1
GATE ECE 2026
MCQ (Single Correct Answer)
+1
-0.33

The response of a discrete time system $\mathrm{y}[\mathrm{n}]$ obeys the following relation:

$$ y[n]=\frac{5}{6} y[n-1]-\frac{1}{6} y[n-2]+x[n] . $$

The input to the system is $x[n]=\delta[n]-\frac{1}{3} \delta[n-1]$.

Which of the following options is TRUE for $y[n]$ ?

A

Stable and causal response

B

Stable and non-causal response

C

Unstable and causal response

D

Unstable and non-causal response

2
GATE ECE 2026
MCQ (Single Correct Answer)
+2
-0.67

The continuous time signal $x(t)$ is real, periodic with period $T$ and satisfies the Dirichlet conditions.

The Fourier series representation of $x(t)=\sum_{n=-\infty}^{\infty} a_n e^{j\left(\frac{2 \pi n t}{T}\right)}$ and $x(t)$ satisfies the following:

$$ x\left(t-\frac{T}{2}\right)=-x(t) $$

For any integer $m$, which of the following options is correct?

A

$a_{2 m}=0$

B

$a_{2 m}=1$

C

$a_{2 m}=a_{2 m+1}$

D

$a_{2 m}=-1$

3
GATE ECE 2026
MCQ (Single Correct Answer)
+2
-0.67

Consider a real signal $x(t),-\infty

Let $E[x(t)]=\int_{-\infty}^{\infty}[x(t)]^2 d t$.

Which of the following options correctly represents the ratio, $E[x(t)] / E[3 x(-3 t+)]$ ?

A

3

B

1

C

$1 / 3$

D

$1 / 9$

4
GATE ECE 2026
MCQ (Single Correct Answer)
+2
-0.67

Consider a real baseband signal $x(t)=e^{-2 t}$, for $t$ (in seconds) $\geq 0$. If $99 \%$ of energy of $x(t)$ lies within $B \mathrm{~Hz}$, then which of the following options is TRUE for the value of $B$ ?

A

$B>1 \mathrm{kHz}$

B

$63 / \pi \mathrm{Hz}

C

$126 / \pi \mathrm{Hz}<\mathrm{B}<128 / \pi \mathrm{Hz}$

D

$B<1 \mathrm{~Hz}$