Modulation Question & AnswersMarch 9, 2021 By admin This article lists 100+ Modulation MCQs for engineering students. All the Modulation Questions & Answers given below include a solution and link wherever possible to the relevant topic. This is helpful for users who are preparing for their exams, interviews, or professionals who would like to brush up their fundamentals on Modulation topic which is core in Electronics Engineering.In digital communication, information is transmitted by encoding and decoding process using various modulation techniques. Modulation is a process of converting analog data into a digital signal form with a piece of information added to the carrier signal. It mainly consists of a modulator on the transmitter side for modulation purposes and a demodulator on the receiver side for the demodulation purpose. They are classified into 4 types, namely analog-type modulation, digital type modulation, pulse type modulation, spread spectrum type modulation. Where analog modulation refers to the process of transferring a low-frequency signal over a high-frequency signal. These analog-type modulations are classified into 3 types like Amplitude type modulation (AM), frequency type modulation (FM), Phase type modulation (PM). Digital type modulation is the process of encoding the signals information in digital form to amplitude, phase, frequency of transmitted signals. These are classified into two types namely single carrier modulation types like amplitude type shift keying ASK, frequency type shift keying FSK, Phase type shift keying PSK, Orthogonal type amplitude modulation. and multicarrier frequency division multiplexing (OFDM).Pulse-type modulation is a process where the signal pulse is varied with respect to the amplitude or width of a signal. Spread type spectrum modulation is a process where signals are spread in the frequency domain using various spread spectrum techniques. The main advantage of using modulation techniques is that it reduces the size of the antenna in the circuit and improves the quality of signal in communication. 1). A signal is a _____ that carries data from one network to another.ElectromagneticElectrical currentElectronic signNone of the aboveHintA signal is an electrical current that carries data from one network to another. 2). A signal can be in which form?AudioVideoSpeechAll the aboveHintA signal can be in audio, video, speech, speech, image forms. 3). Modulation is of _____ types.Analog modulationDigital modulationPulse modulationSpread spectrum modulationAll the aboveHintIn electronics, modulation is of 4 types, analog type modulation, digital type modulation, Pulse type modulation, and Spread spectrum type modulation. These modulations are classified based on signal form ( analog signal or digital signal) 4). Examples of analog modulation techniquesFrequency type modulation FMAmplitude type modulation AMBoth a and bNone of the aboveHintExamples of analog modulation techniques are frequency type modulation and amplitude type modulation. Such modulations are used in radio broadcast applications. Read more about Analog Modulation. 5). What is modulation?It is a process of converting data into electrical signals optimized for transmissionIt is a process of converting data into analog signals optimized for transmissionIt is a signalNone of the aboveHintIt is a process of converting data into electrical signals optimized for transmission. Read more about Modulation 6). What are the different types of digital modulation?Single carrier modulationMulticarrier modulationBoth a and bOnly bHintDigital modulation is classified into two types single carrier modulation and multicarrier modulation. Single carrier modulation exploits only one signal frequency. Multicarrier modulation exploits multiple signal frequencies. 7). Which of the following is single carrier modulation?Amplitude type shift type keying ASKFrequency type shift type keying FSKPhase type shift type keying PSKOrthogonal amplitude modulation QAMAll the aboveHintSingle-carrier modulation is classified into 4 types namely Amplitude type shift keying ASK, Frequency type shift keying FSK, Phase type shift keying PSK, Orthogonal amplitude modulation QAM. 8). Which type of modulation method is used in multicarrier modulation?Amplitude type shift keying ASKFrequency type shift keying FSKOrthogonal frequency division multiplexing OFDMNone of the aboveHintMulticarrier modulation uses Orthogonal frequency division multiplexing OFDM methodology. 