Editing Electrical engineering (section)

==Subfields==
One of the properties of electricity is that it is very useful for energy transmission as well as for information transmission. These were also the first areas in which electrical engineering was developed. Today, electrical engineering has many subdisciplines, the most common of which are listed below. Although there are electrical engineers who focus exclusively on one of these subdisciplines, many deal with a combination of them. Sometimes, certain fields, such as [[electronic engineering]] and [[computer engineering]], are considered disciplines in their own right.

===Power and energy===
{{Main|Power engineering|Energy engineering}}
[[File:Power pole.jpg|thumb|The top of a [[Utility pole|power pole]]]]

Power & Energy engineering deals with the [[electricity generation|generation]], [[electric power transmission|transmission]], and [[electric power distribution|distribution]] of electricity as well as the design of a range of related devices.{{Sfn|Grigsby|2012}} These include [[transformer]]s, [[electric generator]]s, [[electric motor]]s, high voltage engineering, and [[power electronics]]. In many regions of the world, governments maintain an electrical network called a [[power grid]] that connects a variety of generators together with users of their energy. Users purchase electrical energy from the grid, avoiding the costly exercise of having to generate their own. Power engineers may work on the design and maintenance of the power grid as well as the power systems that connect to it.<ref name="UNESCO"/> Such systems are called ''on-grid'' power systems and may supply the grid with additional power, draw power from the grid, or do both. Power engineers may also work on systems that do not connect to the grid, called ''off-grid'' power systems, which in some cases are preferable to on-grid systems.

===Telecommunications===
{{Main|Telecommunications engineering}}
[[File:Erdfunkstelle Raisting 2a.jpg|thumb|right|[[Satellite dish]]es are a crucial component in the analysis of satellite information.]]
Telecommunications engineering focuses on the [[transmission (telecommunications)|transmission]] of information across a [[communication channel]] such as a [[coax cable]], [[optical fiber]] or [[free space optical communications|free space]].{{sfn|Tobin|2007|p=15}} Transmissions across free space require information to be encoded in a [[carrier signal]] to shift the information to a carrier frequency suitable for transmission; this is known as [[modulation]]. Popular analog modulation techniques include [[amplitude modulation]] and [[frequency modulation]].{{Sfn|Chandrasekhar|2006|p=21}} The choice of modulation affects the cost and performance of a system and these two factors must be balanced carefully by the engineer.

Once the transmission characteristics of a system are determined, telecommunication engineers design the [[transmitter]]s and [[receiver (radio)|receiver]]s needed for such systems. These two are sometimes combined to form a two-way communication device known as a [[transceiver]]. A key consideration in the design of transmitters is their [[power consumption]] as this is closely related to their [[signal strength]].{{sfn|Smith|2007|p=19}}{{sfn|Zhang|Hu|Luo|2007|p=448}} Typically, if the power of the transmitted signal is insufficient once the signal arrives at the receiver's antenna(s), the information contained in the signal will be corrupted by [[signal noise|noise]], specifically static.

===Control engineering===
{{Main||Control engineering|Control theory}}
[[File:Space Shuttle Columbia launching.jpg|thumb|[[Control system]]s play a critical role in [[spaceflight]].]]

[[Control engineering]] focuses on the [[Mathematical model|modeling]] of a diverse range of [[dynamic system]]s and the design of [[Controller (control theory)|controller]]s that will cause these systems to behave in the desired manner.{{sfn|Bissell|1996|p=17}} To implement such controllers, electronics control engineers may use [[electronic circuit]]s, [[digital signal processor]]s, [[microcontroller]]s, and [[programmable logic controller]]s (PLCs). [[Control engineering]] has a wide range of applications from the flight and propulsion systems of [[commercial airliner]]s to the [[cruise control]] present in many modern [[automobile]]s.{{sfn|McDavid|Echaore-McDavid|2009|p=95}} It also plays an important role in [[industrial automation]].

Control engineers often use [[feedback]] when designing [[control system]]s. For example, in an [[automobile]] with [[cruise control]] the vehicle's [[speed]] is continuously monitored and fed back to the system which adjusts the [[Internal combustion engine|motor's]] [[Power (physics)|power]] output accordingly.{{sfn | Åström | Murray | 2021 | p=108}} Where there is regular feedback, [[control theory]] can be used to determine how the system responds to such feedback.

