CAN207 Continuous and Discrete Time Signals and Systems Assignment 2
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CAN207
Continuous and Discrete Time Signals and Systems
Assignment 2: DT Signals and Systems
Question 1 ( 10 marks).
Perform the ideal sampling to the following continuous-time signal x(t):
x t = 5 cos (2휋푡) − 3 cos 3휋푡 + 2 cos 6휋푡 + cos (8휋푡)
1) Sketch the frequency spectrum of x(t);
2) The frequency which, under the sampling theorem, must be exceeded by the sampling frequency is called the Nyquist rate. Find the Nyquist rate of x(t) in Hz;
Question 2 (20 marks).
A signal whose energy is concentrated in a frequency
band is often referred to as a bandpass signal. There
are a variety of techniques for sampling such signals,
generally referred to as bandpass-sampling
techniques. To examine the possibility of sampling a
bandpass signal as a rate less than the total
bandwidth, consider the system shown in Figure
Q2(b).
Assuming that 휔1 > 휔2 − 휔1 , find the maximum
value of T and the values of the constants A, 휔푎 , and
휔푏 such that 푥푟 ( 푡) = 푥 ( 푡).
Question 3 (20 marks).
An LTI system with impulse response ℎ 1 [푛] = 푛 푢 [푛] is connected in parallel with another causal LTI system with impulse response h2 [n]. The resulting parallel interconnection has the frequency response
퐻(푒푗휔 ) = 12 7푒(12)휔5 푒(푗)2푗휔
1) Determine h2 [n];
2) Use adders, multipliers, and delay units to draw the block-diagrams of 퐻(푒푗휔 ) in Direct form I, Direct form II, cascaded form and parallel forms.
Question 4 ( 10 marks).
The DTFT of x [n] is X( ω ). Express the DTFT of following signals using X( ω ).
1) x1n = x 1 − n + x[ − 1 − n]
2) x2n = (푛 − 1)2x n
푥 푛 , 푛 푖푠 푒푣푒푛
0, 푛 푖푠 표푑푑
Question 5 (20 marks).
A) Two sequences:
x n = n + 1; 0 ≤ n ≤ 3
− 1, 0 ≤ n ≤ 4
1, 5 ≤ n ≤ 6
1) Calculate the linear convolution x n ∗ h[n];
2) Calculate the circular convolution x n ⊛ h n
B) With the knowledge of DFT values at even indices of a 7-point real sequence: X(0) = 4.8; X(2) = 3.1+j2.5; X(4) = 2.4+j4.2; X(6) = 5.2+j3.7; Find the DFT values at odd indices.
Question 6 (20 marks).
A causal LTI system is defined by the following CCLDE:
y [n] = y [n − 1] + y [n − 2] + x [n − 1]
1) Find the transfer function H(z) and ROC of the system and draw the zero-pole plot;
2) Find the impulse response of the system h[n];
3) The given system is unstable. Find a system g [n], satisfying the given CCLDE but being stable.
2022-12-03
DT Signals and Systems