9). What is the function of a modulator?Modulates signalDemodulates signalMaintains signalNone of the aboveHintA modulator modulates signal, by controlling input audio signal called carrier. 10). What is the function of demodulation?Modulates signalDemodulates signalMaintains signalNone of the aboveHintA demodulator demodulates the received signal from the modulator. 11). What are the units of modulation rate?SecondsBaudMetersCentimetersHintModulation rate is expressed in terms of baud. 12). On which component modulation is performed?TransmitterSignalJammerNone of the aboveHintModulation is performed between transmitter and receiver. 13). Which oscillator is used in the transmitter?Crystal oscillatorRC oscillatorHartley oscillatorBoth a and cHintCrystal oscillator used in the transmitter. 14). Which type of modulation is used for radio transmission in India?Amplitude modulationFrequency modulationPhase modulationBoth a and bHintAmplitude modulation is used in India for radio transmission. 15). The useful power in amplitude modulation is carried by ________.SidebandsCarriersSignalsBoth a and cHintThe useful power in amplitude modulation is carried by sidebands. Read more about Amplitude Modulation. 16). The relation between bandwidth and audio signal frequency in amplitude modulation is __________.Bandwidth = 3 FrequencyBandwidth = 4 FrequencyBandwidth = 2 FrequencyBandwidth = 6 FrequencyHintIn amplitude, modulation bandwidth is 2 times of frequency audio signal. 17). In AM, the strength of _____ is varied with respect to the strength of _____.Carrier, signalSignal, carrierSignal, signalCarrier, carrierHintIn AM, the strength of the carrier is varied with respect to the strength of the signal. 18). At what condition over modulation occur?When the signal amplitude is greater than carrier amplitudeWhen signal amplitude and carrier amplitude are equalWhen the signal amplitude is equal to zeroWhen the signal amplitude is infinityHintOvermodulation occurs in telecommunication when the signal amplitude is greater than carrier amplitude. This results in spurious emission by the modulated carrier and distortion of the recovered modulated signal. 19). What should be the value of modulation index for under modulation?<10>1InfinityHintThe value of modulation index for under modulation should be less than 1. 20). What should be the value of modulation index for perfect modulation?<11>1InfinityHintThe value of the modulation index for perfect modulation should be 1. 21). Modulation index is also called as _________.Modulation waveModulation heightModulation depthModulationHintThe modulation index is also called modulation depth. 22). Modulation index is denoted as __________.µƟΦΩHintThe modulation index is denoted as µ. 23). Percentage modulation is denoted as __________.NmnMHintPercentage modulation is denoted as m. 24). If the value of the modulation index is 0.8 then the modulation is called __________.Over modulationUnder modulationPerfect modulationBoth a and cHintIf the value of the modulation index is 0.8 then the modulation is called under modulation. 25). If the value of the modulation index is 1.3 then the modulation is called ___________.Over modulationUnder modulationPerfect modulationBoth a and cHintIf the value of the modulation index is 1.3 then the modulation is called over modulation.Modulation Interview Questions 26). If the value of the modulation index is 1 then the modulation is called __________.Over modulationUnder modulationPerfect modulationBoth a and cHintIf the value of the modulation index is 1 then the modulation is called perfect modulation. 27). Bandwidth is expressed in terms of __________.Bits per secondHertzCentimetersSecondsHintThe amount of data that is transferred from one end to another end in a network within a specific time is called bandwidth. It is usually expressed in terms of bits per second. 28). What happens when overmodulation occurs?Signal gets weakMore carrier powerDistortionBoth a and cHintOver modulation is a condition where the modulation index is greater than 1, at this point signal gets distorted. 29). Demodulation occurs in __________.Receiving antennaTransmitterRadio receiverNone of the aboveHintDemodulation occurs in a radio receiver. 