Modulation Question & Answers March 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 None Hint 2). A signal can be in which form? Audio Video Speech All the above None Hint 3). Modulation is of _____ types. Analog modulation Digital modulation Pulse modulation Spread spectrum modulation All the above None Hint 4). Examples of analog modulation techniques Frequency type modulation FM Amplitude type modulation AM Both a and b None of the above None Hint 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 None Hint Read more about Modulation None 6). What are the different types of digital modulation? Single carrier modulation Multicarrier modulation Both a and b Only b None Hint 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 None Hint 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 None Hint 9). What is the function of a modulator? Modulates signal Demodulates signal Maintains signal None of the above None Hint 10). What is the function of demodulation? Modulates signal Demodulates signal Maintains signal None of the above None Hint 11). What are the units of modulation rate? Seconds Baud Meters Centimeters None Hint 12). On which component modulation is performed? Transmitter Signal Jammer None of the above None Hint 13). Which oscillator is used in the transmitter? Crystal oscillator RC oscillator Hartley oscillator Both a and c None Hint 14). Which type of modulation is used for radio transmission in India? Amplitude modulation Frequency modulation Phase modulation Both a and b None Hint 15). The useful power in amplitude modulation is carried by ________. Sidebands Carriers Signals Both a and c None Hint 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 None Hint 17). In AM, the strength of _____ is varied with respect to the strength of _____. Carrier, signal Signal, carrier Signal, signal Carrier, carrier None Hint 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 None Hint 19). What should be the value of modulation index for under modulation? <1 0 >1 Infinity None Hint 20). What should be the value of modulation index for perfect modulation? <1 1 >1 Infinity None Hint 21). Modulation index is also called as _________. Modulation wave Modulation height Modulation depth Modulation None Hint 22). Modulation index is denoted as __________. µ Ɵ Φ Ω None Hint 23). Percentage modulation is denoted as __________. N m n M None Hint 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 None Hint 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 None Hint Modulation Interview Questions 26). If the value of the modulation index is 1 then the modulation is called __________. Over modulation Under modulation Perfect modulation Both a and c None Hint 27). Bandwidth is expressed in terms of __________. Bits per second Hertz Centimeters Seconds None Hint 28). What happens when overmodulation occurs? Signal gets weak More carrier power Distortion Both a and c None Hint 29). Demodulation occurs in __________. Receiving antenna Transmitter Radio receiver None of the above None Hint 30). Which medium is used in radio transmission? Air Water Space Cable None Hint 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 None Hint 32). Modulating signal has a reference line up to _____ limit Line with zero The peak of carrier line Modulated highest point Unmodulated highest point None Hint 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 None Hint 34). Which circuit is used to produce Amplitude Modulation? Transmitter Modulator Duplexer Receiver None Hint 35). The signal is modulated at 7.5 V and carrier voltage is of 9V, calculate modulation percentage. 200 83.33 80.33 81 None Hint 36). If Vmax = 5.9v and Vmin = 1.2V, calculate modulation index. 0.5 0.662 0.4 0.55 None Hint 37). If carrier voltage is 10v , which voltage of Modulating signal causes over modulation? 11 12.6 12 14 None Hint 38). Find voltage of modulating signal, if Vmin and Vmax are 5.9 v and 1.2v. 2.35v 2v 2.8v 3v None Hint 39). Which modulation technique is equipped in all EDM instruments? Frequency modulation Amplitude modulation Pulse modulation Both a and b None Hint 40). Calculate the maximum value of wavelength, if accuracy is 10mm for 1/1000 parts 10m 10cm 100m 100cm None Hint 41). Phase comparison cannot be done in which zone? Frequency zone Amplitude zone Phase zone None of the above None Hint 42). Distance transmission is not compatible for ________ frequency. High frequency Low frequency Equal frequency Zero frequency None Hint 43). Which phase technique is capable of resolving wavelength? Amplitude phase Frequency phase Modern phase None of the above None Hint 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 None Hint 45). What is the advantage of an RF amplifier? Good selectivity Good sensitivity Good SNR All the above None Hint 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 None Hint 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 None Hint 48). What is the formula of image frequency? fs + fi fs + 2fi 2fs + fi 2( fs + fi) None Hint 49). What is cross-talk? Disturbance in channel Rejection of frequency Both a and b None of the above None Hint 50). What is the need for costas receiver? FM signal Double sideband – SC signal Pulse code modulation signal DM signal None Hint Modulation Quiz Questions and Answers 51). What is the job of frequency mixer in a superheterodyne receiver? Amplification Filtering Multiplies incoming signal and locally generated carrier None of the above None Hint 52). Which of the following is a continuous wave in analog modulation? Pulse code modulation Digital modulation