21118.pdf

Module 1.0 Monday, 12 August 2024 8:44 pm Introduction to Communication Systems Theory Communication - process of exchanging information ○ Main barriers: language, distance Historical Events Significant Events People Events Mors...

Module 1.0 Monday, 12 August 2024 8:44 pm Introduction to Communication Systems Theory Communication - process of exchanging information ○ Main barriers: language, distance Historical Events Significant Events People Events Morse Invention of telegraph Morse code Maxwell Formulated the electromagnetic theory Proposed existence of radio waves Hertz Confirmed existence of radio waves Marconi Demonstrated wireless communication Discovered ground-wave radio signals Fessenden Invented the first successful transatlantic xmsn of radio signals Invented Amplitude Modulation (AM) De Forest Invented the triode Alexanderson Invented the Tuned Radio Frequency (TRF) Receiver Graham Bell, Invented the telephone that transmits voice signals Watson Tesla Outlined basic principles of radio xmsn and reception Armstrong Invented Superheterodyne Receiver Invented Frequency Modulation (FM) Clarke Proposed the use of satellites for long-distance radio transmissions Moon - first passive satellite AT&T Introduced the first mobile telephone system (MTS) Kao, Bockam Proposed the use of cladded fiber cables as a transmission medium Berners-Lee Developed World Wide Web Electronic Communication Electronic Communication Systems ○ The fundamental purpose of an electronic communications system is to transfer information from one place to another. Parts ○ Information Source ▪ Information/Intelligence signal - the message being sent ▪ Sources: □ Analog signals - time-varying; continuous □ Digital signals - discrete ○ Transmitter (Tx) ▪ Transducers - converts physical characteristics (temperature, pressure, light intensity, etc.) into electrical signals ▪ Collection of electronic components and circuits designed to convert the electrical signal to a signal suitable for transmission over a given communication medium. ▪ Made up of oscillators, amplifiers, tuned circuits, filters, modulators, frequency mixers, frequency synthesizers, and other circuits ○ Communication Channel / Transmission Media ▪ Medium by which the electronic signal converted by the transmitter is sent from one place to another ▪ Types: □ Guided/Bounded channel (wireline channel) - using wire conductors, fiber-optic cable, or waveguides Electronic conductors, optical media □ Unguided/Unbounded channel (wireless channel) - transmitted over free space Free space (resulting system is radio), acoustic, optical ○ Receiver (Rx) ▪ Accepts the transmitted message, converts signal back to a form understandable by humans/machines ▪ Retrieves the transmitted signal at the receiver end ▪ Contains demodulator ○ Noise ▪ Unwanted signals that tend to disturb quality of received signal ▪ Can be external or internal to the system ▪ Measure of noise is usually expressed in terms of signal-to-noise ratio (SNR) PS - Signal Power PN - Noise Power -> in decibel 21118 Page 1  -> in decibel Types of Electronic Communication ○ One-way (simplex) or two-way (half duplex or full duplex) transmissions ▪ One-way: Simplex □ Simplest method of electronic communication □ Communication in one direction ONLY (cannot send back/receive or send only) □ Examples: AM and FM radio broadcasting, TV broadcasting, Beeper ▪ Two-way or Duplex □ Half Duplex - only one party transmits at a time Communication in same direction but NOT at the same time Examples: military radio transmissions, citizen band (CB), amateur radio □ Full Duplex - when people can talk and listen simultaneously (e.g. telephone) Communication in the same direction at the same time ○ Analog or digital signals ▪ Analog signal - smoothly and continuously varying ▪ Digital signal - usually use binary or two-state codes (discrete) □ Many transmissions are of digital form but must be converted to analog form to match the transmission medium They are first digitized with an analog-to-digital converter (A/D) The data can then be transmitted and processed by computers and other digital circuits ○ Baseband or Modulated signals ▪ Baseband signals - refers to the information signal, regardless if analog or digital (intelligence) □ Unmodified signal ▪ Modulated signals (broadband) □ To transmit baseband signals by radio, modulation technique must be used □ Radio-frequency (RF) wave (radio wave) - an EM signal that is able to travel long distances through space Internet uses a modem (modulator-demodulator) □ Modulation - the process of having a baseband voice, video or digital signal modify another, high-frequency