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EECE 252 Final Project effects of demodulation frequency variations in Am radio

EECE 252 Final Project effects of demodulation frequency variations in Am radio . Tim Altmansberger Seth dean. background. AM radio in Air Traffic Control is susceptible to noise and error Examine when receiving Demodulation Freq. is not equal to Carrier Freq.

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EECE 252 Final Project effects of demodulation frequency variations in Am radio

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  1. EECE 252 Final Projecteffects of demodulation frequency variations in Am radio Tim Altmansberger Seth dean

  2. background • AM radio in Air Traffic Control is susceptible to noise and error • Examine when receiving Demodulation Freq. is not equal to Carrier Freq. • Analyze the quality of resulting audio signal

  3. design • Record two audio files – one from air traffic control and one Mayday transmission • Add both recordings together for a combined audio signal • Utilize DSB-SC modulation to transmit combined signal • Create a user interface to easily test various demodulation frequencies

  4. implementation • Setup • Load and modulate audio signals, interpolate to change sampling frequency • Create low-pass filter • Loop • Get user input (demodulation frequency) • Demodulate signal, interpolate to return to normal sampling frequency • Apply LPF to the signal • Play the resulting signal for the user

  5. results

  6. conclusions • There is a +/- 5% tolerance in demodulation frequency for meaningful sound • Current atmospheric and device noises pose no major threat for the ability to react to a Mayday transmission

  7. Questions?

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