Description
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Compute the impulse response functions h(t) for each of the LTI systems given below. Comment on the causality and BIBO stability of the systems.
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(a)
S1 :
y(t) = −t−∞1 et cos(2τ + 2 − 2t)x(τ)e−τ+2dτ
(b)
S2 :
y(t) = e−t
−t∞ eτ [cos(t) cos(τ) − sin(t) sin(τ)]x(τ)dτ
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S3 : y(t) = −t−∞1 e−(t−τ)x(τ − 2)dτ
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Given below are two cascaded LTV systems S1 and S2. The input-output relation for system S1 is given by eqn. (1), where x(t) and y(t) are inputs and output of system S1, respectively. The input-output relation for system S2 is given by eqn. (2), where y(t) and w(t) are inputs and output of system S2 respectively.
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y(t) = x(t)u(t)
−
t−2
e−(t−τ)x(τ)u(τ)dτ, t
∈
( ,
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(1)
−∞
−∞ ∞
t
(2)
w(t) =
y(σ)u(σ)dσ, t ∈ (−∞, ∞)
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−∞
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Compute IRF of S1 and S2 : h1(t, τ) and h2(t, τ) respectively.
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Compute IRF h12(t, τ) of cascaded system S1S2.
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Is the cascaded system (with input x(t) and output w(t) ) a stable system? Explain.
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Obtain the IRF h21(t, τ)
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Matlab assignment 2: For the following problems, include screenshots/images of your MATLAB figures. You should have 5 total figures for this problem. Also, copy and paste your MATLAB code into your homework.
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Using MATLAB, plot x(t) and h(t) individually over the range t ∈ [−3, 3].
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x(t) = sin(2πt)u(t + 1)u(−t + 1) ; h(t) = u(t) − u(t − 1)
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Compute y1(t) = x(t) ∗ h(t) (∗ : convolution operator) analytically as a piecewise function.
(c) Solve for y2(t) = x(t) · h(t) (where · is the multiplication operator) analytically.
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Using MATLAB, plot y1(t) and y2(t) individually over the range t ∈ [−3, 3]. Are y1(t) and y2(t) the same?
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Using MATLAB, numerically convolve x(t) and h(t) and plot the result over the same range. Confirm that the result is the same as y1(t).
Hint for Matlab assignments: Here is a sample code snippet to help you get started. The following code plots the signal z(t) = sin (2πt) − 12 cos 3 π5 − π3 t in the time interval [−3, 3].
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clear; clc; close all; |
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t=linspace(-3,3); |
% Define time axis : 100 equally spaced points in [-3,3] |
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z = sin(2*pi*t) – 0.5*cos(3*pi/5-pi/3*t); |
% Define signal z(t) as a function of |
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t |
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figure(1); % Create figure with label (1) |
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plot(t,z); % Plot signal z(t) against t |
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xlabel(’t’,’Interpreter’,’latex’,’fontsize’,16); ylabel(’z(t)’,’Interpreter’,’latex |
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’,’fontsize’,16); % Label the x and y axes |
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title(’z(t) vs t’,’Interpreter’,’latex’,’fontsize’,18); % Set the graph title |
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grid on; % Apply a mesh grid to the graph |
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Some useful Matlab functions:
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heaviside(x) : generates unit step function. eg. u=heaviside(t); generates function u(t)
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conv(x,y): returns convolution of input signals/vectors x and y.
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Elementwise multiplication of vectors in matlab: x.*y
Figure 1: Output of sample code snippet
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