signal called the carrier in accordance to a message signal Carrier is modulated by the information signal Wave parts ○ Frequency (f) - no. of cycles taken by EM wave in 1 sec ▪ Unit: cycles/sec or Hertz (Hz) ○ Wavelength - distance covered by an EM wave in one cycle ○ Period (T) - time it takes for an EM wave to complete one cycle 21118 Page 2 Modulation and Multiplexing Baseband Transmission - can be sent directly and unmodified over the medium or can be used to modulate a carrier for transmission over the medium Broadband Transmission - when a carrier signal is modulated, amplified, and sent to the antenna for transmission ○ Most common methods of modulation are: ▪ Amplitude Modulation (AM) ▪ Frequency Modulation (FM) ○ *Phase modulation (PM) - the phase angle of sine wave is varied 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 ○ Multiplexing - allows more than one signal to be transmitted concurrently over a single medium Modulation: Broadband transmission ○ When baseband signals are incompatible with the medium, this is normally used to modulate a high -frequency signal (carrier) ○ The higher-frequency carriers radiate into space more efficiently than the baseband signals themselves ○ Simply the process of changing one or more properties of the analog carrier in proportion with the information signal ▪ Information signal (modulating signal) and the higher-frequency signal which is being modulated is called the carrier or modulated wave ▪ Carrier - usually a sine wave generated by an oscillator ▪ Expressed as: Types of Modulation ○ Three ways to make baseband signal change the carrier sine wave: varying amplitude, frequency and phase angle ▪ Amplitude modulation (AM) - amplitude varies ▪ Frequency modulation (FM) - varies the value of f in the first angle term of the sinusoidal signal □ Phase is also varied ▪ Phase modulation - the second term of (theta) of the sinusoidal signal is made to vary by the intelligence signal □ Produces frequency modulation ○ Digital signals ▪ Amplitude shift keying (ASK) ▪ Frequency shift keying (FSK) ▪ Phase shift keying (PSK) Demodulation - reverse process of modulation and converts the modulated carrier back to the original information ○ Performed in a receiver circuit called a demodulator 21118 Page 3  Multiplexing - process of allowing two or more signals to share the same medium or channel ○ Converts the individual baseband signals to a composite signal that is used to modulate a carrier in the transmitter ○ Demultiplexer - the individual baseband signals are demodulated ○ Types of multiplexing ▪ Frequency division - modulate subcarriers (non-overlapping) on different frequencies that are then added together, and the composite signal is used to modulate the carrier ▪ Time division - multiple intelligence signals are sequentially sampled, and a small piece of each is used to modulate the carrier ▪ Code division - combination of FDM and TDM □ The signals to be transmitted are converted to digital data that is then uniquely coded (chip code) with a faster binary code Electromagnetic Spectrum The information is converted into electromagnetic signals that consists of both electric and magnetic fields These signals oscillates and varies sinusoidally which may occur at a very low or at an extremely high frequency 21118 Page 4  International Telecommunications Union, Federal Communications Commission, National Telecommunication Commission Radio Frequency Spectrum ○ Extremely Low - ac power line ○ Voice - normal range of human speech ○ Very Low - musical instruments, some government and military communication ○ Low - aeronautics and marines ○ Medium - AM radio broadcasting ○ High - short waves; simple and half duplex comm ○ Very high - analog TV, FM broadcasting ○ Ultra High - UHF TV channels, land mobile comm ○ Microwave and Super High - satellite comm, radar, LANs ▪ ISM (Industrial, Scientific and Medical) band (unlicensed) - 2.45 GHz ○ Extremely High - millimeter waves Optical Spectrum ○ Right above the millimeter wave ○ Region occupied by light waves ○ Infrared - basis for all fiber optic comm ○ Visible - wavelength measured in Angstrom ▪ Can handle a tremendous amount of info ○ Ultraviolet - not used for communications; primarily for medical use Problems Determine the wavelength in meters for following frequencies: Bandwidth and Information Capacity Bandwidth (BW or B) - difference between the highest and the lowest frequencies contained in the information ○ Minimum passband (range of frequencies) required to propagate the source information through the system ○ Channel bandwidth - range of frequencies required to transmit the desired information (the