FREE BEE Bachelor of Electrical Engineering Signals and Systems Questions and Answers

Question 1

Which of the following properties distinguishes a Linear Time-Invariant (LTI) system from other types of systems?

Accepted Answer

It satisfies both the superposition principle and time-invariance.

Answer

Its output depends only on the current input, not past inputs.

Answer

It always produces a periodic output for a periodic input.

Answer

Its impulse response is always a unit step function.

Question 2

A continuous-time signal x(t) = cos(2πf₀t) is sampled at a rate f_s. To avoid aliasing, what must be the relationship between f_s and f₀?

Accepted Answer

f_s ≥ 2f₀

Answer

f_s < f₀

Answer

f_s = f₀

Answer

f_s ≥ f₀/2

Question 3

Consider a system with impulse response h(t) = e^(-at)u(t) where 'a' is a positive constant and u(t) is the unit step function. Is this system stable and causal?

Accepted Answer

Stable and causal

Answer

Stable but not causal

Answer

Causal but not stable

Answer

Neither stable nor causal

Question 4

Which of the following is a characteristic of a causal system?

Accepted Answer

The output at any time depends only on present and past inputs.

Answer

The system's impulse response is symmetric around t=0.

Answer

The system introduces a time delay proportional to the input magnitude.

Answer

The system's output is always zero before the input begins.

Question 5

The convolution of two signals x(t) and h(t) is given by y(t) = x(t) * h(t). In the frequency domain, what does this operation correspond to?

Accepted Answer

Y(jω) = X(jω)H(jω)

Answer

Y(jω) = X(jω) + H(jω)

Answer

Y(jω) = X(jω) / H(jω)

Answer

Y(jω) = X(jω) * H(jω)

Question 6

A system is described by the input-output relationship y[n] = x[n] + x[n-1]. Is this system linear, time-invariant, and causal?

Accepted Answer

Linear, time-invariant, and causal

Answer

Linear, but not time-invariant and not causal

Answer

Not linear, time-invariant, and causal

Answer

Linear and causal, but not time-invariant