Slide 1: Introduction to Amplitude Modulation

  • Definition: Amplitude modulation (AM) is a modulation technique used in electronic communication for transmitting information through a carrier wave.
  • In AM, the amplitude of the carrier wave is varied in accordance with the instantaneous amplitude of the modulating signal.
  • AM is widely used in broadcasting, especially for AM radio transmissions.
  • The main advantage of AM is its simplicity, but it is limited in terms of bandwidth efficiency.

Slide 2: Carrier Wave and Modulating Signal

  • Carrier Wave: The high-frequency sine wave that is used to carry the information is called the carrier wave.
  • Modulating Signal: The time-varying signal that contains the information to be transmitted is called the modulating signal.

Slide 3: Amplitude Modulated Waveform

  • A modulated waveform is obtained by multiplying the carrier wave with the modulating signal.
  • The amplitude of the carrier wave changes in proportion to the instantaneous amplitude of the modulating signal.
  • The variation in the amplitude of the carrier wave encodes the information carried by the modulating signal.

Slide 4: Equation for Amplitude Modulation

  • The equation for amplitude modulation can be represented as:
    • AM(t) = (Ac + Am sin ωmt) sin ωct
    • AM(t): Amplitude Modulated Waveform
    • Ac: Amplitude of the carrier wave
    • Am: Amplitude of the modulating signal
    • ωct: Angular frequency of the carrier wave
    • ωmt: Angular frequency of the modulating signal

Slide 5: Modulation Index

  • Modulation Index, denoted by µ, determines the extent of variation in the amplitude of the carrier wave.
  • It is defined as the ratio of the amplitude of the modulating signal to the amplitude of the carrier wave.
  • Modulation Index (µ) = Am / Ac

Slide 6: Types of AM Waves

  • There are two types of Amplitude Modulated Waves:
    1. Double Sideband - Full Carrier (DSB-FC): Both upper and lower sidebands are transmitted along with the carrier wave.
    2. Double Sideband - Suppressed Carrier (DSB-SC): The carrier wave is suppressed, and only the upper and lower sidebands are transmitted.

Slide 7: Generation of AM Waves

  • Procedure to Generate Amplitude Modulated Waves:
    1. Oscillator generates a carrier wave with high frequency.
    2. Modulating signal modifies the amplitude of the carrier wave.
    3. Mixer combines the carrier wave and modulating signal to obtain the modulated waveform.

Slide 8: Example: AM Radio Transmission

  • AM radio uses the amplitude modulation technique for transmitting audio signals over long distances.
  • The audio signal, which includes music or voice, is used as the modulating signal.
  • The carrier wave is generated using a high-frequency oscillator.
  • The modulated waveform is transmitted through antennas and received by radio receivers.

Slide 9: Advantages of AM

  • Simplicity: AM modulation technique is simple and easy to implement.
  • Compatibility: AM receivers can receive signals from multiple AM transmitters at the same frequency.
  • Coverage: AM signals can propagate over long distances due to their lower frequency range.

Slide 10: Disadvantages of AM

  • Low Bandwidth Efficiency: AM signals occupy a large bandwidth, which limits the number of simultaneous transmissions.
  • Susceptible to Noise: AM signals are more prone to noise and interference, affecting the quality of the received signals.
  • Limited Quality: AM signals may have lower audio quality compared to FM signals.
  1. Amplitude and Phase Frequency Modulation
  • Amplitude modulation (AM) and frequency modulation (FM) are two common modulation techniques used in electronic communication.
  • In AM, the amplitude of the carrier wave is varied, while in FM, the frequency of the carrier wave is varied.
  • Phase frequency modulation (PM) is a variation of FM, where the phase of the carrier wave is varied instead of the frequency.
  1. Advantages of Frequency Modulation (FM)
  • Better Signal Quality: FM signals are less susceptible to noise and interference, resulting in improved signal quality.
  • Greater Bandwidth Efficiency: FM signals occupy a narrower bandwidth, allowing for more simultaneous transmissions.
  • Higher Fidelity: FM signals provide a higher fidelity audio quality compared to AM.
  1. Disadvantages of Frequency Modulation (FM)
  • More Complex Implementation: FM modulation technique is more complex and requires precise frequency control.
  • Limited Coverage: FM signals have a limited range compared to AM signals due to higher frequency attenuation.
  • Less Compatibility: FM receivers can only receive signals from FM transmitters operating at the same frequency and modulation index.
  1. Frequency Deviation in FM
  • Frequency deviation, denoted by Δf, is a key parameter in FM, representing the maximum variation in frequency from the carrier’s center frequency.
  • It determines the extent of frequency modulation and is measured in Hertz (Hz).
  • The frequency deviation is directly proportional to the amplitude of the modulating signal.
  1. Equation for Frequency Modulation (FM)
  • The equation for frequency modulation can be represented as:
    • FM(t) = Ac sin (ωct + β sin ωmt)
    • FM(t): Frequency Modulated Waveform
    • Ac: Amplitude of the carrier wave
    • ωct: Angular frequency of the carrier wave
    • β: Modulation index (β=Δf / fm)
    • ωmt: Angular frequency of the modulating signal
    • Δf: Maximum frequency deviation
    • fm: Maximum frequency of the modulating signal
  1. Generation of FM Waves
  • The generation of frequency modulated (FM) waves involves the process of frequency modulation, where the frequency of the carrier wave is varied.
  • The modulating signal is used to modify the frequency of the carrier wave.
  • The final output is a frequency modulated waveform that carries the information from the modulating signal.
  1. Example: FM Radio Transmission
  • FM radio transmission uses frequency modulation to transmit audio signals over long distances with improved sound quality.
  • The audio signal, containing music or voice, is used as the modulating signal.
  • The carrier wave is generated using a high-frequency oscillator.
  • The modulated waveform is transmitted through antennas and received by FM radio receivers.
  1. Phase Frequency Modulation (PM)
  • Phase frequency modulation (PM) is a variation of frequency modulation (FM) where the phase of the carrier wave is varied instead of the frequency.
  • PM is commonly used in digital communication systems and is known for its robustness against noise.
  • The modulating signal directly influences the phase of the carrier wave, resulting in varying phase shifts.
  1. Phase Deviation in PM
  • Phase deviation, denoted by Δθ, is a crucial parameter in PM, representing the maximum variation in phase from the carrier’s center phase.
  • It determines the extent of phase modulation and is measured in radians.
  • The phase deviation is directly proportional to the amplitude of the modulating signal.
  1. Equation for Phase Frequency Modulation (PM)
  • The equation for phase frequency modulation can be represented as:
    • PM(t) = Ac sin (ωct + β sin (ωmt + δ))
    • PM(t): Phase Frequency Modulated Waveform
    • Ac: Amplitude of the carrier wave
    • ωct: Angular frequency of the carrier wave
    • β: Modulation index (β =Δθ / φm)
    • ωmt: Angular frequency of the modulating signal
    • φm: Maximum phase of the modulating signal
    • Δθ: Maximum phase deviation
    • δ: Phase deviation constant

