Communications - Online Test
Q1. A memory less source emits n symbols each with a probability p. The entropy of the source as a function of n
Answer : Option A
Explaination / Solution:
Q2. A signal flow graph of a system is given below
The set of equalities that corresponds to this signal flow graph is
Answer : Option C
Explaination / Solution:
Q3.
A rectangular waveguide of internal dimensions (a = 4 cm and b = 3 cm) is to be operated in TE11 mode. The minimum operating frequency is
Answer : Option A
Explaination / Solution:
Q4. One end of a loss-less transmission line having the characteristic impedance of 75Ω and length of 1 cm is short-circuited. At 3 GHz, the input impedance at the other end of transmission line is
Answer : Option D
Explaination / Solution:
Q5. In the design of a single mode step index optical fibre close to upper cut-off, the single-mode operation is not preserved if
Answer : Option C
Explaination / Solution:
No Explaination.
Q6. At 20 GHz, the gain of a parabolic dish antenna of 1 meter and 70% efficiency is
Answer : Option D
Explaination / Solution:
Q7.
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:
Q8. 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.
Q9. 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
Q10.
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:
