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. Electromagnetic Electrical current Electronic sign None of the above HintA signal is an electrical current that carries data from one network to another.2). A signal can be in which form? Audio Video Speech All the above HintA signal can be in audio, video, speech, speech, image forms.3). Modulation is of _____ types. Analog modulation Digital modulation Pulse modulation Spread spectrum modulation All the above HintIn 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 techniques Frequency type modulation FM Amplitude type modulation AM Both a and b None of the above HintExamples 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 transmission It is a process of converting data into analog signals optimized for transmission It is a signal None of the above HintIt 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 modulation Multicarrier modulation Both a and b Only b HintDigital 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 ASK Frequency type shift type keying FSK Phase type shift type keying PSK Orthogonal amplitude modulation QAM All the above HintSingle-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 ASK Frequency type shift keying FSK Orthogonal frequency division multiplexing OFDM None of the above HintMulticarrier modulation uses Orthogonal frequency division multiplexing OFDM methodology.9). What is the function of a modulator? Modulates signal Demodulates signal Maintains signal None of the above HintA modulator modulates signal, by controlling input audio signal called carrier.10). What is the function of demodulation? Modulates signal Demodulates signal Maintains signal None of the above HintA demodulator demodulates the received signal from the modulator.11). What are the units of modulation rate? Seconds Baud Meters Centimeters HintModulation rate is expressed in terms of baud.12). On which component modulation is performed? Transmitter Signal Jammer None of the above HintModulation is performed between transmitter and receiver.13). Which oscillator is used in the transmitter? Crystal oscillator RC oscillator Hartley oscillator Both a and c HintCrystal oscillator used in the transmitter.14). Which type of modulation is used for radio transmission in India? Amplitude modulation Frequency modulation Phase modulation Both a and b HintAmplitude modulation is used in India for radio transmission.15). The useful power in amplitude modulation is carried by ________. Sidebands Carriers Signals Both a and c HintThe 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 Frequency Bandwidth = 4 Frequency Bandwidth = 2 Frequency Bandwidth = 6 Frequency HintIn 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, signal Signal, carrier Signal, signal Carrier, carrier HintIn 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 amplitude When signal amplitude and carrier amplitude are equal When the signal amplitude is equal to zero When the signal amplitude is infinity HintOvermodulation 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? <1 0 >1 Infinity HintThe value of modulation index for under modulation should be less than 1.20). What should be the value of modulation index for perfect modulation? <1 1 >1 Infinity HintThe value of the modulation index for perfect modulation should be 1.21). Modulation index is also called as _________. Modulation wave Modulation height Modulation depth Modulation HintThe modulation index is also called modulation depth.22). Modulation index is denoted as __________. µ Ɵ Φ Ω HintThe modulation index is denoted as µ.23). Percentage modulation is denoted as __________. N m n M HintPercentage modulation is denoted as m.24). If the value of the modulation index is 0.8 then the modulation is called __________. Over modulation Under modulation Perfect modulation Both a and c HintIf 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 modulation Under modulation Perfect modulation Both a and c HintIf the value of the modulation index is 1.3 then the modulation is called over modulation.Modulation Interview Questions26). If the value of the modulation index is 1 then the modulation is called __________. Over modulation Under modulation Perfect modulation Both a and c HintIf the value of the modulation index is 1 then the modulation is called perfect modulation.27). Bandwidth is expressed in terms of __________. Bits per second Hertz Centimeters Seconds HintThe 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 weak More carrier power Distortion Both a and c HintOver modulation is a condition where the modulation index is greater than 1, at this point signal gets distorted.29). Demodulation occurs in __________. Receiving antenna Transmitter Radio receiver None of the above HintDemodulation occurs in a radio receiver.30). Which medium is used in radio transmission? Air Water Space Cable HintSpace 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. Amplitude Frequency Signal Both a and b HintIn 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 _____ limit Line with zero The peak of carrier line Modulated highest point Unmodulated highest point HintModulating 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 information An error is introduced in the information Information gets attenuated None of the above HintWhen 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? Transmitter Modulator Duplexer Receiver HintA 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. 200 83.33 80.33 81 HintModulating 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. 