FM Transmitter

Design Report

Project Team: Dec06-01

ClientIowa State University-Senior Design

Faculty AdvisorDr. John W. Lamont

Prof. Ralph E. Patterson III

Team MembersGrant Blythe

Tony HunzikerLuke Erichsen

Jacob Sloat

Disclaimer Notice:This document was developed as a part of the requirements of an electrical and computer engineering course at Iowa State University, Ames, Iowa. This document does not constitute a professional engineering design or a professional land surveying document. Although the information is intended to be accurate, the associated students, faculty, and Iowa State University make no claims, promises, or guarantees about the accuracy, completeness, quality, or adequacy of the information. The user of this document shall ensure that any such use does not violate any laws with regard to professional licensing and certification requirements. This use includes any work resulting from this student-prepared document that is required to be under the responsible charge of a licensed engineer or surveyor. This document is copyrighted by the students who produced this document and the associated faculty advisors. No part may be reproduced without the written permission of the senior design course coordinator.

Date SubmittedMay 3, 2006

Table of Contents

List of Figures iiList of Tables iiiList of Definitions iv

Executive Summary 11. Introduction Materials 3

1.1 Problem Statement 31.2.1 General Problem Statement 31.2.2 General Solution Approach 3

1.2 Operating Environment 41.3 Intended User(s) and Intended Use(s) 4

1.3.1 Intended User(s) 41.3.2 Intended Use(s) 4

1.4 Assumptions and Limitations 51.4.1 List of Assumptions 51.4.2 List of Limitations 5

1.5 Expected End-Product and Other Deliverables 62. Approach and Product Design Results 7

2.1 Approach Used 72.1.1 Design Objectives 72.1.2 Functional Requirements 82.1.4 Technical Approach Considerations and Results 102.1.5 Testing Approach Considerations 112.1.6 Recommendations Regarding Project Continuation 12

2.2 Detailed Design 122.2.1 Inputs 132.2.2 Processing 142.2.3 Outputs 202.2.4 Overview schematic 21

3. Resources and Schedules 213.1 Resource Requirements 21

3.1.1 Personal Effort Requirements 223.1.2 Other Resource Requirements 243.1.3 Financial Requirements 24

3.2 Schedule of Tasks 264. Project Team Information 28

4.1 Client 284.2 Faculty Advisors 284.3 Team Members 29

5. Closing Summary 306. References 31

List of Figures

Figure 1: Block diagram of device systems.......................................................................13Figure 2: PIC16F873A Microcontroller............................................................................16Figure 3: Rohm BH1415F.................................................................................................17Figure 4: Data Packet Diagram..........................................................................................18Figure 5: Transmission Frequency Encoding....................................................................19Figure 6: BH1415F Package and Dimensions...................................................................19Figure 7: VIM-404-DP-FC-S-HV.....................................................................................20Figure 8: Overall circuit schematic....................................................................................21Figure 9: Gantt chart of expected project flow and time span...........................................26Figure 10: Revised Gantt chart of expected project flow and time span...........................27Figure 11: Gantt chart of schedule of deliverables............................................................27

List of Tables

Table 1: Original personal effort time table......................................................................22Table 2: Revised personal effort time table.......................................................................22Table 3: Original other costs..............................................................................................24Table 4: Revised other costs..............................................................................................24Table 5: Original product cost analysis.............................................................................25Table 6: Revised project cost analysis...............................................................................25

List of Definitions

FCC: Federal Communications Commission

Gantt chart: a schedule showing the specific tasks of a project, start dates, and completion dates.

LCD: liquid crystal display

MP3 player: digital music player, (i.e. ipod)

Satellite radio: subscription radio signal sent via satellite, (i.e. XM radio, Sirius radio)

Transmission frequency: The frequency at which the device is transmitting the FM modulated signal to the FM radio.

Wall wart: AC power transformer designed to plug into a standard wall outlet

Executive Summary

The FM transmitter project solves a problem facing many consumers with linking their personal music device to car audio systems. With no inputs readily available on most car stereos, this project uses FM transmission to solve the problem. The audio signal that is generated by personal music devices is accepted by a device, manipulated into an FM signal, and transmitted to the FM tuner in their car. This device offers flexibility by accepting a range of personal music devices and transmitting to a wide range of car stereo systems.

The project adheres to a wide collection of requirements. The transmission frequency will be chosen by the user between 88MHz and 108 MHz, in compliance with the FCC regulations. The transmission range is a minimum of 12 feet. To operate in a car the device must to accept power from a car cigarette lighter. The on/off operation is to be dictated by the input signal. With the presence of an input signal the device would turn on. The absence would turn it off after a short period of time. The controls of the device need to include a set of 4 preset stations to transmit at, much like the preset stations of a radio. The current transmission frequency will be displayed on an LCD screen, for the user to be able to tune the station in on their car radio.

