Original signal came to be retraced from sampled version using

Let x(t) = 2cos(800πt) + cos(1400πt).x(t) is sampled with the rectangular pulse train shown in the figure. The only spectral components (in kHz) present in the sampled signal in the frequency range 2.5 kHz to 3.5 kHz are
Digital Communication mcq question image

Digital Communication mcq question image

A

2.7, 3.4

B

3.3, 3.6

C

2.6, 2.7, 3.3, 3.4, 3.6

D

2.7, 3.3

Assertion (A): Nyquist rate of sampling is the theoretical minimum sampling rate at which the signal can be sampled and still be reconstructed from its samples. Reason (R): When the Nyquist rate sampling is used, only an ideal low pass filter can be used to extract signal x(t) from sampled signal xs(t). Code:

A

Both (A) and (R) are true and (R) is the correct explanation of (A).

B

Both (A) and (R) are true, but (R) is not the correct explanation of (A)

C

(A) is true, but (R) is false.

D

(A) false, but (R) is true

A 1 kHz sinusoidal signal is ideally sampled at 1500 samples/sec and the sampled signal is passed through an ideal low-pass filter with cutoff frequency 800 Hz. The output signal has the frequency

A

Zero Hz

B

0.75 kHz

C

0.5 kHz

D

0.25 kHz

Consider the following statements regarding modulation : 1. The communication systems, where a weak signal is transmitted by the use of a modulation is essential in carrier signal. 2. When the frequency of the high frequency signal is varied in accordance with the intensity of the low-frequency weak signal, the modulation is said to be frequency modulation. 3. The process of recovering original baseband signal from the modulated signal is called phase modulation. Which of the above statements are correct ?

A

1 and 3 only

B

1 and 2 only

C

2 and 3 only

D

1, 2 and 3

If a continuous time signal x(t) with spectrum X(F) is sampled at a rate Fs=1/T samples per second, the spectrum of the sampled signal is _____________

A

Non periodic repetition

B

Non periodic non-repetition

C

Periodic repetition

D

None of the mentioned

The signal $$\cos \left( {10\pi t + \frac{\pi }{4}} \right)$$ is ideally sampled at a sampling frequency of 15 Hz. The sampled signal is passed through a filter with impulse response $$\left( {\frac{{\sin \left( {\pi t} \right)}}{{\pi \tau }}} \right)\cos \left( {40\pi t - \frac{\pi }{2}} \right).$$ The filter output is

A

$$\frac{{15}}{2}\cos \left( {40\pi t - \frac{\pi }{4}} \right)$$

B

$$\frac{{15}}{2}\left( {\frac{{\sin \left( {\pi t} \right)}}{{\pi t}}} \right)\cos \left( {10\pi t + \frac{\pi }{4}} \right)$$

C

$$\frac{{15}}{2}\cos \left( {10\pi t - \frac{\pi }{4}} \right)$$

D

$$\frac{{15}}{2}\left( {\frac{{\sin \left( {\pi t} \right)}}{{\pi t}}} \right)\cos \left( {10\pi t - \frac{\pi }{2}} \right)$$

If the signal to be analyzed is an analog signal, we would pass it through an anti-aliasing filter with B as the bandwidth of the filtered signal and then the signal is sampled at a rate __________

A

Fs ≤ 2B

B

Fs ≤ B

C

Fs ≥ 2B

D

Fs = 2B

A signal is sampled at 8 kHz and is quantized using 8-bit uniform quantizer. Assuming SNR_q for a sinusoidal signal, the correct statement for PCM signal with a bit rate of R is

A

R = 32 kbps, SNR_q = 25.8 dB

B

R = 64 kbps, SNR_q = 49.8 dB

C

R = 64 kbps, SNR_q = 55.8 dB

D

R= 32 kbps, SNR_q = 49.8 dB

A continuous-time function x(t) is periodic with period T. The function is sampled uniformly with a sampling period ??. In which one of the following cases is the sampled signal periodic?

A

${\rm{T\;}} = {\rm{\;}}\sqrt 2 {\rm{\;Ts}}$

B

𝑇 = 1.2 𝑇𝑠

C

Always

D

Never

A continuous time function x(t) is periodic with period T. The function is sampled uniformly with a sampling period T_s. In which one of the following cases is the sampled signal periodic?

A

$$T = \sqrt 2 {T_s}$$

B

T = 1.2T_s

C

Always

D

Never

Original signal came to be retraced from sampled version using

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