UNIVERSITI MALAYSIA PERLIS
Pusat Pengajian Kejuruteraan Komputer dan Perhubungan
Semester 2, 2014/2015
DKT 226 – Basic Communication Engineering
TUTORIAL 1 (PART 2)
CHAPTER 1: Noise, Transmission Media and EM Propagation and
Introduction to Basic Filter
Part A – Noise
1. Define the following:
i)
Noise
ii)
Interference
iii)
Distortion
2. Briefly explain what thermal noise is.
3. Convert the following temperatures to Kelvin:
(a)
(b)
(c)
(d)
170C
270C
-500C
-180C
4. Calculate the thermal noise power in watts and dBm for the following bandwidth
and temperatures:
(a) B = 100Hz, T = 170C
(b) B = 100kHz, T = 1000C
(c) B = 1MHz, T = 5000C
*Use k = 1.38 x 10-23 joules per Kelvin
5. Determine the bandwidth necessary to produce 8 x 10-17 watss of thermal power
at a temperature of 170C.
6. 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.
7. An amplifier has noise equivalent bandwidth of 15 kHz. When a 10 kΩ resistor at
300K is connected to the input, determine the thermal noise voltage of the
amplifier by assuming the meter is impedance matched to the amplifier.
8. For an amplifier operating at a temperature of 270C with a bandwidth of 20kHz,
determine:
(a) The total noise power in watts and dBm
(b) The rms noise voltage (VN) for a 50Ω internal resistance and a 50Ω load
resistor.
9. An amplifier is quoted as having a noise figure 3.5 dB. Calculate the noise factor,
noise temperature and noise power. Use 290 K as the reference temperature.
10. Determine the overall noise factor and noise figure for three cascaded amplifiers
with the following parameters:
A1 = 10dB
A2 = 10dB
A3 = 20dB
NF1 = 3dB
NF2 = 6dB
NF3 = 10B
11. 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.
Antenna
Ta = 15 K
G2 = 20dB
Te2 = 6 K
G3 = 15dB
F3 = 4 dB
Waveguide loss = 0.3 dB
12. Determine the equivalent noise temperature for a noise figure of 10dB. Use
reference temperature, Ti = 290K..
Part B – Transmission Media and EM Propagation
13. States four types of channels.
14. Briefly explain three mode of propagations for electromagnetic waves.
Part C – Introduction to Basic Filter
15. Briefly explain types of filters.
16. What is cutoff frequency?
17. What is the bandwidth of a filter with a Q of 75 and center frequency of 375
MHz?
18. If the 6dB bandwidth of a filter is 3.1 kHz, determine the 60-dB bandwidth if the
filter shape factor is 1.45.
19. Calculate the cutoff frequency for the LPF and HPF circuit shown below:
(a) Low-pass filter:
R = 4.7 kΩ, C = 10 nF
(b) High-pass filter:
R = 10 kΩ, C = 7 µF