Communications - Online Test
Q1. At 20 GHz, the gain of a parabolic dish antenna of 1 meter and 70% efficiency is
Answer : Option D
Explaination / Solution:
Q2. Repeaters used in electronic communication generally
Answer : Option A
Explaination / Solution:
In telecommunications, a repeater is an electronic device that receives a signal and retransmits it.Repeaters are used to extend transmissions so that the signal can cover longer distances or be received on the other side of an obstruction.A repeater is a combinatin of a transmitter,an amplifier and retransmits it to the receiver somtimes witha a change of carrier frequency.
Q3.
Noise with double-sided power spectral density on K over all frequencies is passed through a RC low pass filter with 3 dB cut-off frequency of fc. The noise power at the filter output is
Answer : Option C
Explaination / Solution:
Q4. Fourier analysis of a periodic signal implies
Answer : Option A
Explaination / Solution:
The concept is that there are two descriptions of a signal according to Fourier. The time domain in form of time waveform and the frequency domain form in form of a combination of complex periodic signal with frequency as a variable instead of t. Hence Fourier analysis of a periodic signal implies periodic signal can be regarded as a superposition of sine wave signals
Q5. Consider a Binary Symmetric Channel (BSC) with probability of error being p. To transmit a bit, say 1, we transmit a sequence of three 1s. The receiver will interpret the received sequence to represent 1 if at least two bits are 1. The probability that the transmitted bit will be received in error is
Answer : Option D
Explaination / Solution:
No Explaination.
Q6. Fourier series of a repeating sine wave has a
Answer : Option C
Explaination / Solution:
No Explaination.
Q7. Four messages band limited to W,W,2W and 3W respectively are to be multiplexed using Time Division Multiplexing (TDM). The minimum bandwidth required for transmission of this TDM signal is
Answer : Option D
Explaination / Solution:
Bandwidth of TDM is
= 1/2 (sum of Nyquist Rate)
= 1/2 [2W + 2W + 4W + 6W] = 7W
Q8. Fourier series of a periodic rectangular pulse has a
Answer : Option B
Explaination / Solution:
No Explaination.
Q9.
Consider the frequency modulated signal 
with carrier frequency of 105 Hz. The modulation index is
with carrier frequency of 105 Hz. The modulation index is
Answer : Option B
Explaination / Solution:
Q10. Fourier series of a periodic rectangular wave has a
Answer : Option B
Explaination / Solution:
No Explaination.
