History of Electronics

Recently we have witnessed the biggest event in the history of electronics – the invention of the semiconductor devices. It made a real revolution in the world of electronics. The semiconductors are small, accurate and low cost devices. Transistors and diodes are made of crystalline solid materials, which have electrical properties that are capable of variations, an extremely wide range, by the addition of little quantities of other elements like resistors, inductors and capacitors. Early semiconductors were produced using germanium as the material, but since 1960 silicon quickly became the preferred material, because it was less expensive and it could operate in wide range of the temperatures. Since 1960 transistors have quickly supplanted vacuum tubes. Electronic system became more complex and smart. Computers included hundred of thousands of transistors each. This fact, together with the need for compact, lightweight electronic missile guidance systems, led to the invention of the integrated circuit (IC). Early ICs contained about 10 individual semiconductor elements but their number rapidly increased during next ten years. In 1970 the number was 1,000 in a chip and the result of hard work of physicists, electronics and mechanical engineers was developing and producing of first microprocessor with memory interface in 1971. This event was the beginning of computerization and smart digital electronics.

UNIT 3

AM Receivers and RF spectrum

"The term Radio Frequency refers to the electromagnetic field that is generated when an alternating current is input to an antenna. This field, also called an RF field or radio wave, can be used for wireless broadcasting and communications over a significant portion of the electromagnetic radiation spectrum -- from about 9 kilohertz to thousands of gigahertz. This portion is referred to as the RF Spectrum. As the frequency is increased beyond the RF spectrum, electromagnetic energy takes the form of infrared, visible light, ultraviolet, X rays, and gamma rays."

Antennas, Decibels, and Space flight Telecommunications 

"The antenna is the most visible part of the satellite communication system. The antenna transmits and receives the modulated carrier signal at the radio frequency (RF) portion of the electromagnetic spectrum. For satellite communication, the frequencies range from about 0.3 GHz to 30 GHz and beyond. These frequencies represent microwaves, with wavelengths on the order of one meter down to below one centimeter. High frequencies, and the corresponding small wavelengths, permit the use of antennas having practical dimensions for commercial use.

UNIT 4

Electronic Diagram

Circuit diagrams are one method of describing electronic equipment. They are made up of standard circuit symbols. READING a circuit diagram is the ability to look at the diagram and understand how the circuitry works. Be aware that the layout of the circuit diagram may be nothing like the physical layout of the actual equipment. Although the circuit diagram shows all capacitors the same size and shape, in reality they will be of assorted sizes, shapes and colour. Different electronic diagrams will consist of different components. For instance, audio amplifier system will consists of a microphone, pre-amplifier, tone and volume controls, power amplifier and loudspeaker as well as Radio Receiver System will include an aerial, a tuner, detector, audio and loudspeaker.

There are also many other components that can be included into a certain electronic diagram and of course describe their own functions.

UNIT 5