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What Electrical & Computer Engineering Can Do for You? Science & Engineering Saturday Seminar 23 January, 2010 Marinos N. Vouvakis [email protected] Special Thanks to: Baird Soules, Kris Hollot, Maciej Ciesielski, Wayne Burleson, Pat Kelly, Sandip Kundu, Russ Tessier Electrical and Computer Engineering Who Am I? Professional: • Assistant Professor in ECE (5 years at UMass) • Teaching: Electromagnetics, Mathematics, Antennas • Research: Computational Electromagnetics & Antennas Education: • PhD 2005, The Ohio State University • MS 2002, Arizona State University • Dipl. Ing 1999, Democritus University of Thrace, Greece Personal: • Hellenic National, Crete • 33 years old (single) • Favorite Music: Velvet Underground, Slint, Fugazi • Favorite Sport: Basketball • Hobbies: Traditional Greek music, politics, history, play with my cats. Electrical and Computer Engineering 2 Seminar Objectives Why am I doing this? Science vs. Engineering? What is Electrical & Computer Engineering? • What are major ECE sub-areas? • What are the trends? A Closer look at some basic concepts ECE: • Analog CKTs (sensing & signals) • Digital (entering the Digital world) • Wireless (the communications revolution) Demos • Sensing & Transducers (Chris) • Sampling & Bits (Baird, Marinos) Electrical and Computer Engineering 3 Why am I participation on this Seminar Series? The Vision • I want to make impact on society. • Engineering is key to a better future for humans and our environment. The Problem • Low engineering enrolments nationwide. • Alarming enrolment trends. • Most teachers do not have engineering background. A Possible solution • When incoming students are aware about engineering is, they are likely to choose it. • Educate teachers about engineering. Electrical and Computer Engineering 4 Science and Engineering Electrical and Computer Engineering 5 Science vs. Engineering Science: Why things happen the way they happen? Example: Movement of objects (force, friction, etc) Engineering: Creative problem solving. • More formally: engineering is the discipline, art and profession of acquiring and applying knowledge to design and implement materials, structures, machines, devices, systems, and processes that realize a desired objective. Example: Wheel!! Engineering = applied science Electrical and Computer Engineering 6 Science vs. Engineering (cont’d) The Taxonomy of Learning Create Evaluate Engineering Analyze Apply Understand Remember Q: Can we have engineering without science (or vise-versa)? Electrical and Computer Engineering 7 Science and Engineering Instrumentation Science Electrical and Computer Engineering Mathematics Engineering 8 Science and Engineering (cont’d) Science Technology Society Engineering Technology logic = (art/craft)+(knowledge/logic) Electrical and Computer Engineering 9 Engineering Grand Challenges* 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. Make solar energy economical Provide energy from fusion Provide access to clean water Reverse-engineer the brain Advance personalized learning Develop carbon sequestration methods Engineer the tools of scientific discovery Restore and improve urban infrastructure Advance health informatics Prevent nuclear terror Engineer better medicines Enhance virtual reality Manage the nitrogen cycle Secure cyberspace *Source: US. National Academy of Engineering Electrical and Computer Engineering 10 Electrical & Computer Engineering Electrical and Computer Engineering 11 What do Electrical and Computer Engineers do? Electrical and Computer Engineering 12 What do Electrical and Computer Engineers do? “Any sufficiently advanced technology is indistinguishable from