Digital Communications

Course Nos. 0909-402-03 (Senior Elective) & 0909-504-01 (Grad)

Fall 2002

Pre-Lab 1

Synthesis of Noisy Sinusoids with Specified SNR

Objective

To generate noisy sinusoids with specified SNR using Simulink blocks

Software

MATLAB
Simulink DSP Blockset

Background

SNR in dB = 10 log₁₀ (s_s²/s_n²); where s_s²:signal variance, s_n²: noise variance
Given signal, s(t), find s_s²
Compute required s_n²
Generate noise signal, n(t) = s_n N(0,1), where N(0,1) is a Normally (Gaussian) distributed random variable with Zero mean and Unit variance
Message signal with desired SNR, m(t) = s(t) + n(t)

Procedure

Run the demo labeled "Statistical Functions" in the DSP Blockset toolbox of Matlab.
Adapt this demo to synthesize noisy sinusoids with varying SNRs (experiment with the range -3dB to +3dB).
Confirm that the SNR of the noisy sinusoid agrees with theory - demonstrate this.
Experiment with variations in signal frequency and amplitude.

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