Transcript Slide 1
Wally is a slacker, he is always looking for the easy way out of doing anything Pointy Haired Boss saves a million Various electronic devices similar to a watch Mobile internet access via satellite using pedal powered electric generator Where there is a need, an engineer will come up with a solution Transistors are the building block of all electronics. As the manufacturing cost comes down, electronics become very cheap. AC vs. DC Circuits DC and AC devices in everyday life DC Devices • Batteries • Automotive electronics • Portable electronics • • • • IPod Cellular Phone PDA Laptop computers Desktop computers Solar cells Computer and memory chips AC Devices • Electric wall outlets • Household appliances • High voltage transmission lines • Electromagnetic transmissions Mobile phone signals Satellite signals Radio signals AC Frequency Number of complete cycles per unit time Units are hertz, Hz Units are cycles per second Household electrical outlets operate at 60 hertz or 60 cycles per second Electromagnetic waves operate at much higher frequencies Sun burn Frequency Allocations Broadcast Frequencies Use of frequencies for broadcast are controlled by the Federal Government – the FCC - Federal Communications Commission License required to use a given frequency Companies purchase licenses to use these frequencies Specific bands are setup for all transmissions • Police/Fire/EMS radio • Commercial aircraft • Marine radios • Mobile phones • Military applications • Citizen band radio Typical large broadcast antenna Very tall, often on mountains, to transmit over long distances Some common frequencies AM Radio • 535 to 1605 KHz FM Radio • 88-108 MHz Broadcast TV (old)- requires external antenna • Channels 2-4 54-72 MHz • Channels 5-6 76-88 MHz • Channels 7-13 174-216 MHz • Channels 14-36 470-608 MHz • Channels 38-69 614-806 MHz Today, most TV transmissions are digitized and sent via cable, fiber optics, or satellite Broadcast Frequencies One notable exception is the Unlicensed Band (ULB) at 2400 MHz or 2.4 GHz, also known as the Industrial, Scientific, and Medical band • Microwave ovens • Cordless phones • Bluetooth devices • Wi-Fi devices • Any new device can use this frequency without a FCC license provided it follows set specifications on power, range, and data transmission rates A second band at 5.0 GHZ is also available but has limited use due to a lack of inexpensive chips that operate at 5.0 GHz Wireless frequencies for the EE project Older “analog” phones - 824-894 MHz PCS digital phones - 1850-1990 MHz – Current frequency of operation of most mobile phones Bluetooth and Wi-Fi devices - 2400-2497 MHz (2.4 – 2.497 GHz) GPS – 1575.42 and 1227.60 MHz RFID – multiple frequencies – 860 to 960 MHz very common Assignment due next class HW #3 from the web site • Write a one page report on “How a Cellular Phone System Works” • Why is it called “cellular”? • Is it really a phone or something else? • Be sure to include the frequency of operation on current cellular phones • Include at least two references