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Frequency Modulation Question & Answers

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This article lists 100+ Frequency Modulation MCQs for engineering students. All the Frequency Modulation Questions & Answers given below include a hint and wherever possible link to the relevant topic. This is helpful for the users who are preparing for their exams, interviews, or professionals who would like to brush up their fundamentals on the Frequency Modulation topic.

Digital signals are preferred for transmission, but it is not always feasible as it needs high bandwidth with low pass characteristics. To overcome such issues analog transmission is considered, as it possesses low bandwidth and bandpass characteristics.

Information about the source gets imposed on the carrier signal by modifying certain characteristics of it. This process in the analog transmission is termed modulation.

Move the signal spectrum to a frequency that is less susceptible to attenuation in a medium is necessary.   Further, the modulations are classified into two types. They are Amplitude modulation and angle modulation. Frequency modulation is part of an Angle modulation.

1). Modulation in which the carrier wave angle varies in accordance with the baseband signal is termed as ___________.
HintPhase and Frequency modulation
2). The man behind the invention of frequency modulation is ______________.
Hint FM method described by Edwin Howard Armstrong
3). The original signal of source in modulation is known as _________.
HintSource signals
4). Conversion of analog or digital data into analog form is known as ___________.
HintModulation technique
5). To encode the information in the carrier signal by altering the wave frequency instantaneously is known as ____________.
HintVarying frequencies
6). What types categorized under Analog modulation?
HintAmplitude and angle modulation prefer analog signals
7). What are the various Frequency modulations?
HintBoth variants of analog and digital
8). Modulation index in frequency modulation can be determined by using _________.
HintRatio of frequency deviation (δf) to the modulating frequency (fm)
9). A carrier signal of 100 MHz modulated using a sine wave whose frequency is 75 kHz with a deviation frequency of 50 kHz. What will be the modulation index?
Hintβ = δf/ fm
10). NBFM bandwidth is ________.
HintBandwidth of amplitude modulation
11). What is the basic difference between NBFM and AM signal?
HintAM and NBFM differ by the reverse sign at the lower side frequency
12). Bandwidth of WBFM is ________.
HintCarson’s rule
13). A 12 MHz carrier gets modulated by a sine signal with a frequency of 500 Hz bearing the frequency deviation of about 50 kHz. Find the bandwidth?
HintCarson’s rule, B = 2(δf + fm)
14). Based on modulation index FM is classified as __________.
HintModulation index classifies the FM
15). In NBFM the modulation index is ____________.
HintNBFM utilizes a small part of the channel
16). Modulation of the source signal with multiple frequency components in it is called _______________.
HintSingle component of frequency known as modulated single tone signal
17). Modulation index will be greater than 1 in _________________.
HintWide range of frequencies
18). The transmitted power is independent of modulation index in _________________.
HintFrequency-modulated signals are more immune to noise
19). Noise immunity is superior in ________________.
HintFM more superior in terms of noise immunity
20). Modulation index in Frequency modulation is proportional to _______________.
HintModulating signal and frequency are proportional to its index
21). In _____________ angle is in direct proportion with the integral of modulating signal.
HintAmplitude will always remain constant but angle varies
22). Departure of maximum instantaneous frequency from the carrier’s frequency is known as ________________.
HintTo describe the range of a modulating frequency signal
23). Side bands present in frequency modulation are ____________.
HintSidebands in the FM is large
24). Total variation of frequency from its low to high point is termed as __________.
Hint2 times of δf of FM
25). In FM signals the amount of frequency deviated is dependent upon ________.
HintModulating signal's amplitude