30). Which medium is used in radio transmission?AirWaterSpaceCableHintSpace is used as a medium in radio transmission. 31). In amplitude modulation the carrier amplitude with instantaneous values changes with change in the _____ and _____ variation of modulation.AmplitudeFrequencySignalBoth a and bHintIn amplitude type modulation, the sine wave amplitude varies with the signal applied. the instantaneous values of carrier amplitude changes with change in the amplitude and frequency variation of the modulation. 32). Modulating signal has a reference line up to _____ limitLine with zeroThe peak of carrier lineModulated highest pointUnmodulated highest pointHintModulating signal uses the peak value of carrier, and the envelope varies above and below the peak carrier amplitude. The zero reference line of modulating signal coincides with the peak value of the unmodulated carrier. 33). Distortion causes _____ in the signal.There will be a loss in complete informationAn error is introduced in the informationInformation gets attenuatedNone of the aboveHintWhen the amplitude of modulating signal is greater than the amplitude of the carrier signal distortion will occur. Due to this, an error is introduced in the information of the transmitted signal. Hence in amplitude type modulation, the modulating signal peak value should be less than the carrier signal peak value. 34). Which circuit is used to produce Amplitude Modulation?TransmitterModulatorDuplexerReceiverHintA modulator is used to generate amplitude modulation. Generally, it has 2 input signals namely, a carrier signal and a modulating signal, and one output signal called modulated signal, which is the product of input signals. 35). The signal is modulated at 7.5 V and carrier voltage is of 9V, calculate modulation percentage.20083.3380.3381HintModulating signal = 7.5V, carrier voltage = 9V ; m = Vm / Vc = 7.5 / 9 * 100 = 83.33. 36). If Vmax = 5.9v and Vmin = 1.2V, calculate modulation index.0.50.6620.40.55HintModulation index = m= Vmax – Vmin / Vmax + V min = 5.9 – 1.2 / 5.9 + 1.2 = 0.662 37). If carrier voltage is 10v , which voltage of Modulating signal causes over modulation?1112.61214HintWhen the voltage of Modulating signal exceeds carrier signal voltage it causes over modulation, where m>1; 12/10 = 1.2 which is greater than 1. 38). Find voltage of modulating signal, if Vmin and Vmax are 5.9 v and 1.2v.2.35v2v2.8v3vHintVoltage of Modulating signal = V max – Vmin / 2 = 5.9 – 1.2 / 2 = 2.35v. 39). Which modulation technique is equipped in all EDM instruments?Frequency modulationAmplitude modulationPulse modulationBoth a and bHintIn frequency modulation, the amplitude and frequency of carrier wave vary in proportion to the amplitude of modulating wave. Hence frequency modulation is used in all EDM instruments. 40). Calculate the maximum value of wavelength, if accuracy is 10mm for 1/1000 parts10m10cm100m100cmHintMax wavelength is calculated by the product of assumed wavelength and accurate wavelength; Wavelength = 10 * 1000 = 10m 41). Phase comparison cannot be done in which zone?Frequency zoneAmplitude zonePhase zoneNone of the aboveHintPhase comparison cannot be done in a high-frequency zone. 42). Distance transmission is not compatible for ________ frequency.High frequencyLow frequencyEqual frequencyZero frequencyHintLow frequency is not suitable for distance transmission, due to several atmospheric conditions like interference, reflection, fading, and scattering. This decreases both frequencies and transmitted information. 43). Which phase technique is capable of resolving wavelength?Amplitude phaseFrequency phaseModern phaseNone of the aboveHintThe modern phase technique is capable of resolving wavelength, at 1/1000 part of a wavelength. 44). Calculate carrier frequency of amplitude modulation wave, if highest frequency component is 850 Hz and signal bandwidth is 50Hz.800 Hz678 Hz825 Hz900 HzHintUpper frequency = 850 Hz ; bandwidth = 50 Hz ; low frequency = 850 - 50 = 800 Hz; Carrier frequency = 850 -800 / 2 = 825 Hz 45). What is the advantage of an RF amplifier?Good selectivityGood sensitivityGood SNRAll the aboveHintRF amplifier has a high gain property which provides good sensitivity, also they amplify a weak signal. They have better-required signal selectivity ability from a group of signals. RF amplifier improves SNR ratio by raising incoming weak signal to a higher level. Read more about Amplifiers. 