There are inherent requirements for this device as a result of its intended use. It must to be small and rugged. The environment that this device is will work in includes extreme temperatures, constant movement, and small space. The power consumption of the device must be low in order to prevent drain on the power source, the car battery.

After considering numerous technologies, the team settled on a set of solutions that will satisfy or exceed all requirements while still remaining inexpensive enough to remain under budget and be completed in the given time frame.

The completed device design can be separated into three different sections; inputs, processing, and outputs. The inputs to the device include frequency tuner, preset buttons, power, and the source signal input. These are the only inputs to the device. The processing category includes a transmission component that would include amplification and modulation. It also includes a microcontroller circuit. This circuit manipulates the transmission component and the LCD output based on the device inputs. An example of the microcontrollers function is to determine whether an input exists and turn on the surrounding components. The outputs of the device include a LCD display and an antenna. The LCD is used to display the transmission frequency and be controlled by the microcontroller. The antenna would simply be transmitting the actual signal from the transmission component.

The transmission component has been found in a single IC from ROHM. This unit includes the modulation circuit and amplification circuit in stereo. The information signal and the carrier signal are kept in-line with a phase locked loop. This IC allows for a variable frequency transmission with a “mute” feature that effectively turns the transmission off. These features are controlled by the microcontroller. The fact that this

component is solid state allows it to function within the environment above. This IC needs a clock signal so a 555 timer IC will be added to perform this function.

The microcontroller circuit will also be supplied in a single IC. This IC will be a PIC processor from Microchip. This IC also uses the clock signal from a 555 timer. It includes analog devices that would aid in implementing some evaluation functionality. It also contains flash memory and EPROM programmable circuitry. These will be used to implement most of the control of the other components including the LCD, transmission circuit, and input data. The IC comes equipped with 28 pins that make a perfect candidate to control an LCD screen.

At this time the team has been able to complete all design tasks successfully. The project is on time and consistent with labor estimates. The team anticipates that the remainder of the project can be completed meeting all requirements within the time frame and budget specified. For these reasons the team recommends the project be continued.

The FM transmitter project creates a marketable solution to a problem facing many portable audio consumers. Using available technology the team has designed a device to link a portable music device to an FM radio. This device design meets or exceeds all project requirements while meeting the desired product price point. The project is currently on time and under budget. The FM transmitter project has been successful to date and will continue to be so through to completion.

1. Introduction Materials

This section will introduce the project, including the abstract, acknowledgements, problem statement and solution, operating environment, intended users and uses, limitations and assumptions, expected end-product and other deliverables.

1.1 Problem Statement

The problem statement is broken up into two separate sections; one that defines the general problem area and another that describes the proposed approach to the solution.

1.2.1 General Problem Statement

The problem calls for a device that will receive an input signal and broadcast it on the FM band. The device is to receive its signal input from the headphone jack of an MP3 player or output jack of a Satellite Radio and its power input from the 12V DC cigarette lighter/power socket in an automobile or 120V AC outlet from a house. It should be easily tunable to transmit on any desired frequency in the FM band (88-108 MHz) with the ability to preset four selectable frequencies within this range. The minimum transmission distance is to be at least twelve feet. It should recognize when there is an input signal and turn itself on automatically and automatically turn itself off after one minute if the input signal is absent.

1.2.2 General Solution Approach

The proposed solution to this problem is a FM transmitter. This transmitter will accept power from two types of sources. The two sources will include a “wall wart” and a cigarette lighter outlet adapter. The FM transmitter will modulate the signal, send it through an amplifier, and finally through an internal antenna. An internal memory source will store four programmable station presets from the frequency band. An LCD screen will display the current frequency transmitting. This LCD will be backlit for easy night use. The transmission frequency and presets will be accessible through a button/knob interface that may also include a lighting system. There will be a microcontroller to access memory, automatic turn off/on function, possible lighting, display frequency, and any other controlling concerns.

1.2 Operating Environment

The finished device will operate within a personal vehicle or a household room. The normal conditions for which would be a smaller space that could be potentially exposed to moisture, dust, dirt, and overall reckless negligence. It may be exposed to rougher conditions such as being moved from location to location.

1.3 Intended User(s) and Intended Use(s)

This section is divided into two parts, one to cover the intended user(s), and the second is to cover the intended use(s).

1.3.1 Intended User(s)

The intended user for this product is anyone owning MP3 players or satellite radio devices. This is not exclusive to age, size, sex, or handicap. It does assume the amount of operating knowledge associated with MP3 player/satellite radio users.

