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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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slide1

Radio345

with

ECE 345 Senior Design Project - Fall 1999

Thomas HicksNitin Wadhwa

Advisor: Lee Rumsey

introduction
Introduction
  • 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

description of frequency modulation

Transmitter

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
specifications of an fm wave

Transmitter

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

Transmitter

Operational Amplifier Design

PCSoundcard

Integrator

Summer

VCO

RF

DC PowerSupply

transistor design

Transmitter

Transistor Design

PCSoundcard

Audio

ReactanceModulator

RF

Band-passfilter

transistor design is optimal choice

Transmitter

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
sub circuits of final design

Transmitter

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
testing and verifications

Transmitter

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
performance specifications

Transmitter

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
finishing touches

Transmitter

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
radiomonitor 2000
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
system requirements
System Requirements
  • Nullsoft’s WinAmp 2.5 MP3 player
  • Sambar 4.2 Web Server
  • Cost: FREE!
user interface
User Interface
  • Perl script to parse the M3U playlist file and output an HTML file:

#EXTM3U

#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

winamp interface
WinAmp Interface

RadioMonitor 2000 communicates with the WinAmp Player

HTML is generated (every second)

how it s done
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

In WinAMPFE.BAS:

Public Const IPC_GETOUTPUTTIME = 105

In Main.BAS:

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

TempG = SendMessageM(WinAMPhWnd, WM_WA_IPC, 0, WinAMPFE.IPC_GETOUTPUTTIME)

challenges
Challenges
  • 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)
challenges 2
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
possible improvements
Possible Improvements
  • Voting mechanism for song selection
  • User registration and security features
  • Advertising within pages
concluding remarks
Concluding Remarks
  • Learned more design tools
  • Got accustomed to documenting in thesis format
  • Success with incorporating two disciplines
  • Perseverance