GATE EC question library

A unity feedback control system is characterized by the open-loop transfer function $$G(s)=\frac{2(s+1)}{s^3+ks^2+2s+1}$$ The value of $</em>k$ for which the system oscillates at $2$ rad/s is ___________

A second-order LTI system is described by the following state equations, $$\begin{array}{ll} \frac{d}{dt}x_1(t)-x_2(t)=0 \\ \frac{d}{dt}x_2(t)+2x_1(t)+3x_2(t)=r(t) \end{array}$$ where $x_1(t)$ and $x_2(t)$ are the two state variables and $r(t)$ denotes the input. The output $c(t)=x_1(t)$. The system is

A unity feedback control system is characterized by the open-loop transfer function $$G(s)=\frac{10K(s+2)}{s^3+3s^2+10}$$ The Nyquist path and the corresponding Nyquist plot of $G(s)$ are shown in the figures below. If $0 < K < 1$, then the number of poles of the closed-loop transfer function that lie in the right-half of the $s$-plane is

The signal $x(t)=\sin (14000\pi t)$, where $t$ is in seconds, is sampled at a rate of $9000$ samples per second. The sampled signal is the input to an ideal lowpass filter with frequency response $H(f)$ as follows: $$H(f)=\begin{cases} 1, & \mid f \mid \leq 12 kHz .\\ 0,& \mid f \mid> 12 kHz. \end{cases}$$ What is the number of sinusoids …

The unmodulated carrier power in an AM transmitter is $5$ kW. This carrier is modulated by a sinusoidal modulating signal. The maximum percentage of modulation is $50 \%$. If it is reduced to $40 \%$, then the maximum unmodulated carrier power (in kW) that can be used without overloading the transmitter is _________

A modulating signal given by $x(t)=5\sin (4\pi 10^3t -10\pi \cos 2\pi 10^3t)V$ is fed to a phase modulator with phase deviation constant $k_p=5$ rad/V. If the carrier frequency is $20$ kHz, the instantaneous frequency(in kHz) at $t=0.5$ ms is ____________

Consider a binary memoryless channel characterized by the transition probability diagram shown in the figure. The channel is

An electron $(q_1)$ is moving in free space with velocity $10^5$ m/s towards a stationary electron $(q_2)$ far away. The closest distance that this moving electron gets to the stationary electron before the repulsive force diverts its path is ____________$\times 10^{-8}$ m. [Given, mass of electron $m=9.11\times 10^{-31}$ kg, charge of electron …

Standard air-filled rectangular waveguides of dimensions $a=2.29$ cm and $b=1.02$ cm are designed for radar applications. It is desired that these waveguides operate only in the dominant $TE_{10}$ mode with the operating frequency at least $25 \%$ above the cutoff frequency of the $TE_{10}$ mode but not higher than $95 \%$ of the next higher …

The permittivity of water at optical frequencies is $1.75 \varepsilon _0$. It is found that an isotropic light source at a distance $d$ under water forms an illuminated circular area of radius $5$ m, as shown in the figure. The critical angle is $\theta _c$. The value of $d$ (in meter) is _______________