Hot questions in Communications / GO Electronics

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41

GATE ECE 2014 Set 3 | Question: 23
Consider an $FM$ signal $f(t)= \cos\left [ 2\pi f_{c} t+\beta _{1}\sin2\pi f_{1}t+\beta _{2}\sin2\pi f_{2}t\right ].$ The maximum deviation of the instantaneous frequency from the carrier frequency $f_{c}$ is $\beta _{1}f_{1}+\beta _{2}f_{2}$ $\beta _{1}f_{2}+\beta _{2}f_{1}$ $\beta _{1}+\beta _{2}$ $f _{1}+f _{2}$

Consider an $FM$ signal $f(t)= \cos\left [ 2\pi f_{c} t+\beta _{1}\sin2\pi f_{1}t+\beta _{2}\sin2\pi f_{2}t\right ].$ The maximum deviation of the instantaneous frequency...

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42

GATE ECE 2014 Set 3 | Question: 49
Let $X(t)$ be a wide sense stationary $(WSS)$ random process with power spectral density $S_{X}(f).$ If $Y(t)$ is the process defined as $Y(t)= X(2t-1)$, the power spectral density $S_{Y}( f )$ ... $S_{Y}( f )= \frac{1}{2}S_{X}\left ( \frac{f}{2} \right )e^{-j2\pi f }$

Let $X(t)$ be a wide sense stationary $(WSS)$ random process with power spectral density $S_{X}(f).$ If $Y(t)$ is the process defined as $Y(t)= X(2t-1)$, the power spectr...

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43

GATE ECE 2014 Set 2 | Question: 44
The input-output relationship of a causal stable LTI system is given as $y[n] = \alpha \: y[n-1] + \beta \: x[n]$. If the impulse response $h[n]$ of this system satisfies the condition $\sum_{n=0}^{\infty}h[n]= 2$, the relationship between $\alpha$ and $\beta$ is $\alpha = 1-\beta /2$ $\alpha = 1+\beta /2$ $\alpha = 2\beta$ $\alpha = -2\beta$

The input-output relationship of a causal stable LTI system is given as $$y[n] = \alpha \: y[n-1] + \beta \: x[n]$$. If the impulse response $h[n]$ of this system satisf...

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44

GATE ECE 2012 | Question: 2
The power spectral density of a real process $X(t)$ for positive frequencies is shown below. The values of $E[X^2(t)]$ and $ \mid E[X(t)] \mid$, respectively, are $\frac{6000}{\pi}\:,\:0$ $\frac{6400}{\pi}\:,\:0$ $\frac{6400}{\pi}\:,\:\frac{20}{(\pi\sqrt2)}$ $\frac{6000}{\pi}\:,\:\frac{20}{(\pi\sqrt2)}$

The power spectral density of a real process $X(t)$ for positive frequencies is shown below. The values of $E[X^2(t)]$ and $ \mid E[X(t)] \mid$, respectively, are$\frac{6...

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Milicevic3306 asked Mar 25, 2018

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45

GATE ECE 2013 | Question: 13
The bit rate of a digital communication system is $R$ kbits/s. The modulation used is $32$-QAM. The minimum bandwidth required for ISI free transmission is $R/10\: Hz$ $R/10\: kHz$ $R/5\: Hz$ $R/5\: kHz$

The bit rate of a digital communication system is $R$ kbits/s. The modulation used is $32$-QAM. The minimum bandwidth required for ISI free transmission is $R/10\: Hz$$R/...

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46

GATE ECE 2012 | Question: 27
A BPSK scheme operating over an AWGN channel with noise power spectral density of $\frac{N_o}{2}$, uses equiprobable signals $s_1(t)=\sqrt{\frac{2E}{T}}\sin(\omega_ct)$ and $s_2(t)=-\sqrt{\frac{2E}{T}}\sin(\omega_ct)$ over the symbol interval $(0,T)$. If the local oscillator ... $Q(\sqrt{\frac{E}{N_o}})$ $Q(\sqrt{\frac{E}{2N_o}})$ $Q(\sqrt{\frac{E}{4N_o}})$

A BPSK scheme operating over an AWGN channel with noise power spectral density of $\frac{N_o}{2}$, uses equiprobable signals $s_1(t)=\sqrt{\frac{2E}{T}}\sin(\omega_ct)$ a...

