Basics of Electronic Communication Systems

  • Modulation and Its Necessity
  • Graphical analysis of amplitude modulation

Slide 1: Overview

  • Electronic communication systems transmit information over long distances
  • Modulation is the process of modifying a carrier signal to carry information
  • Amplitude modulation (AM) is a common modulation technique

Slide 2: Modulation

  • In modulation, the baseband signal is superimposed on a carrier signal
  • Modulation allows efficient transmission of information over long distances
  • Types of modulation techniques:
    • Amplitude modulation (AM)
    • Frequency modulation (FM)
    • Phase modulation (PM)

Slide 3: Amplitude Modulation (AM)

  • AM is a modulation technique where the amplitude of the carrier signal is varied
  • The baseband signal is added to the carrier to create sidebands
  • The sidebands carry the information being transmitted
  • AM allows voice and music signals to be transmitted over radio waves
  1. Baseband signal: Represents the information to be transmitted
  1. Carrier signal: High-frequency signal used for transmission
  1. Modulator: Combines baseband and carrier signals to create the modulated signal
  1. Modulated signal: Contains the sidebands with the information
  1. Demodulator: Extracts the baseband signal from the modulated signal

Slide 5: AM Modulation Equation

  • The mathematical expression for AM modulation is:
    • Modulated signal = (Amplitude of carrier + Amplitude of baseband) * Carrier signal
  • The resulting modulated signal consists of the carrier frequency plus the sidebands

Slide 6: Graphical Analysis of AM

  • The graphical representation of AM can be analyzed using time-domain and frequency-domain graphs
  • Time-domain graph shows the variation of the signal with respect to time
  • Frequency-domain graph shows the spectrum of the signal with respect to frequency

Slide 7: Time-Domain Analysis

  • Time-domain graph displays the changes in amplitude of the modulated signal over time
  • The carrier signal is represented by a sine wave
  • The baseband signal modulates the amplitude of the carrier signal

Slide 8: Frequency-Domain Analysis

  • The spectrum of the AM signal consists of the carrier frequency and the sidebands
  • The sidebands are symmetrically spaced around the carrier frequency
  • The bandwidth of an AM signal is twice the highest frequency present in the baseband signal

Slide 9: Example of AM

  • Example Scenario: Transmitting a voice signal over radio waves
  • Voice signal is the baseband signal
  • Carrier signal has a frequency of 1 MHz
  • Modulator combines the voice signal and carrier signal
  • Modulated signal contains the carrier frequency and the sidebands carrying the voice signal

Slide 10: Significance of AM

  • AM is widely used for broadcasting AM radio signals
  • AM allows long-distance transmission and can cover large areas
  • AM signals can be received on simple, low-cost receivers
  • AM signals are less affected by obstacles and can penetrate buildings better than FM signals

Slide 11: Advantages of AM

  • Allows long-distance transmission
  • Can cover large areas with a single transmitter
  • Simple and inexpensive receivers required
  • Can penetrate obstacles and buildings better than FM
  • Well-established technology with widespread use

Slide 12: Disadvantages of AM

  • Susceptible to noise and interference
  • Limited bandwidth and lower audio quality compared to FM
  • Less efficient in power usage compared to FM
  • Limited capacity for multiple channels in a given frequency range
  • Requires careful adjustments for optimal performance

Slide 13: Types of AM

  • Double Sideband - Full Carrier (DSB-FC) AM
    • Modulated signal contains both upper and lower sidebands as well as the carrier
    • Requires more bandwidth than other AM types
  • Double Sideband - Suppressed Carrier (DSB-SC) AM
    • Carrier is completely suppressed, only sidebands are transmitted
    • Requires lower bandwidth than DSB-FC AM
  • Single Sideband (SSB) AM
    • Only one of the sidebands is transmitted, along with the carrier if required
    • Requires even lower bandwidth than DSB-SC AM

Slide 14: Math behind AM

  • AM modulation can be represented mathematically as:
    • $ S(t) = [1 + m \cdot m(t)] \cdot A_c \cdot \cos(2 \pi f_c t) $
    • S(t) represents the modulated signal
    • $ A_c $ is the peak amplitude of the carrier signal
    • $ f_c $ is the frequency of the carrier signal
    • m(t) is the baseband signal
    • m is the modulation index, representing the extent of modulation

Slide 15: Modulation Index

  • The modulation index determines the extent of modulation:
    • m = $ \frac{{A_m}}{{A_c}} $
    • Amplitude of modulating signal (Am)
    • Amplitude of carrier signal (Ac)
  • The modulation index affects the bandwidth of the signal and the quality of modulation

Slide 16: Demodulation

  • The demodulation process involves extracting the baseband signal from the modulated signal
  • There are various demodulation techniques, including envelope detection and synchronous detection
  • Demodulation is essential to retrieve the original information from the modulated signal

Slide 17: Applications of AM

  • Broadcasting: AM radio stations transmit voice, music, news, and other programs
  • Aviation: AM is used for air traffic control and aviation communication
  • Navigation: AM signals are used for radio navigation systems like Non-Directional Beacons (NDBs)
  • Two-Way Radio: AM is commonly used in Citizens Band (CB) radio and amateur radio (HAM)

