178 + Interview Questions in Signals and Systems in Electronics and Communication Engineering Page 4 InterviewSolution

151.	For the function ( - ) = 0 for < and ( - ) = 1 for ≥ , the Laplace transform is
Answer» £f(t) = £-1F(s) = f(t) £[a f1(t) + bf2(t)] = aF1(s) + bF2(s) where £[f(t - T)] = e-sT F(s) £[e-at f(t)] = F(s + a) Initial value theorem Final value theroem Convolution Integral where t is dummy variable for t.

Discussion

152.	Two function () and () with correlation of 6 has average power of 4 and 5 respectively. The power of () + () is
Answer» Power of two correlated signal is P = P1 + P2 +2R1, 2(t).

Discussion

153.	A box has 4 white and 3 red balls. Two balls are taken out in succession. What is the probability that both are white?
Answer» The probability that first ball is white is and the probability the second ball is white is . The probability that both are white is .

Discussion

154.	Z transform is a non-linear operation.
Answer» Z transform is a linear operation.

Discussion

155.	The -transform of a particular signal is given whereThe system after implementation will be
Answer» Include unity circle and exterior of circle hence x(z) will be stable, causal.

Discussion

156.	The system with given pole-zero diagram is
Answer» Because no.of zero is more than Pole, therefore when you find transfer function. Numerator power will higher than denominator, and such transfer functions is not realizable.

Discussion

157.	A pole zero pattern of a certain filter is shown in figure. This filter must be
Answer» In transfer function, no of zeros = no. of poles, hence it is all pass fliter.

Discussion

158.	If transfer function of a system is H() = 6 + + then system is
Answer» H(z) = 6 + z-1 - z-2, solve it by considering H(z) = 0 z = 1/3, -1/2 in H(z) only numerator. Hence z = 1/3, - 1/2 will be zero, and if zero lies inside the unit circle, system will be of minimum phase.

Discussion

159.	The period of the function cos is
Answer» .

Discussion

160.	The energy of constant amplitude complex valued exponential sequence is ...
Answer» .

Discussion

161.	The value of Integral δ() sin is equal to
Answer» Because δ(t) is defined at t = 0 only.

Discussion

162.	A rectangular pulse train () is shown in figure is convolved with the signal cos(4 x 10). The convolved signal will be a
Answer» First find the Fourier series of given pulse that is And fm from (2) &Rightarrow; 4 kHz When we multiply x1(t) and x2(t - t) We get term like fs ± fm, 2fs ± fm, 3fs ± fm, 4fs ± fm and fs = 10 kHz fm = 4kHz Hence from above relation (10+4) kHz &Rightarrow; 14 kHz signal will be present in x(t).

Discussion

163.	A signal () = then () is a
Answer» .

Discussion

164.	The Fourier series of an odd periodic function contains
Answer» For an odd function f(- x) = - f(x) Hence, only sine terms.

Discussion

165.	If , the terms in () will have
Answer» (s + 1) term will give e-t and (s + 2) term will give e-2t .

Discussion

166.	An impulse function consist of
Answer» Because F.T. of δ(t) = 1, 1 is a Constant function ranging from -∞ to +∞.

Discussion

167.	As per time displacement theorem in Laplace transformation, displacement in the time domain by T becomes
Answer» £f(t - T) = e-st F(s).

Discussion

168.	Which one is a causal system?
Answer» For causal output must depend upon Present and past not on future.

Discussion

169.	If , the coefficient of term in () will be
Answer» Coefficient of e-t = .

Discussion

170.	Double integration of a unit step function would lead to
Answer» .

Discussion

171.	If () = A d( - ), F() is
Answer» It is an impulse having area A and originating at t = a.

Discussion

172.	If is the Laplace transform of () then (0) is
Answer» .

Discussion

173.	If and A + B is
Answer» Add elements individually.

Discussion

174.	A voltage V() is a Gaussian ergodic random process with a mean of zero and a variance of 4 volt. If it is measured by a dc meter. The reading will be
Answer» DC meter reads mean value.

Discussion

175.	A first order system will never be able to give a __________ response Choose the correct option
Answer» Because to design band pass or band stop, transfer function of must be second order.

Discussion

176.	In the given figure the ratio T/ is the duty factor.
Answer» .

Discussion

177.	If £[()] = F(), then £[( - )] =
Answer» A linear system is one in which the relationship between input and output is linear. All linear system possess the property of superposition i.e., if input u1 gives output y1 and input u2 gives output y2 then input u1 + u2 will give output y1 + y2. Superposition implies homogencity i.e., if input u gives output y, then input ku gives output ky where k is a rational number. In general a system is linear if a transformation T satisfies the relation T(au1 + βu2) = aT(u1) + βT(u2) where a and β are constant.

Discussion

178.	In an ac circuit the fundamental component of current wave lags the corresponding voltage wave by 20°. The third harmonic component of current wave lags the corresponding voltage by an angle.
Answer» For third harmonic θ = tan-1 = .

Discussion

Explore topic-wise InterviewSolutions in .

For the function ( - ) = 0 for < and ( - ) = 1 for ≥ , the Laplace transform is

Two function () and () with correlation of 6 has average power of 4 and 5 respectively. The power of () + () is

A box has 4 white and 3 red balls. Two balls are taken out in succession. What is the probability that both are white?

Z transform is a non-linear operation.

The -transform of a particular signal is given whereThe system after implementation will be

The system with given pole-zero diagram is

A pole zero pattern of a certain filter is shown in figure. This filter must be

If transfer function of a system is H() = 6 + + then system is

The period of the function cos is

The energy of constant amplitude complex valued exponential sequence is ...

The value of Integral δ() sin is equal to

A rectangular pulse train () is shown in figure is convolved with the signal cos(4 x 10). The convolved signal will be a

A signal () = then () is a

The Fourier series of an odd periodic function contains

If , the terms in () will have

An impulse function consist of

As per time displacement theorem in Laplace transformation, displacement in the time domain by T becomes

Which one is a causal system?

If , the coefficient of term in () will be

Double integration of a unit step function would lead to

If () = A d( - ), F() is

If is the Laplace transform of () then (0) is

If and A + B is

A voltage V() is a Gaussian ergodic random process with a mean of zero and a variance of 4 volt. If it is measured by a dc meter. The reading will be

A first order system will never be able to give a __________ response Choose the correct option

In the given figure the ratio T/ is the duty factor.

If £[()] = F(), then £[( - )] =

In an ac circuit the fundamental component of current wave lags the corresponding voltage wave by 20°. The third harmonic component of current wave lags the corresponding voltage by an angle.