magic.” http://en.wikipedia.org/wiki/Arthur_C._Clarke Electrical and Computer Engineering 13 Inside the iPhone 3G “Any sufficiently advanced technology is indistinguishable from magic.” http://en.wikipedia.org/wiki/Arthur_C._Clarke Electrical and Computer Engineering 14 What do Electrical and Computer Engineers do? Electrical and Computer Engineering 15 Electrical and Computer Engineering “Electrical engineering is an engineering discipline that deals with the study and/or application of electricity, electronics and electro-magnetism.” “Computer engineering is a discipline that combines elements of both electrical engineering and computer science. Computer engineers are involved in many aspects of computing, from the design of individual microprocessors, personal computers, and supercomputers, to circuit design.” Easier to understand by exploring example systems Electrical and Computer Engineering 16 Electrical Engineering Electronics • Circuit Analysis • Electronics Control Fields & Waves • • • • Electromagnetics Microwaves/RF Optics/Photonics Antennas/Remote Sensing • Control Theory • Power Systems • Power Electronics Electrical and Computer Engineering 17 Electrical Engineering Communications • • • • Communication Systems Wireless Comm. Antennas/Radio Wave Propagation Microwaves and RF Signal Processing • Signals and Systems • Signal Processing & Communications • Image Processing Electrical and Computer Engineering 18 Electrical Engineering Semiconductor Technologies • • Solid State Physics Nano-electronics 32nm TRIGATE Transistor: 2005 First Transistor: 1947 Microelectronics • VLSI Ckts • Embedded Ckts • Fabrication Technologies Electrical and Computer Engineering Pentium processor19 Computer Engineering Computer Programming Software • Algorithms • Computer Graphics Computer Design • Hardware Organization & Design • Embedded Systems Systems • Computer Architecture Electrical and Computer Engineering 20 Computer Engineering Networking • Computer Networks & Internet • Cryptography • Trustworthy Computing Bioengineering • Bio-informatics • Bio-sensors • Bio-electronics Electrical and Computer Engineering 21 EE/CE Salary In Electrical Engineering salary rises fast with experience • Mobility, Flexibility, Job Satisfaction among highest Do not focus just on starting salaries EETIMES salary survey 2006 Electrical and Computer Engineering 22 Job Satisfaction: EETIMES Survey Electrical and Computer Engineering 23 Future ECE Job Prospects* Computer hardware engineers are expected to have employment growth of 4 percent over the projections decade, for all occupations. Although the use of information technology continues to expand rapidly, the manufacture of computer hardware is expected to be adversely affected by intense foreign competition. As computer and semiconductor manufacturers contract out more of their engineering needs to both domestic and foreign design firms, much of the growth in employment of hardware engineers is expected to take place in the computer systems design and related services industry. Electrical engineers are expected to have employment growth of 2 percent over the projections decade. Although strong demand for electrical devices including electric power generators, wireless phone transmitters, high-density batteries, and navigation systems should spur job growth, international competition and the use of engineering services performed in other countries will limit employment growth. Electrical engineers working in firms providing engineering expertise and design services to manufacturers should have better job prospects. Electronics engineers, are expected to experience little to no employment change over the projections decade. Although rising demand for