GATE EC Analog Communications questions

The input to a coherent detector is DSB-SC signal plus noise. The noise at the detector output is

The noise at the input to an ideal frequency detector is white. The detector is operating above threshold. The power spectral density of the noise at the output is

A DSB-SC signal is to be generated with a carrier frequency $f_{t}=1 \; \mathrm{MHz}$ using a non-linear device with the input-output characteristic $$v_{0}=a_{0} v_{i}+a_{1} v_{i}^{3}$$ where $a_{0}$ and $a_{1}$ are constants. The output of the non-linear device can be filtered by an appropriate band-pass filter. Let …

The data for Q. 75-76 are given below. Solve the problems and choose the correct answers. Let $m(t)=\cos \left[\left(4 \pi \times 10^{3}\right) t\right]$ be the message signal and $\left.c(t)=5 \cos \left[2 \pi \times 10^{b}\right) t\right]$ be the carrier $c(t)$ and $m(t)$ are used to generate an AM signal. The modulation index of the generated AM …

The data for Q. 75-76 are given below. Solve the problems and choose the correct answers. Let $m(t)=\cos \left[\left(4 \pi \times 10^{3}\right) t\right]$ be the message signal and $\left.c(t)=5 \cos \left[2 \pi \times 10^{b}\right) t\right]$ be the carrier $c(t)$ and $m(t)$ are used to generate an $\text{FM}$ signal. If the peak frequency deviation …

Choose the correct one from among the alternative $\text{A, B, C. D}$ after matching an item in Group $1$ with the most appropriate item in Group $2.$ …

A superheterodyne receiver is to operate in the frequency range $550 \; \mathrm{kHz}-1650 \; \mathrm{kHz}$, with the intermediate frequency of $450 \; \mathrm{kHz}$. Let $\mathrm{R}=\frac{\mathrm{C}_{\operatorname{max}}}{\mathrm{C}_{\text{min}}}$ denote the required capacitance ratio of the local oscillator and $\text{I}$ denote the image frequency …

The line-of-sight communication requires the transmit and receive antennas to face each other. If the transmit antenna is vertically polarized, for best reception the receive antenna should be

A $1 \; \mathrm{MHz}$ sinusoidal carrier is amplitude modulated by a symmetrical square wave of period $100 \; \mu \mathrm{sec}$. Which of the following frequencies will NOT be present in the modulated signal?

A person with a receiver is $5 \; \mathrm{Km}$ away from the transmitter. What is the distance that this person must move further to detect a $3-d B$ decrease in signal strength?

An angle-modulated signal is given by $s(t)=\cos 2 \pi\left(2 \times 10^{6} t+30 \sin 150 t+40 \cos 150 t\right)$.The maximum frequency and phase deviations of $s(t)$ are

The frequency range for satellite communication is

The amplitude modulated wave form $s(t)=A_{c}\left[1+K_{a} m(t)\right] \cos \omega_{c} t$ is fed to an ideal envelope detector. The maximum magnitude of $\mathrm{K}_{0} m(t)$ is greater than $1$. Which of the following could be the detector output?

In an $\text{FM}$ system, a carrier of $100\; \mathrm{MHz}$ is modulated by a sinusoidal signal of $5 \; \mathrm{kHz}$. The bandwidth by Carson's approximation is $1 \; \mathrm{MHz}$. If $y(t)=(\text{modulated waveform})^{3}$, then by using Carson's approximation, the bandwidth of $y(t)$ around $300 \; \mathrm{MHz}$ and the spacing of spectral …

A message $m(t)$ bandlimited to the frequency $f_{m}$ has a power of $P_{m}$. The power of the output signal in given figure is

A modulated signal is given by, $$s(t)=m_{1}(t) \cos \left(2 \pi f_{c} t\right)+m_{2}(t) \sin \left(2 \pi f_{c} t\right)$$ where the baseband signal $m_{1}(t)$ and $m_{2}(t)$ have bandwidths of $10 \; \mathrm{kHz}$ and $15 \; \mathrm{kHz}$, respectively. The bandwidth of the modulated signal, in $\mathrm{kHz}$, is

The input to a channel is a bandpass signal. It is obtained by linearly modulating a sinusoidal carrier with a single-tone signal. The output of the channel due to this input is given by $$y(t)=(1 / 100) \cos \left(100 t-10^{-6}\right) \cos \left(10^{6} t-1.56\right)$$ The group delay $\left(t_{g}\right)$ and the phase delay $\left(t_{p}\right)$ in …

The maximum usable frequency of an ionospheric layer at $60^{\circ}$ incidence and with $8 \; \mathrm{mHz}$ critical frequency is

Quadrature multiplexing is

A $\text{DSB-SC}$ signal is generated using the carrier $\cos \left(\omega_{c}, t+\theta\right)$ and modulating signal $x(t)$. The envelope of the $\text{DSB-SC}$ signal is