Lab 1: (i) TIMS introduction (ii) Modeling an Equation Keyur Desai ECE458-Spring 2007 Michigan State University

TIMS Telecommunications Instructional Modeling System Block diagram based approach: each block implements mathematical operations related to Comm. Lots of information at http://www.tims.com.au/ The maximum frequency covered by TIMS = 100KHz; Why not more? Why not 1MHz? TIMS will handle generation and manipulation of signals; how about visualization and measurements?

Pico Scope Pico Scope: 3 channel ADC + software. 2 channels for signals, 1 channel for scope trigger Preferably set scope trigger on Auto and Ext. To save figures in Pico scope, save as, xyz.wmf (windows meta file). Paste this figure in MS word.

Modeling an Equation Objectives: (i) In a laboratory set-up learn addition of waveforms, Amplitude and phase adjustments (ii) Say in your favorite audio track there is a hum of 1KHz (sinusoid); how would you remove it? Your not so smart neighbor generates a hum of 5KHz while you are recording a conversation; What would you do? Objective (i): Two waveforms: Remember the sine function

Sine wave Sine function arose first in trigonometry Sine has a phenomenal property in terms of calculus Especially useful in continuous Linear time invariant (LTI) systems; hence, you will see sine all the time Back to the experiment: Find  and g,G such that Obviously g=G What about ?

Objective 2: Hum removal Now consider a band-limited speech signal s(t) With the help of Fourier Theory we can visualize speech signal as a linear combination of sinusoids with different frequencies For human speech all important information is contained within f=300Hz to f=3400Hz, so we can band- limit the speech via band-pass filtering. But why? Many times, a hum (a sinusoid and its harmonics) gets added in the speech signal Challenge: remove V1(t)

Objective 2: Hum removal Use part 1 to cancel V1(t). Now in real-life applications to remove hum you will have to build circuits. Speech has lots of silence segments: build circuits to extract phase and amplitude of hum using silence.

Objective 2: Hum removal In the case of your not so smart neighbor, do you have to do anything fancy? Remember Low pass filtering. Remember speech has all vital information in the band of 300Hz-3400Hz.