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Kabs > Exit > Flashcards

Exit Flashcards

1
Q

Which of the following is NOT a classification of signals?

a) Continuous-time
b) Discrete-time
c) Dynamic-time
d) Analog

A

c) Dynamic-time

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2
Q

What defines a periodic signal?

a) It has a repeating pattern over a specific interval
b) It has a continuous spectrum
c) It does not repeat its pattern
d) It has no fundamental frequency

A

a) It has a repeating pattern over a specific interval

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3
Q

What is the Nyquist rate?

A

Twice the highest frequency

(Using one-half the given sample rate)

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4
Q

Aliasing in signal processing occurs when

A

The sampling frequency is too low.

(Sampled at less than twice the highest frequency present. Undersampling, basically)

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5
Q

What differentiates a Finite Impulse Response (FIR) fiter from an Infinite Impulse Response (IIR) filter?

A

FIR fiters have recursive difference equations

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6
Q

Which type of filter exhibits linear phase characteristics?

a) IR Filter
b) FIR filter
c) Both FIR and IIR
d) Neither FIR and IIR

A

b) FIR filter

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7
Q

Which of the following is a characteristic of Finite Impulse Response (FIR) filters?

a) They exhibit recursive behavior
b) They have an infinite impulse response
c) They can have feedback loops
d) They have a finite duration impulse response

A

d) They have a finite duration impulse response

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8
Q

The Z-transform is used to:

a) Convert time-domain signals to frequency-domain signals
b) Convert frequency-domain signals to time-domain signals
c) Evaluate poles and zeros of a system
d) Perform convolution operations

A

a) Convert time-domain signals to frequency-domain signals

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9
Q

pole-zero-gain filters are characterized by

A

Number of poles, zeros, and gain

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10
Q

In signal processing, Fourier transforms are primarily used for

A

Converting frequency-domain signals to time-domain signals

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11
Q

What is the main purpose of a modulator in a communication system?

A

To encode date in a carrier wave

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12
Q

Which of the following is NOT a characteristic of digital communication?

a) High noise immunity
b) Increased bandwidth requirement
c) Reduced error rate
d) Greater security in transmission

A

c) Reduced error rate

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13
Q

What does the term ‘bandwidth’ refer to in communication systems?

A

The capacity of data transmission

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14
Q

What component of a communication system is responsible for signal reception?

A

Receiver

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15
Q

Noise from random acoustic or electric noise that has equal per cycle over a specified frequency band

a) Thermal Noise
b) Gaussian Noise
c) White Noise
d) All of the choices
e) None of the choices

A

White Noise

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16
Q

The signal in the channel is measured to be 23dB white while noise in the same channel is measured to be 9 dB. The signal to noise ratio therefore_____.

A

14dB

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17
Q

What factor affects thermal noise in communication system?

A

Temperature

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18
Q

An amplifier has an output S/N that is half of its input S/N. What is its noise figure?

A

3dB

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19
Q

If an ampifier has a bandwidth B=20kHz and a total noise power N=2x10 ^-17 W, determine the total noise power in dBu if the bandwidth increases to 80kHz.

A

100 dBu

N= kTB
Solved T = 75.75
(7.9999 + 2) x e-17

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20
Q

Modulation is the process of

A

combining audio and radio frequency waves at the transmitting end of a communication system

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21
Q

What does the term “carrier suppression” refer to in modulation?

A

Carrier wave’s power is not transmitted

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22
Q

A transmitter supplies 10kW of carrier power to the antenna. The total radiated power with 40% modulation is _____ kW.

A

10.8

10k (1 + 0.4^2/2)

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23
Q

100% modulation is produced in AM when the carrier:

a) frequency equals signal frequency
b) frequency exceeds signal frequency
c) amplitude equals signal amplitude
d) amplitude exceeds signal amplitude

A

c) amplitude equals signal amplitude

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24
Q

Which of the following statement regarding single sideband transmission is not correct?

a) In such transmission, only one sideband is transmitted, leaving off the other side and the carrier
b) It has gained general acceptance for the use home entertainment equipment
c) It is generally reserved for point to point communication
d) The amount of power and the bandwidth necessary to be transmitted for a given amount of information are appreciably reduced

A

b) It has gained general acceptance for the use home entertainment equipment

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25
Q

The difference between phase and frequency modulation

a) is purely theoretical because the same in practice
b) is too great to make the two systems are compatible
c) lies in the poorer audio response of the phase modulation index
d) lies in the different definition of the modulation index

A

a) is purely theoretical because the same in practice

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26
Q

In superheterodyne broadcast receiver, the frequency of the local oscillator is ______ the incoming signal frequency.

a) higher than
b) lower than
c) equal to
d) cannot be determine

A

a) higher than

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27
Q

What is the primary function of a mixer in a superheterodyne receiver?

