Signal Processing - Study Mode

[#361] For the discrete-time system shown in the figure, the poles of the system transfer function are located at
Correct Answer

(C) $$frac{1}{2},frac{1}{3}$$

[#362] Let $$xleft[ n
ight] = {left( { - {1 over 9}}
ight)^n}uleft( n
ight) - {left( { - {1 over 3}}
ight)^n}uleft( { - n - 1}
ight).$$ The Region of Convergence (ROC) of the z-transform of x[n]
Correct Answer

(C) Is $${1 over 3} > left| z ight| > {1 over 9}$$

[#363] Let x[n] = x[-n]. Let X(z) be the z-transform of x[n]. If 0.5 + j0.25 is a zero of X(z), which one of the following must also be a zero of X(z).
Correct Answer

(B) $${1 over {left( {0.5 + j0.25} ight)}}$$

[#364] If G(f) represents the Fourier transform of a signal g(t) which is real and odd symmetric in time, then
Correct Answer

(B) G(f) is imaginary

Explanation

Solution: Okay, let's break down this Fourier Transform question for beginners! The question is asking what happens to the Fourier Transform (G(f)) of a signal g(t) , when that signal is both real and odd-symmetric . Let's define each part: * Fourier Transform: Think of it as a way to see what frequencies make up a signal. It transforms a signal from the time domain (how it changes over time) to the frequency domain (how much of each frequency is present). * Real Signal: A signal is real if its values are real numbers (no imaginary part). Most signals we deal with in the real world are real (e.g., sound waves, voltage). * Odd Symmetry: A signal g(t) is odd-symmetric if g(-t) = -g(t). This means if you flip the signal around the y-axis and then flip it around the x-axis, you get the same signal back. A simple example is g(t) = t. Now, here's the key concept: The Fourier Transform has some properties related to symmetry. Important Relationship: When g(t) is real and odd , its Fourier Transform G(f) will be purely imaginary . Let's look at why the other options are incorrect. * Option A: G(f) is complex: While *any* Fourier Transform *can* be complex, the combination of real and odd symmetry *simplifies* it. * Option C: G(f) is real: A real and even signal in the time domain would give a real fourier transform. * Option D: G(f) is real and non-negative: A real and non-negative time-domain signal doesn't guarantee the same characteristics in the frequency domain. Therefore, the answer is Option B: G(f) is imaginary .

[#365] Consider the sequence x[n] = {-4 - j5, 1 + j2, 4} The conjugate antisymmetric part of the sequence is
Correct Answer

(A) {-4 - j2.5, j2, 4 - j2.5}