# EE200_amradio - EE200Lab5TunedIn 1 Introduction .You

This preview shows pages 1–3. Sign up to view the full content.

Last Revised: 10/6/2008 1 EE 200 Lab 5 ‐ Tuned In 1 Introduction In this lab you will be given a raw data signal representing an AM radio communication modulating some recorded audio at a particular frequency. You will perform some analysis on the signal and then attempt to demodulate it to recover the original sound signal. 2 What you will learn You will learn to use Fourier analysis (frequency domain) methods and understand their properties to extract useful information from a signal. In addition, basic concepts of modulation (in this lab we only focus on amplitude modulation rather than FM or other methods) will be introduced. 3 Background Information and Notes Amplitude Modulation : Amplitude modulation works by taking a signal and multiplying it with a higher (usually much higher) frequency carrier signal. The result is that the original signal controls the amplitude or acts as an envelope function of the modulated frequency. Mathematically, given a signal A(t), AM modulation at a frequency, f c , is achieved by performing the operation: ܣܯሺݐሻൌܣሺݐሻכcosሺ2ߨ݂ ݐ൅ߠሻ An example is shown below where an 8Hz sinusoid is amplitude modulated at a carrier frequency of 100 Hz. The resulting modulated signal is then shown. 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 -1.5 -1 -0.5 0 0.5 1 1.5 Original signal: Sinusoid of f=8 Hz 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 -1.5 -1 -0.5 0 0.5 1 1.5 Modulation frequency: f=100 Hz

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
EE 200 Lab 5 ‐ Tuned In 2 Last Revised: 10/6/2008 Figure 1 - a.) Original 8Hz signal. b.) Carrier Frequency. c.) Resulting AM signal. Note: Recall that Matlab uses discrete time signals. Thus we need to sample the carrier and AM signal at an even higher sampling rate (frequency), F s . Fourier Series Representation : Any periodic signal can be represented as a Fourier Series. By using Fourier analysis, we can find the frequency domain representation of a signal. Given some Fourier spectrum that results from the original signal, multiplying it by the carrier frequency is equivalent to shifting the frequency
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 5

EE200_amradio - EE200Lab5TunedIn 1 Introduction .You

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online