A

To amplify the received signal

(Changes the incoming radio frequency signal to a higher or lower, fixed, intermediate frequency (IF).)

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28
Q

The standard intermediate frequency for the FM radio is

A

10.7 MHz

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29
Q

Which type of modulation is commonly used in digital communication systems?

A

Pulse Wwidth Modulation (PWM)

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30
Q

What is the primary function of a modem in a communication system?

A

To convert digital signals into analog signals

(Modulation involves encoding digital data onto a carrier analog signal, allowing it to traverse through telephone lines or radio frequencies)

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31
Q

What factor affects the power density of a transmitted signal?

A

Transmitting antenna material

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32
Q

A microwave transmitting antenna is 550ft high. The receiving antenna 200ft high. The minimum transmission distance is ___.

A

53.2 mi

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33
Q

Effective earth radius to true earth radius ratio

a) Fresnel zone
b) index of refraction
c) Path profile
d) K-factor

A

d) K-factor

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34
Q

A measure of distribution of radiated power over a given area is called

A

Power density

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35
Q

The power density at a certain distance from a 5kW isotropic source in free space is 15.9 x 10^-14 W/m2. How far away is the source?

a) 50,024.36 mi
b) 50,024.36 m
c) 50,024.36 km
d) 50,024.36 ft

A

b) 50,024.36 m

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36
Q

What is the Free Space Loss (FSL) in dB at 300MHz between the earth station and a satellite at 37,000 km?

A

173.4 dB

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37
Q

A 500-kHz transmitter produces a field strength of 100 uv/m at 100 mi. What is the theoretical strength at 200 mi?

A

50 uv

38
Q

A space that does not interfere with the normal radiation and propagation of waves.

A

Free space

39
Q

What does the term “polarization” refer to in antenna systems?

A

The orientation of the electromagnetic wave’s electric field.

40
Q

A device designed to radiate electromagnetic energy into space.

A

Antenna

41
Q

The amount of electromagnetic spectrum needed or allocated for a particular communication channelo group of channels.

A

Bandwidth

42
Q

What is meant by antenna gain?

A

the numeric ratio relating the radiated signal strength of an antenna to that of another antenna

(Pinoybix)

43
Q

What is the primary function of a directive antenna?

A

To concentrate electromagnetic waves in one direction

44
Q

What is the primary advantage of using a full-duplex transmission mode?

A

Higher data transmission rates

45
Q

Which transmission mode allows simultaneous transmission and reception of data?

A

Full-duplex

46
Q

Which network component acts as an interface between a computer and a network?

A

LCU (Line Control Unit)

47
Q

What type of synchronization ensures that sender and receiver clocks are synchronized periodically during data transmission?

A

Isochronous synchronization

48
Q

What network component manages multiple data streams onto a single communication channel?

A

Multiplexer

49
Q

In the OSI model, which layer ensures data integrity and provides eror detection?

A

Data Link Layer (Layer 2)

50
Q

What character-oriented protocol is commonly used for email communication?

A

ASCII

51
Q

Which laver of the OSI model is responsible for establishing, managing, and terminating connections between applications?

A

Session layer (Layer 5)

52
Q

Which layer of the TCP/IP model is responsible for routing packets across different networks?

A

Network layer

53
Q

Which bit-oriented protocol is widely used for synchronous communication in WANs?

A

HDLC (High-Level Data Link Control)

54
Q

What distinguishes a WAN from a LAN?

A

WANs cover larger geographical areas than LANs

55
Q

What does ISDN stand for in telecommunications?

A

Integrated Services Digital Network

56
Q

Which network type covers a broad geographical area, such as a city or town?

A

MAN (Metropolitan Area Network)

57
Q

An analog pulse modulation technique in which the duration of each resulting pulse is varied in step with the amplitude of the modulating signal at the time it is sampled and that the sampled pulses have the same amplitude.