channels allows a specific frequency to pass through) ○ Signals transmitting on the same frequency or on overlapping frequencies interfere with one another ○ Using higher frequencies for communication carriers is that a signal of a given bandwidth represents a smaller percentage of the spectrum at the higher frequencies than at the lower frequencies Examples: ○ Calculate the bandwidth if a frequency range from 902 MHz to 928 MHz is available ○ If an analog TV signal covers a bandwidth of 6 MHz anf the low freq limit of channel 2 is 54 MHz, determine the upper frequency limit Information theory ○ A highly theoretical study of the efficient use of bandwidth to propagate information through electronic communications systems ▪ Entropy - a key measure in information □ Quantifies the amount of uncertainty involved in the value of a random variable or the outcome of a random process Information Capacity - measure of how much info can be propagated through a comm system and a function of bandwidth and transmission time ○ Represents the number of independent symbols that can be carried through a system per unit time ▪ Binary digit (bit) - most basic digital symbol used to represent information 21118 Page 5  ▪ Entropy - a key measure in information □ Quantifies the amount of uncertainty involved in the value of a random variable or the outcome of a random process Information Capacity - measure of how much info can be propagated through a comm system and a function of bandwidth and transmission time ○ Represents the number of independent symbols that can be carried through a system per unit time ▪ Binary digit (bit) - most basic digital symbol used to represent information ○ Information capacity is conveniently expressed as bit rate which is the number of bits transmitted per second (bps) ○ Claude E. Shannon expressed this mathematically as: Challenges in Communication System Communication systems are designed to provide efficient utilization of two primary communication resources: ○ Transmit power - ave. power of the transmitted signal ○ Channel bandwidth - width of the passband channel Channel classification ○ Power-limited channels ▪ Wireless channels - where it is desirable to keep the transmitted power low to prolong battery life ▪ Satellite channels - where the available power is on board the satellite transponder is limited which necessitates keeping the transmitted power on the downlink at a low-level ○ Bandwidth-limited channels ▪ Telephone channels - minimizing frequency band allocated to the transmission of each voice signal ▪ Television channels - the available channel bandwidth is limited by regulatory agencies ○ The design of comm systems is complex and challenging due to: limited spectrum, power consumption, interference, seamless access, system on chip design ○ A good comm system should strike a balance between: small signal power (W or dBm), small bandwidth (Hz), large data rate (bps), low distortion (SNR or BER), low cost 21118 Page 6  Module 1.1 Saturday, 24 August 2024 6:11 PM Signal Generation Feedback Oscillators Oscillator - building block of electronic communication; converts DC to AC in a sense that it provides oscillation Synthesis - creating a system based on given specs Signal generation/frequency synchronization/frequency synthesis ○ Oscillate - fluctuate between two states ▪ Damped (decay) ▪ Undamped (self-sustaining) Module 1.1 - Signal G... 21118 Page 7 r 21118 Page 8 21118 Page 9 21118 Page 10 21118 Page 11 21118 Page 12 21118 Page 13 21118 Page 14 21118 Page 15 21118 Page 16 21118 Page 17 21118 Page 18 21118 Page 19 21118 Page 20 21118 Page 21 21118 Page 22 21118 Page 23 21118 Page 24 Module 2.0 Tuesday, 3 September 2024 8:40 pm 21118 Page 25 21118 Page 26 21118 Page 27 21118 Page 28 21118 Page 29 21118 Page 30 21118 Page 31 21118 Page 32  Thermal noise is always present due to resistive elements IF temp. cannot be computed from the given, use 290 K 21118 Page 33 21118 Page 34 21118 Page 35 21118 Page 36 21118 Page 37 21118 Page 38 21118 Page 39 21118 Page 40 21118 Page 41 21118 Page 42 21118 Page 43 21118 Page 44 21118 Page 45 21118 Page 46 21118 Page 47 21118 Page 48 21118 Page 49 21118 Page 50 21118 Page 51 21118 Page 52 21118 Page 53 21118 Page 54 21118 Page 55 21118 Page 56 Module 3.0 - Amplitude Modulation.pdf Saturday, 21 September 2024 6:01 PM Module 3.0 - Amplitu... 21118 Page 57 21118 Page 58 21118 Page 59 21118 Page 60 21118 Page 61 21118 Page 62 21118 Page 63 21118 Page 64 21118 Page 65 21118 Page 66 21118 Page 67 21118 Page 68 21118 Page 69 21118 Page 70 21118 Page 71 21118 Page 72 21118 Page 73 21118 Page 74 21118 Page 75 21118 Page 76 21118 Page 77 21118 Page 78