Frequency Modulation Multiple Choice Question & Answers

26). Sidebands in FM are controlled based on selected ____________.
HintLesser deviation leads to few sidebands
27). Maximum deviation is due to __________.
HintTransmitter configuration and design
28). Good audio quality needs ________.
HintHigh deviation is preferred for better audio quality
29). Human speech prefers _______.
HintLower maximum frequency of modulation is present in human speech. Hence low deviation is preferred.
30). WBFM possess ________.
HintHigher ratio of deviation possessed by WBFM
31). If the deviation is +20 KHz indicates _________.
Hint+ and – indicates the carrier present above or below
32). What are the methods used to produce FM waves?
HintTwo methods are used in producing FM waves
33). The wave originated from the transmitter and its frequency varies concerning modulation source is possible in __________ of FM.
HintHigh-power FM signals
34). Phase of the originated wave is a function of modulation in ______________ of FM.
HintWBFM waves are generated
35). Armstrong method is categorized as ____________.
HintAlternative of a direct method
36). _______________ is used to estimate the bandwidth of FM signal.
HintCarson's rule can be used to estimate the bandwidth
37). Spectrum of NBFM is similar to the spectrum of _____________.
HintBandwidth of AM wave is similar to the NBFM
38). Carson’s rule formula for bandwidth calculation is _____________.
HintComponents present in communications
39). The Δf in the Carson’s rule stands for _________.
HintMaximum deviation in the frequency
40). _____________ device is used to convert the received FM signal converted to voltage.
HintThe converted FM signal into voltage
41). Other than frequency discriminator ________ can be used for FM demodulation.
HintFor noisy environments
42). FM is normally used above _____________ MHz.
HintAbove 30 MHz
43). What are the two common applications of frequency modulation?
HintFM radio and two-way
44). An FM receiver consisting of Amplitude limiters serves the purpose of _________.
Hint Noise results in the amplitude variations
45). Circuit consisting of differentiator that allows to pass _______.
HintPre-emphasis is a circuit that possesses a high-pass filter
46). __________ circuits are used in FM.
HintPre-emphasis and de-emphasis
47). Boosting the high-level audio frequencies artificially according to the prearranged curve of response is known as ___________.
HintPassage of high-frequency components
48). ________ circuit used at the transmitter of FM.
HintHigh pass filter present at the transmitter
49). _______ circuit present at the receiver of FM.
HintTo nullify the artificially boosted signals coming from the transmitter
50). __________ filter is used in De-emphasis circuit.
HintLPF to nullify the signals

Frequency Modulation MCQs for Exams

51). Parameters constant in FM are _____________.
HintCarrier frequency is varied
52). Pre-emphasis is performed before ____________.
HintModulation to boosts the voltage of the modulating signal
53). Pre-emphasis can be done __________.53). Pre-emphasis can be done __________.
HintPre-emphasis circuit is present in the transmitting section
54). What will be the change in bandwidth of the FM signal as the frequency of modulation tends to increase from 14 kHz to 28 kHz?
HintCarson’s rule B= 2(Δf+fm)
55). The characteristics of WBFM are _____________.
HintLarge frequency sensitivity and wide bandwidth
56). The characteristics of NBFM are _________.
HintSmaller frequency sensitivity
57). PLL can be used as _______.
HintFrequency demodulation
58). NBFM operates at a range of ________ modulating frequencies.
HintNBFM operates at a narrow bandwidth
59). FM signal with 7 as modulation index applied to the ‘Frequency Tripler’. What will be the modulation index at the output obtained?
HintN-times Frequency Multiplier
60). FM signal passed from mixer makes the deviation ____________.
HintDeviation doesn’t get affected
61). Digitally encoded data transmitted with frequency-modulated signals referred to as _________.
HintFrequencies in FSK are represented using digits
62). FM broadcast requires ____________ max. Bandwidth for commercial uses.
Hint200 kHz is the max. Bandwidth
63). The purpose of Guard bands in FM is to _________.
HintInterferences occur due to adjacent channels
64). In Armstrong method FM is obtained by using ____________.
HintFM can be generated from the Phase modulator
65). To generate WBFM, components present are _____.
HintOutcome of the NBFM modulator
66). Frequency multiplier is a __________ device.
HintInput signals are multiplied with a factor given making the multiplier non-linear
67). What are the direct methods of FM generation?
HintNBFM signals are generated
68). Parameter variation for FM generation is a ___________ method.
HintMaintaining carrier frequency-stable for an extended period is difficult
69). Carrier is in phase with upper sidebands where the carrier is out of phase with the lower sideband in ____________.
HintCarrier is in out phase with LSB
70). Crystal controlled oscillator used in FM generation is to provide ____________.
HintSource signal is integrated and the phase gets modulated with a crystal oscillator
71). NBFM signal’s frequency multiplied using frequency multiplier and produces _______.
HintIndirect method
72). PLL is __________ feedback system.
HintIndirect demodulation of frequency is possible using PLL
73). PLL FM detector can be used in ___________ applications.
HintIndirect method of frequency demodulation
74). PLL FM detector consists of _________________.
HintMixer, LPF followed by VCO
75). Phase Locked Loop compares the input signal’s phase with the output signals phase using ________.
HintFeedback provided by VCO