electronic goods including communications equipment, defense-related equipment, medical electronics, and consumer products should continue to increase demand for electronics engineers, foreign competition in electronic products development and the use of engineering services performed in other countries will limit employment growth. Growth is expected to be fastest in service-providing industries particularly in firms that provide engineering and design services. *Bureau of Labor & Statistics Electrical and Computer Engineering 24 Electrical & Computer Engineering Systems An advanced “engineering” system React Electrical and Computer Engineering 25 Analog Electrical CKTs (Sensing & Power) React Electrical and Computer Engineering 26 Charge & Electric Current Each electron carries an electrical charge, q of –1.602x10-19 coulombs [C] 1 [C] = the charge of 6.242x1018 electrons Current, I or i • flow rate of electrical charge through a conductor or a circuit element • Unit: ampere [A]. 1A=1C/s • Current-charge relationship: d i (t ) q(t ) dt Electrical and Computer Engineering 27 Direct Current (DC) & Alternating Current (AC) DC • Current that is constant with time • For examples, I=3A or V=12V AC • Current that varies with time and reverses its direction periodically (sinusoidal) • For example, Thomas Edison (1847 – 1931) v(t) VP cos 2 ft Nikola Tesla (1856 – 1943) Electrical and Computer Engineering 28 Water-Model Analogy We cannot see electric current flowing in a wire Water-model or fluid-flow analogy helps us visualize the behaviors of electrical circuits and elements Electric Current = flow of electrical charges (Water) Current = flow of water molecules Assumptions wire / pipe • Frictionless pipes • No gravity effect • Incompressible water i(t) cross section Electrical and Computer Engineering 29 Material Types Conductors • Electric currents flow easily. • Examples: copper, gold, aluminum… Insulators • Do not conduct electricity. • Examples: ceramics, plastic, glass, air… Semiconductors • Sometimes conductors, sometimes insulators • Examples: silicon, germanium • Applications: transistors Superconductors • Perfect conductors when cooled • Applications: MRI, astronomy Electrical and Computer Engineering 30 Voltage Voltage • Measured between two points (terminals) • Energy transferred per unit of charge that flows from one terminal to the other • Intuitive interpretations: potential difference, water pressure in water model • Variable: v(t ), Vin ,Vout ,V1 ,V2 • Unit: volt [V] Alessandro Volta (1745 – 1827) Water models • For constant voltage sources • Constant-pressure water pump • Constant-torque motor Electrical and Computer Engineering 31 Rules of Current Flow - Kirchhoff’s Current Law Kirchhoff’s current law (KCL) N i • Conservation of electrical currents n 1 • The sum of all the currents into a node is zero • The sum of the currents entering a node equals the sum of the currents leaving a node n (t ) 0 node i3 i1 i2 i1 i2 i3 0 i1 i2 i3 Electrical and Computer Engineering i3 i1 i2 Gustav Kirchhoff (1824 – 1887) 32 Rules of Current Flow - Kirchhoff’s Voltage Law N v Kirchhoff’s voltage law (KVL) n (t ) 0 • Conservation of energy n 1 • The sum of the voltages around any closed path (loop) is zero loop 3 Example +1 _ 3+ Loop 1 : 1V 5V 3V 9V 0 + 5_ loop 2 + 12 _ +4 _ loop 1 _ + 9_ _3 + Loop 2 : 3V 12V 4V 5V 0 Loop 3 : 1V 3V 12V 4V 3V 9V 0 Electrical and Computer Engineering 33 CKT Components - The Resistor Resistor • Electrical component that resists the current flow • Variable: R [ohm] or Water models for a resistor R ~ = R constriction Electrical and Computer Engineering R sponge 34 Resistors in Practice Incandescent Light Bulb Resistive Touch-screen Electrical