Digital Communications Notes
Chapter-1: Introduction The purpose of a Communication System is to transport an information bearing signal from a source to a user destination via a communication channel. MODEL OF A COMMUNICATION SYSTEM(ANALOG)
Information Source and Input Transducer
I/P Signal
TRANSMITTER CHANNEL
Destination and Output Transducer
O/P Signal
RECEIVER
Fig. 1.1: Block diagram of Communication System. The three basic elements of every communication systems are Transmitter, Receiver and Channel. The Overall purpose of this system is to transfer information from one point (called Source) to another point, the user destination. The message produced by a source, normally, is not electrical. Hence an input transducer is used for converting the message to a time – varying electrical quantity called message signal. Similarly, at the destination point, another transducer converts the electrical waveform to the appropriate message. The transmitter is located at one point in space, the receiver is located at some other point separate from the transmitter, and the channel is the medium that provides the electrical connection between them. The purpose of the transmitter is to transform the message signal produced by the source of information into a form suitable for transmission over the channel. The received signal is normally corrupted version of the transmitted signal, which is due to channel imperfections, noise and interference from other sources.The receiver has the task of operating on the received signal so
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as to reconstruct a recognizable form of the original message signal and to deliver it to the user destination. Communication Systems are divided into 3 categories: 1. Analog Communication Systems are designed to transmit analog information using analog modulation methods. 2. Digital Communication Systems are designed for transmitting digital information using digital modulation
Information Source and Input Transducer
I/P Signal
TRANSMITTER CHANNEL
Destination and Output Transducer
O/P Signal
RECEIVER
Fig. 1.1: Block diagram of Communication System. The three basic elements of every communication systems are Transmitter, Receiver and Channel. The Overall purpose of this system is to transfer information from one point (called Source) to another point, the user destination. The message produced by a source, normally, is not electrical. Hence an input transducer is used for converting the message to a time – varying electrical quantity called message signal. Similarly, at the destination point, another transducer converts the electrical waveform to the appropriate message. The transmitter is located at one point in space, the receiver is located at some other point separate from the transmitter, and the channel is the medium that provides the electrical connection between them. The purpose of the transmitter is to transform the message signal produced by the source of information into a form suitable for transmission over the channel. The received signal is normally corrupted version of the transmitted signal, which is due to channel imperfections, noise and interference from other sources.The receiver has the task of operating on the received signal so
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www.Vidyarthiplus.com Einstein College of Engineering
as to reconstruct a recognizable form of the original message signal and to deliver it to the user destination. Communication Systems are divided into 3 categories: 1. Analog Communication Systems are designed to transmit analog information using analog modulation methods. 2. Digital Communication Systems are designed for transmitting digital information using digital modulation