Communications

The first operation in digital communications is the sampling. Almost all the natural signals exist in analog form. For example, voice, any moving scene, environmental data etc. exist in analog or continuous form. Such information can be transmitted from one place to another by continuous modulation of the suitable carrier. Then this type of communication

All the diodes exhibit small junction capacitance in the reverse biased condition. The varactor diodes are specially designed to optimize this characteristic. The junction capacitance of the varactor diode changes as the reverse bias across it is varied. The variations in capacitance of this diose are aide and linear. The varactor diodes provide the junction

The performance of a radio receiver is measured on the basis of its selectivity, sensitivity, fidelity and image frequency rejection. Selectivity   The selectivity is the ability of the receiver to select a signal of a desired frequency while rejecting all others. The selectivity of the receiver is obtained partially by RF amplifier and mainly

The problems of TRF receiver are overcome in this receiver. The superheterodyne receiver converts all incomming RF frequencies to a fixed lower frequency, called Intermediate Frequency (IF). This IF is then amplified and detected to get the original signal. Fig shows the block diagram of superheterodyne receiver. The antenna receives all the frequency signals and

Fig shows the basic elements of a digital communication system. The source and the destination are the two physically separate points. When the signal travels in the communication channel, noise interferes with it. Because of this interference, the smeared or disturbed version of the input signal is received at the receiver. Therefore the signal received

Before discussing about modulation and demodulation directly, we will consider an interesting example first. Let us consider that you want to send some “parcel” from Pune to Nasik. It is obvious that the parcel cannot move from Pune to Nasik on its own. What all you need to do is, to contact some courier company.

From the examples of communication discussed so far, now we can prepare the model of basic communication system. We know that for any communication to take place, three things are essential. They are, Transmitter (talker) Receiver (listener) and Channel or transmission medium. The above three things are present in any communication system. Whenever two people