Recent questions and answers in Communications - GO Electronics

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GATE2017 EC-2: 52
Consider a binary memoryless channel characterized by the transition probability diagram shown in the figure. The channel is lossless noiseless useless deterministic

asked Nov 25, 2017 in Communications by admin (2.8k points)

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2

GATE2017 EC-2: 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 ____________

asked Nov 25, 2017 in Communications by admin (2.8k points)

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3

GATE2017 EC-2: 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 _________

asked Nov 25, 2017 in Communications by admin (2.8k points)

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4

GATE2017 EC-2: 49
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 $H(f)$ ... $= 7$ Number $= 3$, frequencies $= 2,7,11$ Number $= 2$, frequencies $= 2,7$ Number $= 2$, frequencies $= 7,11$

asked Nov 25, 2017 in Communications by admin (2.8k points)

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5

GATE2017 EC-2: 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 __________

asked Nov 23, 2017 in Communications by admin (2.8k points)

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6

GATE2017 EC-2: 21
Which one of the following graphs shows the Shannon capacity (channel capacity) in bits of a memoryless binary symmetric channel with crossover probability $p$ ?

asked Nov 23, 2017 in Communications by admin (2.8k points)

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7

GATE2017 EC-1: 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

asked Nov 17, 2017 in Communications by admin (2.8k points)

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8

GATE2017 EC-1: 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 $t$ ... $T$ (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

asked Nov 17, 2017 in Communications by admin (2.8k points)

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9

GATE2017 EC-1: 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 used The ... of message signal sample and a random signal is quantized The difference of message signal sample with its prediction is quantized

asked Nov 17, 2017 in Communications by admin (2.8k points)

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10

GATE2017 EC-1: 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?

asked Nov 17, 2017 in Communications by admin (2.8k points)

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11

GATE2017 EC-1: 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_______.

asked Nov 17, 2017 in Communications by admin (2.8k points)

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