46). What is the value of standard intermediate frequency used in AM receiver?460 MHz455 KHz700 Hz900 HzHint455 kHz is the value of standard intermediate frequency used in AM receiver. 47). What is the advantage of analog communication over digital communication?Low data ratethe bandwidth of transmission channel is lowNo synchronization is requiredAll the aboveHintThe advantage of analog communication over digital communication is that it has a low data rate, low bandwidth of transmission, no synchronization required. 48). What is the formula of image frequency?fs + fifs + 2fi2fs + fi2( fs + fi)HintImage frequency f image = f s + 2 fi. 49). What is cross-talk?Disturbance in channelRejection of frequencyBoth a and bNone of the aboveHintThe disturbance caused in a nearby channel or circuit in a transmitter signal is a cross-talk. It usually occurs due to an electromagnetic interface. 50). What is the need for costas receiver?FM signalDouble sideband – SC signalPulse code modulation signalDM signalHintCostas receiver is used in Double sideband – SC signal, it is a synchronous receiver system.Modulation Quiz Questions and Answers 51). What is the job of frequency mixer in a superheterodyne receiver?AmplificationFilteringMultiplies incoming signal and locally generated carrierNone of the aboveHintFrequency mixer in superheterodyne receiver multiplies incoming signal and locally generated carrier. 52). Which of the following is a continuous wave in analog modulation?Pulse code modulationDigital modulationAmplitude modulationPulse amplitude modulationHintAmplitude modulation is a continuous wave in analog modulation. 53). At what conditions intermediate frequency is selected?At high intermediate frequency it gives weak selectivityHigh intermediate frequency it is difficult to track signalsAt low-frequency frequency of image is rejectedAll the aboveHintIntermediate frequency should be considered at - The high intermediate frequency that leads to weak selectivity and cause problems in the tracking of signals and at low-frequency images, frequency rejection becomes poor. 54). Which of the parameters does selectivity of a receiver has?It varies with incoming signal frequencyAt high frequency it has a poor ratioBoth a and bNone of the aboveHintThe selectivity of a receiver varies with incoming signal frequency and At high frequency, it has a poor ratio value. 55). What kind of modulation is used in television for sound signal?Amplitude modulationFrequency modulationPhase modulationBoth a and bHintFrequency modulation is used in television to transmit an audio signal. 56). At what frequency RF and detection stages are tuned in a TRF radio receiver?IFRadio frequencyAudio frequencyVideo frequencyHintIn the TRF radio receiver, the RF and detection stages are tuned to radiofrequency. 57). After how many stages of amplification the diode detector in an AM radio receiver is found?Several stagesAfter the single stageAfter two stagesAfter three stagesHintAfter several stages of amplification, the diode detector in an AM radio receiver is found. 58). Why is difference frequency chosen as the IF in a superheterodyne receiver, rather than sum frequency?Both difference frequency and oscillator frequency are equalIt is easy to amplify lower frequenciesDifference frequency alone can be modulatedNone of the aboveHintSince it’s easy to amplify lower frequencies difference frequency chosen as the IF in a superheterodyne receiver, rather than sum-frequency. 59). What does ferrite antenna does?Reduce stray capacitanceReduce noiseStabilize dc biasIncreases Q of the tuned circuitHintFerrite antenna, Increases Q of the tuned circuit. 60). Which modulation signal controls the frequency of the carrier?Phase modulationFrequency modulationAmplitude modulationNone of the aboveHintIn Frequency modulation, the modulation signal controls the frequency of the carrier. 61). What is the advantage of FM over AM?Less noisy in receptionCarrier frequency Is highBandwidth is lessFrequency deviation is smallHintThe main advantage of FM over AM it produces less noise. 62). What is the input used at the mixer stage at the superheterodyne receiver?IF and RFRF and AFIFRF and the local oscillator signalHintThe input used at the mixer stage at the superheterodyne receiver is RF and local oscillator signal. 63). At what stage of superheterodyne we can observe selectivity?Radio FrequencyIntermediate FrequencyAudioBefore Radio FrequencyHintAt the Intermediate Frequency stage of superheterodyne, we can observe selectivity. 