1.3.2 Intended Use(s)

The FM transmitter is intended to make personal music players more accessible to listen to through home and car stereos. It should do so in a cost efficient and highly functional design.

1.4 Assumptions and Limitations

This section contains the assumptions and limitations of the project.

1.4.1 List of Assumptions

This is the list of assumptions that will be considered in the design. The transmitter may be used for all varieties of personal music players. The transmitter may be used in a variety of environments including varying

temperatures, humidity, seismic conditions, and electromagnetic noise. The transmitter may be used at all hours of the day. Similar products may come directly from the personal music players producers

as competition. The device will be used with standard North American FM radio equipment. The input audio signal will consist of standard music with a frequency range of

20 Hz to 20 kHz. The device design will implement solid state electronics. The user will have access to a steady power source able to supply the rated

voltage and frequency (if AC) within a 10 percent tolerance.

1.4.2 List of Limitations

This is a list of limitations that are inherent in the design preventing it to function in certain ways.

The cost to purchase this product shall be competitive. The transmitter must conform to FCC regulations. The transmission frequency band must stay within 88-108 MHz. The device shall be capable of obtaining power from both a 120 V AC from a

wall wart or a 12 V DC source from a car battery. The form of the device must be manageable for ease of transportation and storage. There must be at least 4 programmable preset transmission frequencies. The device must transmit at least 12 feet. Transmission frequency must be adjustable. Transmission frequency must be displayed. The size shall not exceed 6 in. by 6 in. by 3 in. The weight shall not exceed 1 lb. The device shall be compatible with both digital and analog tuned radios.

1.5 Expected End-Product and Other Deliverables

The end product shall be a small handheld device to carry on ones self for use with their personal music player. It shall be taken in the car or used at home to allow a person to easily listen to their personal music player on any FM radio via FM transmission.

The device case will be made of some type of plastic. The form of the device case will allow for easy hand manipulation and transportation of the device. The design will also take into consideration the requirements of use in a vehicle. These requirements include storage, accessibility, and stability.

The device will implement an LCD screen displaying the transmission frequency. The user input interface will consist of six buttons. These buttons include an “up” and a “down” button to adjust transmission frequency. The remaining four buttons will each access a programmable preset frequency. Pushing and releasing a preset button, in less than 3 seconds, will adjust the transmission frequency to the stored frequency assigned to that button. Pushing and holding a preset button for greater than 3 seconds will assign and store the current transmission frequency to that preset button.

Both the LCD display screen and the buttons may be backlit for use in low ambient light environments.

This device shall come with an adaptor for use with an American standard wall outlet to avoid the use of the battery. This will be a simple wall wart device. The output from this adapter will be a male power jack.

The transmitter will also come with an adaptor for the standard cigarette outlet for automobile use. This is to avoid the use of battery power as well. This will be a smaller device similar to a wall wart. The output of this adapter will be a male power jack.

Both adapters will connect to the device through a common female jack. The adapters will be designed so that the device will receive the same power input regardless of which adapter is being used.

An instruction manual will also be included. This will describe the basic operations to the user.

The device and accessories should be deliverable by December 2006.

2. Approach and Product Design Results

This section will describe the approach for designing the device and a detailed description of the product design.

2.1 Approach Used

This section will explain the methods used to design the device. The design of this project will be split into the following sub-sections; design objectives, functional requirements, design constraints, technical approach, testing approach, and recommendations regarding project continuation.

2.1.1 Design Objectives

The following objectives shall be achieved in the design of the device. These objectives were defined from the project problem statement.

The device shall receive an input signal and broadcast it on the FM band.

The device will receive a stereo audio signal through a wired connection. The device will transmit the signal using the standard FM radio band.

The device shall receive its signal input from the output jack of an MP3 player or the output jack of a satellite radio.

The device will have one stereo input jack. This will accept signals of various amplitudes. Varying outputs from the MP3 or satellite radio will be connected using an adapter cable.

The device shall receive its power input from a cigarette lighter/power socket in an automobile or a standard wall outlet.

An adapter will be provided for each of these two sources. Both adapters will provide a common output to the device. The device will have one power input jack that will be capable of connecting to either adapter.

The device shall be capable of storing 4 programmable transmission frequencies.

Four programmable frequencies shall be stored in memory for easy user access. These four presets will be non-volatile and each will be accessed through a single button.

The device shall be capable of transmitting within a range encountered during normal use.

The transmission range of the device should be large enough to support normal use. Normal use is within a single vehicle or within 1 average sized residential room.

The device should power on and off automatically.

While connected, the device should be capable of detecting the input signal. The device shall turn on and off automatically based on the absence of this signal.

2.1.2 Functional Requirements

The following functions will be implemented into this project and are required to complete this project successfully. These primary requirements were specified by the client as well as the faculty advisors.