and Computer Engineering Power Supplies 35 Rules of Current Flow - Ohm’s Law v(t ) i (t ) R Ohm’s Law i (t ) + v(t) R _ v (t ) Power dissipated in a resistor i(t) Georg Ohm (1789 – 1854) 2 v (t ) 2 p(t ) i(t ) v(t ) i (t ) R R Electrical and Computer Engineering 36 Resistors in Series + v (t ) _ i (t ) R1 + v1 _ + + v2 _ v3 + _ R2 = i (t ) v (t ) + _ Req _ R3 KCL : i(t ) i1 (t ) i2 (t ) i3 (t ) KVL : v(t ) v1 (t ) v2 (t ) v3 (t ) Ohm' s Law : v(t ) i(t ) R1 i(t ) R2 i(t ) R3 i(t )( R1 R2 R3 ) v(t) i(t)Req Electrical and Computer Engineering Req R1 R2 R3 37 Resistors in Parallel + v (t ) i (t ) i1 (t ) i2 (t ) R1 _ + i3 (t ) R2 R3 = v (t ) i (t ) + _ Req _ KCL : i(t ) i1 (t ) i2 (t ) i3 (t ) KVL : v(t ) v1 (t ) v2 (t ) v3 (t ) 1 1 v(t ) v(t ) v(t ) 1 Ohm' s Law : i(t ) v(t ) R1 R2 R3 R1 R2 R3 v(t) 1 i(t) Req Req 1 R1 1 R2 1 R3 Electrical and Computer Engineering 38 CKT Components - The Capacitor Capacitor & Capacitance • Stores energy through storing charge • Construction: separating two sheets of conductor by a thin layer of insulator • Variable: C • Unit: Farad [F]. 1F=1 coulomb per volt Michael Faraday (1791-1867) C q(t ) Cv(t ) Electrical and Computer Engineering capacitor 39 CKT Components - The Capacitor (cont’d) _ + v (t ) i(t) CKT Model: + + + + + + _ _ _ _ _ _ electron flow Water Model: piston Electrical and Computer Engineering spring 40 Capacitor Equations dv(t) i(t) C dt Current: i (t ) C Voltage: + v_(t ) t 1 v(t ) i(t )dt v(t 0 ) C t0 Energy Stored: 1 2 e(t) Cv (t) 2 MATH (Integration) = CKT (capacitor) !!! Electrical and Computer Engineering 41 Basic Capacitors Arrangements i (t ) + i (t ) i1 Parallel:v (t ) i3 i2 C2 C1 + C3 v (t ) _ + _ C1 i (t ) + v 1 Series: v (t ) _ + _ C C C C eq 1 2 3 + _ + v2 v _ 3+ _ C3 Electrical and Computer Engineering C2 v (t ) _ + _ 1 1 1 1 Ceq C1 C2 C3 42 CKT Components - The Inductor • Stores energy through storing magnetic field • Construction: coiling a wire around some type of form • Variable: L [Henry] or [H]. • When the electric current changes in the coil, it creates a magnetic field around the wire which induces voltage across the coil i (t ) Joseph Henry (1797-1878) + L v (t ) _ Electrical and Computer Engineering 43 CKT Components - The Inductor (cont’d) Operation • When the electric current changes in the coil, it creates a magnetic field around the wire which induces voltage across the coil d v(t ) L i (t ) dt Water model analogy Electrical and Computer Engineering Bi-directional turbine driving a flywheel Passive, driven by current; no motor Momentum 44 Inductor Equations Current: t 1 i(t ) v(t )dt i(t 0 ) L t0 Voltage: d v(t ) L i (t ) dt Energy Stored: 1 2 e(t) Li (t) 2 i (t ) + L v (t ) _ MATH (differentiation) = CKT (inductor) !!! Electrical and Computer Engineering 45 Basic Inductor Arrangements i (t ) L1 + + v1 _ Parallel: v (t ) _ v3 _ + + v2 L2 v (t ) + _ _ i (t ) Leq L1 L2 L3 L3 + Series: v (t ) i (t ) + L1 L2 _ Electrical and Computer Engineering L3 v (t ) i (t ) 1 1 1 1 Leq L1 L2 L3 _ 46 CKT Components - The Transistor Transistor is active component (generates energy) Controls the flow of currents Construction: combine semiconductor materials (many different implementations) The key element in any ECE application C (collector) B (base) John Bareen Walter Brattain William Shockley (1947) E (emitter) Electrical and Computer Engineering *Julius Edgar Lilienfield (1925)!! 