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In Frequency Modulation (FM), the carrier wave's _____ varies according to the message signal.

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RRB JE ECE 22 Apr 2025 Shift 1 CBT 2 Official Paper
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  1. phase
  2. wavelenth
  3. amplitude
  4. frequency

Answer (Detailed Solution Below)

Option 4 : frequency
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In Frequency Modulation (FM), the carrier wave's frequency varies according to the message signal. 

Explanation:

Frequency Modulation (FM):

Frequency modulation is a method of encoding information in a carrier wave by varying the instantaneous frequency of the wave. It is widely used in radio broadcasting, telecommunications, and signal processing due to its resilience to signal degradation and noise.

Applications: FM is widely used in various applications, including:

  • FM radio broadcasting: FM radio stations use frequency modulation to transmit high-fidelity audio signals over the airwaves.
  • Two-way radio communication: FM is commonly used in walkie-talkies, police radios, and other communication devices due to its noise immunity.
  • Television audio transmission: FM is used to transmit audio signals in analog television broadcasts.
  • Data transmission: FM is used in some data communication systems to achieve reliable and efficient data transfer.

 

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More Frequency Modulation Questions

Q1.Which of the following statements about FM detection using PLL circuit are correct? S1: At the error amplifier output, we get demodulated FM output. S2: FM signal is applied to the input of the PLL.
Q2.According to Carson’s Rule, what is the approximate bandwidth required for a VHF/UHF two-way radio signal using FM with a 5 kHz maximum frequency deviation and a maximum audio frequency of 3 kHz?
Q3.In a PLL-based FM demodulator, the output of the phase detector is proportional to _______.
Q4.In Frequency Modulation (FM), the carrier wave's _____ varies according to the message signal.
Q5.A modulating signal m(t) = 10cos (2π × 103 t) is amplitude modulated with a carrier signal c(t) = 50cos(2π × 105t). Assume R = 1Ω. Find the carrier power required for transmitting this AM wave.
Q6.An audio signal s(t) is normalized, whose Fourier transform S(f) is shown in the figure, so that |s(t)| ≤ 1. This signal is to be transmitted using FM with a frequency deviation constant kf = 90 kHz/V. What is the bandwidth required for transmission of the FM audio signal?
Q7.An FM audio signal with single-tone modulation has a frequency deviation of 25 kHz and a bandwidth of 75 kHz. What is the frequency of the modulating signal using Carson's rule?
Q8.An FM modulator operates at carrier frequency of 250 kHz with frequency deviation sensitivity of 1.5 kHz/V. A PM modulator operates at carrier frequency of 500 kHz with phase deviation sensitivity of 1.5 rad/V. If both FM and PM modulators are modulated by the same modulating signal having peak amplitude of 5 V and modulating frequency of 5 kHz, then what is the relationship between frequency modulation index and phase modulation index?
Q9.Let a frequency modulated (FM) signal  \(\rm x(t)=A\cos(\omega_ct+k_f\int_{-\infty}^{t}m(\lambda)d\lambda)\), where 𝑚(𝑡) is a message signal of bandwidth W. It is passed through a non-linear system with output 𝑦(𝑡) = 2𝑥(𝑡) + 5(𝑥(𝑡))2 . Let 𝐵𝑇 denote the FM bandwidth. The minimum value of 𝜔𝑐 required to recover 𝑥(𝑡) from 𝑦(𝑡) is

More Angle Modulation Questions

Q1.Which of the following statements about the AM detection using PLL circuit is/are correct? S1: It has higher noise immunity than the conventional peak detector type AM detector. S2: The PLL is locked to the carrier frequency of the AM signal.
Q2.Which of the following statements about FM detection using PLL circuit are correct? S1: At the error amplifier output, we get demodulated FM output. S2: FM signal is applied to the input of the PLL.
Q3.According to Carson’s Rule, what is the approximate bandwidth required for a VHF/UHF two-way radio signal using FM with a 5 kHz maximum frequency deviation and a maximum audio frequency of 3 kHz?
Q4.In a PLL-based FM demodulator, the output of the phase detector is proportional to _______.
Q5.In Frequency Modulation (FM), the carrier wave's _____ varies according to the message signal.
Q6.Which of the following statements w.r.t. FSK demodulation using PLL circuit is/are correct? S1: If the input signal frequency changes, the PLL adjusts its frequency output to match the input frequency. S2: The phase-locked loop is used to track the changes in the frequency of the modulated signal.
Q7.For 8-ary signal or symbol the number of likelihood functions are :
Q8.A modulating signal m(t) = 10cos (2π × 103 t) is amplitude modulated with a carrier signal c(t) = 50cos(2π × 105t). Assume R = 1Ω. Find the carrier power required for transmitting this AM wave.
Q9.In phase modulation, frequency deviation is-

More Communication Systems Questions

Q1.Which of the following components is required to detect (demodulate) Pulse Position Modulation (PPM)? a) Pulse Generator b) RS Flip-Flop c) PWM Demodulator
Q2.Which of the following statements about the AM detection using PLL circuit is/are correct? S1: It has higher noise immunity than the conventional peak detector type AM detector. S2: The PLL is locked to the carrier frequency of the AM signal.
Q3.In a 100% modulated AM signal with a carrier power of 100 W, what is the power in the lower sideband?
Q4.Which of the following is NOT a commonly used pulse-shaping filter in communication systems?
Q5.In which modulation technique is the carrier modulated using phase shifts of 0°, 90°, 180°, and 270°?
Q6.What is another name for PWM in communication engineering?
Q7.Which of the following statements about FM detection using PLL circuit are correct? S1: At the error amplifier output, we get demodulated FM output. S2: FM signal is applied to the input of the PLL.
Q8.In PLL as frequency synthesizer, if the crystal oscillator having frequency 500 MHz is passed through divide by 2 network, then the input frequency to PLL is _______ MHz.
Q9.The following block diagram represents which type of signal generation in communication?
Q10.What is a primary application of VSB (Vestigial Sideband) modulation?
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