List of top Electronics and Communication Engineering Questions

In a given sequential circuit, initial states are $Q_1 = 1$ and $Q_2 = 0$. For a clock frequency of 1 MHz, the frequency of signal $Q_2$ in kHz, is ___________ (rounded off to the nearest integer).

Consider a discrete-time periodic signal with period $N=5$. Let the discrete-time Fourier series (DTFS) representation be \[ x[n] = \sum_{k=0}^{4} a_k e^{j\frac{2\pi kn}{5}}, \] where $a_0 = 1$, $a_1 = 3j$, $a_2 = 2j$, $a_3 = -2j$, and $a_4 = -3j$. The value of the sum \[ \sum_{n=0}^{4} x[n] \sin\left(\frac{4\pi n}{5}\right) \] is _____________

Let an input $x[n]$ having discrete-time Fourier transform \[ X(e^{j\Omega}) = 1 - e^{-j\Omega} + 2e^{-j3\Omega} \] be passed through an LTI system whose frequency response is \[ H(e^{j\Omega}) = 1 - \tfrac12 e^{-j2\Omega}. \] The output $y[n]$ of the system is

Let $x(t) = 10\cos(10.5Wt)$ be passed through an LTI system having impulse response \[ h(t) = \pi\left(\dfrac{\sin(Wt)}{\pi t}\right)^2 \cos(10Wt). \] The output of the system is _____________

Let $x_1(t)$ and $x_2(t)$ be two band-limited signals having bandwidth $B = 4\pi \times 10^{3}$ rad/s each. In the figure below, the Nyquist sampling frequency, in rad/s, required to sample $y(t)$, is _____________

The S-parameters of a two port network is given as \[ [S] = \begin{bmatrix} S_{11} & S_{12} \\[2pt] S_{21} & S_{22} \end{bmatrix} \] with reference to $Z_0$. Two lossless transmission line sections of electrical lengths $\theta_1 = \beta l_1$ and $\theta_2 = \beta l_2$ are added to the input and output ports for measurement purposes, respectively. The S-parameters $[S']$ of the resultant two port network is

The standing wave ratio on a $50\ \Omega$ lossless transmission line terminated in an unknown load impedance is found to be $2.0$. The distance between successive voltage minima is $30\ \text{cm}$ and the first minimum is located at $10\ \text{cm}$ from the load. $Z_L$ can be replaced by an equivalent length $l_m$ and terminating resistance $R_m$ of the same line. The value of $R_m$ and $l_m$, respectively, are _____________

The electric field of a plane electromagnetic wave is \[ E = \mathbf{a_x}\,C_{1x}\cos(\omega t - \beta z) + \mathbf{a_y}\,C_{1y}\cos(\omega t - \beta z + \theta)\ \text{V/m}. \] Which of the following combination(s) will give rise to a left handed elliptically polarized (LHEP) wave?

The following circuit(s) representing a lumped element equivalent of an infinitesimal section of a transmission line is/are

The signal-to-noise ratio (SNR) of an ADC with a full-scale sinusoidal input is given to be 61.96 dB. The resolution of the ADC is ___________ bits (rounded off to the nearest integer).

For the two port network shown below, the [Y]-parameters is given as \[ [Y] = \frac{1}{100} \begin{bmatrix} 2 & -1 \\ -1 & \frac{4}{3} \end{bmatrix} \text{ S}. \] The value of load impedance $ Z_L $, in $ \Omega $, for maximum power transfer will be ___________ (rounded off to the nearest integer).

Let $x_1(t) = u(t+1.5) - u(t-1.5)$ and $x_2(t)$ is shown in the figure below. For $y(t) = x_1(t) x_2(t)$, the $\int_{-\infty}^{\infty} y(t)dt$ is ___________ (rounded off to the nearest integer).

Let X(t) be a white Gaussian noise with power spectral density $\frac{3}{2}$ W/Hz. If X(t) is input to an LTI system with impulse response $e^{-t}u(t)$. The average power of the system output is ___________ W (rounded off to two decimal places).

A transparent dielectric coating is applied to glass ($\epsilon_r = 4, \mu_r = 1$) to eliminate the reflection of red light ($\lambda_0 = 0.75 \mu m$). The minimum thickness of the dielectric coating, in $\mu$m, that can be used is ___________ (rounded off to two decimal places).

The frequency of occurrence of 8 symbols (a-h) is shown in the table below. A symbol is chosen and it is determined by asking a series of "yes/no" questions which are assumed to be truthfully answered. The average number of questions when asked in the most efficient sequence, to determine the chosen symbol, is ___________ (rounded off to two decimal places).

The switch $S_1$ was closed and $S_2$ was open for a long time. At $t=0$, switch $S_1$ is opened and $S_2$ is closed, simultaneously. The value of $i_c(0^+)$, in amperes, is _____________

The open loop transfer function of a unity negative feedback system is \[ G(s) = \frac{k}{s(1+sT_1)(1+sT_2)}, \] where $k$, $T_1$ and $T_2$ are positive constants. The phase cross-over frequency, in rad/s, is

A closed loop system is shown in the figure where $k > 0$ and $\alpha > 0$. The steady state error due to a ramp input $(R(s)=\alpha/s^{2})$ is _____________

In the following block diagram, R(s) and D(s) are two inputs. The output Y(s) is expressed as Y(s) = G$_1$(s)R(s) + G$_2$(s)D(s).
G$_1$(s) and G$_2$(s) are given by

In the circuit shown below, the current i flowing through 200 $\Omega$ resistor is ___________ mA (rounded off to two decimal places).

In the circuit shown below, switch S was closed for a long time. If the switch is opened at t = 0, the maximum magnitude of the voltage $V_R$, in volts, is ___________ (rounded off to the nearest integer).

The asymptotic magnitude Bode plot of a minimum phase system is shown in the figure. The transfer function of the system is $(s) = \frac{k(s+z)^a}{s^b(s+p)^c}$, where k, z, p, a, b and c are positive constants. The value of $(a+b+c)$ is ___________ (rounded off to the nearest integer).

In the circuit shown below, $D_1$ and $D_2$ are silicon diodes with cut-in voltage of 0.7 V. $V_{IN}$ and $V_{OUT}$ are input and output voltages in volts. The transfer characteristic is _____________

In a semiconductor, if the Fermi energy level lies in the conduction band, then the semiconductor is known as

For an intrinsic semiconductor at temperature $T=0K$, which of the following statement is true?