47 Transistor Operation Use base voltage to control current flow on collector • Amplification (analog CKTs) • Switching (digital CKTs) C (collector) 1 B (base) 0 E (emitter) Electrical and Computer Engineering switch amplifier 48 Circuit Schematics connection wires R resistor + V battery no connection + _ V voltage source I current source L C terminals ground Electrical and Computer Engineering capacitor inductor transistor 49 An Analog CKT System High-End Sound Amplifier CKT design Hardware Implementation Electrical and Computer Engineering 50 Digital Electrical CKTs (Process) React Electrical and Computer Engineering 51 The Digital World Biological Systems: 1 agccccagtc agcgtcacca cgccgtatgt 61 cctctactgc agtaaactgc tggacctggc 121 ggaggctgag tttgatgtgc taaaggtctt 181 ctcccagaag cggatccgtg tggccgtggt 241 cgacctcagg gacaggaagc agccttcgga ggaggacatc cttcctgctg tgtggtggac ggagtaccac gctgcggcgc tcagagccgc gacggctcct atgatggagc gatggctcgc atcgctggtc ccctgcatga ccaagctgtc ggctgcacat actcctacat aggtgaagta Electrical Systems: 1 01000101 00101011 11010010 61 00111011 00101110 00010000 121 10101010 00110111 11000110 181 00000000 11011101 01011110 241 00101011 01010111 01011110 Electrical and Computer Engineering 11110011 00000001 01011100 00101111 00101010 01111000 10000000 01110001 00010010 10000101 00101101 01101111 00111011 10010100 01011010 52 The Digital World Biological Systems: Electrical Systems: Electrical and Computer Engineering 53 Binary in History Yin-Yang Emblem Pa Kua: Eight Trigrams G. Leibniz (1646-1716) Binary exists for thousand of years in ancient Chinese history: yin-yang 8 trigrams 64 hexagrams G. Leibniz, 1679: formal development of the system of binary arithmetic Electrical and Computer Engineering 54 Signal, Signals, Signals Continuous -Time (Space) Continuous-Amplitude Discrete-Amplitude x(t) x(t) t t Local telephone, cassettetape recording,photograph telegraph x[n] Discrete -Time (Space) x[n] n Switched capacitor filter, speech storage chip, halftone photography Electrical and Computer Engineering n CD, DVD, cellular phones, digital camera & camcorder 55 Why Digital? Robust (less susceptible to noise) Simple (deals with 0s & 1s) Electrical and Computer Engineering 56 Entering and Exiting the Digital World… Electrical and Computer Engineering 57 Entering and Exiting the Digital World… (cont’d) Electrical and Computer Engineering 58 Sampling ^x(t) x(t) t t Increases the sampling rate and the amplitude resolution by a factor of 2 ^ x(t) x(t) Electrical and Computer Engineering t t 59 Sampling (cont’d) Sampling rate: • How fast should we sample? • Fewer samples are needed for a slowly-changing signal. More samples are required for fast-changing signals • What is the critical sampling rate? Consider the sampling of a simple sinusoid 300Hz 700Hz Sampling rate: 1000Hz Electrical and Computer Engineering 60 Sampling (cont’d) Aliasing • Ambiguity in the reconstruction: 700Hz sinusoid can be mistakenly identified as a 300Hz sinusoid in example • Generally, aliasing error results from not having enough samples for fast-changing signals • To avoid aliasing, sample fast enough! 700Hz Sampling rate increases to: 1400Hz Electrical and Computer Engineering 61 Sampling & Aliasing in Digital Images Electrical and Computer Engineering 62 Example: Digital Audio processing or storage of digital signal (e.g., MP3) Electrical and Computer Engineering 63 Analog to Digital Recording Chain ADC • Microphone converts acoustic waves to electrical energy. It’s a transducer. • Analog signal: continuously varying electrical energy of the sound pressure wave. • ADC (Analog to Digital Converter) converts analog to digital electrical signal. • Digital signal: digital representation of signal in binary numbers. • DAC (Digital to Analog Converter) converts digital signal in computer to analog for your headphones. Electrical and Computer Engineering 64 Digital Quantization 3-bit quantization: use 3 bits to represent values 0,1,…7 7 Amplitude 6 5 4 3 2 1 0 Measure amplitude at each tick of sample clock 5 6 7 7 