Slide 21: Amplitude and Phase Frequency Modulation

  • Amplitude modulation (AM) and frequency modulation (FM) are two common modulation techniques used in electronic communication.
  • In AM, the amplitude of the carrier wave is varied, while in FM, the frequency of the carrier wave is varied.
  • Phase frequency modulation (PM) is a variation of FM, where the phase of the carrier wave is varied instead of the frequency.

Slide 22: Procedure to Generate Amplitude Modulated Waves

  • Oscillator generates a carrier wave with high frequency.
  • Modulating signal modifies the amplitude of the carrier wave.
  • Mixer combines the carrier wave and modulating signal to obtain the modulated waveform.
  • Example: AM radio transmission uses this procedure to transmit audio signals over long distances.

Slide 23: Generation of Amplitude Modulated Wave

  • The modulating signal is a low-frequency audio signal.
  • The carrier wave is a high-frequency sine wave.
  • The modulating signal is multiplied with the carrier wave to obtain the amplitude modulated waveform.
  • The variation in the amplitude of the carrier wave encodes the information carried by the modulating signal.

Slide 24: Example: AM Modulation of a 1000 Hz Signal

  • Carrier Wave Frequency: 1 MHz (1,000,000 Hz)
  • Modulating Signal Frequency: 1,000 Hz (1 kHz)
  • Modulation Index (µ): 0.5
  • The amplitude of the carrier wave varies with the amplitude of the modulating signal.

Slide 25: Equation for Amplitude Modulation

  • The equation for amplitude modulation can be represented as:
    • AM(t) = (Ac + Am sin ωmt) sin ωct
    • AM(t): Amplitude Modulated Waveform
    • Ac: Amplitude of the carrier wave
    • Am: Amplitude of the modulating signal
    • ωct: Angular frequency of the carrier wave
    • ωmt: Angular frequency of the modulating signal

Slide 26: Procedure to Generate Frequency Modulated Waves

  • Oscillator generates a carrier wave with high frequency.
  • Modulating signal modifies the frequency of the carrier wave.
  • Phase modulator or frequency modulator is used to apply phase shifts corresponding to the modulating signal.
  • Example: FM radio transmission follows this procedure to transmit audio signals.

Slide 27: Generation of Frequency Modulated Wave

  • The modulating signal is a low-frequency audio signal.
  • The carrier wave is a high-frequency sine wave.
  • The frequency of the carrier wave changes proportionally to the instantaneous amplitude of the modulating signal.
  • Frequency deviation determines the extent of frequency modulation.

Slide 28: Example: FM Modulation of a 1000 Hz Signal

  • Carrier Wave Frequency: 100 MHz
  • Modulating Signal Frequency: 1,000 Hz
  • Frequency Deviation: 50 kHz
  • The frequency of the carrier wave changes with the amplitude of the modulating signal.

Slide 29: Equation for Frequency Modulation

  • The equation for frequency modulation can be represented as:
    • FM(t) = Ac sin (ωct + β sin ωmt)
    • FM(t): Frequency Modulated Waveform
    • Ac: Amplitude of the carrier wave
    • ωct: Angular frequency of the carrier wave
    • β: Modulation index (β = Δf / fm)
    • ωmt: Angular frequency of the modulating signal
    • Δf: Maximum frequency deviation
    • fm: Maximum frequency of the modulating signal

Slide 30: Conclusion

  • Amplitude modulation (AM), frequency modulation (FM), and phase modulation (PM) are important modulation techniques in electronic communication.
  • AM is simple but has low bandwidth efficiency and is susceptible to noise.
  • FM provides better signal quality and higher bandwidth efficiency.
  • PM is a variation of FM where the phase of the carrier wave is varied.
  • Understanding these modulation techniques is crucial in various communication systems.