Amplitude modulation Pulse amplitude modulation None Hint 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 None Hint 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 None Hint 55). What kind of modulation is used in television for sound signal? Amplitude modulation Frequency modulation Phase modulation Both a and b None Hint 56). At what frequency RF and detection stages are tuned in a TRF radio receiver? IF Radio frequency Audio frequency Video frequency None Hint 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 None Hint 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 None Hint 59). What does ferrite antenna does? Reduce stray capacitance Reduce noise Stabilize dc bias Increases Q of the tuned circuit None Hint 60). Which modulation signal controls the frequency of the carrier? Phase modulation Frequency modulation Amplitude modulation None of the above None Hint 61). What is the advantage of FM over AM? Less noisy in reception Carrier frequency Is high Bandwidth is less Frequency deviation is small None Hint 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 None Hint 63). At what stage of superheterodyne we can observe selectivity? Radio Frequency Intermediate Frequency Audio Before Radio Frequency None Hint 64). AVC stands for __________. Audio voltage control Automatic volume control Advance voltage control Abrupt voltage control None Hint 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 None Hint 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 None Hint 67). At what order does signal voltage is induced in the aerial of a radio receiver? mV µV V None of the above None Hint 68). Which type of modulation is a man made called? Amplitude modulation Frequency modulation Pulse modulation Phase modulation None Hint 69). Which type of modulation is used in TV for picture signals? Amplitude modulation Frequency modulation Pulse modulation Phase modulation None Hint 70). What happens if the modulation level is increased? Increases carrier power Increases sideband power Increases carrier and sideband power None of the above None Hint 71). What is the advantage of using modulation techniques? Antenna size is reduced No signal mixing Improves signal quality All the above None Hint 72). What is a carrier signal? It has information It does not have information It has amplitude, phase, and frequency Both b and c None Hint 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 None Hint 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 None Hint 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 None Hint Modulation Questions and Answers 76). Angle modulation is __________. Frequency and phase modulation Frequency modulation Amplitude modulation Phase modulation None Hint 77). Which sequence of rectangular pulses is used as a carrier wave? Periodic sequence Aperiodic sequence Both a and b None of the above None Hint 78). Noise is a _________ signal. Useful signal Unwanted signal Aperiodic signal None of the above None Hint 79). Which of the following are noise examples? Hiss Buzz Flicker All the above None Hint 80). Hiss sound is observed in. Radio receivers Telephone receiver Mobile receivers Television receivers None Hint 81). Buzz sound is observed in. Radio receivers Telephone receiver Mobile receivers Television receivers None Hint 82). Flicker sound is observed in. Radio receivers Telephone receiver Mobile receivers Television receivers None Hint 83). Noise affects _________. System performance Radio Amplitude Frequency None Hint 84). Noise ________ the operating range of the system. Increases Decreases Limits None of the above None Hint 85). Noise classification is done based on ________. Types of source used Transmitter used Receiver used All the above None Hint 86). Noise is produced by ________. Internal source External source Internal and external source used of a system None of the above None Hint 87). Examples of external source noise. Atmospheric noise Extra-terrestrial noise Industrial noise All the above None Hint 88). Examples of internal source noise. Thermal agitation Shot noise Transit time All the above None Hint 89). SNR stands for? Signal to noise ratio Standard noise ration Standard N turns ratio Standard Noise transmission ratio None Hint 90). Figure of merit is given as? Ratio of output SNR to input SNR Output SNR value Input SNR value Both a and b None Hint 91). Signal is represented in _________ domains. Time domain Frequency domain Both a and b None of the above None Hint 92). Time domain in graphical representation has _______ on the x-axis and _______ on the y axis. Time, amplitude Time, frequency Frequency, time Frequency, amplitude None Hint 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 None Hint 94). Frequency is expressed in terms of ________. Hertz Cm Meters Seconds None Hint 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 None Hint 96). DSBSC stands for? Double sideband suppressed carrier Double slide band superior carrier Double standard band stationary carrier All the above None Hint 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 None Hint 98). SSBSC stands for? Single sideband suppressed carrier Single signal suppressed carrier Signal sign the suppressed carrier None of the above None Hint 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 None Hint 100). Which of the following are the advantages of sideband modulation? High power signal Low power signal Less noise Both a and c None Hint 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 None Hint 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 None Hint Time's up
