During transmission over a certain binary communication channel, bit errors occur independently with probability p. The probability of AT MOST one bit in error in a block of n bits is given by

**A. ** p^{n}

**B. ** 1 - p^{n}

**C. ** np( - p)n + ( + p)n
**D. ** 1 - (1 - p)n
**Answer : ****Option C**

**Explaination / Solution: **

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Two 4-array signal constellations are shown. It is given that φ1 and φ2 constitute an orthonormal basis for the two constellation. Assume that the four symbols in both the constellations are equiprobable. Let N0/2 denote the power spectral density of white Gaussian noise.

**A. ** Probability of symbol error for Constellation 1 is lower

**B. ** Probability of symbol error for Constellation 1 is higher

**C. ** Probability of symbol error is equal for both the constellations

**D. ** The value of N will determine which of the constellations has a lower probability of symbol error

**Answer : ****Option A**

**Explaination / Solution: **

No Explaination.

If these constellations are used for digital communications over an AWGN channel, then which of the following statements is true ?

No Explaination.

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At 20 GHz, the gain of a parabolic dish antenna of 1 meter and 70% efficiency is

**A. ** 15 dB

**B. ** 25 dB

**C. ** 35 dB

**D. ** 45 dB

**Answer : ****Option D**

**Explaination / Solution: **

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In the following network, the switch is closed at t = 0^{-} and the sampling starts from t = 0. The sampling frequency is 10 Hz.

The expression and the region of convergence of the z -transform of the sampled signal are

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Consider a baseband binary PAM receiver shown below. The additive channel noise n(t) is with power spectral density The lowpass filter is ideal with unity gain and cut-off frequency 1 MHz. Let Yk represent the random variable y(tk).

Yk = Nk , if transmitted bit bk = 0

Yk = a + Nk if transmitted bit bk = 1

Where Nk represents the noise sample value. The noise sample has a probability density function, (This has mean zero and variance 2/α2). Assume transmitted bits to be equiprobable and threshold z is set to a/2 = 10-6 V.

The probability of bit error is

Probability of error is given by

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The longitudinal component of the magnetic field inside an air-filled rectangular waveguide made of a perfect electric conductor is given by the following expression The cross-sectional dimensions of the waveguide are given as a = 0.08 m and b = 0.033 m. The mode of propagation inside the waveguide is

TM_{12}

TM_{21}

TE_{21}

TE_{12}

We have the expression,

and the cross sectional dimension is

a = 0.08 m, b = 0.033m

Now, we compare the equation for TE_{m,n} mode whose H_{z} is given as

Hence, given mode is TE21 mode

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The modes in a rectangular waveguide are denoted by where
m n and are the eigen numbers along the larger and smaller dimensions of the
waveguide respectively. Which one of the following statements is TRUE?

**A. ** The TM_{10} mode of the wave does not exist

**B. ** The TE_{10} mode of the wave does not exist

**C. ** The TM_{10} and TE_{10} the modes both exist and have the same cut-off
frequencies

**D. ** The TM_{10} and TM_{01} modes both exist and have the same cut-off
frequencies

**Answer : ****Option A**

**Explaination / Solution: **

TM_{11} is the lowest order mode of all the TM_{mn} modes

TM

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The propagation constant of a lossy transmission line is (2 + 𝑗5) m-1 and its characteristic impedance is (50 + j0)𝜔 at 𝜔 = 106 rad s-1. The values of the line constants L, C, R, G are, respectively,

**A. ** L = 200 μH/m, C = 0.1 μH/m, R = 50 Ω/m, G = 0.02 S/m

**B. ** L = 250 μH/m, C = 0.1 μH/m, R = 100 Ω/m, G = 0.024S/m

**C. ** L = 200 μH/m, C = 0.2 μH/m, R = 100 Ω/m, G = 0.02 S/m

**D. ** L = 250 μH/m, C = 0.2 μH/m, R = 50 Ω/m, G = 0.04 S/m

**Answer : ****Option B**

**Explaination / Solution: **

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A zero mean random signal is uniformly distributed between limits –a and +a and its mean square value is equal to its variance. Then the r.m.s value of the signal is

**A. **

**B. **

**C. **

**D. **

**Answer : ****Option A**

**Explaination / Solution: **

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The impulse response of a continuous time system is given by h(t) = δ(t - 1) + δ(t - 3). The value of the step response at t = 2 is

**A. ** 0

**B. ** 1

**C. ** 2

**D. ** 3

**Answer : ****Option B**

**Explaination / Solution: **

No Explaination.

No Explaination.

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