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Milicevic3306 asked Mar 25, 2018

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47

GATE ECE 2012 | Question: 3
In a baseband communications link, frequencies upto $3500\:Hz$ are used for signaling. Using a raised cosine pulse with $75\%$ excess bandwidth and for no inter-symbol interference, the maximum possible signaling rate in the symbols per second is $1750$ $2625$ $4000$ $5250$

In a baseband communications link, frequencies upto $3500\:Hz$ are used for signaling. Using a raised cosine pulse with $75\%$ excess bandwidth and for no inter-symbol in...

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Milicevic3306 asked Mar 25, 2018

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48

GATE ECE 2018 | Question: 15
Consider the following amplitude modulated signal: $s\left ( t \right )=\cos\left ( 2000\:\pi t \right )+4\cos\left ( 2400\:\pi t \right )+ \cos\left ( 2800\:\pi t \right ).$The ratio (accurate to three decimal places) of the power of the message signal to the power of the carrier signal is _________.

Consider the following amplitude modulated signal:$$s\left ( t \right )=\cos\left ( 2000\:\pi t \right )+4\cos\left ( 2400\:\pi t \right )+ \cos\left ( 2800\:\pi t \right...

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49

GATE ECE 2018 | Question: 28
Consider a white Gaussian noise process $\text{N(t)}$ with two-sided power spectral density $S_{N}\left ( f \right )=0.5\:W/Hz$ as input to a filter with impulse response $0.5e^{-t^{2}/2}$ (where $t$ is in seconds) resulting in output $Y(t)$. The power in $Y(t)$ in watts is $0.11$ $0.22$ $0.33$ $0.44$

Consider a white Gaussian noise process $\text{N(t)}$ with two-sided power spectral density $S_{N}\left ( f \right )=0.5\:W/Hz$ as input to a filter with impulse response...

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gatecse asked Feb 19, 2018

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50

GATE ECE 2018 | Question: 16
Consider a binary channel code in which each codeword has a fixed length of $5\: bits$. The Hamming distance between any pair of distinct codewords in this code is at least $2$. The maximum number of codewords such a code can contain is __________.

Consider a binary channel code in which each codeword has a fixed length of $5\: bits$. The Hamming distance between any pair of distinct codewords in this code is at le...

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51

GATE ECE 2018 | Question: 17
A binary source generates symbols $X\in \left \{ -1,1 \right \}$ which are transmitted over a noisy channel.The probability of transmitting $X=1$ is $0.5.$ Input to the threshold detector is $R=X+N$ ... is shown below. If the detection threshold is zero, then the probability of error (correct to two decimal places) is __________.

A binary source generates symbols $X\in \left \{ -1,1 \right \}$ which are transmitted over a noisy channel.The probability of transmitting $X=1$ is $0.5.$ Input to the t...

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52

GATE ECE 2018 | Question: 27
Let $c\left ( t \right )=A_{c} \cos \left ( 2\pi f_{c}t\right )$ and $m\left ( t \right )=\cos \left ( 2\pi f_{m}t\right )$. It is given that $f_{c}>> 5f_{m}.$ The signal $c\left ( t \right )+m\left ( t \right )$ is applied to ... wave. If it is desired to have the sideband power of the AM wave to be half of the carrier power, then $a/b$ is $0.25$ $0.5$ $1$ $2$

Let $c\left ( t \right )=A_{c} \cos \left ( 2\pi f_{c}t\right )$ and $m\left ( t \right )=\cos \left ( 2\pi f_{m}t\right )$. It is given that $f_{c}> 5f_{m}.$ The signal ...