Electrical and Computer Engineering 5 4 3 1 2 5 7 5 7 Time 4 65 Decimal-Binary Conversion Divide the decimal number repeatedly until the quotient is zero. The remainders in reverse order give the number’s equivalent binary form 343 10 = 101010111 2 1 x 2 8 + 0 x 27 + 1 x 2 6 + 0 x 2 5+ 1 x 2 4 0 + 0 x 2 3+ 1 x 2 2 + 1 x 2 1 + 1 x 2 = 343 Electrical and Computer Engineering Quotient Remainder 343/2 171 1 171/2 85 1 85/2 42 1 42/2 21 0 21/2 10 1 10/2 5 0 5/2 2 1 2/2 1 0 1/2 0 1 66 The Digital Audio Stream A series of sample numbers, to be interpreted as instantaneous amplitudes • one number for every tick of the sample clock From previous example: 5 6 7 7 5 4 3 1 2 5 7 5 7 4 This is what appears in a sound file, along with a header that indicates the sampling rate, bit depth and other things Each number is then converted to binary and stored in a register 101 110 111 111 101 Electrical and Computer Engineering 100 101 001 010 101 111 101 111 100 67 Examples of quantization vs. resolution 256x256, 8 bit, 64 kB 256x256, 4 bit, 32 kB 256x256, 2 bit, 16 kB 256x256, 1 bit, 8 kB 64x64, 8 bit, 4 kB Lower resolution Electrical and Computer Engineering 68 Digital Technology: DVD Digital Versatile Disc or Digital Video Disc First appeared in the US market in March 1997 Employ the same red laser as in CDs Higher-density multi-layer discs to improve storage capacity DVD Audio: 192-kHz 24-bit sampling rate! Electrical and Computer Engineering 69 Digital Technology: DVD Specification CD DVD Track Pitch 1600 nm 740 nm Min. Pit Length 830 nm 400/440 nm Storage Capacity 780 MB 4.38-15.9 GB Electrical and Computer Engineering 70 Binary Logic - Logic Gates Electrical and Computer Engineering 71 Binary Arithmetic - Addition Simple observation Addition Binary Decimal 0+0=0 0+0=0 0+1=1 0+1=1 1+0=1 1+0=1 1+1=10 1+1=2 Electrical and Computer Engineering 72 Binary Arithmetic - Addition (cont’d) Truth Table of Half-Adder Inputs A B Sum Carry What about n-bit inputs? Electrical and Computer Engineering Outputs A B Sum Carry 0 0 0 0 0 1 1 0 1 0 1 0 1 1 0 1 XOR AND 73 Principle of Binary Addition Binary addition • Very similar to decimal addition • Starting from least significant bit (LSB), keep track of partial sum & carry until reaching most significant bit (MSB) • Simpler than decimal addition: only 0 and 1 are involved Example 111110 0 1101100 carry + MSB 1011101 11001001 Binary Addition Electrical and Computer Engineering + LSB 11 108 carry 93 201 Decimal Addition 74 Binary Arithmetic - Addition the Full Adder Inputs We need to add three bits (A, B, and Carry), not two as in the halfadder This is called a full adder Ai Bi Carry-out Co FA Sum S Electrical and Computer Engineering Carry-in Ci Outputs Ai Bi Ci S Co 0 0 0 0 0 0 0 1 1 0 0 1 0 1 0 0 1 1 0 1 1 0 0 1 0 1 0 1 0 1 1 1 0 0 1 1 1 1 1 1 75 Binary Arithmetic - the N-bit Full Adder A7 B7 A6 B6 A5 B5 A4 B4 A3 B3 A2 B2 A1 B1 A0 B0 Co Ci S8 S7 S6 S5 S4 S3 S2 S1 S0 8-bit Full Adder last carry out, overflow bit first carry in, set to 0 here CKT = MATH (= $$$$$) Electrical and Computer Engineering 76 The Systems Approach (divide and conquer) Electrical and Computer Engineering 77 System - An external view System (Perform Function) Inputs Outputs System: A collection of interacting elements that form an integrated whole Electrical and Computer Engineering 78 Digital Hardware Building Block Hierarchy Digital system (1) Circuit board (1-4) Chip (5-100) Logic gate (1k-500k) Transistor (1M-10M) Electrical and Computer Engineering 79 PC Motherboard Level I/O bus slots Electrical and Computer Engineering Disk & USB interfaces Processor interface Memory Processor Graphics 80 Chip Level (Pentium 4 Processor) Electrical and Computer Engineering 81 Logic