Analog circuits are electronics systems with analog signals with any continuously variable signal. While operating on an analog signal, an analog circuit changes the signal in some manner. It can be designed to amplify, attenuate, provide isolation, distort, or modify the signal in some other way. It can be used to convert the original signal into some other format such as a digital signal. Analog circuits may also modify signals in unintended ways such as adding noise or distortion.

There are two types of analog circuits: passive and active. Passive analog circuits consume no external electrical power while active analog circuits use an electrical power source to achieve the designer’s goals. An example of a passive analog circuit is a passive filter that limits the amplitude at some frequencies versus others. A similar example of an active analog circuit is an active filter. It does a similar job only it uses an amplifier to accomplish the same task.

Computer-Aided Design (CAD) is the use of a wide range of computer-based tools that assist engineers, architects and other design professionals in their design activities. CAD is used to design and develop products, which can be goods used by end consumers or intermediate goods used in other products. CAD is also extensively used in the design of tools and machinery used in the manufacture of components. Current CAD packages range from 2D vector based drafting systems to 3D parametric surface and solid design modelers.

The electronic applications of CAD, or Electronic Design Automation (EDA) includes schematic entry, PCB design, intelligent wiring diagrams (routing) and component connection management. Often, it integrates with a lite form of CAM (Computer Aided Manufacturing). Computer-aided design is also starting to be used to develop software applications. Software applications share many of the same Product Life Cycle attributes as the manufacturing or electronic markets. As computer software becomes more complicated and harder to update and change, it is becoming essential to develop interactive prototypes or simulations of the software before doing any coding. The benefits of simulation before writing actual code cuts down significantly on re-work and bugs.

A digital circuit is based on a number of discrete voltage levels, as distinct from an analog circuit that uses continuous voltages to represent variables directly. In most cases the number of voltage levels is two: one near to zero volts and one at a higher level depending on the supply voltage in use. These two levels are often represented as “Low” and “High.”

Digital circuits are the most common mechanical representation of Boolean algebra and are the basis of all digital computers. They can also be used to process digital information without being connected up as a computer. Such circuits are referred to as “random logic”.

An antenna is an electrical device designed to transmit or receive radio waves or, more generally, any electromagnetic waves. Antennas are used in systems such as radio and television broadcasting, point-to-point radio communication, radar, and space exploration. Antennas usually work in air or outer space, but can also be operated under water or even through soil and rock at certain frequencies.

Physically, an antenna is an arrangement of conductors that generate a radiating electromagnetic field in response to an applied alternating voltage and the associated alternating electric current, or can be placed in an electromagnetic field so that the field will induce an alternating current in the antenna and a voltage between its terminals.

An electromagnetic field is a physical influence (a field) that permeates through all of space, and which arises from electrically charged objects and describes one of the four fundamental forces of nature – electromagnetism. It can be viewed as the combination of an electric field and a magnetic field. Charges that are not moving produce only an electric field, while moving charges produce both an electric and a magnetic field.

Microwaves, also referred to as “micro-kilowaves”, are electromagnetic waves that have wavelengths approximately in the range of 1 GHz to 300 GHz, which is relatively short for radio waves.

Microwaves can be generated by a variety of means, generally divided into two categories: solid state devices and vacuum-tube based devices. Solid state microwave devices are based on semiconductors such as silicon or gallium arsenide, while vacuum tube based devices operate on the ballistic motion of electrons in a vacuum under the influence of controlling electric or magnetic fields.

Very-large-scale integration (VLSI) is the process of creating integrated circuits by combining thousands of transistor-based circuits into a single chip. VLSI began in the 1970s when complex semiconductor and communication technologies were being developed.

The first semiconductor chips held one transistor each. Subsequent advances added more and more transistors, and as a consequence more individual functions or systems were integrated over time. The microprocessor is a VLSI device.

The first “generation” of computers relied on vacuum tubes. Then came discrete semiconductor devices, followed by integrated circuits. The first Small-Scale Integration (SSI) ICs had small numbers of devices on a single chip – diodes, transistors, resistors and capacitors (no inductors though), making it possible to fabricate one or more logic gates on a single device. The fourth generation consisted of Large-Scale Integration (LSI), i.e. systems with at least a thousand logic gates. The natural successor to LSI was VLSI (many tens of thousands of gates on a single chip). Current technology has moved far past this mark and today’s microprocessors have many millions of gates and hundreds of millions of individual transistors.