Transmit audio through frequency modulation on the standard North American FM bands.

The device will transmit on the standard North American FM radio bands. This range is 88.1-107.9 MHz stepped by 200 kHz intervals.

Turn off and on automatically according to the existence of an input signal.

Upon detection of an input signal, the device shall power on and begin transmitting within 1 second. After detecting no input signal for 1 minute, the device shall power down within 1 second.

Work at a distance of at least twelve feet.

The device transmission range shall be a radius of at least 12 ft around the device in open air. This transmission range should not violate any FCC standards or regulations.

Have 4 programmable frequency presets.

Four programmable preset frequencies shall be stored in non-volatile memory in the device. The transmission frequency shall be adjusted to any of these frequencies by pushing one of the four corresponding buttons. A preset shall be programmed to the current frequency by pushing and holding the corresponding button for greater than 3 seconds. These four buttons will be backlit for use in low light environments.

Include an input for a MP3 player or a satellite radio.

The device shall accept a stereo input audio signal through a standard 3.5 mm stereo jack.

Operate on a 5 volt DC source.

The device shall receive its power input from a 12 V DC cigarette lighter/power socket in an automobile or a standard 120 V AC wall outlet. An adapter will be provided for each of these two sources. Both adapters will provide a common 5 V DC output to the device. The device will have one power input jack that will be capable of connecting to either adapter.

.Designed for handheld use.

The dimensions of the device will not exceed 6 x 6 x 3 inches. The device weight shall not exceed 1 lb. The form of the device case will allow for hand manipulation and transportation of the device. The design will also take into consideration the requirements of use in a vehicle. These requirements include storage, accessibility, and stability.

Possible lighting for night time use.

If possible, the device will include backlighting for easy use in low light environments. This includes a backlit display and backlit buttons.

The transmission frequency shall be displayed.

The device shall include an LCD to display the current transmission frequency. The format of this display will be “XXX.X” (i.e. “102.7”).

Note: These are the current design specifications of this project. Changes may occur later during the design and implementation process. Functional applications may also be added to improve the quality and market appeal of the product.

2.1.3 Design Constraints

These design constraints were developed from the functional requirements and the limitations and assumptions that were defined. The entire project will be designed and constructed to perform under the following conditions and constraints.

Size: The device dimensions will not exceed 6 x 6 x 3 inches. Weight: The total device weight will not exceed 1 lb. Operation Environment: The device will operate within a temperature range

of 32 to 100 degrees Fahrenheit. The device will operate within normal humidity levels and atmospheric pressure. The case should be sealed adequately to protect from dust and moisture. The device will operate in the presence of minor vibrations and shocks.

Transmission power: The FCC has regulation broadcast strength of .1kW. The transmitter must not exceed this strength. The device shall conform with FCC rules Part 15 concerning unlicensed FM broadcasting. The RF field strength 3 meters from the device should not exceed 250uV/m.

Power requirements: The device shall receive its power input from a 12 V DC cigarette lighter/power socket in an automobile or a standard 120 V AC / 12V DC wall outlet. While there is no maximum power usage limit, the device power consumption should not interfere with operation of the automobile.

Budget considerations: The project budget may not exceed $150 as described in the project description. The cost of programming and labor is not included. The final market cost ideally should not exceed $40.

2.1.4 Technical Approach Considerations and Results

There were many different proposed ideas on which technologies are best suited for this project. This section includes the methods considered for amplification, antenna design, and logic controllers.

Modulation & amplification: There are primarily two type of amplification used in audio electronics. The first is steady state; the use of a transistor to amplify the signal. This is cheaper, smaller, and is much more portable. The second of which is tube technology. This would use vacuum tube as the amplifying device. This is not very portable but provides better clarity of signal during amplification. It is generally used only on expensive, high-end systems.

After examining the available technologies and comparing each technology to the team’s list of design requirements, the decision was made to use a solid state device. In order to satisfy the requirements for powering on time and the requirements for durability and portability, solid state was the only logical solution.

Antenna design: This technology is important to the transmitter due to how effective different designs are at transmitting their signals. It must remain internal as to not take up space, yet provide adequate coverage area. The effective usage of power is important to this project.

The team found that the cheapest and simplest antenna design that will meet the project needs is a small wire antenna. A small wire antenna will provide the necessary signal transmission while taking up a small amount of case space and costing very little.

Logic controllers: Logic controllers are needed to save/retrieve station frequencies for preset use, run the LCD, and run the automatic on/off detection. This can be taken care of by personal designs or can be used by programmed microcontrollers. Both accomplish the task at hand. The personal designs would be more labor intensive. The microcontroller would be more expensive.