Gate Level NAND Gate Chip Electrical and Computer Engineering 82 Transistor Level Capacitor M1 word line Metal word line SiO2 Poly n+ Field Oxide n+ Poly Inversion layer induced by plate bias Cross-section Diffused bit line Polysilicon gate Polysilicon plate Layout Uses Polysilicon-Diffusion Capacitance Electrical and Computer Engineering 83 Software Software • Contains instructions for the computer to accomplish certain tasks • Flexible, easy to modify, copy, and transport Data manipulations • Arithmetic operations: additions, multiplications, logarithms, trigonometric functions… • Logic operations: from OR, AND, NOT to complex logic functions… • Conditional operations: if then else… For ECE research and development • Matlab, Mathematica, Maple, Mathcad, Labview, Cadence, develop our own software using programming languages such as C++, Java, FORTRAN… Electrical and Computer Engineering 84 Software Building Block Hierarchy Assembly code • Most basic low-level programming codes • Different and need to be optimize per processor type Operating System (OS) • Set of basic instructions for I/O, file system, resource sharing, security, graphical user interface (GUI) • UNIX/Linux, Windows, MS-DOS, MacOS… High-level programming language • Provide more general, more powerful, more abstract instructions for the computer • Visual BASIC, FORTRAN, C, C++, Java… Application MOV 520 R0 ADD R0 R1 UNIX: ls –l rm *.* DOS: dir del *.* C++: x++ Fortran: x=x+1 • User-friendly software package for popular applications • Word processors, email & web browser, games… Electrical and Computer Engineering Word Explorer Sims 85 Communication CKTs (Sense/React) React Electrical and Computer Engineering 86 Cell Phone A cell phone is a very complex system that can receive input signals in various forms (electromagnetic waves from base station, sound from microphone, text from key pad) and convert them to several desired types of output signals (sound through speaker, electromagnetic waves to base station, graphics to screen) Electrical and Computer Engineering 87 Cell Phones: Inside front microprocessor Electrical and Computer Engineering back flash memory LCD & keypad speaker, microphone 88 Cell Phone System Electrical and Computer Engineering 89 Sound Fundamentals Electrical and Computer Engineering Sound waves: vibrations of air particles Fluctuations in air pressure are picked up by the eardrums Vibrations from the eardrums are then interpreted by the brain as sounds 90 Harmonics in Music Signals Electrical and Computer Engineering The spectrum of a single note from a musical instrument usually has a set of peaks at harmonic ratios If the fundamental frequency is f, there are peaks at f, and also at (about) 2f, 3f, 4f… Best basis functions to capture speech & music: cosines & sines 91 Frequency How fast a vibration happens • High frequency -> fast vibration (voice/music: soprano) • Low frequency -> slow vibration (voice/music: baritone) The frequency f is the inverse of the period T Sinusoidal frequency Units 1 f T 1 f T 2 • Period: second (unit of time) • Frequency: 1/sec or hertz [Hz] • Phase: radians Electrical and Computer Engineering 92 Music Signals: Piano Electrical and Computer Engineering 93 Frequency Spectrum - Audio 0 0 Human Auditory System 20Hz-20kHz 10k FM Radio Signals 100Hz-12kHz 10k 20k 20k AM Radio Signals 100Hz-5kHz 0 10k 20k f (Hz) f (Hz) f (Hz) Telephone Speech f max 3.3kHz f sampling 6.6kHz 300Hz-3.5kHz f (Hz) 0 10k 20k Electrical and Computer Engineering 94 Frequency Spectrum - Music Signals 2f fundamenta l frequency x(t ) cost 0.75 cos3t 0.5 cos5t 0.14 cos7t 0.5 cos9t 0.12 cos11t 0.17 cos13t Electrical and Computer Engineering 95 Transmitting & Receiving Information