Control engineers also work in [[robotics]] to design autonomous systems using control algorithms which interpret sensory feedback to control actuators that move robots such as [[autonomous vehicle]]s, autonomous drones and others used in a variety of industries.{{sfn|Fairman|1998|p=119}}

===Electronics===
{{Main|Electronic engineering}}

[[File:Componentes.JPG|thumb|left|[[Electronic component]]s]]
Electronic engineering involves the design and testing of [[electronic circuit]]s that use the properties of [[electrical element|component]]s such as [[resistor]]s, [[capacitor]]s, [[inductor]]s, [[diode]]s, and [[transistor]]s to achieve a particular functionality.<ref name="UNESCO">{{cite book|title=Engineering: Issues, Challenges and Opportunities for Development|url=https://books.google.com/books?id=09i67GgGPCYC&pg=PA128|year=2010|publisher=UNESCO|isbn=978-92-3-104156-3|pages=127–8}}</ref> The [[tuned circuit]], which allows the user of a radio to [[electronic filter|filter]] out all but a single station, is just one example of such a circuit. Another example to research is a pneumatic signal conditioner.

Prior to the Second World War, the subject was commonly known as ''radio engineering'' and basically was restricted to aspects of communications and [[radar]], [[radio|commercial radio]], and [[television|early television]].<ref name="UNESCO"/> Later, in post-war years, as consumer devices began to be developed, the field grew to include modern television, audio systems, computers, and [[microprocessor]]s. In the mid-to-late 1950s, the term ''radio engineering'' gradually gave way to the name ''electronic engineering''.

Before the invention of the [[integrated circuit]] in 1959,{{Sfn|Thompson|2006|p=4}} electronic circuits were constructed from discrete components that could be manipulated by humans. These discrete circuits consumed much space and [[electric power|power]] and were limited in speed, although they are still common in some applications. By contrast, [[integrated circuit]]s packed a large number—often millions—of tiny electrical components, mainly [[transistor]]s,{{Sfn|Merhari|2009|p=233}} into a small chip around the size of a [[coin]]. This allowed for the powerful computers and other electronic devices we see today.

===Microelectronics and nanoelectronics===
{{Main|Integrated circuit design|Semiconductor device modeling|Semiconductor device fabrication}}
{{Further|Microelectronics|Nanoelectronics|Chip design}}
[[File:80486dx2-large.jpg|thumb|right|[[Microprocessor]]]]
[[Microelectronics]] engineering deals with the design and [[microfabrication]] of very small electronic circuit components for use in an [[integrated circuit]] or sometimes for use on their own as a general electronic component.{{Sfn|Bhushan|1997|p=581}} The most common microelectronic components are [[semiconductor]] [[transistor]]s, although all main electronic components ([[resistor]]s, [[capacitor]]s etc.) can be created at a microscopic level.

[[Nanoelectronics]] is the further scaling of devices down to [[nanometer]] levels. Modern devices are already in the nanometer regime, with below 100&nbsp;nm processing having been standard since around 2002.{{Sfn|Mook|2008|p=149}}

Microelectronic components are created by chemically fabricating wafers of semiconductors such as silicon (at higher frequencies, [[compound semiconductor]]s like gallium arsenide and indium phosphide) to obtain the desired transport of electronic charge and control of current. The field of microelectronics involves a significant amount of chemistry and material science and requires the electronic engineer working in the field to have a very good working knowledge of the effects of [[quantum mechanics]].{{sfn|Sullivan|2012}}

===Signal processing===
{{Main|Signal processing}}
[[File:Bayer pattern on sensor.svg|thumb|left|A [[Bayer filter]] on a [[Charge-coupled device|CCD]] requires signal processing to get a red, green, and blue value at each pixel.]]
[[Signal processing]] deals with the analysis and manipulation of [[signal]]s.{{Sfn|Tuzlukov|2010|p=20}} Signals can be either [[analog signal|analog]], in which case the signal varies continuously according to the information, or [[Digital signal (signal processing)|digital]], in which case the signal varies according to a series of discrete values representing the information. For analog signals, signal processing may involve the [[amplifier|amplification]] and [[Filter (signal processing)|filtering]] of audio signals for audio equipment or the [[modulation]] and [[demodulation]] of signals for telecommunications. For digital signals, signal processing may involve the [[Data compression|compression]], [[error detection]] and [[error correction]] of digitally sampled signals.{{Sfn|Manolakis|Ingle|2011|p=17}}

Signal processing is a very mathematically oriented and intensive area forming the core of [[digital signal processing]] and it is rapidly expanding with new applications in every field of electrical engineering such as communications, control, radar, [[audio engineer]]ing, [[broadcast engineering]], power electronics, and [[biomedical engineering]] as many already existing analog systems are replaced with their digital counterparts. [[Analog signal processing]] is still important in the design of many [[control system]]s.

