EKT 231 COMMUNICATION SYSTEMS

TUTORIAL 5

CHAPTER 5

  1. Define the following:

i)  Noise

ii)  Interference

iii)  Distortion

2.  A domestic television receives antenna delivers a sky noise power of -105 dBm to a matched coaxial feeder in a radio frequency bandwidth of 8 MHz. Find the antenna noise temperature. (286.4 K)

3.  An amplifier has noise equivalent bandwidth of 15 kHz. When a 10 kΩ resistor at 300 K is connected to the input, determine the thermal noise voltage of the amplifier by assuming the meter is impedance matched to the amplifier. (1.58 µV)

4.  An amplifier is quoted as having a noise figure 3.5 dB. Calculate the noise factor, noise temperature and noise power. (2.24, 360 K,4.97x10-21 W)

5.  An antenna is connected to some receiving system using a waveguide with a loss of 0.3 dB. Calculate the overall effective temperature of the system if antenna temperature, Ta is 15 K. Assume ambient temperature is 300 K. (47.75 K)

6.  Calculate the equivalent noise temperature of a microwave amplifier with an average noise power of 1x10-14 W and operating bandwidth of 25 MHz. (29 K)

7.  An amplifier consists of three identical stages in tandem. Each stage having equal input and output impedances. For each stage, the power gain is 5 dB when correctly matched. Calculate the overall power gain.

(31.62)

8.  For a nonideal amplifier with the following parameters:

Input signal power / 2.5 x 10-10 W
Input noise power / 3 x 10-18 W
Power gain / 1,000,000
Internal noise (Nd) / 4.5 x 10-12 W

Table 1

Determine the following:

(i)  Input Signal-to-Noise ratio (dB).

(ii)  Output Signal-to-Noise ratio (dB).

(iii)  Noise factor and noise figure.

(iv)  Equivalent noise temperature.

9.  States four types of channels.

  1. List down three mode of propagations for electromagnetic waves.
  1. With the aid of diagram, briefly explain Line of Sight (LOS) propagation.

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