Engr 1202 ECE · 2017. 1. 20. · • Mobile phones are two-way radios. They transmit and receive...

Engr 1202 ECE

Clean Room Project

Dilbert the engineer gets

special recognition

September 2005

2014 Version – does not

even have my name!

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

– GPS

– RFID

• Bluetooth and Wi-Fi operate in the scientific unlicensed band where products can be developed without a FCC license

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

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

Wireless technology

• Today’s wireless devices include

– Mobile phones

– Satellite TV

– Satellite radio

– Global Positioning Systems (GPS)

– “Bluetooth” devices

– Wi-Fi systems

– RFID tags

Wireless frequencies for the EE

project

• 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

Smart phones dominate cellular

systems today

Apple iPhone

A computer

that is also a

cell phone

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.

Early Mobile Phones where not cellular but used a common centrally located tall antenna (similar to police and fire radios) and were limited in the number of phone numbers available

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.

My first cell phone - 1992

PCS Band

1850-1990

MHZ

Grid pattern for cellular antenna

Adjacent

grids do not

use the same

frequency

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.

Typical cellular system

antenna tower with two

sets of base station

modules

Base station RF

transmit/receive

modules

Large cell phone

antenna is a

remote location

Communities are trying to disguise

cellular towers

Several cell phone antenna towers like this

are near the campus

First cell phone tower on

campus

“ 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.

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”

Installing a home Wi-Fi network is easy and cheap

A city wide Wi-Fi zone can be

created using multiple routers

similar to the cell phone

antenna network

“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

Smart phones can access the internet

either through a local Wi-Fi access

point or the cellphone network

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

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

Implantable RFID device

Companies like Wal-Mart plan

to use RFID extensively

RFID gate access at UNCC

RFID

Antenna

RFID chip

RFID chip added

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

Stationary Satellites Orbit the

Earth

GPS devices calculate the

signal time from each satellite

and using triangulation

determine location

Communications – the key to

technology progress• Data, voice, and video are all key

elements

• Both electrical and computer engineers

will play a key and vital role

• “Wireless” communications is the

dominate form

• The EE project will focus on

communications systems and a key

element of these system, the antenna.

What is an antenna

The antenna is an essential part of any

wireless communication system that

sends information over the air. An

antenna is a device that provides a

means for radiating or receiving

electromagnetic waves. It provides a

transition from a guided wave on a

transmission line to a free space wave or

vice versa.

Every communications device needs an

antenna

The Engr 1202 EE ProjectResearch, design, and fabricate a miniature planar antenna

for use in:

1) Mobile phone using the PCS frequency of 1850-1990

MHz

2) “Bluetooth” and Wi-Fi antenna using the frequency

band of 2400-2597 MHz

3) RFID antenna using the frequency band of 860-960

MHz

4) GPS antenna using the frequencies of 1227.60 MHz

and 1575.42 MHz

Maximum size of 20mm x 20mm, minimum size of 10mm x

10mm. Can be rectangular. Width on antenna not less

than 1mm. Design to have no sharp corners.

Cell phone showing internal

antenna

Antenna

Example of a miniature antenna for

a mobile phone/watch

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. 1 wavelength

2. ¼ wavelength

3. ½ wavelength

Frequency vs wavelength

Wavelength

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

Sample calculation• Find the wavelength of a frequency of 850 MHz

1. Convert 850 MHz to Hz

850 MHz = 850 x 106 Hz = 8.50 x 108 Hz

2. Use wavelength equation

l= c/f where c = speed of light = 3.0 x 108 m/sec

3. l = (3.0 x 108 m/sec ) / (8.50 x 108 cycles/sec)

4. l = .353 m/cycle

Convert to cm gives

5. l = 35.3 cm/cycle

6. For a ¼ wavelength antenna =

(35.3cm/cycle)/4=8.825cm/cycle

To find wavelength

1. Convert frequency to Hz (cycles/sec)

2. Use 3.0 x 108 m/sec for speed of radio

waves (same as speed of light)

3. Use equation wavelength (m/cycle) =

speed of light (m/sec) / frequency

(cycles/sec)

Wavelength is use to determine antenna

length

Wireless frequencies for the EE

project

• 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

Antenna Design

• Design can take an artistic form (not the

best design for an antenna but OK for this

project)

• Design must not be controversial

– Not religious

– Not gang sign

– Not sexual

– Not offensive to any group

Example of antenna design

Dimension Drawing Design arrayed for 4” wafer

Example of antenna design

Dimension Drawing Design arrayed for 4” wafer

Example of antenna design

Dimension Drawing Design arrayed for 4” wafer

Example of antenna design

Dimension Drawing Design arrayed for 4” wafer

Example of antenna design

Dimension Drawing Design arrayed for 4” wafer

Assignment due next lecture

Frequency / wavelength

work sheet

After your visit to the clean room – complete

the team choice worksheet and submit

before the next clean room visit. This will

determine the application and length of your

antenna design