http://pocs1.blogspot.com/2012/03/types-of-communication-systems.htmlThe most general form of communication system consists of the following components:
|Communication System Generic Block Diagram|
Transmitter:The upper portion of the channel as a whole is called transmitter.
The information provided to a communication system is called baseband. One may define as " any information signal is known as baseband signal".
The baseband signal is passed through some processing unit where necessary operations are performed. These operations may include filtering, sampling etc. This is helpful in separating unwanted information from baseband.
The process of modulation is required to make the baseband signal ready for transmission. The modulator produces a varying signal at its output which is proportional in some way to the signal appearing across its input terminal (baseband signal). For example , a sinusoidal modulator may vary the amplitude, frequency or phase of a sinusoidal signal in direct proportion to the input baseband.
For wireless communication , antenna is used to send modulated information into the channel or medium.
The transmission medium or channel is vital link between the system. Without it there would be no communication problem. The transmission medium may include wired transmission line, atmosphere (wireless) which may include the ionosphere, the trooposphere, free space etc.
It causes noise (unwanted addition to baseband signal) , attenuation and distortion in the form of electrical signal. This results interference with our error-free reception at receiving end.
The portion below the channel as whole called receiver.
The demodulator performs the inverse process of modulator to recover the information signal in its original form.
The RF amplifier is used to tune the receive to frequency of the transmitted bandwidth.
This shows us the received signal in the form by which we are familiar.