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FM Audio Transmitter

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To design and build an FM transmitter that allows you to listen to your portable ... and simple, only one transistor. Easy to build with high probability ... – PowerPoint PPT presentation

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Title: FM Audio Transmitter


1
FM Audio Transmitter
  • Andrew Suk and Mike Portscheller
  • University of Illinois, Urbana-Champaign
  • Professor Swenson
  • TA Julio Urbina

2
Introduction
  • Goals
  • To design and build an FM transmitter that allows
    you to listen to your portable audio devices in
    your car
  • To learn about Frequency Modulation with a 3
    transistor circuit
  • BENEFITS
  • Very cheap
  • Much cheaper than buying and installing an audio
    system in a car

3
Overview
  • Block Diagram
  • Process of circuit design
  • Theoretical and Data analysis
  • Demonstration
  • Room for improvement
  • Conclusion

4
Block Diagram
5
Detailed Block Diagram
6
Process of circuit design
  • First circuit design

7
The good and bad of circuit one
  • Good
  • Very cheap and simple, only one transistor
  • Easy to build with high probability of working
  • Bad
  • Takes 5-10 minutes for the transmitter to reach
    thermal equilibrium

8
Process of circuit design
  • Second circuit design

9
The good and bad of circuit two
  • Good
  • Two transistor to amplify signal before the VCO
  • Bad
  • Very sensitive. Hard to get a stable signal

10
Our design
  • Good
  • Three transistors, but still very easy and cheap
    to build
  • Very stable
  • Bad
  • Frequency pulling, but still stable signal

11
Theoretical Analysis
  • Transfer function
  • Small signal diagram

12
Data Analysis
  • Power input 18 mW
  • Power at antenna with 1k resistor
    (3.21v)(3.21v)/1k 10.30 mW
  • Efficiency 0.5724

13
Demonstration
  • Will it work?

14
Room for improvement
  • Antenna
  • At 98.5 MHz needed a 3.04 meter antenna for full
    wavelength
  • Try other sizes such as half wavelength and
    quarter at 1.52 and 0.76 meters respectively

15
Antenna design
  • At 98.5 Mhz
  • Quarter wave 0.76 meters
  • Half wave 1.52
  • Full wave 3.04

16
Room for improvement
  • Antenna
  • Marketable case
  • Adjustable inductor to change frequency

17
Conclusion
  • Optimization
  • Buy a dipole antenna (none in town)

18
Conclusion
  • Learning
  • How to build an FM transmitter
  • Optimization techniques
  • Applications of ECE 210, 342, and 359 in real
    life engineering
  • More Information
  • www.radioshack.com

19
Summary
  • Block Diagram of FM Transmitter
  • Process of circuit design
  • Theoretical and Data analysis
  • Demonstration
  • Room for improvement
  • Conclusion

20
Conclusion
  • Questions?
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