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Question 1

Which of the following is NOT a classification of signals?

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

Answer 1

c) Dynamic-time

Question 2

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

Answer 2

a) It has a repeating pattern over a specific interval

Question 3

What is the Nyquist rate?

Answer 3

Twice the highest frequency

(Using one-half the given sample rate)

Question 4

Aliasing in signal processing occurs when

Answer 4

The sampling frequency is too low.

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

Question 5

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

Answer 5

FIR fiters have recursive difference equations

Question 6

Which type of filter exhibits linear phase characteristics?

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

Answer 6

b) FIR filter

Question 7

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

Answer 7

d) They have a finite duration impulse response

Question 8

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

Answer 8

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

Question 9

pole-zero-gain filters are characterized by

Answer 9

Number of poles, zeros, and gain

Question 10

In signal processing, Fourier transforms are primarily used for

Answer 10

Converting frequency-domain signals to time-domain signals

Question 11

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

Answer 11

To encode date in a carrier wave

Question 12

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

Answer 12

c) Reduced error rate

Question 13

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

Answer 13

The capacity of data transmission

Question 14

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

Answer 14

Receiver

Question 15

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

Answer 15

White Noise

Question 16

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_____.

Answer 16

14dB

Question 17

What factor affects thermal noise in communication system?

Answer 17

Temperature

Question 18

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

Answer 18

3dB

Question 19

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.

Answer 19

100 dBu

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

Question 20

Modulation is the process of

Answer 20

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

Question 21

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

Answer 21

Carrier wave’s power is not transmitted

Question 22

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

Answer 22

10.8

10k (1 + 0.4^2/2)

Question 23

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

Answer 23

c) amplitude equals signal amplitude

Question 24

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

Answer 24

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

Question 25

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

Answer 25

a) is purely theoretical because the same in practice

Question 26

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

Answer 26

a) higher than

Question 27

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

Answer 27

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

Question 28

The standard intermediate frequency for the FM radio is

Answer 28

10.7 MHz

Question 29

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

Answer 29

Pulse Wwidth Modulation (PWM)

Question 30

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

Answer 30

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)

Question 31

What factor affects the power density of a transmitted signal?

Answer 31

Transmitting antenna material

Question 32

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

Answer 32

53.2 mi

Question 33

Effective earth radius to true earth radius ratio a) Fresnel zone b) index of refraction c) Path profile d) K-factor

Answer 33

d) K-factor

Question 34

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

Answer 34

Power density

Question 35

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

Answer 35

b) 50,024.36 m

Question 36

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

Answer 36

173.4 dB

Question 37

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

Answer 37

50 uv

Question 38

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

Answer 38

Free space

Question 39

What does the term "polarization" refer to in antenna systems?

Answer 39

The orientation of the electromagnetic wave's electric field.

Question 40

A device designed to radiate electromagnetic energy into space.

Answer 40

Antenna

Question 41

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

Answer 41

Bandwidth

Question 42

What is meant by antenna gain?

Answer 42

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

Question 43

What is the primary function of a directive antenna?

Answer 43

To concentrate electromagnetic waves in one direction

Question 44

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

Answer 44

Higher data transmission rates

Question 45

Which transmission mode allows simultaneous transmission and reception of data?

Answer 45

Full-duplex

Question 46

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

Answer 46

LCU (Line Control Unit)

Question 47

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

Answer 47

Isochronous synchronization

Question 48

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

Answer 48

Multiplexer

Question 49

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

Answer 49

Data Link Layer (Layer 2)

Question 50

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

Answer 50

ASCII

Question 51

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

Answer 51

Session layer (Layer 5)

Question 52

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

Answer 52

Network layer

Question 53

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

Answer 53

HDLC (High-Level Data Link Control)

Question 54

What distinguishes a WAN from a LAN?

Answer 54

WANs cover larger geographical areas than LANs

Question 55

What does ISDN stand for in telecommunications?

Answer 55

Integrated Services Digital Network

Question 56

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

Answer 56

MAN (Metropolitan Area Network)

Question 57

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

Answer 57

Note: PWD, PDM, and PLM are all the same. Pulse Width Modulation (PWM) or Pulse Duration Modulation (PDM) or Pulse Time Modulation (PTM) is an analog modulating scheme 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

Question 58

What does Pulse Code Modulation (PCM) primarily involve? Modulating pulse width Converting analog signals to digital signals Varying pulse amplitude Modulating pulse position

Answer 58

Converting analog signals to digital signals

Question 59

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

Answer 59

Note: DPCM requires less Bandwidth than PCM for transmitting the same signal. DPCM is used to decrease quantization noise.  Answer: Reduced bandwidth requirement

Question 60

What is the primary characteristic of Spread Spectrum modulation techniques? 

Answer 60

Spreading signal energy over a wide bandwidth

Question 61

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

Answer 61

Greater resistance to noise

Question 62

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

Answer 62

Greater resistance to noise

Question 63

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

Answer 63

Carrier wave generator

Question 64

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

Answer 64

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

Question 65

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

Answer 65

Encoding the analog signal into binary code

Question 66

Which modulation technique encodes information in the timing of pulses?

Answer 66

Pulse Width Modulation (PWM) also called pulse duration modulation

Question 67

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

Answer 67

higher data transmission rates

Question 68

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

Answer 68

Greater resistance to noise

Question 69

In digital communications, what does ASK stand for?

Answer 69

Amplitude Shift Keying

Question 70

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

Answer 70

2 (Starting with Binary Phase Shift Keying)

Question 71

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

Answer 71

Entropy (Claude Shannon's Entropy Theory)

Question 72

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

Answer 72

To identify if errors have occurred during transmission

Question 73

CDMA stands for

Answer 73

Code Division Multiple Access

Question 74

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.

Answer 74

WDM Wavelength-division multiplexing (WDM)

Question 75

Which of the following is not a common FDM application?

Answer 75

Secure comminucations (Pinoy BIx)

Question 76

lt is the basic building block of the FDM hierarchy

Answer 76

Message Channel (Pinoy Bix)

Question 77

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

Answer 77

Impedance Transformer

Question 78

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

Answer 78

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

Question 79

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.

Answer 79

2.09 mm (Pinoy Bix0

Question 80

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

Answer 80

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

Question 81

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

Answer 81

Characteristic impedance

Question 82

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

Answer 82

Effective radiated power

Question 83

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

Answer 83

12cm