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Communication Systems
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Q181

Noise with double-sided power spectral density of K over all frequencies is passed through a RC low pass filter with 3 dB cut-off frequency of f_c. The noise power at the filter output is

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Q182

A system has a receiver noise resistance of 50 Ω. It is connected to an antenna with an input resistance of 50 Ω. The noise figure of the system is

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Q183

Noise performance of PAM is

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Q184

A signal m(t) = 5cos2π100t frequency modulates a carrier. The resulting FM signal is 10cos{(2π10⁵t) + 15sin(2π100t)}. The approximate bandwidth of FM would be

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Q185

If transmitter bandwidth is doubled in FM, then SNR is

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Q186

Consider the wave form V(t) = (1 + mcosω_mt)cosωt.
Show that, it the demodulated wave is to follow the envelope of V(t), it is required that at any time t₀

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Q187

Which of the following is NOT one of the type of amplitude modulation?

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Q188

Eye diagram gives us an idea of-

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Q189

Power spectral density of white noise . . . . . . . . with frequency.

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Q190

In a typical frequency multiplier application using a PLL, a decade counter was inserted between the VCO output and the relevant phase comparator input. If the input frequency is 10 kHz, the VCO output frequency would be

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Q191

A signal with frequency f_m modulates a carrier f_c(where f_c >> f_m), then the output of the AM-DSBSC signal will contain frequencies.

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Q192

An FM signal with a deviation δ is passed through a mixer and has its frequency reduced five fold. The deviation in the output of the mixer is

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Q193

The probability density function F(x) = ae^-b|x|, where x is a random variable whose allowable value range is from x = -∞ to x = +∞. The CDF for this function for x ≥ 0 is

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Q194

High value of Q factor is preferred for coil used in radio receiver because

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Q195

Noise factor of a system is defined as

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Q196

A 4 GHz carrier is DSB-SC modulated by a low pass message signal with maximum frequency of 2 MHz. The resultant signal can be ideally sampled by sampling impulse train with frequency of

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Q197

An angle modulated signal with carrier frequency ω_c = 2π × 10⁵ is described by the equation s(t) = 10cos(ω_ct + 5sin(3000πt) + 10sin(2000πt). What is the frequency deviation ∆f?

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Q198

Determine whether the following statements are true or false with respect to Pulse Amplitude Modulation.
1. Instantaneous sampling of the message signal m(t) every T_s seconds, where the sampling rate

f_{s} = \frac{1}{T _{s}}

is chosen in accordance with the sampling theorem.
2. Lengthening the duration of each sample obtained to some constant value T

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Q199

Narrow band FM is considered same as Double sideband AM but differ in

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Q200

Which one of the following expressions represents a frequency modulated signal?

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