INTRODUCTION TO COMMUNICATION SYSTEM:
Communication is the process of establishing connection (or link) between two points for information exchange.
The Science of Communications involving long distances is called Telecommunication ( the world Tele standing for long distance)
The Two basic types of communication systems are
In Analog Systems: Both the information and the carrier are analog signals.
In Digital Systems: The digital pulses are transferred between two or more points in a communication system.
The modulation systems or techniques in which one of the characteristics of the carrier is changed in proportion with the instantaneous value of modulating signal is called analog communication system.
Advantages of Analog communications
· Transmitters and Receivers are simple
· Low bandwidth requirement
· FDM can be used
Disadvantages of analog communication
· Noise affects the signal quality
· It is not possible to separate noise and signal
· Repeaters can‘t be used between transmitte
· Coding is not possible
· It is not suitable for the transmission of secret information
General Communication Systems:
Fig: Block diagram of a general communication system
Drawbacks of Baseband Transmission (without Modulation)
· Excessively large antenna heights.
· Signals get mixed up.
· Short range of communication.
· Multiplexing is not possible.
· Poor quality of reception.
The above drawbacks can be overcome by means of modulation techniques: