All India Institute of Medical Sciences 2007 B.Com Computer Science Auto cad University - Question Paper

(C) r_cost —sint
L—sint cost
(D) rcost —sint
Lcost sint
48. The minimum step-size needed for a Delta-Modulator operating at 32 K samples/sec to
track the signal (here u (t) is the unit-step function)
x(t)=125t(u(t)_u(t_1))+(250_125t)(u(t_1)_u(t_2))
So that slope-overload is avoided, would be
(A) two 10
(B) two 8
(C) two 6
(D) 2
49. A zero-mean white Gaussian noise is passed through an ideal lowpass filter of bandwidth
10 kHz. The output is then uniformly sampled with sampling period t = 0.03 msec. The
samples so found would be
(A) correlated
(B) statistically independent
(C) uncorrelated
(D) orthogonal
50. A source generates 3 symbols with probabilities 0.25, 0.25, 0.50 at a rate of
3000 symbols per second. Assuming independent generation of symbols, the most efficient
source encoder would have avg. bit rate as
(A) 6000 bits/sec
(B) 4500 bits/sec
(C) 3000 bits/sec
(D) 1500 bits/sec
51. The diagonal clipping in Amplitude Demodulation (using envelope detector) can be avoided
if RC time-constant of the envelope detector satisfies the subsequent condition, (here W is
message bandwidth and a is carrier frequency both in rad/sec)
(A) RC<--w
(B) RC>--w
(C) RC<—--o)c
(D) RC>—-o)c
52. A message signal with bandwidth 10 kHz is Lower-Side Band SSB modulated with carrier
frequency t = 1O Hz: The resulting signal is then passed through a
Narrow-Band Frequency Modulator with carrier frequency two = iO Hz.
The bandwidth of the output would be:
(A) 4x104 Hz
(B) 2x106 Hz
(C) 2x109 Hz
(D) 2x101° Hz
53. A medium of relative permittivity two = two forms an interface with free-space. A point source
of electromagnetic energy is located in the medium at a depth of one meter from the interface.
Due to the total internal reflection, the transmitted beam has a circular cross-section over the
interface. The area of the beam cross- part at the interface is provided by
(A) 2,rm2
(B) r2m2
(C) -m2
(D) rm2
54. A medium is divided into regions I and II about x = 0 plane, as shown in the figure beneath.

Earning:   Approval pending.