0.5 0.662 0.4 0.55 HintModulation index = m= Vmax – Vmin / Vmax + V min = 5.9 – 1.2 / 5.9 + 1.2 = 0.66237). If carrier voltage is 10v , which voltage of Modulating signal causes over modulation? 11 12.6 12 14 HintWhen 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. 2.35v 2v 2.8v 3v HintVoltage 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 modulation Amplitude modulation Pulse modulation Both a and b HintIn 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 parts 10m 10cm 100m 100cm HintMax wavelength is calculated by the product of assumed wavelength and accurate wavelength; Wavelength = 10 * 1000 = 10m41). Phase comparison cannot be done in which zone? Frequency zone Amplitude zone Phase zone None of the above HintPhase comparison cannot be done in a high-frequency zone.42). Distance transmission is not compatible for ________ frequency. High frequency Low frequency Equal frequency Zero frequency HintLow 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 phase Frequency phase Modern phase None of the above HintThe 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 Hz 678 Hz 825 Hz 900 Hz HintUpper frequency = 850 Hz ; bandwidth = 50 Hz ; low frequency = 850 - 50 = 800 Hz; Carrier frequency = 850 -800 / 2 = 825 Hz45). What is the advantage of an RF amplifier? Good selectivity Good sensitivity Good SNR All the above HintRF 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 MHz 455 KHz 700 Hz 900 Hz Hint455 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 rate the bandwidth of transmission channel is low No synchronization is required All the above HintThe 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 + fi fs + 2fi 2fs + fi 2( fs + fi) HintImage frequency f image = f s + 2 fi.49). What is cross-talk? Disturbance in channel Rejection of frequency Both a and b None of the above HintThe 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 signal Double sideband – SC signal Pulse code modulation signal DM signal HintCostas receiver is used in Double sideband – SC signal, it is a synchronous receiver system.Modulation Quiz Questions and Answers51). What is the job of frequency mixer in a superheterodyne receiver? Amplification Filtering Multiplies incoming signal and locally generated carrier None of the above HintFrequency 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 modulation Digital modulation Amplitude modulation Pulse amplitude modulation HintAmplitude modulation is a continuous wave in analog modulation.53). At what conditions intermediate frequency is selected? At high intermediate frequency it gives weak selectivity High intermediate frequency it is difficult to track signals At low-frequency frequency of image is rejected All the above HintIntermediate 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 frequency At high frequency it has a poor ratio Both a and b None of the above HintThe 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 modulation Frequency modulation Phase modulation Both a and b HintFrequency 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? IF Radio frequency Audio frequency Video frequency HintIn 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 stages After the single stage After two stages After three stages HintAfter 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 equal It is easy to amplify lower frequencies Difference frequency alone can be modulated None of the above HintSince 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 capacitance Reduce noise Stabilize dc bias Increases Q of the tuned circuit HintFerrite antenna, Increases Q of the tuned circuit.60). Which modulation signal controls the frequency of the carrier? Phase modulation Frequency modulation Amplitude modulation None of the above HintIn Frequency modulation, the modulation signal controls the frequency of the carrier.61). What is the advantage of FM over AM? Less noisy in reception Carrier frequency Is high Bandwidth is less Frequency deviation is small HintThe 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 RF RF and AF IF RF and the local oscillator signal HintThe 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 Frequency Intermediate Frequency Audio Before Radio Frequency HintAt the Intermediate Frequency stage of superheterodyne, we can observe selectivity.64). AVC stands for __________. Audio voltage control Automatic volume control Advance voltage control Abrupt voltage control HintAVC stands for Automatic volume control.65). If all the signal frequencies in a radio receiver are amplified equally, then it has a high _______. High sensitivity High fidelity High selectivity High distortion HintIf 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 used It uses a push and pulls the circuit Obtains low fixed intermediate frequency Both a and c HintSuperheterodyne principle obtains low fixed intermediate frequency.67). At what order does signal voltage is induced in the aerial of a radio receiver? mV µV V None of the above HintAt µV order, the signal voltage is induced in aerial of a radio receiver.68). Which type of modulation is a man made called? Amplitude modulation Frequency modulation Pulse modulation Phase modulation HintThe modulation made by man is called amplitude modulation.69). Which type of modulation is used in TV for picture signals? Amplitude modulation Frequency modulation Pulse modulation Phase modulation HintThe type of modulation is used in TV for picture signals is amplitude modulation.70). What happens if the modulation level is increased? Increases carrier power Increases sideband power Increases carrier and sideband power None of the above