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Radio345 - PowerPoint PPT Presentation

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Radio345 with ECE 345 Senior Design Project - Fall 1999 Thomas Hicks Nitin Wadhwa Advisor: Lee Rumsey Introduction A Web based interactive FM radio station The server/transmitter processes song requests and maintains an informational Web page

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ECE 345 Senior Design Project - Fall 1999

Thomas HicksNitin Wadhwa

Advisor: Lee Rumsey

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  • A Web based interactive FM radio station

The server/transmitterprocesses song requests andmaintains an informationalWeb page

While listening to their radio, users look-up song info and make requests through the Web

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Description of Frequency Modulation

  • Protects signal from atmospheric noise

  • The carrier’s frequency becomes a function of time

  • AM broadcasts are more susceptible to distortion

  • FM waves allow for higher fidelity

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Specifications of an FM Wave

  • Equation of an FM wave:

  • Broadcast frequency of 88.7 MHz

  • Bandwidth of modulated carrier  150 kHz

  • Modulating frequency  15 kHz

  • Sufficient power to reach in-lab receiver(approximately 0-1 dBm)

Operational amplifier design l.jpg


Operational Amplifier Design






DC PowerSupply

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Transistor Design






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Transistor Design is Optimal Choice

  • Op-amp design has many more components

  • Each op-amp requires a battery

  • Voltage-controlled oscillator is very expensive

  • Transistor design powered by one 9V battery

  • Transistor design circuit is smaller

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Sub-Circuits of Final Design

  • Common-emitter (CE) audio amplifier

  • Loss-less Pi matching network

  • LC tank oscillator with feedback

  • CE Radio Frequency Amplifier

  • Radio Frequency Traps

  • Feedback and emitter resistors

  • DC blocking and bypass capacitors

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Testing and Verifications

  • Output connected to an oscilloscope to verify FM waveform and to measure the modulated frequency

  • Output connected to a spectrum analyzer to locate broadcast frequency and to measure the output power

  • Input connected to a function generator to apply various input waveforms

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Performance Specifications

  • Broadcast frequency of 88.7 MHz

  • Bandwidth of modulated carrier:42 kHz  150 kHz

  • Modulating frequency = 1 kHz  15 kHz

  • Output power of 7.70 dBm

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Finishing Touches

  • Cascade low cost amplifier chips at output for greater range

  • Add a frequency detection circuit to warn the listener that the frequency has shifted because of a low battery

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User interface

Displays the current song playlist

Obtains users’ song selections/requests

WinAmp interface

Gets information from the WinAmp MP3 player

Generates an HTML file with information about the current song

RadioMonitor 2000

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System Requirements

  • Nullsoft’s WinAmp 2.5 MP3 player

  • Sambar 4.2 Web Server

  • Cost: FREE!

User interface l.jpg
User Interface

  • Perl script to parse the M3U playlist file and output an HTML file:


#EXTINF:339,Jamiroquai - Virtual Insanity

C:\music\Jamiroquai - Virtual Insanity.mp3

#EXTINF:222,Lou Bega - Mambo No. 5

C:\music\Lou Bega - Mambo no. 5.mp3

#EXTINF:227,Will Smith - Gettin' Jiggy Wit It

C:\music\Will Smith - Gettin' Jiggy Wit It.mp3

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WinAmp Interface

RadioMonitor 2000 communicates with the WinAmp Player

HTML is generated (every second)

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How it’s done!

  • Control Panel written in VisualBasic

  • Makes API calls to WinAmp for info

  • For example, to obtain Output Time:

API defined: “An acronym for Application Program Interface, the set of commands that an application uses to request and carry out lower-level services performed by a computer's operating system.”

Source: MSDN Library Visual Studio 6.0


Public Const IPC_GETOUTPUTTIME = 105

In Main.BAS:

WinAMPhWnd = FindWindow("Winamp v1.x", vbNullString)


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  • Topic not documented anywhere!

  • Updating playlist:

  • WinAmp only reads the playlist on startup

  • Solution: winamp /add demo2.mp3

  • WinAmp only writes the playlist on close

  • Solution: Control panel makes an API call at regular intervals: SendMessageM(WinAMPhWnd, WM_WA_IPC, 0, WinAMPFE.IPC_WRITEPLAYLIST)

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Challenges 2

  • How often to refresh user’s pages?

  • Song info HTML (options in the control panel):

  • Dynamic update: if the host and WinAmp are running without interruption or intervention, page updates can occur at song’s end(When a user enters the page, the page refresh time is set to time remaining in the current song).

  • Fixed interval: Refresh page at host selected intervals from 5s to 30s

  • Playlist HTML:

  • Fairest way: fixed interval of 20s

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Possible Improvements

  • Voting mechanism for song selection

  • User registration and security features

  • Advertising within pages

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Concluding Remarks

  • Learned more design tools

  • Got accustomed to documenting in thesis format

  • Success with incorporating two disciplines

  • Perseverance