Virtual Labs

Analog amplitude, frequency and phase modulation and demodulation with spectrum analysis

1. In a standard Amplitude Modulation (AM) system with a single-tone message signal, which of the following correctly describes the frequency components present in the modulated signal?

a: Only the carrier frequency and the lower sideband are present. Explanation

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b: Only the upper sideband and baseband frequencies are present. Explanation

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c: The carrier, upper sideband, and lower sideband frequencies are present. Explanation

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d: The modulated signal contains frequencies unrelated to the message or carrier. Explanation

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2. Which of the following statements best explains the spectral behavior of a frequency modulated (FM) signal when the amplitude of the modulating signal is increased?

a: The bandwidth remains the same, as FM does not depend on amplitude. Explanation

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b: The number of significant sidebands increases, leading to a wider bandwidth. Explanation

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c: The carrier frequency shifts, but bandwidth remains fixed. Explanation

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d: The FM signal collapses into an AM signal at high modulation index. Explanation

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3. What is the main advantage of using Phase Modulation (PM) over Amplitude Modulation (AM)?

a: PM is less susceptible to noise. Explanation

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b: PM requires less bandwidth. Explanation

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c: PM is easier to implement. Explanation

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d: PM has a simpler demodulation process. Explanation

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4. In which modulation technique does the bandwidth of the signal depend on the amplitude of the modulating signal?

a: Amplitude Modulation (AM) Explanation

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b: Frequency Modulation (FM) Explanation

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c: Phase Modulation (PM) Explanation

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d: None of the above Explanation

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5. Which of the following correctly describes the relationship between carrier frequency and modulating signal in Amplitude Modulation (AM)?

a: The carrier frequency remains constant. Explanation

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b: The carrier frequency varies with the modulating signal. Explanation

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c: The carrier frequency increases with the modulating signal. Explanation

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d: The carrier frequency decreases with the modulating signal. Explanation

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6. In Phase Modulation (PM), how is the modulating signal encoded?

a: By varying the amplitude of the carrier signal. Explanation

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b: By varying the frequency of the carrier signal. Explanation

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c: By varying the phase of the carrier signal. Explanation

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d: By varying the power of the carrier signal. Explanation

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7. What is the primary cause of distortion in an Amplitude Modulated (AM) signal?

a: Noise interference Explanation

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b: Non-linearities in the modulating signal Explanation

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c: High modulation index Explanation

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d: Low carrier frequency Explanation

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8. What happens to the carrier signal's frequency in Frequency Modulation (FM) when the modulating signal increases in amplitude?

a: It increases in frequency. Explanation

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b: It decreases in frequency. Explanation

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c: It remains constant. Explanation

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d: It increases or decreases depending on the modulating signal. Explanation

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9. In a Phase Modulated (PM) system, if the frequency of the modulating signal increases, what effect does this have on the phase of the carrier signal?

a: The phase changes more rapidly. Explanation

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b: The phase changes more slowly. Explanation

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c: The phase remains unchanged. Explanation

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d: The phase change becomes unpredictable. Explanation

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10. What is the significance of the modulation index in Amplitude Modulation (AM)?

a: It determines the efficiency of the AM signal. Explanation

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b: It determines the bandwidth of the AM signal. Explanation

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c: It determines the power of the AM signal. Explanation

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d: It determines the distortion in the AM signal. Explanation

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