Communication Systems PDF

IT2311 Communication Systems Basics of Communication Systems (Frenzel, 2022) In its simplest form, communication is exchanging any type of message between...

IT2311 Communication Systems Basics of Communication Systems (Frenzel, 2022) In its simplest form, communication is exchanging any type of message between a sender and receiver. It can be a plain conversation between friends about their thoughts, ideas, and feelings, either in person (verbal) or by using communication channels such as smartphones, computers, or telephones. The process of communication can also be nonverbal (body language), print, and electronic processes. In electronics, “communication systems” refers to communication that uses a transmitter, communication channel, and receiver. The message is called information, or an intelligence signal, in the form of an electronic signal. Transmitter The first step in sending a message is to convert it into an electronic form suitable for transmission. Common examples include the following: A microphone is used to convert the sound to an electronic audio signal for voice messages. For TV, a camera converts light information in the scene to a video signal. In computer systems, the message is typed on a keyboard and converted to binary codes stored in memory or transmitted serially. Physical characteristics such as temperature, pressure, and light intensity use transducers to convert them into electronic signals. Communication Channel It is the medium wherein an electronic signal is sent from one point to another. Several types of communication channels include: Electrical Conductor – a material that conducts electricity and allows the flow of charge such metals and metal alloys. The channel can be as simple as a pair of wires that carry a voice signal from a microphone to a headset. Optical Media can be a fiber-optic cable or light pipe that carries the message on a light wave. These are used today to carry long-distance calls and all Internet communications. Free Space: The resulting system is known as radio when free space is the channel. Radio is the term applied to any wireless communication from point to point. Others: Other communication channels are used in special communication systems such as sonar; water is used as the medium. Passive sonar “listens” for underwater sounds with sensitive hydrophones. In contrast, active sonars use an echo-reflecting technique for determining how far away objects underwater are and in what direction they are moving. Receiver It is a set of electronic components and circuits that accept transmitted messages from the channel and translate them back, which humans understand. A receiver contains the following: Amplifiers – produce an increased version of the input signal. Oscillators – produce a continuous, repeated, and alternating waveform without input. Mixers – combine two or more electronic signals into one or two output signals. Tuned Circuits – or resonant circuits, combine an inductor and capacitor to make a circuit responsive to a frequency. Filters – a circuit capable of amplifying specific frequencies while attenuating others. 01 Handout 1 *Property of STI  [email protected] Page 1 of 6  IT2311 Block Diagram of Communication Systems This diagram consists of five (5) blocks that represent elements used in the system that go in this order: Information Source, Transmitter, Channel, Receiver, and Destination. The process starts with the information source wherein the message originates, whether in the form of words, codes, symbols, or sound signals, and goes through a transmitter, a channel, and a receiver, and ends with the destination block, which is the final stage that receives the message signal and processes it to understand the information. Figure 1. Retrieved from Frenzel, L. (2022). Principles of electronic communication systems: Fifth edition. McGraw Hill. Overview of the History of Communication Systems (Frenzel, 2022) Electronic communication has undergone various innovations, developments, and changes throughout time. From the invention of the telephone by Alexander Graham Bell in 1976 to the rise of Apple’s iPhone in 2007, here are some milestones in electronic communication's history. Year Invention/Event People/Country Involved 1837 The invention of the telegraph (patented in 1844) Samuel Morse 1876 The invention of the telephone Alexander Graham Bell 1887 The discovery of radio waves Heinrich Hertz 1901 The first transatlantic radio contact made Guglielmo Marconi 1906 The invention of amplitude modulation Reginald Fessenden 1920 The first radio broadcast KDKA Pittsburgh 1923 The invention and demonstration of the television Vladimir Zworykin 1939 The first use of two-way radios (walkie-talkies) United States 1948 The invention of the transistor Bell Laboratories 1958-1969 The invention of the integrated circuit Jack Kilby & Robert Noyce 1975 The first personal computers United States 1982-1990 The development and the first use of the Internet Tim Burners-Lee 1995 The deployment of Global Positioning System (GPS) United States 1996-2001 The first smartphones by BlackBerry, Nokia, and Palm Worldwide 1997 The first wireless local area networks (LANs) United States 2004-2006 The rise of social media United States 2007 The development of Apple’s iPhone United States 2009 The first fourth-generation LTE cellular networks Worldwide 2019 The beginning of 5G cellular service Uruguay Table 1. Electronic communication milestones 01 Handout 1 *Property of STI  [email protected] Page 2 of 6  IT2311 Categories of Electronic Communication (Frenzel, 2022) Electronic communications are categorized as whether they are one-way or two-way