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FM Transmitter
Dec06-01
Team:
Grant Blythe
Tony Hunziker
Luke Erichsen
Advisors:
Dr. John W. Lamont
Prof. Ralph E. Patterson III
Client:
Iowa State University - Senior Design
Date:
December 5, 2006
Presentation Outline
Introduction
Introductory Material
Project Activities
 Design
 Implementation
Resources and Schedules
Conclusion
Project Overview
Objective:
Design a portable short range FM transmitter for
use with MP3 players or satellite radios
Definitions
FCC:
FM:
LCD:
MP3 player:
Federal Communications Commission
frequency modulation, a method of modulating an audio
signal for wireless transmission
liquid crystal display
portable digital music player, (i.e. ipod)
PLL:
phase-lock loop
RF:
radio frequency
Transmission frequency:
VCO:
the frequency at which the device is transmitting the FM
modulated signal to the FM radio
voltage controlled oscillator
Acknowledgement
The team would like to thank the following people
for their help and support.
Jason Boyd:
For showing us various possibilities for prototyping surface
mount components.
Dr. John W. Lamont and Prof. Ralph E. Patterson III:
For your knowledge and guidance in helping us with part
selection and referring us to expert advice when needed.
Dr Geiger:
For help understanding the phase lock loop
Fredo:
For a helpful reference.
Yesuratnam Thommandru:
For help uderstanding programming PIC’s
Problem Statement
General Problem Statement:
Currently many people use MP3 players and satellite radios, but do not
have a way to connect them to their other audio equipment. It should be
easily tunable to transmit on any desired frequency in the FM band (88108 MHz) with the ability to preset four selectable frequencies within this
range. The minimum transmission distance is to be at least twelve feet.
General Solution Approach:
Most of this existing equipment has FM radio capabilities, so the solution
approach was to develop a portable FM transmitter to link MP3 players
and satellite radios to any FM receiver.
Operating Environment
The finished device will operate within a personal
vehicle or a household room that could be
exposed to:
 Moisture
 Dust/Dirt
 Impacts
 Temperatures from 32° - 100° F
 Normal humidity/pressure
Intended Users/Uses
Intended Users:
The intended user for this product is anyone owning a MP3
player or satellite radio device.
Intended Uses:
The FM transmitter is intended to make personal music devices accessible
through home and car stereos.
Assumptions
 The device will receive a 20 Hz to 20 kHz input audio signal from all varieties
of personal music devices.
 The device will output to standard North American FM radio equipment.
 The transmitter will be subjected to a variety of environments including
varying temperatures, humidity, vibration levels, and electromagnetic noise.
 The device will be operated in varying ambient light conditions.
 The user will have access to a steady power source.
Limitations
 The cost to purchase this product shall not become uncompetitive.
 The transmitter must conform to FCC regulations.
 Part 15 concerning unlicensed FM broadcasting
 Broadcast strength: ≤ 0.1W
 Broadcast band: 88 -108 MHz
 The device shall be capable of obtaining power from readily available power
sources.
 The size shall not exceed 6 in. by 6 in. by 3 in.
 The weight shall not exceed 1 lb.
Expected End Product
 The device case will be made
of plastic
 The case will allow for easy
hand manipulation and
transportation
 The device will implement an
LCD screen displaying the
transmission frequency.
 The device will be
accompanied by a user
manual.
 The user input interface will consist of six
buttons.
 “up” and a “down” button to adjust
transmission frequency
 4 buttons will each access a programmable
preset frequency
 Transmit a minimum of 12 ft
Present Accomplishments
Problem Defined
Successfully completed
Research Completed
Successfully completed
Technologies Selected
Successfully completed
Design Completed
Successfully completed
Design prototyped
Completed
Prototype testing
Partially completed
Project documented
Successfully completed
Approaches Considered
Logic Approach
The logic for the transmitter could be implemented either with a microcontroller
and software or with dedicated hardware logic.
Microcontroller/Software
Cost ≈$7.00
Ease of Requires software to be written,
Implementation compiled and loaded
Weight/Size One large IC
Expandability & Requires software to be
Modifiability changed and recompiled
Hardware Logic
Advantage
≈$7.00
none
Requires detailed
design and intricate
implementation with
more components
Microcontroller
Several small
components
none
Requires full
redesign of entire
circuit
Microcontroller
Approaches Considered
Display Approach
Due to self-imposed assumptions, transflective LCD’s were only considered.
Transflective LCD’s allow data to be viewed with and without a backlight.
VIM - 404
Cost ≈$5.00
VI - 415
Advantage
≈$10.00
VIM - 404
Ease of Controlled by three 1/3 duty
Implementation cycle signals as common
Controlled by multiple
drivers which receive
binary input.
VI - 415
Number of Pins 20
40
VI - 404
inputs.
Approaches Considered
Programming Approach
It was possible to program the PIC in two different languages. The two
different languages were Assembly or C.
Assembly
Ease of Closer to machine language.
Implementation Requires writing to specific
C
Advantage
Abstract language that
is more user friendly.
C
The compiler yields
less efficient memory
use in translation.
Assembly
More familiar with
commands.
C
registers.
Memory Space Allows more control for
memory use.
Group Minimal practice, unfamiliar
Understanding with commands.
