Review Safety Test

1
(No Transcript)
2
(No Transcript)
3
(No Transcript)
4
(No Transcript)
5
(No Transcript)
6
Wireless Technology

• Wireless devices transmit information via
  Electromagnetic waves
• Early wireless devices
• Radios often called wireless in old WWII movies
• Broadcast TV
• TV remote controls
• Garage door openers

7
Wireless technology

• Todays wireless devices include
• Mobile phones
• Satellite TV
• Satellite radio
• Global Positioning Systems (GPS)
• Bluetooth devices
• Wi-Fi systems
• RFID tags

8
Smart phones dominate cellular systems today
9
Apple iPhone A computer that is also a cell phone
10
Mobile Phone (Cellular) Systems

• Mobile phones are two-way radios. They transmit
  and receive RF signals. Old style phones are not
  radios.
• Original mobile phones used a single large
  central antenna and had limited channels
  available to carry signals. Only a small number
  of mobile phones were available in a city due to
  the limited amount of usable frequency bands.
• Cellular technology allowed for a near limitless
  number of mobile phones to operate in a city.

11
Mobile Phone (Cellular) Systems

• Cellular systems operate at a frequency of 824 to
  894 Mhz, and 1850 to 1990 Mhz . Other bands are
  also being used as demand increases.
• These frequency bands are controlled by the
  Federal government.
• The original cell phones operated at 824-894 MHz.
  Sometimes these phones are referred to as
  analog phones since digital technology had not
  yet been developed.
• Many systems today operate at 1850 to 1990 Mhz,
  the PCS band in the digital mode but can also
  operate at the lower frequency band. These
  phones are called dual band phones.
• The term cellular refers to the fact that
  service areas are divided into cells typically
  1- 10 miles apart. Cell size is dependent on the
  population density of the area. Large population
  areas require closer spaced cells.
• Each cellular company has their own towers, thus
  the large number of towers throughout the area.
  Sometimes towers will have multiple sets for the
  same system or multiple systems.

12
PCS Band 1850-1990 MHZ
13
Grid pattern for cellular antenna
Adjacent grids do not use the same frequency
14
Mobile Phone (Cellular) Systems

• Each phone has a unique code.
• If your cell phone is on, it is transmitting a
  signal to the nearest cell tower.
• This signal locates you and allows you to receive
  calls.
• It also identifies your phone, carrier, and
  status of your account.
• When you make a call, it is transmitted to the
  nearest tower and it is then routed to the person
  you called.
• The call may go via radio waves, land lines, or
  satellite.
• As you move, the call can be transferred to the
  next cell. This is done automatically as signal
  strength changes
• Phones typically transmit with around 600mW of
  power.

15
Base station RF transmit/receive modules
Typical cellular system antenna tower with two
sets of base station modules
16
Large cell phone antenna is a remote location
17
Communities are trying to disguise cellular towers
Several cell phone antenna towers like this are
near the campus
18
(No Transcript)
19
(No Transcript)
20
Bluetooth

• Bluetooth named after a Swedish King that
  united the country. First proposed by Ericsson
• The systems utilizes an unregulated band of
  frequencies at 2.4 GHz that operate on a
  relatively short distance, about 10m.
• Bluetooth uses a frequency hop transceiver to
  handle device traffic. A radio channel is shared
  by a group of devices and is synchronized by one
  device known as the master. This forms a piconet.
• Bluetooth devices can be used to connect a
  headset to a cellular phone, a printer to a
  computer, a digital camera to a computer, etc.
• Because Bluetooth circuits are low power with
  low battery requirements, the chipsets are
  relatively inexpensive.
• Many newer devices have Bluetooth already built
  into them.

21
(No Transcript)
22
Wi-Fi provides access to internet wirelessly

• Uses IEEE standard 802.11
• Transmits at
• 2.4 GHz (802.11b and 802.11g)
• 5.0 GHz (802.11a)
• Transfer Rates
• 802.11a and 802.11g (54 Megabits per second)
• 802.11b (11 Mega bits per second)
• Frequency hopping for security
• Range about 100 meters (300 feet)
• Range limited by output power level.
• Often called a Hotspot

23
Installing a home Wi-Fi network is easy and cheap
24
A city wide Wi-Fi zone can be created using
multiple routers similar to the cell phone
antenna network
25
Bluetooth vs. Wi-Fi

• Both use the 2.4 GHz frequency band
• Both could use the same antenna
• Bluetooth is for short range, about 10m
• Wi-Fi has a longer range, about 100m
• Bluetooth can operate from a small battery
• Wi-Fi requires higher power, usually plugs into a
  home electrical outlet

26
Instead of using a Wi-Fi location, you can access
the internet through the cellular phone network
BUT you will pay for the time. Could be
expensive unless you have unlimited data downloads
Allows for your laptop to access the internet via
the cellular system
27
Smart phones can access the internet either
through a local Wi-Fi access point or the
cellphone network
28
RFID tags

• Passive -uses the incoming signal for power to
  transmit
• Active- requires an internal power supply, more
  expensive and less widely used
• Could replace bar codes and security attachments
  on merchandise
• Implantable for medical and security data

29
Implantable RFID device
30
Companies like Wal-Mart plan to use RFID
extensively
31
RFID gate access at UNCC
32
GPS systems uses orbiting satellites The primary
frequency of operation is 1575.42 MHz with a
secondary frequency of 1227.6 MHz

• Cellular GPS systems use local cellular antennas

33
Stationary Satellites Orbit the Earth
34
GPS devices calculate the signal time from each
satellite and using triangulation determine
location
35
Antenna Design

• In antenna design, an important design parameter
  is the wavelength of the EM wave
• Wavelength is a function of frequency
• Antenna length is typically either
• 1 wavelength
• ¼ wavelength
• ½ wavelength

36
Frequency vs wavelength
Wavelength
37
Wavelength Calculations

• Wavelength units
• l (wavelength) m/cycle
• f (frequency) cycles/sec hertz
• c (speed of light) m/sec 3.0 x 108 m/sec
• Wavelength equation
• l c / f
• m/cycle (m/sec) / (cycles/sec)
• Frequency must be converted to Hz

38
Sample calculation

• Find the wavelength of a frequency of 850 MHz
• Convert 850 MHz to Hz
• 850 MHz 850 x 106 Hz 8.50 x 108 Hz
• Use wavelength equation
• l c/f where c speed of light 3.0 x 108
  m/sec
• l (3.0 x 108 m/sec ) / (8.50 x 108 cycles/sec)
• l .353 m/cycle
• Convert to cm gives
• l 35.3 cm/cycle
• For a ¼ wavelength antenna (35.3cm/cycle)/48.82
  5cm/cycle

39
Assignment due next class

• HW 7 from the web site
• Frequency and wavelength work sheet
• Short multiple choice test next class on all
  lectures to date including the frequency/wavelengt
  h work sheet