DSP processor ICs are found in many types of modern electronic devices, such as digital [[television set]]s,{{sfn|Bayoumi|Swartzlander|1994|p=25}} radios, [[hi-fi]] audio equipment, mobile phones, [[Portable Media Player|multimedia player]]s, camcorders and digital cameras, automobile control systems, [[noise cancelling]] headphones, digital [[spectrum analyzer]]s, missile guidance systems, [[radar]] systems, and [[telematics]] systems. In such products, DSP may be responsible for [[noise reduction]], [[speech recognition]] or [[Speech synthesis|synthesis]], [[Codec|encoding or decoding]] digital media, wirelessly [[Transceiver|transmitting or receiving]] data, triangulating positions using [[GPS]], and other kinds of [[image processing]], [[video processing]], [[audio signal processing|audio processing]], and [[speech processing]].{{Sfn|Khanna|2009|p=297}}

===Instrumentation===
{{Main|Instrumentation engineering}}
[[File:F-18E cockpit m02006112600499.jpg|thumb|right|[[Flight instrument]]s provide pilots with the tools to control aircraft analytically.]]
[[Instrumentation engineering]] deals with the design of devices to measure physical quantities such as [[pressure]], [[Volumetric flow rate|flow]], and temperature.{{Sfn|Grant|Bixley|2011|p=159}} The design of such instruments requires a good understanding of [[physics]] that often extends beyond [[electromagnetic theory]]. For example, [[flight instrument]]s measure variables such as [[wind speed]] and altitude to enable pilots the control of aircraft analytically. Similarly, [[thermocouple]]s use the [[Peltier-Seebeck effect]] to measure the temperature difference between two points.{{sfn|Fredlund|Rahardjo|Fredlund|2012|p=346}}

Often instrumentation is not used by itself, but instead as the [[sensor]]s of larger electrical systems. For example, a thermocouple might be used to help ensure a furnace's temperature remains constant.<ref>{{cite book|title=Manual on the Use of Thermocouples in Temperature Measurement|url=https://books.google.com/books?id=Pos-MXDWb6MC&pg=PA154|date=1 January 1993|publisher=ASTM International|isbn=978-0-8031-1466-1|page=154}}</ref> For this reason, instrumentation engineering is often viewed as the counterpart of control.

===Computers===
{{Main|Computer engineering}}
[[File:MEGWARE.CLIC.jpg|thumb|right|[[Supercomputer]]s are used in fields as diverse as [[computational biology]] and [[geographic information system]]s.]]
Computer engineering deals with the design of computers and [[computer system]]s. This may involve the design of new [[computer hardware|hardware]]. Computer engineers may also work on a system's software. However, the design of complex software systems is often the domain of software engineering, which is usually considered a separate discipline.{{sfn|Jalote|2006|p=22}} [[Desktop computer]]s represent a tiny fraction of the devices a computer engineer might work on, as computer-like architectures are now found in a range of [[embedded device]]s including [[video game console]]s and [[DVD player]]s. Computer engineers are involved in many hardware and software aspects of computing.<ref>{{cite book|isbn=0471605018|title=Fundamentals of Computer Engineering: Logic Design and Microprocessors|last1=Lam|first1=Herman|last2=O'Malley|first2=John R.|date=26 April 1988|publisher=Wiley }}</ref> [[Robot]]s are one of the applications of computer engineering.

===Photonics and optics===
{{Main|Photonics|Optics|Fiber-optic communication}}
[[File:Spectre.svg|thumb|280x280px|Electromagnetic spectrum showing wavelengths from radio waves (1&nbsp;km) to gamma rays (0.01&nbsp;nm). Visible light Information transmission in electrical engineering applications most frequently uses [[infrared light]] in the [[C band (infrared)|C band]] (1530–1565&nbsp;nm).]]

[[Photonics]] and [[optics]] deals with the generation, transmission, amplification, modulation, detection, and analysis of [[electromagnetic radiation]]. The application of optics deals with design of optical instruments such as [[lens]]es, [[microscope]]s, [[telescope]]s, and other equipment that uses the properties of electromagnetic radiation. Other prominent applications of optics include [[electro-optical sensor]]s and measurement systems, [[laser]]s, [[fiber-optic communication]] systems, and optical disc systems (e.g. CD and DVD). Photonics builds heavily on optical technology, supplemented with modern developments such as [[optoelectronics]] (mostly involving [[semiconductor]]s), laser systems, [[optical amplifier]]s and novel materials (e.g. [[metamaterial]]s).