List of top Electronics and Communication Engineering Questions on Signals and Systems

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 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).

Let $X(t)$ be a white Gaussian noise with power spectral density $\dfrac{1}{2}$ 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).

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

For the two port network shown below, the [Y]-parameters is given as [Y] = (1/100) * [[2 -1], [-1 4/3]] S. The value of load impedance Z_L, in ohms, for maximum power transfer will be _____________ (rounded off to the nearest integer).

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

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).