Pulse Width Modulation (PWM)
Pulse Duration Modulation (PDM)
Pulse Length Modulation (PLM)
All of the choices
None of the choices

A

Note: PWD, PDM, and PLM are all the same.

PulseWidth Modulation (PWM) or Pulse Duration Modulation (PDM) or Pulse Time Modulation (PTM) is ananalog modulatingscheme in which the duration or width or time of the pulse carrier varies proportional to the instantaneous amplitude of the message signal.

Answer: All of them

58
Q

What does Pulse Code Modulation (PCM) primarily involve?

Modulating pulse width
Converting analog signals to digital signals
Varying pulse amplitude
Modulating pulse position

A

Converting analog signals to digital signals

59
Q

What is the advantage of using Differential Pulse Code Modulation (DPCM) over Pulse Code Modulation (PCM)?

Higher data transmission rate
Lower quantization noise
Reduced bandwidth requirement
Better resistance to channel noise

A

Note: DPCM requires less Bandwidth than PCM for transmitting the same signal. DPCM is used todecrease quantization noise.

Answer: Reduced bandwidth requirement

60
Q

What is the primary characteristic of Spread Spectrum modulation techniques?

A

Spreading signal energy over a wide bandwidth

61
Q

What is the main advantage of digital modulation over analog modulation?

A

Greater resistance to noise

62
Q

What is the primary advantage of digital communication over analog communication?

A

Greater resistance to noise

63
Q

Which of the following is not a component of a digital communication system?

A

Carrier wave generator

64
Q

What is the primary difference between Pulse Amplitude Modulation (PAM) and Pulse Width Modulation (PWM)?

A

PAM uses a fixed pulse width, while PWM uses variable pulse widths

65
Q

In Pulse Code Modulation (PCM), what does quantization refer to?

A

Encoding the analog signal into binary code

66
Q

Which modulation technique encodes information in the timing of pulses?

A

Pulse Width Modulation (PWM) also called pulse duration modulation

67
Q

What is the primary advantage of Quadrature Amplitude Modulation (QAM) over other modulation techniques?

A

higher data transmission rates

68
Q

What is the main advantage of Frequency Shift Keying (FSK) over Amplitude Shift Keying (ASK)?

A

Greater resistance to noise

69
Q

In digital communications, what does ASK stand for?

A

Amplitude Shift Keying

70
Q

In Phase Shift Keying (PSK), how many phase states can a signal have to encode information?

A

2 (Starting with Binary Phase Shift Keying)

71
Q

Which information theory concept measures the average amount of information produced by a source of data?

A

Entropy (Claude Shannon’s Entropy Theory)

72
Q

What is the primary purpose of error detection codes in digital communication?

A

To identify if errors have occurred during transmission

73
Q

CDMA stands for

A

Code Division Multiple Access

74
Q

An analog multiplexing technique where the optical fiber data rate is higher than the data rate of the metallic transmission cable. It is also used to combine optical signals.

A

WDM
Wavelength-division multiplexing (WDM)

75
Q

Which of the following is not a common FDM application?

A

Secure comminucations
(Pinoy BIx)

76
Q

lt is the basic building block of the FDM hierarchy

A

Message Channel

(Pinoy Bix)

77
Q

A quarter-wave length of a line is used as a/an

A

Impedance Transformer

78
Q

What causes the characteristic impedance of a transmission line to change?

A

Note: The characterstic impedance is independent of the length factor. It is dependent on the material and geometric factors.

Answer: AItering the cross-sectional area of the line

79
Q

A coaxial line with an outer diameter of 6mm has a 50Ω characteristic impedance. lf the dielectric constant of the insulation in 1.60, calculate the inner diameter.

A

2.09 mm

(Pinoy Bix0

80
Q

Indicate the false statement. The SWR on a transmission line is infinity; the line is terminated in

A

Note: SWR of infinity means that there is a complete mismatch between the load and the transmission line

Answer: Complex impedance

81
Q

Which parameter of a transmission line determines its ability to transfer signals without distortion?

A

Characteristic impedance

82
Q

In a given direction, the relative gain of a transmitting antenna with respect to the maximum directivity of a half-wave dipole multiplied by the net power accepted by the antenna from the connected transmitter

A

Effective radiated power

83
Q

What is the cut-off wavelength of a 6cm x 3cm waveguide? Assume the dominant mode of operation

A

12cm

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