Slide 18: Comparing AM and FM

  • In Frequency Modulation (FM), the frequency of the carrier signal is varied instead of its amplitude
  • FM provides higher audio quality and less susceptibility to noise than AM
  • FM has a wider bandwidth requirement compared to AM
  • FM signals require more complex receivers and are more expensive to implement

Slide 19: Real-Life Examples

  • Radio Broadcasting: AM radio signals are used by hundreds of stations worldwide
  • AM Walkie-Talkies: Used for communication in various industries and outdoor activities
  • AM Aircraft Communication: AM signals are used for air traffic control and pilot communication
  • AM Naval Communication: AM is used for shortwave marine communications
  • AM Emergency Broadcast Systems: AM is used for emergency alerts and public announcements

Slide 20: Summary

  • Modulation is the process of modifying a carrier signal to carry information
  • Amplitude Modulation (AM) is a widely used modulation technique for broadcasting voice and music signals over radio waves
  • AM uses the variation of the carrier signal’s amplitude to carry the baseband signal
  • AM has advantages like long-distance transmission and simplicity, but also disadvantages like limited bandwidth and susceptibility to noise
  • Different types of AM include DSB-FC, DSB-SC, and SSB AM
  • Demodulation is used to extract the baseband signal from the modulated signal
  • AM has various applications, including broadcasting, aviation, navigation, and two-way radio communication

Slide 21: Advantages of AM

  • Allows long-distance transmission
  • Can cover large areas with a single transmitter
  • Simple and inexpensive receivers required
  • Can penetrate obstacles and buildings better than FM
  • Well-established technology with widespread use

Slide 22: Disadvantages of AM

  • Susceptible to noise and interference
  • Limited bandwidth and lower audio quality compared to FM
  • Less efficient in power usage compared to FM
  • Limited capacity for multiple channels in a given frequency range
  • Requires careful adjustments for optimal performance

Slide 23: Types of AM

  • Double Sideband - Full Carrier (DSB-FC) AM
    • Modulated signal contains both upper and lower sidebands as well as the carrier
    • Requires more bandwidth than other AM types
  • Double Sideband - Suppressed Carrier (DSB-SC) AM
    • Carrier is completely suppressed, only sidebands are transmitted
    • Requires lower bandwidth than DSB-FC AM
  • Single Sideband (SSB) AM
    • Only one of the sidebands is transmitted, along with the carrier if required
    • Requires even lower bandwidth than DSB-SC AM

Slide 24: Math behind AM

  • AM modulation can be represented mathematically as:
    • S(t) = [1 + m * m(t)] * Ac * cos(2 * pi * fc * t)
    • S(t) represents the modulated signal
    • Ac is the peak amplitude of the carrier signal
    • fc is the frequency of the carrier signal
    • m(t) is the baseband signal
    • m is the modulation index, representing the extent of modulation

Slide 25: Modulation Index

  • The modulation index determines the extent of modulation:
    • m = Am / Ac
    • Am is the amplitude of the modulating signal
    • Ac is the amplitude of the carrier signal
  • The modulation index affects the bandwidth of the signal and the quality of modulation

Slide 26: Demodulation

  • The demodulation process involves extracting the baseband signal from the modulated signal
  • There are various demodulation techniques, including envelope detection and synchronous detection
  • Demodulation is essential to retrieve the original information from the modulated signal

Slide 27: Applications of AM

  • Broadcasting: AM radio stations transmit voice, music, news, and other programs
  • Aviation: AM is used for air traffic control and aviation communication
  • Navigation: AM signals are used for radio navigation systems like Non-Directional Beacons (NDBs)
  • Two-Way Radio: AM is commonly used in Citizens Band (CB) radio and amateur radio (HAM)

Slide 28: Comparing AM and FM

  • In Frequency Modulation (FM), the frequency of the carrier signal is varied instead of its amplitude
  • FM provides higher audio quality and less susceptibility to noise than AM
  • FM has a wider bandwidth requirement compared to AM
  • FM signals require more complex receivers and are more expensive to implement

Slide 29: Real-Life Examples

  • Radio Broadcasting: AM radio signals are used by hundreds of stations worldwide
  • AM Walkie-Talkies: Used for communication in various industries and outdoor activities
  • AM Aircraft Communication: AM signals are used for air traffic control and pilot communication
  • AM Naval Communication: AM is used for shortwave marine communications
  • AM Emergency Broadcast Systems: AM is used for emergency alerts and public announcements

Slide 30: Summary

  • Modulation is the process of modifying a carrier signal to carry information
  • Amplitude Modulation (AM) is a widely used modulation technique for broadcasting voice and music signals over radio waves
  • AM uses the variation of the carrier signal’s amplitude to carry the baseband signal
  • AM has advantages like long-distance transmission and simplicity, but also disadvantages like limited bandwidth and susceptibility to noise
  • Different types of AM include DSB-FC, DSB-SC, and SSB AM
  • Demodulation is used to extract the baseband signal from the modulated signal
  • AM has various applications, including broadcasting, aviation, navigation, and two-way radio communication ``