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Saturday, 18 May 2013

Digital Communication

Digital Communication

A digital communication systems offers many advantages to the user, that cannot be achieved with a analog system. Digital communication system may make use of analog links and concepts.

A digital system is a more general case of a binary system. In binary systems, only two signals values can exists. They are often called 0 and 1, but these names represent specific voltages.

The term data is commonly used in digital communication systems. Data is any form of information, that has been put into digital form, so that it can be handled by a digital system. The data itself is measured as bit.(bit is a contraction of the term 'binary digit')

The binary signals are easy to generate and process with digital circuits. These digital circuits are available in the IC form and can generate and process digital data at high speeds.

Wednesday, 1 May 2013

Principle of Radar

Principle of Radar

Radar works on the principle of 'radio echoes'. The transmitter in a radar, radiates the high power electrical pulses into space. When these pulses are incident on any distant target such as a mountain, ship or aircraft, they get scattered in all directions. The transmitter antenna receives a part of the scattered energy. This transmitter antenna also acts as receiving antenna for receiving pulse. The pulse travels with the speed of light 3*108  ms-1.In other words, these pulse cover a distance of 300 meters for every micro second. hence by measuring the time taken by the pulse to reach the target and back to the transmitter, the range or distance of the target can be easily determined. To locate the direction of the target, directional antennas are used.