via Electromagnetic Aeronautical comm 120 - 130 MHz Maritime comm 157 - 162 MHz VHF wireless, TV 169 - 600 MHz Cellular phones 900, 1800, 2400 MHz Detection of buried land mines (900 - 2000 MHz) Microwave imaging of tumors 1100 - 1200 MHz Radio astronomy 1413 MHz Microwave ovens 2400 MHz Bluetooth wireless 2400 MHz Global position sat 1600, 1200 MHz Airport appr. radar 2700 MHz Satellite weather 12 GHz Satellite TV 14 GHz Satellite comm 20 - 22 GHz Adv. environ. radars 37, 98, 220 GHz Small size devices Large Bandwidth Large antenna gain Small penetration Large resolution Large size devices Small bandwidth Small antenna gain Large penetration Small resolution Electrical and Computer Engineering c f c : speed of light f : frequency 96 Modulation Electrical and Computer Engineering 97 Modulation (cont’d) Modulation • Using higher-frequency sinusoids to carry signals • More efficient transmission & allow multi-user sharing Pulse modulation Morse code, infrared remote control… Amplitude modulation AM radio stations, video part of TV signals… Frequency modulation FM radio stations, Cell phones, cordless phones… Electrical and Computer Engineering 98 Radio Frequency Systems An advanced RF /microwave system waveguidePA T/R Antenna switch LNA Mixer VCO DSP/ A/D Processor LO Power Supply Electrical and Computer Engineering 99 Modem Transmission Frequency-shift keying (FSK) • Uses analog sinusoids of different frequencies to carry digital signals 0 1 0 Transmit 0 1 Receive frequency 300 1070 1270 0 Electrical and Computer Engineering 1 2025 2225 0 3300 1 100 Cell Phones Frst cell phone 1973 DynaTAC 1983 Motorola Razr Sony Ericsson Xperia X1 Nokia N96 Electrical and Computer Engineering Google G1 BlackBerry Apple iPhone 101 The Cell Approach Cellular telephone system is based on the principle of radio communication Coverage area is divided into hexagonal cells (each covers around 10 square miles) Non-adjacent cells can reuse the same frequencies Low-power transmitters: both phones & base stations Each city has a Mobile Each carrier: 832 radio frequencies Telephone Switching Office Duplex system: 395 voice channels & (MTSO) 42 control channels Each cell: 56 voice channels Electrical and Computer Engineering 102 From Cell to Cell System Identification (SID) code to check for available service MTSO uses the control channels to identify where the user is & assign frequencies MTSO handles the handoff switching between cells based on signal strengths Everything happens within seconds or even less! Electrical and Computer Engineering 103 Cell Phone Tower Antenna Array Switching, RF and Power Electronics Electrical and Computer Engineering 104 What Next? 1. Connect & collaborate with UMass Amherst ECE faculty 1. Teacher development grants 2. Summer research experience for teachers 2. Recommend exceptional high-school juniors/seniors summer research at UMass. 3. Invite UMass Profs to High-school student seminars. 4. M5 Open house for students and Teachers. 5. Spread the word to students & colleagues. 6. Participate on upcoming ECE SESS(more in-depth). Marinos N. Vouvakis [email protected] Electrical and Computer Engineering 105 Disclaimer Some materials (drawings, figures, text) presented in these slides was obtained from the following web resources: 1. 2. 3. 4. 5. 6. 7. 8. http://images.google.com/imghp?hl=en&tab=wi http://www.ecs.umass.edu/ece/engin112/ http://thanglong.ece.jhu.edu/Course/137/Lectures/ http://www.ecs.umass.edu/public/ece_docs/ECE_303_ syllabus_S09.pdf http://www.nae.edu/ http://www.bls.gov/oco/ocos027.htm#outlook http://www.engtrends.com/IEE/0806D.php http://www.eetimes.com/news/latest/showArticle.jhtml ?articleID=206903802 Electrical and Computer Engineering 106