In this article, we are going to learn about the Digital Communication MCQ for ESE.
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Digital Communication MCQ for ESE
Q.1 The bandwidth of a ‘N’ bit binary coded PCM signal for modulating a signal having a bandwidth of ‘f’ Hz is
- (a) \frac{f}{N}Hz
- (b) \frac{f}{N^2}Hz
- (c) Nf\;Hz
- (d) N^2f\;Hz
Q.2 Time division multiplexing requires
- (a) constant data transmission
- (b) transmission of data samples
- (c) transmission of data at random
- (d) transmission of data of only one measured
Q.3 Quadrature multiplexing is
- (a) same as FDM
- (b) same as TDM
- (c) a combination of FDM and TDM
- (d) the scheme where the same carrier frequency is used for two different signals
Q.4 The ramp signal m(t) = at is applied to a delta modulator with sampling period Ts and step size \delta. Slope overload distortion would occur if
- (a) \delta < a
- (b) \delta > a
- (c) \delta < aT_s
- (d) \delta > aT_s
Q.5 In a PCM system each quantization level is encoded into 8 bits. The signal-to-quantization noise ratio is equal to
- (a) 24 dB
- (b) 48 dB
- (c) 64 dB
- (d) 256 dB
Q.6 Generally, a transversal type equalizer with 5 taps can take care of distorted signal due to intersymbol interference in the received signal at
- (a) 4 sampling instants
- (b) 5 sampling instants
- (c) 9 sampling instants
- (d) 10 sampling instants
Q.7 For a 10-bit PCM system, the signal-to-quantization noise ratio is 62 dB. if the number of bits is increased by 2, then the signal-to-quantization noise ratio will
- (a) increased by 6 dB
- (b) increased by 12 dB
- (c) decreased by 6 dB
- (d) decreased by 12 dB
Q.8 For a given data rate, the bandwidth \beta_p of a BPSK signal and the bandwidth \beta_0 of the OQPSK signal are related as
- (a) \beta_p = \beta_0/2
- (b) \beta_p = 2\beta_0
- (c) \beta_p = \beta_0/4
- (d) \beta_p = \beta_0
Q.9 In a certain ’12 channel TDM’ system, it is found that channel number 3 and channel number 8 are connected to the same input signal. The technique
- (a) wastes the channel capacity
- (b) takes care of different sampling rates
- (C) is required when different bandwidth signals are to be transmitted
- (d) reduces noise
Q.10 Which one of the following pulse modulating is analog?
- (a) PCM
- (b) Diffrential PCM
- (c) PWM
- (d) Delta
Q.11 In an asynchronous TDM, for n signal sources, each frame contains m slots, where m is usually
- (a) less than n
- (b) 2n
- (c) n
- (d) greater than 2n
Q.12 The number of signaling bits per channel per frame in T1 multiplexer following CCITT hierarchy is
- (a) 64000
- (b) 128
- (c) 4
- (d) 400
Q.13 In a BPSK signal detector, the local oscillator has a fixed phase error of 200. By what factor does this phase error deteriorate in the SNR at the output?
- (a) cos2 20o
- (b) cos 20o
- (c) cos 40o
- (d) cos 70o
Q.14 What is the SNR improvement with FSK over ASK in most types of noise environments?
- (a) 200 to 300 dB
- (b) 3 to 4 dB
- (c) 10 to 12 dB
- (d) 0 dB
Q.15 WHich one of the following statements is correct? Digital modulation techniques are used in satellite communication systems since
- (a) they are easier to handle
- (b) large bandwidth utilization is possible
- (c) they have a higher spectral efficiency
- (d) they are less prone to interference
Q.16 A continuous signal has a voltage range of -2v to +2v. if this is quantized to 8 bits, what does the resulting signal have?
- (a) 255 level of step size 4/255
- (b) 25 levels of step size 4/8
- (c) 8 bits plus 2 levels at -2 and +2 volts
- (d) 8 bits per sample if properly sampled
Q.17 Signal x(t) = 3 \sin 2\pi 10^3 t + s \sin 2\pi 660t. At what sampling frequency should this signal be sampled to avoid aliasing?
- (a) 2 \times 660\; Hz
- (b) 2 \times 1000\; Hz
- (c) 2 [1000+600] \; Hz
- (d) 2 [1000-600] \; Hz
Q.18 An analog signal has significant spectral components from 1 kHz to 5 kHz. What is the Nyquist sampling rate for this signal?
- (a) 5 k samples/s
- (b) 4 k samples/s
- (c) 8 k samples/s
- (d) 10 k samples/s
Q.19 In delta modulation, when is the slope overloading noise absent? (h is the pulse height and sampled every Ts seconds, f(t) is the input signal, h and Ts are step-size of integration and sampling period, respectively:)
- (a) \frac{df(t)}{dt} \leq (h/T_S)
- (b) \frac{df(t)}{dt} > (h/T_S)
- (c) \frac{df(t)}{dt} \leq (h.T_S)
- (d) \frac{df(t)}{dt} > (h.T_S)
Q.20 which one of the following statements is correct?
- (a) Equalisation is required in telephone lines but not in wireless communication
- (b) Equalisation is required both in telephone lines and wireless communication
- (c) Equalisation is required in wireless communication whereas this is not required in telephone lines
- (d) Equalisation is not required in wireless communication since phase equalization is required only when lines are used
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