The team considered several different approaches toward solving the logic problem. After comparing the project needs with the available technologies, the team decided to implement the logic controller with a PIC processor. PIC processors will give the team the necessary computing power to control all components of the device including the LCD. At the same time PIC processors are inexpensive and will fall within the project budget. PIC processors also possess the non-volatile memory necessary to store the preset stations.

2.1.5 Testing Approach Considerations

The methods for testing and the criteria for acceptance will be discussed here. Testing is another consideration that should not be overlooked. This project will be tested by the following means

Testing of amplifier: The ability to successfully amplify the signal to the desired strength without distortion. This will use simulation as well as physical testing.

Testing of transmission: The antenna as well as the amplifier will be tested together to see how successful it is at transmitting data over an array of distances and frequencies.

Testing of powering scheme: This test will be a physical test of how steady of a power source received from the two different adaptors as well as the automatic powering function that depends on the input jack.

Testing of control circuits: The control circuits will go through a simulated test of all the possible functions to see the response. This test will be repeated as a physical test to assure that the controlling device is working properly.

Client testing: The final product will undergo a demonstration of its features step by step in front of the client.

2.1.6 Recommendations Regarding Project Continuation

At this time the team feels that the project should be continued as originally envisioned. To make this recommendation the team considered all portions of the project and the feasibility of each. Existing technologies are available to solve all technical problems encountered in the project. The team also feels that the project can be completed in conformance with all legal standards regarding wireless audio transmission. The project is also on schedule at this time and can be completed by the original deadline.

2.2 Detailed Design

The following is an elaboration of the device design including tasks necessary for project completion. This includes the different systems within the design, the parts currently considered to implement these systems, and preliminary prices of these components.

Figure 1: Block diagram of device systems

The figure above is a block diagram displaying the top level systems to be implemented in the device. The diagram has been split up into three different stages: inputs, processing, and outputs. Below each stage is elaborated on

2.2.1 Inputs

The inputs to the device are on the left section of the diagram. The three inputs specified in the diagram are preset inputs, power supply, and audio input signal.

2.2.1.1 Manual Input

The manual inputs allow the user to adjust and fine tune the transmission frequency manually. There will be two buttons for the manual input function; one to adjust the transmission frequency up and one button to adjust the transmission frequency down. Adjustment of the transmission frequency will happen in increments of 200 kHz. For example 102.7 MHz will increase to 102.9 MHz or decrease to 102.5 MHz in response to the received input.

2.2.1.2 Preset Inputs

The preset inputs are the input signal that will be seen by the microcontroller when one of the four preset buttons is pressed. The four programmable preset frequencies shall be stored in non-volatile memory in the device. The transmission frequency shall be adjusted to any of these frequencies by pushing one of the four corresponding buttons. A preset shall be programmed to the current frequency by pushing and holding the corresponding button for greater than 3 seconds. These four buttons will be backlit for use in low light environments.

2.2.1.3 Power Supply

The device shall receive its power input from a 12V DC cigarette lighter/power socket in an automobile or a standard 120V AC / 12V DC wall adapter. An adapter will be provided for each of these two sources above. The device will have one power input jack that will be capable of connecting to either adapter.

The adapter for the cigarette lighter will be a single stage adapter that plugs directly into the standard cigarette lighter/ power outlet of and automobile.

The source from the wall outlet will be a wall wart; that converts the 120V AC to a 12V DC output for the device. This wall wart will be provided by the EE/CprE senior design group for the prototype testing and demonstrations.

2.2.1.4 Input Signal

The input signal may come from an MP3 player, or a satellite radio system. The device shall accept a stereo input audio signal through a standard 3.5 mm stereo jack. The output from the MP3 player, the satellite radio system or another source of audio input may have different output connections but it is assumed that the user will provide proper adapters to convert the output to the specified 3.5mm input jack of the device. The audio signal input is expected to consist of audio frequencies within the range of 20Hz to 20 kHz.

2.2.2 Processing

The processing consists of the microcontroller, modulator, and amplifier. The bulk of the functions of the device are performed by these three systems. The following is a detailed design of the three systems.

2.2.2.1 Microcontroller

The microcontroller will be the control center for the device. It will take in the manual and preset inputs and tune the device to a transmission frequency depending on which buttons are pushed. It will also allow the device to store transmission frequencies into the preset buttons. The microcontroller will also implement the auto turn on/turn off function with respect to the input signal. The LCD display will also be controlled by the microcontroller. This can be taken care of by personal designs or can be used by programmed microcontrollers. Both accomplish the task at hand. The personal designs would be more labor intensive. The microcontroller would be more expensive.

Frequency tuning is taken care of in the modulation and amplification chip. The control of this is handled by the microcontroller.

