Discrete Time Signals and Systems Questions and Answers

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The World’s first microprocessor, 4004, was introduced by Intel in 1968. It was a 4 bit processor, but later it has introduced a new processor almost every year, like 8080, 8085, 8086, 8031 and 8051. Only 8086 processor handles 16 bit data and a micro computer was developed based on this processor. Intel also introduced 80186, 80286, 80386, 80486 and made possible to get mini computers and personal computers.

Other companies like Texas instruments, Motorola, Zilog and Analog devices have specialized in signal processing processors, communication oriented processors, better architectural processor, and discrete signal processing devices.

All the advancements mentioned above are made possible because of continuous upgradation of VLSI technology. Some of the features like cache, pipelining and branch prediction have contributed for improving performance parameters, like execution speed, large memory, fast data transfers and reduction in number of instructions. A transformation has been seen from CISC to RISC.

Identification of application and its potential for marketing provides the opportunity to companies to produce ASICs sometimes. Digital Signal Processors are employed for processing streamed data of either voice or video data.

Which of the following is not signal processing ?

A.Date filtering
B.Convolution
C.Noise addition
D.Date storing

Exam Year(s)

UGC NET - 2012,

Answer: D

Signal processing means operating on a signal to change or analyse it, as in filtering, convolution and noise addition, which change the signal. Storing the data only saves it and does not process it, so it is not signal processing. The words 'date' in the options are misprints for 'data' in the booklet. Filtering removes unwanted frequency components, convolution gives the output of a linear system for a given input, and adding noise changes the waveform, so each of these three acts on the signal, whereas storing only keeps a copy of it. The answer is data storing.

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Match the following :

List-I	List-II
(a) Digital Filters	(i) More channels are accommodated
(b) Signal Processing	(ii) Slow speed of data transfer
(c) Time Division Mulplexing	(iii) Hardware techniques
(d) Frequency Division Multiplexing	(iv) Software techniques

A.a-iv, b-iii, c-ii, d-i
B.a-i, b-ii, c-iii, d-iv
C.a-iii, b-iv, c-i, d-ii
D.a-iv, b-iii, c-i, d-ii

Exam Year(s)

UGC NET - 2012,

Answer: A

The matching is a-iv, b-iii, c-ii, d-i, as the key has it. Digital filters are realised by software techniques, as programs on a processor. Signal processing is paired with hardware techniques, the remaining choice in the list. Time division multiplexing sends the samples in turn, so it is the one with a slow speed of data transfer to each channel. Frequency division multiplexing places many channels in different frequency bands, so more channels are accommodated. Options (B), (C) and (D) place time division or frequency division on the wrong property. The pairing of signal processing with hardware techniques is loose, but the other three fix the answer.

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Assertion (A) : An LTI discrete system represented by the difference equation \(y(n+2) - 5y(n+1) + 6y(n) = x(n)\) is unstable.

Reason (R) : A system is unstable if the roots of the characteristic equation lie outside the unit circle.

A.Both (A) and (R) are true and (R) is the correct explanation of (A).
B.Both (A) and (R) are true, but (R) is not correct explanation of (A).
C.(A) is true, but (R) is false.
D.(A) is false, but (R) is true.

Exam Year(s)

UGC NET - 2013,

Answer: A

Both statements are true and the reason explains the assertion, so the answer is option (A).

The characteristic equation of the system is:

\[ z^{2} - 5z + 6 = 0 \]

\[ (z - 2)(z - 3) = 0 \]

so the roots are 2 and 3. Both lie outside the unit circle, so the system is unstable, which is exactly the criterion in the reason.

Option (B) is wrong because the criterion in the reason is what settles the assertion. Options (C) and (D) call a true statement false.

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Discrete Time Signals and Systems Questions and Answers

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Discrete Time Signals and Systems Questions and Answers

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