# Communications [GATE (Graduate Aptitude Test in Engineering) Electronics]: Questions 103 - 106 of 106

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## Question 103

Appeared in Year: *2020*

### Question

Numeric Answer▾A binary random variable X takes the value + 2 or -The probability . The value of (rounded off to one decimal place) , for which the entropy of X is maximum, is

## Question 104

Appeared in Year: *2021*

### Question

Numeric Answer▾Consider a polar non-return to zero (NRZ) waveform using + 2 V and -2 V for representing binary ‘1’ and ‘0’ respectively, is transmitted in the presence of additive zero-mean white Gaussian noise with variance 0.4 . If the a priori probability of transmission of a binary ‘1’ is 0.4, the optimum threshold voltage for a maximum a posteriori (MAP) receiver (rounded off to two decimal places) is ________ V.

## Question 105

Appeared in Year: *2021*

### Question

Numeric Answer▾A 4 kHz sinusoidal message signal having amplitude 4 V is fed to a delta modulator (DM) operating at a sampling rate of 32 kHz. The minimum step size required to avoid slope overload noise in the DM (rounded off to two decimal places) is ________ V.

## Question 106

Appeared in Year: *2020*

### Question

Numeric Answer▾and as defined below, are the phase modulated and frequency modulated waveforms, respectively, corresponding to the message signal m (t) shown in the figure.

And

Where is the phase deviation constant in radians/volt and is the frequency deviation constant in radians/second/volt. If the highest instantaneous frequencies of and are same, then the value of the ratio is ________ seconds.