# Electronics and Communication Engineering - Exam Questions Papers

1.
Px(X) = M exp(- 2 |x|) + N exp(- 3 |x|) is the probability density function for the real random variable X, over the entire x axis. M and N are both positive real numbers. The equation relating M and N is
M + N = 1
M + N = 3
Explanation:

Using property of probability density of Pxdx = 1

[M exp(- 2 |x|) + N exp(- 3|x|)]dx

1 ⇒ .

2.
The electric field component of a time harmonic plane EM wave travelling in a non magnetic lossless dielectric medium has an amplitude of 1 V/m. If the relative permittivity of the medium is 4, the magnitude of the time-average power density vector (in W/m2) is
Explanation:

3.
The open loop transfer function of a unity feedback control system is given as The phase cross over frequency and the gain margin are respectively.
and
and
and
and
Explanation:

At phase cross over frequency

-90° - tan- 1 ωT1 - tan- 1 ωcT2 = - p

= 90°

GM = 1/a where a = | G()|ω=ωc

.

4.
A unity negative feedback closed loop system has a plant with the transfer function and a controller Gc(S) in the feed forward path. For a unit set input, the transfer function of the controller that gives minimum steady state error is
Explanation:

so, Gc(s)|s → 0 should be maximum for low error = ∞

Gc(s)|s → 0.

5.
Find current i.
4/5 A
5/4 A
1.23 A
1.32 A