HintIf the modulation level is increased, sideband power is also increased.71). What is the advantage of using modulation techniques? Antenna size is reduced No signal mixing Improves signal quality All the above HintThe advantage of using modulation techniques are - Antenna size is reduced, No signal mixing, Improves signal quality.72). What is a carrier signal? It has information It does not have information It has amplitude, phase, and frequency Both b and c HintA 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 modulation Carry the bits to receiver after modulation. Listens to channel None of the above HintThe 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 signal It is the product of modulating signal and information signal It is an input signal None of the above HintThe 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 value The product of carrier wave and modulating signal It is a carrier wave It is a modulated wave HintThe carrier wave varies with respect to instantaneous modulating signal value is called angle modulation.Modulation Questions and Answers76). Angle modulation is __________. Frequency and phase modulation Frequency modulation Amplitude modulation Phase modulation HintAngle modulation is classified into frequency and phase modulation.77). Which sequence of rectangular pulses is used as a carrier wave? Periodic sequence Aperiodic sequence Both a and b None of the above HintPeriodic sequence of rectangular pulses is used as a carrier wave.78). Noise is a _________ signal. Useful signal Unwanted signal Aperiodic signal None of the above HintNoise is an unwanted signal.79). Which of the following are noise examples? Hiss Buzz Flicker All the above HintNoise can be of hiss, buzz, flicker types.80). Hiss sound is observed in. Radio receivers Telephone receiver Mobile receivers Television receivers HintHiss sound is observed in radio receivers.81). Buzz sound is observed in. Radio receivers Telephone receiver Mobile receivers Television receivers HintBuzz sound is observed in the Telephone receiver.82). Flicker sound is observed in. Radio receivers Telephone receiver Mobile receivers Television receivers HintFlicker sound is observed in Television receivers.83). Noise affects _________. System performance Radio Amplitude Frequency HintNoise affects system performance.84). Noise ________ the operating range of the system. Increases Decreases Limits None of the above HintNoise limits the operating range of the system.85). Noise classification is done based on ________. Types of source used Transmitter used Receiver used All the above HintNoise is classified based on types of source used, transmitter-receiver used.86). Noise is produced by ________. Internal source External source Internal and external source used of a system None of the above HintNoise is produced by internal and external sources of a system.87). Examples of external source noise. Atmospheric noise Extra-terrestrial noise Industrial noise All the above HintExternal 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 agitation Shot noise Transit time All the above HintInternal 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 ratio Standard noise ration Standard N turns ratio Standard Noise transmission ratio HintSNR stands for the signal-to-noise ratio. 90). Figure of merit is given as? Ratio of output SNR to input SNR Output SNR value Input SNR value Both a and b HintFigure of merit is the ratio between output SNR and input SNR.91). Signal is represented in _________ domains. Time domain Frequency domain Both a and b None of the above HintA 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, amplitude Time, frequency Frequency, time Frequency, amplitude HintTime-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, amplitude Time, frequency Frequency, amplitude None of the above HintThe frequency-domain in graphical form has frequency on the x-axis and amplitude on the y-axis.94). Frequency is expressed in terms of ________. Hertz Cm Meters Seconds HintFrequency is expressed in terms of Hertz.95). Double sideband full carrier has _________. A carrier and two sidebands Two carriers and two side bans One carrier and one sideband Has a carrier alone HintThe double sideband full carrier has a carrier and two sidebands.96). DSBSC stands for? Double sideband suppressed carrier Double slide band superior carrier Double standard band stationary carrier All the above HintDSBSC 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 sidebands It is a carrier that is suppressed on two sidebands It is powerful distributed to two sidebands None of the above HintA 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 carrier Single signal suppressed carrier Signal sign the suppressed carrier None of the above HintSSBSC 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 carrier Double sideband suppressed carrier Amplitude modulation Digital modulation HintThe 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 signal Low power signal Less noise Both a and c HintThe 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 voltage Carrier voltage and voltage of Modulating signal The voltage of Modulating signal and the un-modulates signal voltage None of the above HintModulation 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 carrier Voltage of Modulating signal <; carrier voltage Voltage of Modulating signal = carrier voltage Voltage of Modulating signal = 0 HintWe can obtain max power output at transmitter without distortion at the voltage of Modulating signal = carrier voltage condition. Time is Up! Time's up
