UP Board - Class 12 physics - Chapter 15: Communication Systems Handwritten Notes
A communication system is a set of equipment and protocols used for transmitting information from a source to a destination. This chapter deals with the basics of communication systems, including the components involved, methods of transmission, and types of modulation used in communication technologies.
Key Points:
Basic Elements of a Communication System:
- Source of Information: The entity that generates the message (e.g., a person, a computer).
- Transmitter: Converts the information into a signal suitable for transmission (e.g., modulation of the signal).
- Transmission Medium: The physical pathway through which the signal is transmitted (e.g., air, optical fibers, coaxial cables).
Types of Signals:
- Analog Signals: Continuous signals that vary in amplitude and frequency, representing data in a continuous form.
- Digital Signals: Discrete signals represented by binary values (0 and 1). Digital communication systems are more reliable and less prone to noise.
Modulation:
- Modulation is the process of modifying a carrier signal to transmit information over a medium. The carrier wave is altered in terms of amplitude, frequency, or phase to carry the information signal.
- Amplitude Modulation (AM): The amplitude of the carrier wave is varied according to the information signal.
- Frequency Modulation (FM): The frequency of the carrier wave is varied in accordance with the information signal.
Types of Communication Systems:
- Analog Communication Systems: Use analog signals for transmission, typically used for broadcasting (e.g., AM radio, television).
- Digital Communication Systems: Use digital signals for transmission, more accurate and efficient for long-distance communication.
- Satellite Communication: Uses satellites for transmitting signals over long distances, typically used for television broadcasting, GPS, and international communication.
Noise in Communication Systems:
- Noise refers to any unwanted signal or disturbance that interferes with the transmission of the message. It can distort or degrade the quality of the received signal.
- Types of noise include thermal noise, impulse noise, and cross-talk.
Multiplexing:
- Multiplexing is the technique of combining multiple signals into one signal over a shared medium, maximizing the use of available bandwidth.
- Frequency Division Multiplexing (FDM): Different frequency bands are used for transmitting multiple signals simultaneously.
- Time Division Multiplexing (TDM): Different signals are transmitted in different time slots over the same frequency.
Bandwidth and Data Rate:
- Bandwidth: The range of frequencies that a communication channel can carry. A wider bandwidth allows for higher data transmission rates.
- Data Rate: The speed at which data is transmitted, typically measured in bits per second (bps).
Applications of Communication Systems:
- Telecommunication: Systems for voice and data communication, including mobile phones and the internet.
- Broadcasting: Transmission of radio and television signals to a wide audience.
- Satellite Communication: Used in global communication, GPS systems, and weather forecasting.
Conclusion:
Communication systems are integral to modern society, enabling the transfer of information across vast distances. From analog signals to sophisticated digital communication, these systems have evolved with advancements in technology. The study of modulation, multiplexing, and noise management is crucial to ensuring efficient, reliable communication.
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