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53

GATE ECE 2017 Set 1 | Question: 22
Which one of the following statements about differential pulse code modulation (DPCM) is true? The sum of message signal sample with its prediction is quantized The message signal sample is directly quantized, and its prediction is not ... signal sample and a random signal is quantized The difference of message signal sample with its prediction is quantized

Which one of the following statements about differential pulse code modulation (DPCM) is true?The sum of message signal sample with its prediction is quantizedThe message...

admin

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admin asked Nov 17, 2017

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54

GATE ECE 2017 Set 2 | Question: 23
A sinusoidal message signal is converted to a PCM signal using a uniform quantizer. The required signal-to-quantization noise ratio (SQNR) at the output of the quantizer is $40$ dB. The minimum number of bits per sample needed to achieve the desired SQNR is __________

A sinusoidal message signal is converted to a PCM signal using a uniform quantizer. The required signal-to-quantization noise ratio (SQNR) at the output of the quantizer ...

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admin asked Nov 23, 2017

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55

GATE ECE 2017 Set 2 | Question: 52
Consider a binary memoryless channel characterized by the transition probability diagram shown in the figure. The channel is lossless noiseless useless deterministic

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

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admin asked Nov 25, 2017

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56

GATE ECE 2017 Set 2 | Question: 21
Which one of the following graphs shows the Shannon capacity (channel capacity) in bits of a memoryless binary symmetric channel with crossover probability $p$ ?

Which one of the following graphs shows the Shannon capacity (channel capacity) in bits of a memoryless binary symmetric channel with crossover probability $p$ ?

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admin asked Nov 23, 2017

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57

GATE ECE 2017 Set 2 | Question: 50
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 _________

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 $50 \%$...

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admin asked Nov 25, 2017

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58

GATE ECE 2017 Set 1 | Question: 23
In a digital communication system, the overall pulse shape $p(t)$ at the receiver before the sampler has the Fourier transform $P(f)$. If the symbols are transmitted at the rate of $2000$ symbols per second, for which of the following cases is the inter symbol interference zero?

In a digital communication system, the overall pulse shape $p(t)$ at the receiver before the sampler has the Fourier transform $P(f)$. If the symbols are transmitted at t...

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59

GATE ECE 2017 Set 2 | Question: 51
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 ____________

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 f...

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admin asked Nov 25, 2017

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60

GATE ECE 2017 Set 1 | Question: 50
In binary frequency shift keying (FSK), the given signal waveforms are $u_{0}(t)=5\, \cos(20000\pi t)\, ;0\leq t\leq T \text{, and } \\ u_{1}(t)=5\, \cos(22000\pi t)\, ;0 \leq t \leq T,$ where $T$ is the bit-duration interval and $t$ is in seconds ... (in milliseconds) required to have $u_{0}(t)$ and $u_{1}(t)$ uncorrelated is $0.25$ ms $0.5$ ms $0.75$ ms $1.0$ ms

In binary frequency shift keying (FSK), the given signal waveforms are $$u_{0}(t)=5\, \cos(20000\pi t)\, ;0\leq t\leq T \text{, and } \\ u_{1}(t)=5\, \cos(22000\pi t)\, ;...

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admin asked Nov 17, 2017

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61

GATE ECE 2017 Set 1 | Question: 21
Let $\left ( X_{1},X_{2} \right )$ be independent random variables. $\left ( X_{1} \right )$ has mean $0$ and variance $1$, while $\left ( X_{2} \right )$ has mean $1$ and variance $4$. The mutual information $I\left (X_{1},X_{2} \right )$ between $X1$ and $X2$ in bits is_______.

Let $\left ( X_{1},X_{2} \right )$ be independent random variables. $\left ( X_{1} \right )$ has mean $0$ and variance $1$, while $\left ( X_{2} \right )$ has mean $1$ an...

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admin asked Nov 17, 2017

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62

GATE ECE 2017 Set 1 | Question: 51
Let $X(t)$ be a wide sense stationary random process with the power spectral density $S_{X}(f)$ as shown in Figure (a), where $f$ is in Hertz$(Hz)$. The random process $X(t)$ ... Select the correct option: only I is true only II and III are true only I and II are true only I and III are true

Let $X(t)$ be a wide sense stationary random process with the power spectral density $S_{X}(f)$ as shown in Figure (a), where $f$ is in Hertz$(Hz)$. The random process $X...

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admin asked Nov 17, 2017