Project Definition
A successful project will result in a device that:
 shall receive an input signal and broadcast it on the FM band
 shall receive its signal input from a 3.5mm input port
 shall accept power from a cigarette lighter/power socket of an automobile or
a standard wall outlet
 shall be capable of storing 4 programmable transmission frequencies
 shall display the transmission frequency on a back-lit display
Research Activities
FM Radio Transmission
 Uses transmission band of 88-108 MHz
 Signal Modulated onto carrier frequency
 Backwards compatible with stereo/mono
Research Activities
FCC Rules
 Part 15 concerning unlicensed FM broadcasting
 Broadcast strength: ≤ 0.1 W
 Broadcast band: 88 -108 MHz
LCD Displays
 Reflective technology
 Transflective technology
 Backlights
Design Activities
Functional Diagram
 Inputs
 Processing
 Outputs
Design Activities
Microcontroller
 PIC 16F877
 28 Pin DIP
 Non-Volatile Memory
 I/O
Handles all device logic
 Controls user interface
 Data connection to signal
processor, LCD display
 Controls backlighting
Design Activities
Signal Processor
 Rohm BH1415F
 SOP22
 Phase Locked Loop
 Stereo Capability
 Built in pilot tone
 Serial communication
with microcontroller
Design Activities
Design Activities
Overall Schematic
Design Activities
Component Communication
 Serial Connection from microcontroller to signal processor
Design Activities
Component Communication
For Example: in the case of 99.7 MHz carrier frequency.
99.7 MHz / 100 kHz (fref) = 997  3E5 (HEX)
Implementation Activities
Changes From Original Design
• LCD display
• Switched to VI – 415 from VIM – 404 because of ease of
connecting to PIC.
• Clock
• Switched from a clock to a ceramic resonator.
• Serial connection
• Used output pin instead of serial connection.
Implementation Activities
Problems
• PIC
• Problems getting compilers installed and working in senior design
labs. Solved by downloading free compiler online and bugging the
Computer Support Group.
• Problems getting PIC to work. Initial registers were not initialized.
Once watchdog timer, code-protection, and low – voltage
program were disabled and the clock type was selected, PIC
worked.
• Transmitter Circuit
• Problems getting the output signal. Solved by enabling the
transmitter chip.
Implementation Activities
How Implementation Process Can Be Improved
• Make sure all necessary programs were installed before needed.
• Read all documentation on device.
• Schedule extra time for delays
Testing/Modification
Device Subsystem Testing
 Testing of signal modulation
 Test composite signal generation
 Test RF oscillator
 Test output power
 Transmission occurs across frequency band
 Power system tested for reliability
 Control system tested for proper function
Prototype Testing
 Integration of all subsystems
 Verifying prototype meets or exceeds all design requirements
 User testing
 Advisor/Client acceptance testing
Testing/Modification Results
Device Subsystem Testing Results
 Testing of signal modulation
 Composite signal generates successfully
 RF voltage controlled oscillator does not initialize
 Testing output power
 Output ≈ .085 W which is less than FCC broadcast strength of .1 W
 Control system tested for proper function
 I/O control works successfully
Prototype Testing Results
 Integration of all subsystems
Verifying prototype meets or exceeds all design requirements
 RF VCO failure causes transmission system failure
 Advisor/Client acceptance testing
 Not completed
Resources
Personnel Efforts
 4 Team members first semester
 3 Team members second semester
 Jacob Sloat studying abroad
Personnel Ef f orts
235
227
232
250
200
137
150
100
50
0
Grant
Jacob
Luke
Tony
Resources
Project Finances
Parts
Financial Requirements
$35
Printing &
Binding
$15
Poster
$100
`
$23
$12
Case
PCB
Resources
Project Schedule
Problem Definition
Design Research
Finalization of Design
Prototype Implementation
Prototype Testing
Final Product Implementation
Final Product Testing
Final Documentation
J
F
M
A
M
J
J
A
S
O
N
D
Project Evaluation
Milestone Evaluation Criteria
Evaluation Result
Numerical Score
Exceeded/Met
90% +
Partially Met
1 - 89%
Did not Meet Standard
0%
Project Evaluation
Relative
Importance
Evaluation
Score
Resultant
Score
Problem definition
15%
100%
15
Research
10%
100%
10
Technology selection
10%
100%
10
End-product design
15%
100%
15
Prototype implementation
10%
70%
7
End-product testing
10%
70%
7
End-product documentation
10%
95%
9.5
Project reviews
5%
100%
5
Project reporting
10%
100%
10
End-product demonstration
5%
50%
2.5
Milestones
Total
100%
Previously defined passing score = 80%
91%
Commercialization / Additional Work
Commercialization
 Product market already exists
 Several competitors established in market
 Will be difficult to establish in market
 Must provide unique features to compete
Recommendations for Additional Work
 Commercialization of product
 Expanded functionality
 Auto-Seek frequency to broadcast on
 Multiple input sources
 HD radio output
Lessons Learned
What went well?
 Team member interaction
 Programming (after initial configuration error)
 Documentation
What did not go well?
 Configuring PIC programmer
 Transmission circuit debugging
 Device implementation
Lessons Learned
Knowledge gained
 FM modulation process
 Microcontroller programming
 LCD display drivers
 Soldering skills
What would we change?
 Make sure necessary programs were installed before needed
 Talk to someone with background in RF
 Have a computer engineer on the team
 Project schedule
Risk Management
Anticipated Potential Risks
Risk:
Management:
Loss of a team member
Increase remaining members efforts
Risk:
Management:
Component Failure
Ordered multiples of the less common components
Risk:
Management:
Delay Receiving Parts
Rescheduling of tasks
Risk Management
Encountered Risk - Anticipated
Loss of a team member:
Delay receiving parts:
Component failure:
Successfully managed through increased
efforts
Successfully managed through task
rescheduling
Ordered extra parts
Encountered Risk - Unanticipated
Complexity of technology: Marginally managed with additional
research
Summary
The FM Transmitter project was meant to create a device that allowed the
output of a personal music device to be utilized by a car or home stereo. While
a fully functional device was not sucessfullly implemented, the groups
technical knowledge was expanded and its project management skills refined.