Frequency Modulation MCQs for Quiz

76). FM discriminator consists of ______________.
HintFM Discriminator comprises slope circuits and Envelope detectors
77). To ensure the input signal amplitude in FM discriminator maintained constant __________ is used.
HintLimiter placed to maintain the amplitude
78). Single slope discriminator has poor ____________.
HintLinearity can be improved by using a balanced discriminator
79). Two signals of FM in which one signal’s amplitude is twice the other strongest signal gets captured and weaker one gets rejected known as ___________.
HintA stronger signal dominates the weaker signal
80). ______________ improves the Signal to Noise ratio (SNR).
HintThe energy of the higher contents increased using pre-emphasis

Read More About Frequency Modulation

81). AFC stands for _________________.
HintAFC loop in Crosby Direct FM makes the frequency of modulation unaffected
82). What are the advantages of Indirect method to generate FM?
HintTo attain frequency stability crystal oscillators are preferred
83). The maximum amount of deviation in frequency allowed for the broadcasting of FM commercially is __________.
HintMaximum deviation in frequency of about 75 kHz
84). ____________ is an experimental technique utilized by FM systems to set the deviation of frequency with precision.
Hint Carrier null method to set frequency deviation
85). Audio oscillators analog output connected to the input of the buffer amplifier in _________ method.
Hint Bessel null method connects the output as the input
86). VCO is used in _______ method to generate FM.
HintVCO is replaced with Crystal oscillator in indirect method
87). ____________ method used in the generation of FM because the frequency of the oscillator varies directly based on the modulating signals.
HintVaractor diodes offers AFC
88). What are the advantages of Varactor diode modulators of FM?
HintVaractor diodes are accepted widely because of their simplicity, reliability, and stability
89). What is the drawback of Varactor diode modulators?
HintPeak deviation of frequency is limited in varactor diode-based modulators
90). FM circuit made using inductors known as ____________.
HintInductors whose inductance in the LC circuit varied based on the modulating signals
91). Frequency Modulation can be achieved using _____________.
HintUsing Voltage controlled oscillators or devices
92). Varactor diode in the frequency modulation is __________.
HintCapacitance in the circuit is dependent upon the reverse voltages
93). VCO’s frequency of oscillations has _________dependent on the voltage applied.
HintLarge deviation of frequencies offered by using VCO
94). Armstrong’s modulator using ‘frequency-up’ conversion involves __________ methods.
HintFrequency conversion involves two methods
95). The modulator made using Armstrong method consists of ______________.
HintModulate the phase of the Crystal oscillator phase shifter offering 90-degree
96). Desired deviation of frequency in Armstrong modulators can be attained using _________.
HintCombination of mixers and multipliers is used to achieve the desired frequency deviation
97). Which detector can detect either WBFM or NBFM modulated signals?
HintPLL demodulators can detect either WBFM or NBFM
98). Double tuned transformer for FM generation is used in ____________ detector.
HintA double-tuned transformer used in the ratio detector
99). Noise suppressed without limiters in _______ detectors.
HintRatio detectors perform demodulation on the FM signals
100). What is the disadvantage of FM in comparison to AM?
HintFM is lesser prone to the interference of noise

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