The auto/on off implementation is another feature controlled by the microcontroller. The microcontroller will be in a continuous loop awaiting the input in order to control the peripherals. The input is sampled through one of the input pins of the microcontroller. This is only used to detect the input, no data is sampled and once there is an absence of an input the power off count down begins. This count down is a period to wait for signal before actually powering down. This prevents premature power down.

The microcontroller will control the LCD display as well. When a frequency change occurs, the microcontroller will send the appropriate control signals to the LCD display. Each of the 4 digits displayed will be controlled individually, and will only need to be refreshed when the frequency is change. The display is always backlit. The microcontroller is connected to the inputs of the display.

Figure 2: PIC16F873A Microcontroller

The team considered several different approaches toward solving the logic problem. After comparing the project needs with the available technologies, the team decided to implement the logic controller with a PIC processor. The PIC processor chosen was the PIC16F873A processor. It contains a 28 pin IO interface and the memory and processing power needed for the teams application. PIC processors will give us the necessary computing power to control all components of the device including the LCD. At the same time PIC processors are inexpensive and will fall within the project budget. PIC processors also possess the non-volatile memory necessary to store the preset stations.

2.2.2.2 Transmission Block

After examining the available technologies, an integrated solution was found to provide the modulation, amplification, and transmission. The device will implement a Rohm Electronics BH1415F Wireless Audio Link IC to provide stereo modulation and FM transmission.

The BH1415F is a FM stereo transmitter IC. The stereo modulator generates a composite signal which consists of a MAIN, SUB, and pilot signal from a 38 kHz oscillator. The FM transmitter then radiates FM wave on the air by modulating the carrier signal with a composite signal.

Figure 3: Rohm BH1415F

The BH1415F operates on a 4.0 to 6.0 V DC source. This is consistent with other components in the device and the 5 V DC supplied from the power adapters. The IC will also meet the device environmental requirements. The operation temperature range is -40 to 80 degrees Celsius.

This IC accepts a stereo audio input through two pins, a L-ch input and a R-ch input. The audio input frequency band ranges from 20 Hz to 15 kHz. The signal can then be adjusted through a pre-emphasis circuit, a limiter circuit, and a low pass filter. At this time the team has not determined whether these portions of the IC will be used. The signal is then modulated on a frequency from 76 to 108 MHz. The carrier frequency can be set at any level within that range at 100 kHz intervals. Because FM radio in North America is only broadcast on odd ending frequencies, the device will be stepping the IC on 200 kHz intervals.

The signal is then transmitted with a maximum of 450 mW power dissipation. This will be adjusted and limited to comply with FCC regulations.

The IC transmission settings are controlled via a serial data connection with the microcontroller. The serial connection is implemented through three pins on the BH1415F, CE (Chip Enable), CK (Clock), and DA (Data). The IC is refreshed through a binary data packet.

Figure 4: Data Packet Diagram

The data packet consists of 16 bits transmitted from the microcontroller to the BH1415F. No transmission frequency is specified for the data stream, however, the frequency may not exceed .66 MHz. The transmission frequency is set using the first 10 bits of the packet. The frequency is first divided by 10^5. This is then encoded as a hex value and then transmitted in binary. For example, in the case of 99.7 MHz, the frequency divided by 10^5 is 997 which is 3E5 in hexadecimal. The binary stream uses D0 as the LSB and D10 as the most significant bit.

Figure 5: Transmission Frequency Encoding

The remaining bits of the data packet will not be used in the implementation. This includes control of stereo/mono operation, phase detection manipulation, and test settings.

The BH1515f is available in a SOP22 package that will be easy to mount without a complex manufacturing process.

Figure 6: BH1415F Package and Dimensions

2.2.3 Outputs

There are two outputs from the device. An LCD screen will display the frequency that the device is currently transmitting at. The other output is the FM audio output transmitted by the antenna. These two outputs are described in the following sections.

2.2.3.1 LCD Screen

The LCD Screen will be a 7 segment display with a backlit option. It is equipped with a module for it to interpret the data given from the microcontroller. This will accept the input as a single pin and the display this to the screen. There will be 4 digits and a decimal point.

Figure 7: VIM-404-DP-FC-S-HV

The LCD chosen was the VIM-404-DP-FC-S-HV LCD manufactured by Varitronix. It is a transflective backlit display that meets and exceeds size, temperature, and cost for this part. The way it accepts inputs is dependant upon its programming making it a versatile choice. Its 20 I/O pin interface is typical for LCD components on the market.

2.2.3.2 Antenna

The output to the antenna is broadcasted to the car radio. This is the primary output of the signal.

The device will use a small wire antenna that will remain inside the device case. Because the case is plastic and the transmission range is small, there should not be a need for an external antenna.

