GATE EC Analog Communications questions

In a double side-band (DSB) full carrier AM transmission system, if the modulation index is doubled, then the ratio of total sideband power to the carrier power increases by a factor of __________.

The signal $m(t)$ as shown is applied both to a phase modulator (with $k_p$ as the phase constant) and a frequency modulator (with $k_f$ as the frequency constant) having the same carrier frequency. The ratio $\frac{k_p}{k_f}$ (in $rad/Hz$) for the same maximum phase deviation is

Consider the amplitude modulated (AM) signal $A_{c} \cos \omega_{c} t+2 \cos \omega_{m} t \cos \omega_{c} t$. For demodulating the signal using envelope detector, the minimum value of $A_{c}$ should be

Consider the frequency modulated signal $10 \cos \left[2 \pi \times 10^{5} t+5 \sin (2 \pi \times 1500 t)+7.5 \sin (2 \pi \times 1000 t)\right]$ with carrier frequency of $10^{5} \mathrm{~Hz}$. The modulation index is

The diagonal clipping in Amplitude Demodulation (using envelope detector) can be avoided if RC time-constant of the envelope detector satisfies the following condition, (here $W$ is message bandwidth and $\omega_{c}$ is carrier frequency both in rad/sec)

A message signal with bandwidth $10 \; \mathrm{kHz}$ is Lower-Side Band SSB modulated with carrier frequency $f_{c 1}=10^{6} \mathrm{~Hz}$. The resulting signal is then passed through a Narrow-Band Frequency Modulator with carrier frequency $f_{c_{2}}=10^{9} \; \mathrm{Hz}$. The bandwidth of the output would be

Common Data for Questions 74, 75: Let $g(t)=p(t)^{*} p(t)$, where * denotes convolution and $p(t)=u(t)-u(t-1)$ with $u(t)$ being the unit step function An Amplitude Modulated signal is given as $$x_{\mathrm{AM}}(t)=100(p(t)+0.5 g(t)) \cos \omega_{c} t$$ in the interval $0 \leq t \leq 1$. One set of possible values of the modulating signal and …

Statement for Linked Answer Questions 80 and 81 Consider the following Amplitude Modulated (AM) signal, where $f_{m}<\mathrm{B}$ $$x_{\mathrm{AM}}(t)=10\left(1+0.5 \sin 2 \pi f_{m} t\right) \cos 2 \pi f_{c} t$$ The average side-band power for the $\text{AM}$ signal given above is

Statement for Linked Answer Questions 80 and 81 Consider the following Amplitude Modulated (AM) signal, where $f_{m}<\mathrm{B}$ $$x_{\mathrm{AM}}(t)=10\left(1+0.5 \sin 2 \pi f_{m} t\right) \cos 2 \pi f_{c} t$$ The $\text{AM}$ signal gets added to a noise with Power Spectral Density $S_{n}(f)$ given in the figure below. The ratio of average …

Find the correct match between group $1$ and group $2.$ Group I …

Which of the following analog modulation scheme requires the minimum transmitted power and minimum channel bandwidth?

A device with input $x(t)$ and output $y(t)$ is characterized by: $y(t)=x^{2}(t)$. An FM signal with frequency deviation of $90 \; \mathrm{kHz}$ and modulating signal bandwidth of $5 \; \mathrm{kHz}$ is applied to this device. The bandwidth of the output signal is

A carrier is phase modulated (PM) with frequency deviation of $10 \; \mathrm{kHz}$ by a single tone frequency of $1 \; \mathrm{kHz}$. If the single tone frequency is increased to $2 \; \mathrm{kHz}$, assuming that phase deviation remains unchanged, the bandwidth of the PM signal is

An AM signal is detected using an envelope detector. The carrier frequency and modulating signal frequency are $1 \; \mathrm{MHz}$ and $2 \; \mathrm{kHz}$ respectively. An appropriate value for the time constant of the envelope detector is

An AM signal and a narrow-band FM signal with identical carriers, modulating signals and modulation indices of $0.1$ are added together. The resultant signal can be closely approximated by

The value of $\mathrm{C}$ required for sinusoidal oscillations of frequency $1 \; \mathrm{kHz}$ in the circuit of given figure is

A $1 \mathrm{~mW}$ video signal having a bandwidth of $100 \; \mathrm{MHz}$ is transmitted to a receiver through a cable that has $40 \mathrm{~dB}$ loss. If the effective one-sided noise spectral density at the receiver is $10^{-20}$ Watt $/ \mathrm{Hz}$, then the signal-to-noise ratio at the receiver is

A $100 \; \mathrm{MHz}$ carrier of $1 \mathrm{~V}$ amplitude and a $1 \; \mathrm{MHz}$ modulating signal of $1 \mathrm{~V}$ amplitude are fed to a balanced modulator. The output of the modulator is passed through an ideal high-pass filter with cut-off frequency of $100 \; \mathrm{MHz}$. The output of the filter is added with $100 \; \mathrm{MHz}$ …

Two sinusoidal signals of same amplitude and frequencies $10 \; \mathrm{kHz}$ and $10.1 \; \mathrm{kHz}$ are added together. The combined signal is given to an ideal frequency detector. The output of the detector is

In a microwave test bench, why is the microwave signal amplitude modulated at $1 \; \mathrm{kHz}$?