## Viva Questions on Signals

Viva Questions on Signals, Introduction to signals viva questions, Short Questions on Signals, continuous-time signal viva questions, discrete-time Signals viva questions, digital signal viva questions, Electronics Viva Questions, Signal & Systems Viva Questions.

### Short Questions and Answers

**Q.1.** *Define a signal.*

**Ans.** A signal is defined as any physical quantity that varies with time, space, or any other independent variable.

**Q.2.** *Define deterministic and random signals.*

**Ans.**

** Deterministic Signal:** A deterministic signal is a signal exhibiting no uncertainty of its value at all instants. Its instantaneous value can be accurately predicted by specifying a mathematical relation.

** Random Signal:** A random signal is a signal characterized by uncertainty before its actual occurrence. (or) A random signal can not be predicted before its actual occurrence.

**Q.3.** *Define step function and Delta function.*

**Ans.** A step function is defined as

A delta function is defined as

\int_{-\infty }^{\infty }\delta (t)dt=1and δ(t) = 0 for t ≠ 0.

**Q.4.** *Define periodic and aperiodic signals.*

**Ans.** A signal *x(t)* is periodic with period *T* if and only if

*x(t + T) = x(t)* for all *t*

If there is no value of *T* that satisfies the above equation the signal is called aperiodic.

**Q.5.** *Define symmetric and antisymmetric signals.*

**Ans.** A real valued signal *x(t)* is called symmetric if

*x(-t) = x(t)*

on the otherhand, a signal *x(t)* is called antisymmetric if

*x(-1) = – x(t)*

**Q.6.** *Define energy and power signals.*

**Ans.** The energy of a signal *x(t)* is defined as

A signal *x(t)* is called an energy signals if the energy is finite and power IS Zero.

The average power of a signal *x(t)* is defined as

A signal *x(t)* is called a power signal if the average power *P* is finite and Energy is infinite.

**Q.7.** What is the period *T* of the signal x(t)=2\cos (\frac{t}{4})

**Ans.**

x(t)=2\cos (\frac{t}{4});

\Omega _{0}=\frac{1}{4};

T=\frac{2\Pi }{\Omega _{0}}=\frac{2\Pi }{1/4}=8\Pi sec**Q.8.** *Define continuous-time, discrete-time and digital signals.*

**Ans.**

The signals that are defined at all instants of time are known as continuous-time signals.*Continuous-time signals:*The signals that are defined at discrete instants of time are known as discrete-time signals.*Discrete-time signals:*The signals that are discrete in tune and quantized in amplitude are digital signals*Digital signals:*

**Q.9.** *What is the value of the following integral?*

**Ans.** \frac{1}{\left| a\right|}x\left ( \frac{b}{a} \right )

**Q.10.** *What are the different types of representation of discrete-time signals?*

**Ans.** Discrete-time Signal representation types are:

- Graphical representation
- Functional representation
- Tabular representation
- Sequence representation

**Q.11.** *Consider the discrete-time signal x(n)=1-\sum_{k=3}^{\infty }\delta (n-1-k). Determine the value of the signals M and k so that x(n) may be expressed as x(n)=u(Mn-k)*

The signal *x(n)* is sketched in above figure.

**Ans.**

The signal *x(n)* is equivalent to folding *x(n)* and then shifting the folded signal by 3 to the right. Therefore *x(n) = u(-n+3)*. Comparing *u(-n – 3)* with *u(Mn – n _{k})* we get M = -1 and k = -3.

**Q.12.** *Consider a continuous-time signal x(t)=\delta (t+2)-\delta (t-2). Calculate the value E_{\infty } of for the signal y(t)=\int_{-\infty }^{t}x(\tau )d\tau *

y(t)=\int_{-\infty }^{t}x(\tau )d\tau =\int_{-\infty }^{t}[\delta (\tau +2)-\delta (\tau -2)]dt;

y(t)=u(t+2)-u(t-2);

E_{\infty }=\int_{-2}^{2}\left| y(t)\right|^{2}dt=[t]_{-2}^{2};

=4**Q.13.** *Find the even and components of the signal* x(t)=e^{jt}

**Ans.**

x_{e}(t)=\frac{x(t)+x(-t)}{2}=\frac{e^{jt}+e^{-jt}}{2}=\cos t;

x_{0}(t)=\frac{x(t)+x(-t)}{2}=\frac{e^{jt}-e^{-jt}}{2}=j\sin t
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