2.2.4 Overview schematic

The following is the overall schematic of the teams design. This includes the output pin connections to the input pin connections of the parts listed above.

Figure 8: Overall circuit schematic

3. Resources and Schedules

The following is the project resource requirements, project schedules, and a deliverable schedule. There are primary schedules and revised schedules.

3.1 Resource Requirements

This project will require many hours of planning, researching, designing, and testing, as well as organizational skills, developed methods of communication, and each member’s devotion. The following will contain initial time and money requirements as well as a preliminary milestone timeline.

3.1.1 Personal Effort Requirements

As an assurance to the success of this project, each member of the team has plan on the amount of time to be spent. Table 1 lists the amount of time spent is shown for each task. By looking at the total time to be spent, one can expect the work load of a particular task and be prepared to complete it on time.

Table 1: Original personal effort time tablePersonal Name Time consumption for various tasks in hour

1 2 3 4 5 6 7 8 TotalsGrant Blythe 6 16 78 16 20 18 9 17 180

Luke Erichsen 7 18 75 14 23 15 7 15 174

Tony Hunziker 8 20 78 13 18 16 8 14 175

Jacob Sloat 8 19 82 15 21 17 7 16 185

Totals 29 73 313 58 82 66 31 62 714

Table 2: Revised personal effort time tablePersonal Name Time consumption for various tasks in hour

1 2 3 4 5 6 7 8 Revised Totals

Grant Blythe 7 10 10 16 20 18 9 17 107

Luke Erichsen 24 8 10.5 14 23 15 7 15 116.5

Tony Hunziker 26.5 8.5 9.5 13 18 16 8 14 113.5

Jacob Sloat 19 8 7.5 15 21 17 7 16 110.5

Revised Totals 76.5 34.5 37.5 58 82 66 31 62 447.5

The project plan was a larger commitment than expected. It accumulated almost two times the amount of hours expected. This is reflected later on in the Gantt chart. Task 2, technical considerations did not take as long as expected. This is because within our project definition the team identified the most viable technical opportunities. The third task was significantly less due to two aspects. Most technical aspects concerning the final design are actually taken care of in the surrounding tasks. The team also believes that this step is ongoing and has not been completed. The tables are as follows:

Task 1: Project Plan

Includes statement of the problem, and the requirements, and specification made by the client.

Task 2: Technical Considerations

Contains a list of our choices of technologies that can be used in product design. We will select the best and most feasible approach. Includes extensive research of each technologies and their components

Task 3: End-Product Design

Consists of the design process for the product once a technology is selected. The end result will be a functional design that meets requirements

Task 4: End-Product Implementation

Task consist of the actual implementation of the end product design

Task 5: End-Product Testing

Testing of the prototype will be done in this task. The testing is done in order to ensure that the prototype functions safely and properly.

Task 6: End-Product Documentation

Documentation occurs through out the project and is revised and packaged near completion of the project.

Task 7: End-Product Demonstration

Demonstrate the functionality of device to client and advisor.

Task 8: Project Reporting

Creating a full and detailed report covering the entire process from problem definition to presentation.

3.1.2 Other Resource Requirements

There will be other miscellaneous requirements that will not be estimated but not included in the design budget. These resources are detailed in Table 3 below.

Table 3: Original other costsItem Cost (estimation)

Paper Printing $11.00Photocopy $5.00

Miscellaneous $6.00Total $22.00

Table 4: Revised other costsItem Cost

Printing of project plan

$4.00

Printing of design report $5.00

Project Poster $25.00Miscellaneous $6.00

Total $15.00

3.1.3 Financial Requirements

This section includes financial costs associated with this project. Beside the material cost, the cost due to labor is also calculated base on hourly rate of $10.00. The information on Table 5 lists the closest possible value base on market research through online product.

Table 5: Original product cost analysisItem W/O labor With Labor

Part & Material1. modulator2. amplifier3. antenna4. liquid crystal display5. microcontroller6. case8. DC adapter

Subtotal

$ 2.74$ 2.29$ 2.17$ 1.50$ 12.95$ 3.75$ 5.65

$31.05

$ 2.74$ 2.29$ 2.17$ 1.50$ 12.95$ 3.75$ 5.65

$31.05Other costs (from Table 3) $ 22.00 $ 22.00

Labor at $ 10.00/hrGrant Blythe Luke ErichsenTony HunzikerJacob Sloat

Subtotal $ 53.05

$ 1800.00$ 1740.00$ 1750.00$ 1850.00

$ 7140.00

Total Project Cost $ 53.05 $ 7171.05

Table 6: Revised project cost analysisItem W/O labor With Labor

Part & Material1. amplifier/modulator2. clock3. antenna4. liquid crystal display5. microcontroller6. case8. DC adapter

