Analog Communication Suresh P. Nair [AIE, ME, (PhD)] MIEEE Professor & Head Department of Electronics and Communication Engineering Royal College of Engineering and Technology Chiramanangad PO, Akkikkavu, Thrissur, Kerala,
India INTRODUCTION: INTRODUCTION Telecommunications: Telecommunications Tele (Far) + Communications Early telecommunications smoke signals and drums visual telegraphy (or semaphore in 1792) Telegraph and telephone Telegraph (1839) Telephone (1876) Radio and television Telephony Voice and Data Human Communication: Human Communication Methods of communication: Face to face Written word (letters ) Electrical innovations: Telegraph Telephone Radio Television Internet (computer) Communication Systems: Communication Systems A Communications Model : A Communications Model Basic Communication System: Basic Communication System Basic Communication System: Basic Communication System Basic components: Transmitter Channel or medium Receiver Noise degrades or interferes with transmitted information. Transmitter: 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 medium . Transmitters are made up of oscillators, amplifiers, tuned circuits and filters, modulators, frequency mixers, frequency synthesizers, and other circuits. Communication Channel: Communication Channel The communication channel is the medium by which the electronic signal is sent from one place to another . Types of media include Electrical conductors Optical media Free space System-specific media (e.g., water is the medium for sonar). Physical Transmission Media: Physical Transmission Media Physical Transmission Media: Physical Transmission Media Receivers : Receivers A receiver is a collection of electronic components and circuits that accepts the transmitted message from the channel and converts it back into a form understandable by humans . Receivers contain amplifiers, oscillators, mixers, tuned circuits and filters, and a demodulator or detector that recovers the original intelligence signal from the modulated carrier. Transceivers : Transceivers A transceiver is an electronic unit that incorporates circuits that both send and receive signals . Examples are: Telephones Fax machines Cell phones Computer modems Signal Attenuation: Signal Attenuation Signal attenuation , or degradation, exists in all media of wireless transmission. It is proportional to the square of the distance between the transmitter and receiver. Noise: Noise Noise is random, undesirable electronic energy that enters the communication system via the communicating medium and interferes with the transmitted message. Types of Electronic Communication: Types of Electronic Communication Electronic communications are classified according to whether they are One-way ( S implex ) or two-way ( Half duplex or F ull duplex ) transmissions. Analog or digital signals. Simplex: Simplex The simplest method of electronic communication is referred to as simplex . This type of communication is one-way. Examples are: Radio TV broadcasting Half Duplex : Half Duplex The form of two-way communication in which only one party transmits at a time is known as half duplex . Examples are: Police, military, etc. radio transmissions Walky Talky HAM radio Morse Code Full Duplex : Full Duplex Most electronic communication is two-way and is referred to as duplex . When people can talk and listen simultaneously, it is called full duplex . The telephone is an example of this type of communication. Slide 22: COMMUNICATION SYSTEM ANALOG COMMUNICATION DIGITAL COMMUNICATION Analog Communication: Analog Communication Digital Communication: Digital Communication Slide 25: To be transmitted, data must be transformed to electromagnetic signals. Note Data: Data Data can be analog or digital . The term analog data refers to information that is continuous. Digital data refers to information that has discrete states. Analog data take on continuous values. Digital data take on discrete values. Comparison of analog and digital signals: Comparison of analog and digital signals Analog Signal: Analog Signal Cycle Time Signal Amplitude Frequency = Cycles/Second A typical sine wave Analog Signal: Analog Signal 3 Basic Parameters of analog signal Amplitude Frequency Phase Two signals with the same phase and frequency, but different amplitudes: Two signals with the same phase and frequency, but different amplitudes Frequency: Frequency Frequency is the rate of change of cycle (Positive and Negative) with respect to time. Change in a short span of time means high frequency. Change over a long span of time means low frequency. Slide 32: If a signal does not change at all, its frequency is zero. If a signal changes instantaneously, its frequency is infinite. Note Two signals with the same amplitude and phase, but different frequencies: Two signals with the same amplitude and phase, but different frequencies 3 Sine waves with frequencies 0, 8 & 16: 3 Sine waves with frequencies 0, 8 & 16 Phase: Phase Phase describes the position of the waveform relative to time 0. Note Three sine waves with the same amplitude and frequency, but different phases: Three sine waves with the same amplitude and frequency, but different phases Units of period and frequency: Units of period and frequency Practical Case – Composite Signal: Practical Case – Composite Signal Frequency Spectrum Defined: Frequency Spectrum Defined Available range of frequencies for communication Starts from low frequency communication such as voice and progresses to high frequency communication such as satellite communication The spectrum spans the entire bandwidth of communicable frequencies Frequency Spectrum: Frequency Spectrum Low Frequency High Frequency Radio Frequency Coaxial Cable MHz Satellite Transmission Microwave GHz Voice KHz Bandwidth Definition: Bandwidth Definition Bandwidth, in general, represents a range of frequencies 300 MHz 700 MHz Bandwidth is 400 MHz Bandwidth and Signal Frequency: Bandwidth and Signal Frequency The bandwidth of a composite signal is the difference between the highest and the lowest frequencies contained in that signal. Communication Capacity: Communication Capacity Bandwidth is indicative of the communication capacity Communication speed is proportional to bandwidth Units used to represent bandwidth are Hz, bps etc. The Electromagnetic Spectrum: The Electromagnetic Spectrum Figure 1-13: The electromagnetic spectrum.