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Transcript
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