64). AVC stands for __________.Audio voltage controlAutomatic volume controlAdvance voltage controlAbrupt voltage controlHintAVC stands for Automatic volume control. 65). If all the signal frequencies in a radio receiver are amplified equally, then it has a high _______.High sensitivityHigh fidelityHigh selectivityHigh distortionHintIf all the signal frequencies in a radio receiver are amplified equally, then it has high fidelity. 66). Which of the following statement is related to the superheterodyne principle?It uses a large number of amplifier stages being usedIt uses a push and pulls the circuitObtains low fixed intermediate frequencyBoth a and cHintSuperheterodyne principle obtains low fixed intermediate frequency. 67). At what order does signal voltage is induced in the aerial of a radio receiver?mVµVVNone of the aboveHintAt µV order, the signal voltage is induced in aerial of a radio receiver. 68). Which type of modulation is a man made called?Amplitude modulationFrequency modulationPulse modulationPhase modulationHintThe modulation made by man is called amplitude modulation. 69). Which type of modulation is used in TV for picture signals?Amplitude modulationFrequency modulationPulse modulationPhase modulationHintThe type of modulation is used in TV for picture signals is amplitude modulation. 70). What happens if the modulation level is increased?Increases carrier powerIncreases sideband powerIncreases carrier and sideband powerNone of the aboveHintIf the modulation level is increased, sideband power is also increased. 71). What is the advantage of using modulation techniques?Antenna size is reducedNo signal mixingImproves signal qualityAll the aboveHintThe advantage of using modulation techniques are - Antenna size is reduced, No signal mixing, Improves signal quality. 72). What is a carrier signal?It has informationIt does not have informationIt has amplitude, phase, and frequencyBoth b and cHintA carrier signal is a high-frequency signal which has phase, frequency, and amplitude but no information. The main functionality of a carrier signal is to carry the signal to the receiver after modulation. 73). What is the functionality of the carrier signal?Carry the signal to receiver after modulationCarry the bits to receiver after modulation.Listens to channelNone of the aboveHintThe main functionality of a carrier signal is to carry the signal to the receiver after modulation. 74). What is modulated signal?It is the product of modulating signal and carrier signalIt is the product of modulating signal and information signalIt is an input signalNone of the aboveHintThe product of modulating signal and carrier signal is a modulated signal. 75). What is angle modulation?The carrier wave varies with respect to instantaneous modulating signal valueThe product of carrier wave and modulating signalIt is a carrier waveIt is a modulated waveHintThe carrier wave varies with respect to instantaneous modulating signal value is called angle modulation.Modulation Questions and Answers 76). Angle modulation is __________.Frequency and phase modulationFrequency modulationAmplitude modulationPhase modulationHintAngle modulation is classified into frequency and phase modulation. 77). Which sequence of rectangular pulses is used as a carrier wave?Periodic sequenceAperiodic sequenceBoth a and bNone of the aboveHintPeriodic sequence of rectangular pulses is used as a carrier wave. 78). Noise is a _________ signal.Useful signalUnwanted signalAperiodic signalNone of the aboveHintNoise is an unwanted signal. 79). Which of the following are noise examples?HissBuzzFlickerAll the aboveHintNoise can be of hiss, buzz, flicker types. 80). Hiss sound is observed in.Radio receiversTelephone receiverMobile receiversTelevision receiversHintHiss sound is observed in radio receivers. 81). Buzz sound is observed in.Radio receiversTelephone receiverMobile receiversTelevision receiversHintBuzz sound is observed in the Telephone receiver. 82). Flicker sound is observed in.Radio receiversTelephone receiverMobile receiversTelevision receiversHintFlicker sound is observed in Television receivers. 83). Noise affects _________.System performanceRadioAmplitudeFrequencyHintNoise affects system performance. 