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Electronics and Communication Engineering - Exam Questions Papers

Exercise : Exam Questions Papers - Exam Paper 11
21.
Two discrete time systems with impulse responses h1[n] = δ[n - 1] and h2[n] = δ[n - 2] are connected in cascade. The overall impulse response of the cascaded system is
δ[n - 1] + δ[n - 2]
δ[n - 4]
δ[n - 3]
δ[n - 1] + δ[n - 2]
Answer: Option
Explanation:

h1(n) → delay by 1, h2(n) → delay by 2,

h1(n) * h2(n) → delay by 3.

22.
The magnitude plot of a composite signal x(t) = e2jt + e3jt is
Half wave rectified sinusoid
Full wave rectified sinusoid
Exponentially increasing sinusoid
Exponentially decreasing sinusoid
Answer: Option
Explanation:

x(t) = ej2 . 5t (e-j0.5t + e-j0 . 5t)

x(t) = 2ej2.5t cos (0.5)t

The magnitude of x(t) is

|x(t)| = 2|cos (0.5)t|.

23.
A message signal given by is amplitude modulated with a carrier of frequency ωc to generate s(t) = [1 + m(t)] cos ωct
8.33%
11.11%
20%
25%
Answer: Option
Explanation:

.

24.
A 16 bit counter type ADC uses 1 MHz clock then its maximum conversion time is __________ .
16 μs
15 ms
6.6 ms
66 ms
Answer: Option
Explanation:

Maximum conversion time of counter type ADC = (216 - 1) x 1 μs = 65.5 ms » 66 ms.

25.
A first order system will never be able to give a __________ response.
  1. Band pass
  2. Band reject
  3. All pass
Choose the correct option
1, 2 and 3 are true
1 and 3 are true, 2 is false
1 and 2 are false, 3 is true
1 and 2 are true, 3 is false
Answer: Option
Explanation:

The ideal response of a Band pass filter BRF and APF is as shown

So for BPF we require 0 at ω = 0, p i.e. at least 2 zeroes are required in the Transform.

Hence order has to be atleast 2.

Similarly for band reject filter order should be at least 2. Whereas APF has a constant amplitude.

Hence Zeroes in the function need not matter.

APF function is given as Hence first order can provide APF.

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