transmissions and analog or digital signals. Simplex Communication One-way or simplex communication is considered the simplest way electronic communication is conducted. The information is transmitted from one device to another, but the receiver cannot send any information back to the transmitting device, such as TV broadcasting and remote control. Satellite TV Broadcasting Remote Control Figure 2. Retrieved from Frenzel, L. (2022). Principles of Figure 3. Retrieved from Frenzel, L. (2022). Principles of electronic communication systems: Fifth edition. McGraw Hill. electronic communication systems: Fifth edition. McGraw Hill. A simplex can be a downlink or an uplink. In Figure 2, the satellite transmits the television programming to the home antenna and the television set. The TV does not talk back, so this is a simplex downlink. Once the satellite gets its programming material from a ground-based TV station that transmits to the satellite, a simplex uplink is used. Still, no two-way communication takes place as the up and down links are separated connections. In Figure 3, the control link to the drone is simple. But duplex transmission occurs if the drone’s camera transmits video back to the operator. Duplex Communication A duplex communication can be a full duplex or a half-duplex. Full duplex communication is two-way, wherein people communicating can talk and listen simultaneously, such as using a telephone in Figure 4, or with devices, can send and receive signals simultaneously. Full Duplex Half Duplex Figure 4. Retrieved from Frenzel, L. (2022). Principles of Figure 5. Retrieved from Frenzel, L. (2022). Principles of electronic communication systems: Fifth edition. McGraw Hill. electronic communication systems: Fifth edition. McGraw Hill. 01 Handout 1 *Property of STI  [email protected] Page 3 of 6  IT2311 A half-duplex communication is still a two-way communication, but the direction alternates, and the communicating parties take turns transmitting and receiving, such as the transceiver in Figure 5. Most military, fire, aircraft, and marine radio transmissions also utilize half-duplex communications. Another example is a walkie-talkie. Analog Signal It is a continuously varying voltage or current. Typical analog signals include the following: a) sine wave “tone,” b) voice, and c) TV signal. Figure 6. Retrieved from Frenzel, L. (2022). Principles of electronic communication systems: Fifth edition. McGraw Hill. A sine wave is a single-frequency analog signal. At the same time, voice and video voltages are analog signals that vary based on sound or light variations similar to the information being transmitted. Physical characteristics such as temperature, pressure, or light level produce analog signals when detected by a sensor. Digital Signal Digital signals do not change continuously but vary in discrete increments compared to analog signals. Examples include telegraph (Morse code), continuous-wave (CW) code, and serial binary code. Telegraph (Morse code) It uses Morse code, a system for short (dots) and long (dashes) signals to represent letters and numbers. Here are important reminders to note in the Morse code table in Table 2. The length of a dot is one unit, while a dash is equivalent to three units. The space between parts of the same letter is one unit. The space between letters is three units. The space between words is seven units. 01 Handout 1 *Property of STI  [email protected] Page 4 of 6  IT2311 Table 2. Morse code. Conversion to Telegraph using Morse Code Figure 7. Retrieved from Frenzel, L. (2022). Principles of electronic communication systems: Fifth edition. McGraw Hill. Figure 7 shows the telegraph signal of the capital letter R using its Morse code value, — wherein: Short Mark represents the dot. Long Mark represents the dash. Space represents the space between the unit. Continuous-Wave (CW) Code Also known as radio telegraphy, a sine wave signal is turned off and on for short or long durations to represent the dots and dashes. Conversion to CW Signal Figure 8. Retrieved from Frenzel, L. (2022). Principles of electronic communication systems: Fifth edition. McGraw Hill Figure 8 shows the continuous-wave signal of the capital letter R, wherein: The Morse code value of the letter/number should be obtained first. A short sine wave duration represents a dot. A long sine wave duration represents a dash. Binary Codes and ASCII Binary codes represent numbers, letters, or special symbols in computers transferred serially through a wire, radio, or optical medium. The American Standard Code for Information Interchange, or ASCII, is the most commonly used digital communication code. See Table 3 for the binary and ASCII values. Conversion to Binary Code Signal using ASCII Figure 9. Retrieved from Frenzel, L. (2022). Principles of electronic communication systems: Fifth edition. McGraw Hill Figure 9 shows the conversion of the capital letter V to a binary code signal, wherein: The binary value of the letter/number should be obtained first. 1s are placed concerning the given height/amplitude. 0s are placed concerning the starting voltage. 01 Handout 1 *Property of STI  [email protected] Page 5 of 6  IT2311 Binary and ASCII Code Values Table 2. ASCII and binary codes References: Electronic Post (2020). Block diagram of communication systems [Web Article]. Retrieved on July 3, 2023, from https://electronicspost.com/block-diagram-of-communication-system-with-detailed-explanation/ Frenzel, L. (2022). Principles of electronic communication systems: 5th ed. McGraw Hill. Torrieri, D. (2022). Principles of spread-spectrum communication systems: 5th ed. Springer. 01 Handout 1 *Property of STI  [email protected] Page 6 of 6