84). Noise ________ the operating range of the system.IncreasesDecreasesLimitsNone of the aboveHintNoise limits the operating range of the system. 85). Noise classification is done based on ________.Types of source usedTransmitter usedReceiver usedAll the aboveHintNoise is classified based on types of source used, transmitter-receiver used. 86). Noise is produced by ________.Internal sourceExternal sourceInternal and external source used of a systemNone of the aboveHintNoise is produced by internal and external sources of a system. 87). Examples of external source noise.Atmospheric noiseExtra-terrestrial noiseIndustrial noiseAll the aboveHintExternal noise is produced by external sources, some of the examples are Atmospheric noise, Extra-terrestrial noise, Industrial noise. 88). Examples of internal source noise.Thermal agitationShot noiseTransit timeAll the aboveHintInternal source noise is produced by receiver components while functioning, some of the examples are Thermal agitation, Shot noise, Transit time. 89). SNR stands for?Signal to noise ratioStandard noise rationStandard N turns ratioStandard Noise transmission ratioHintSNR stands for the signal-to-noise ratio. 90). Figure of merit is given as?Ratio of output SNR to input SNROutput SNR valueInput SNR valueBoth a and bHintFigure of merit is the ratio between output SNR and input SNR. 91). Signal is represented in _________ domains.Time domainFrequency domainBoth a and bNone of the aboveHintA signal is represented in both frequency and time domains. 92). Time domain in graphical representation has _______ on the x-axis and _______ on the y axis.Time, amplitudeTime, frequencyFrequency, timeFrequency, amplitudeHintTime-domain in graphical form has time on the x-axis and amplitude on the y-axis. 93). Frequency domain in graphical representation has _______ on the x-axis and _______ on the y axis.Time, amplitudeTime, frequencyFrequency, amplitudeNone of the aboveHintThe frequency-domain in graphical form has frequency on the x-axis and amplitude on the y-axis. 94). Frequency is expressed in terms of ________.HertzCmMetersSecondsHintFrequency is expressed in terms of Hertz. 95). Double sideband full carrier has _________.A carrier and two sidebandsTwo carriers and two side bansOne carrier and one sidebandHas a carrier aloneHintThe double sideband full carrier has a carrier and two sidebands. 96). DSBSC stands for?Double sideband suppressed carrierDouble slide band superior carrierDouble standard band stationary carrierAll the aboveHintDSBSC stands for Double sideband suppressed carrier. 97). What is double sideband suppressed carrier?It is a carrier that is suppressed and saved power is distributed to two sidebandsIt is a carrier that is suppressed on two sidebandsIt is powerful distributed to two sidebandsNone of the aboveHintA double sideband suppressed carrier is a carrier that is suppressed and saved power is distributed to two sidebands. 98). SSBSC stands for?Single sideband suppressed carrierSingle signal suppressed carrierSignal sign the suppressed carrierNone of the aboveHintSSBSC stands for Single sideband suppressed carrier. 99). The process of suppressing one of the sidebands with carrier and transmitting signal is called?Single sideband suppressed carrierDouble sideband suppressed carrierAmplitude modulationDigital modulationHintThe process of suppressing one of the sidebands with carrier and transmitting signal is called Single sideband suppressed carrier. 100). Which of the following are the advantages of sideband modulation?High power signalLow power signalLess noiseBoth a and cHintThe advantages of sideband modulation are high signal power and less noise. 101). Modulation index gives the ratio of ________.The voltage of Modulating signal and carrier voltageCarrier voltage and voltage of Modulating signalThe voltage of Modulating signal and the un-modulates signal voltageNone of the aboveHintModulation index gives the ratio of the voltage of Modulating signal and carrier voltage. It is denoted by “ m “. where m = Vm / Vc. 102). At what condition we can obtain max power output at the transmitter in absence of noise?Voltage of Modulating signal > voltage of the carrierVoltage of Modulating signal <; carrier voltageVoltage of Modulating signal = carrier voltageVoltage of Modulating signal = 0HintWe can obtain max power output at transmitter without distortion at the voltage of Modulating signal = carrier voltage condition. Time is Up!