Subtotal

$ 3.76$ 0.75$0.25$ 4.50$ 7.50$ 8.00$ 3.75

$28.51

$ 3.76$ 0.75$ 0.25$ 4.50$ 7.50$ 8.00$ 3.75

$28.51Other costs (from Table 4) $ 15.00 $ 15.00

Labor at $ 10.00/hrGrant Blythe Luke ErichsenTony HunzikerJacob Sloat

Subtotal $ 43.51

$ 1070.00$ 1165.00$ 1135.00$ 1105.00

$ 4475.00

Total Project Cost $ 43.51 $ 4518.51

3.2 Schedule of Tasks

This is the timeline of projected milestones. There is going to be limited accuracy at this time. This schedule will change as the project takes shape. Figure 2 below shows the team’s initial schedule. Figure 3 shows the revised team’s schedule. Figure 4 below shows the deliverable schedule.

Figure 9: Gantt chart of expected project flow and time span

Figure 10: Revised Gantt chart of expected project flow and time span

The project schedule was updated to show the current status of the project. Completed tasks, and their time span are noted. Actual work for some planning aspects exceeded that initial time scheduled, however the project is still on schedule. Task estimates for future task were changed accordingly.

Figure 11: Gantt chart of schedule of deliverables

Figure 4 has not changed from the original chart in the project plan. The deliverables are mandated through the senior design class schedule.

4. Project Team InformationFollowing are the contact information for every person that is involve in this project.

4.1 Client

Iowa State UniversityDepartment of Electrical and Computer Engineering, Senior DesignAddress: 2215 Coover Hall, Ames, IA 50011Website: www.ece.iastate.edu

4.2 Faculty Advisors

Ralph E. Patterson IIIOffice: 326 TownOffice Phone: 515-294-2428 Home Phone: 515-232-9933Fax: 515-294-6760Home Address: 1807 24th Street Ames, IA 50010-4430Email: repiii@iastate.edu

John W. LamontOffice: 324 Town Office Phone: 515-294-3600Home Phone: 515-292-5541Fax: 515-294-6760 Home Address: 1005 Idaho Ave Ames, IA 50014-3018 Email: jwlamont@iastate.edu

4.3 Team Members

Jacob Sloat – Team LeadMajor: Electrical EngineeringPhone: 563-370-0501Address: 1125 Frederiksen Court, Ames, IA 50010Email: cutsloat@iastate.edu

Grant Blythe – Communications CoordinatorMajor: Electrical EngineeringPhone: 319-431-6032Address: 111 Rockvalley Drive SW, Ames, IA 50014Email: gblythe@iastate.edu

Tony HunzikerMajor: Electrical EngineeringPhone: 515-572-7722Address: 4233 Frederiksen Court, Ames, IA 50010Email: huntz57@iastate.edu

Luke ErichsenMajor: Electrical EngineeringPhone: 515-450-0694Address: 119 Stanton Ave Apt 708, Ames, IA 50014 Email: luke13@iastate.edu

5. Closing Summary

In summary, the designed FM transmitter will be able to take in an audio input from a standard headphone audio output and transmit it to an FM receiver. The transmitter will be able to transmit from 88MHz to 108MHz, and will have 4 preset frequencies. The device will be powered from either a 12V dc automobile cigarette lighter, or through an adapter connected to a 60Hz 120VAC standard outlet. Output will be displayed on a backlit LCD screen.

The design implements all requirements and takes into consideration limitations imposed by internal and external forces. Some of these forces include, client needs, government regulations, and size constraints. After researching possible technologies, the design has been implemented in a simple, yet thorough manner using proven components. The designed solution will meet or exceed all specifications.

The end-product is expected to not only perform the required functions, but prove to be a competitive model in the commercial market of FM transmitters. This design will be capable of meeting the goal of having a product that will stand out in the marketplace. This design should also allow for the project to be completed on time and at or under budget. All current indications are that this project will be successful.

6. References

1. Microelectronic Circuits, fourth edition. By Sedra and Smith. Oxford university press, 1997.

2. Field and Wave Electromagnetics, 2nd. Edition. By David K. Cheng. Prentice Hall, 1989

3. Fundamental of Digital Logic with Verilog design. By Stephen Brown, Zvonko Vranesic. McGraw-Hill, 2002

4. Engineering Circuit Analysis, 6th. Edition. By William H. Hayt, Jack Kemmerly, Steven M. Durbin. McGraw-Hill, 2002

5. EE/CprE 491 Senior Design Course Notes. By John Lamont.6. EE/CprE 491 Senior Design Coursepack Supplement. By John Lamont.7. Fundamentals of Engineering Economics. Chan S. Park. Prentice Hall,

2003