1937 Alec Reeves conceives pulse code modulation World War II 1938-1945 Radar and microwave systems developed; FM used extensively for military communications; improved electronics, hardware, and theory in all areas Statistical communication theory 1944-1947 Rice develops a mathematical representation of noise; Weiner, Kolmogoroff, and Kotel’nikov apply statistical methods to signal detection Information theory and coding 1948-1951 C. E. Shannon publishes the founding papers of information theory; Hamming and Golay devise error-correcting codes 1948-1951 Transistor devices invented by Bardeen, Brattain, and Shockley 1950 Time-division multiplexing applied to telephony 1951 First public color TV broadcast 1953 Color TV standards established in the United States 1955 J. R. Pierce proposes satellite communication systems 1956 First transoceanic telephone cable (36 voice channels) 1957 First earth satellite, Sputnik I 1958 Long-distance data transmission system developed for military purposes 1960 Maiman demonstrates the first laser 1961 Integrated circuits go into commercial production 1962 Satellite communication begins with Telstar I High-speed digital communication Data transmission service offered commercially; wideband channels designed for digital signaling; pulse code modulation proves feasible for voice and TV 1962-1966 transmission; major breakthroughs in the theory and implementation of digital transmission, including error-control coding methods by Viterbi and others, and the development of adaptive equalization by Lucky and co-workers 1963 Solid-state microwave oscillators perfected by Gunn 1964 Fully electronic telephone switching system (No. 1 ESS) goes into service 1965 Mariner IV transmits pictures from Mars to earth 4 Dr. M. Venu Gopala Rao, Professor, Dept. of ECE, KL University Wideband communication systems Cable TV systems; commercial satellite relay service becomes available; 1966-1975 optical links using lasers and fiber optics; the forerunner of the Internet, ARPANET was created in 1969; 1973 Birth of Internet Integrated-circuit communication modules; high-frequency power MOS devices; digital signal processing with microprocessors; filter circuits using 1975-1985 switched capacitors and surface acoustic waves; rate distortion theory and predictive coding applied to data compression 1979 First-generation cellular phone service 1983 TCP/IP became the official protocol of ARPANET/Internet 1985 Fax machines gain popularity 1990 HDTV, second-generation cellular systems 1985 to Gigabit Networks, B-ISDN or ATM Networks, Digital TV present Third- and fourth-generation wireless systems (Advanced mobile beyond 2000 communications) International Mobile Telecommunications (IMT)-2000; Wireless ATM (WATM) 2010 Online social networks, smart phones, LTE, wireless sensor networks (WSNs) 1.2 Electronic Communication Systems: Fig1.1 shows a simplified block diagram of an electronic communications system that includes a transmitter, a transmission medium, a receiver and system and other interference noise. Fig1.1 Simplified block diagram of an electronic communications system Transmitter: The transmitter is a collection of electronic components and circuits that converts the electrical signal into a signal suitable for transmission over a given 5 Dr. M. Venu Gopala Rao, Professor, Dept. of ECE, KL University medium. Transmitters are made up of oscillators, amplifiers, tuned circuits and filters, modulators, frequency mixers, frequency synthesizers, and other circuits. Communication Channel: The communication