A353 – QUIZ 1 c. 290 K d.
580 K
MULTIPLE CHOICE – Choose the best answer. NO 16 A kind of distortion due to sum and difference
ERASURE/S. Correct answer/s with alteration of any 8 It is a kind of noise that is mutually related to of signals entering a non-linear device.
sort will not be given credit. (1 point each) the input and is produced because of non- a. harmonic
linear amplification. b. amplitude distortion
1 A complete communication system must a. Uncorrelated Noise b. Correlated c. intramodulation distortion
include Noise d. intermodulation distortion
a. a transmitter and receiver c. External Noise d. Internal Noise
b. a transmitter, a receiver, and a channel
c. a transmitter, a receiver, and a 9 A naturally occurring disturbance that
spectrum analyzer originates from the earth’s atmosphere 17 An increase in the equivalent resistance
d. a multiplexer, a demultiplexer, and a a. Solar Noise b. Cosmic generating the noise results to
channel Noise a. an increase in the average noise power
c. Atmospheric Noise d. Man made b. an increase in the rms noise voltage
2 The baseband bandwidth for a voice-grade Noise c. a decrease in the average noise power
(telephone) signal is d. a decrease in the average noise voltage
a. approximately 3 kHz 10 It is the relative strength of the desired signal
b. at least 5 kHz power to the noise power measured at the 18 Which of the following is not used for
c. 20 Hz to 15,000 Hz same point. communications?
d. none of the above a. noise figure b. power a. X-rays b. Infrared
ratio c. Millimeter waves d. Microwaves
3 A TV channel can accommodate ___ FM c. signal-to-noise ratio d. noise
stations. voltage 19 In a frequency domain plot, the horizontal axis
a. 6 b. 7 c. 8 d. 9 measures the ______.
11 The equivalent noise temperature of an a. Peak amplitude b. frequency
4 "Man-made" noise can come from amplifier is 25 ºK. What is the noise factor? c. phase d. slope
a. equipment that sparks b. static a. 0.913 b. 0.086
c. temperature d. all of the c. 1.086 d. 10.086 20 Simultaneous 2-way communications is
above called________.
12 The ideal noise figure is a. Half-duplex b. Full-duplex
5 Shot noise is generated in a. 1 dB b. 0 dB c. Bicomm d. Simplex
a. transistors and diodes b. copper wire c. infinity d. none of the
c. resistors d. none of the choices IDENTIFICATION - NO ERASURE/S. Correct
above answer/s with alteration of any sort will not be given
13 An amplifier has output S/N that is half of its credit. (1 point each)
6 Signal-to-Noise ratio is calculated as input S/N. What is its noise figure?
a. signal voltage divided by noise voltage a. 3 dB b. -3 dB 1 Wavelength, in meters, of a 300 GHz
b. signal power divided by noise power c. 2 dB d. none of the electromagnetic wave.
c. first add the signal power to the noise choices 2 The totality of mechanisms that provide
power, then divide by noise power information transfer.
d. none of the above 14 Determine the noise current of a device for a 3 If you have an available number of amplifiers
current of 5 mA and bandwidth of 3.2 kHz. with a gain of 100 each, how many such
7 Noise Figure is a measure of a. 1.6 µA b. 3.2 nA amplifiers do you need to cascade to give an
a. how much noise is in a communications c. 1.6 nA d. none of the overall gain of 60dB?
system choices 4 Mode of transmission of cable television.
b. how much noise is in the channel 5 True or false. Full duplex is a type of
c. how much noise an amplifier adds to a 15 What is the equivalent noise temperature for a transmission mode where a station can
signal noise figure of 3dB? transmit and receive signals at the same time
d. signal-to-noise ratio in dB a. 17 K b. 145 K but not to and from the same station.
6 The standard FM Radio Broadcast is from 88
to 108 MHz. At which FCC frequency
designation is this band located?
7 This is a collection of electronic components
designed to convert the information into a
form suitable for transmission.
8 The frequency spectrum occupied by AM
broadcast system in the Philippines.
9 RF band of TV Channel 13.
10 Normal range of human speech.
11 Noise always affect the signal in a 2. For a non-ideal amplifier and the following
communication systems at the _____. parameters, Determine:
12 If the voltage change equal to twice the (a) Input S/N ratio in dB (2 points)
original value, what is the corresponding (b) Output S/N ratio in dB (2 points)
change in dB? (c) Noise factor and noise figure (3 points)
13 Random noise power is proportional to the Input Signal Power = 6.2 dBn
______ over which it is measured.
Input Noise Power = –62 dBn
14 In the FCC rules, the frequency band from 3 to
30 GHz is known as ______. Power Gain = 75 dB
15 What is the shot noise current for a transistor Internal Noise (Nd) = 10.8 dBp
with a forward bias current of 1.25 mA
operating over a 70kHz bandwidth.
PROBLEMS
1. Four amplifiers with the following characteristics
are to be connected in cascade.
AMPLIFIER Power Gain Noise
Figure
A 8 dB 3 dB
B 6 dB 5 dB
C 15 dB 7 dB
D 13 dB 3 dB
A. What is the lowest overall noise factor
obtainable? (2 points)
B. Draw a diagram showing the connection of
the amplifiers that will give the lowest overall
noise factor. (2 points)
C. If the input signal power is 3 mW and the
input noise power is 5 nW, what is the output
signal power in dBm and the signal-to-noise
ratio at the output. Assume that the
amplifiers does not contribute noise
internally. (4 pts)
