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Microwave engineering pertains to the study and design of
microwave Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ra ...
circuits, components, and systems. Fundamental principles are applied to analysis, design and measurement techniques in this field. The short
wavelengths In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tr ...
involved distinguish this discipline from
electronic engineering Electronics engineering is a sub-discipline of electrical engineering which emerged in the early 20th century and is distinguished by the additional use of active components such as semiconductor devices to amplify and control electric current ...
. This is because there are different interactions with circuits, transmissions and propagation characteristics at microwave frequencies. Some theories and devices that pertain to this field are antennas,
radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, Marine radar, ships, spacecraft, guided missiles, motor v ...
,
transmission line In electrical engineering, a transmission line is a specialized cable or other structure designed to conduct electromagnetic waves in a contained manner. The term applies when the conductors are long enough that the wave nature of the transmi ...
s, space based systems (
remote sensing Remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object, in contrast to in situ or on-site observation. The term is applied especially to acquiring information about Ear ...
), measurements, microwave radiation hazards and safety measures. During
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
, microwave engineering played a significant role in developing radar that could accurately locate enemy ships and planes with a focused beam of EM radiation. The foundations of this discipline are found in
Maxwell's equations Maxwell's equations, or Maxwell–Heaviside equations, are a set of coupled partial differential equations that, together with the Lorentz force law, form the foundation of classical electromagnetism, classical optics, and electric circuits ...
and the work of
Heinrich Hertz Heinrich Rudolf Hertz ( ; ; 22 February 1857 – 1 January 1894) was a German physicist who first conclusively proved the existence of the electromagnetic waves predicted by James Clerk Maxwell's equations of electromagnetism. The uni ...
, William Thomson's waveguide theory, J.C. Bose, the
klystron A klystron is a specialized linear-beam vacuum tube, invented in 1937 by American electrical engineers Russell and Sigurd Varian,Pond, Norman H. "The Tube Guys". Russ Cochran, 2008 p.31-40 which is used as an amplifier for high radio frequen ...
from Russel and Varian Bross, as well as contributions from Perry Spencer, and others.


The microwave domain

Microwave Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ra ...
is a term used to identify electromagnetic waves above 103 megahertz (1 Gigahertz) up to 300 Gigahertz because of the short physical wavelengths of these frequencies. Short
wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tr ...
energy offers distinct advantages in many applications. For instance, sufficient directivity can be obtained using relatively small antennas and low-power transmitters. These characteristics are ideal for use in both military and civilian radar and communication applications. Small antennas and other small components are made possible by microwave frequency applications. The size advantage can be considered as part of a solution to problems of space, or weight, or both. Microwave frequency usage is significant for the design of shipboard radar because it makes possible the detection of smaller targets. Microwave frequencies present special problems in transmission, generation, and circuit design that are not encountered at lower frequencies. Conventional circuit theory is based on voltages and
current Currents, Current or The Current may refer to: Science and technology * Current (fluid), the flow of a liquid or a gas ** Air current, a flow of air ** Ocean current, a current in the ocean *** Rip current, a kind of water current ** Current (stre ...
s while microwave theory is based on
electromagnetic fields An electromagnetic field (also EM field or EMF) is a classical (i.e. non-quantum) field produced by (stationary or moving) electric charges. It is the field described by classical electrodynamics (a classical field theory) and is the classical c ...
. Prepared by FTCM Frank E. Sloan * Apparatus and techniques may be described qualitatively as "microwave" when the wavelengths of signals are roughly the same as the dimensions of the equipment, so that the
lumped-element model The lumped-element model (also called lumped-parameter model, or lumped-component model) simplifies the description of the behaviour of spatially distributed physical systems, such as electrical circuits, into a topology consisting of discrete e ...
is inaccurate. As a consequence, practical microwave technique tends to move away from the discrete
resistor A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active e ...
s,
capacitor A capacitor is a device that stores electrical energy in an electric field by virtue of accumulating electric charges on two close surfaces insulated from each other. It is a passive electronic component with two terminals. The effect of ...
s, and
inductor An inductor, also called a coil, choke, or reactor, is a passive two-terminal electrical component that stores energy in a magnetic field when electric current flows through it. An inductor typically consists of an insulated wire wound into a c ...
s used with lower frequency
radio waves Radio waves are a type of electromagnetic radiation with the longest wavelengths in the electromagnetic spectrum, typically with frequencies of 300 gigahertz ( GHz) and below. At 300 GHz, the corresponding wavelength is 1 mm (s ...
. Instead, the distributed-element model and transmission-line theory are more useful methods for design and analysis. Open-wire and coaxial
transmission line In electrical engineering, a transmission line is a specialized cable or other structure designed to conduct electromagnetic waves in a contained manner. The term applies when the conductors are long enough that the wave nature of the transmi ...
s give way to
waveguide A waveguide is a structure that guides waves, such as electromagnetic waves or sound, with minimal loss of energy by restricting the transmission of energy to one direction. Without the physical constraint of a waveguide, wave intensities de ...
s and
stripline Stripline is a transverse electromagnetic (TEM) transmission line medium invented by Robert M. Barrett of the Air Force Cambridge Research Centre in the 1950s. Stripline is the earliest form of planar transmission line. Description A stri ...
, and lumped-element tuned circuits are replaced by cavity
resonator A resonator is a device or system that exhibits resonance or resonant behavior. That is, it naturally oscillates with greater amplitude at some frequencies, called resonant frequencies, than at other frequencies. The oscillations in a resonator ...
s or resonant lines. Effects of
reflection Reflection or reflexion may refer to: Science and technology * Reflection (physics), a common wave phenomenon ** Specular reflection, reflection from a smooth surface *** Mirror image, a reflection in a mirror or in water ** Signal reflection, in ...
, polarization,
scattering Scattering is a term used in physics to describe a wide range of physical processes where moving particles or radiation of some form, such as light or sound, are forced to deviate from a straight trajectory by localized non-uniformities (including ...
,
diffraction Diffraction is defined as the interference or bending of waves around the corners of an obstacle or through an aperture into the region of geometrical shadow of the obstacle/aperture. The diffracting object or aperture effectively becomes a s ...
and atmospheric
absorption Absorption may refer to: Chemistry and biology *Absorption (biology), digestion **Absorption (small intestine) *Absorption (chemistry), diffusion of particles of gas or liquid into liquid or solid materials *Absorption (skin), a route by which s ...
usually associated with visible light are of practical significance in the study of microwave
propagation Propagation can refer to: *Chain propagation in a chemical reaction mechanism *Crack propagation, the growth of a crack during the fracture of materials * Propaganda, non-objective information used to further an agenda * Reproduction, and other for ...
. The same
equations In mathematics, an equation is a formula that expresses the equality of two expressions, by connecting them with the equals sign . The word ''equation'' and its cognates in other languages may have subtly different meanings; for example, in ...
of electromagnetic theory apply at all frequencies.


Relevance

The microwave engineering discipline has become relevant as the
microwave Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ra ...
domain moves into the commercial sector, and no longer only applicable to 20th and 21st century military technologies. Inexpensive components and digital communications in the microwave domain have opened up areas pertinent to this discipline. Some of these areas are radar,
satellite A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioiso ...
, wireless radio,
optical communication Optical communication, also known as optical telecommunication, is communication at a distance using light to carry information. It can be performed visually or by using electronic devices. The earliest basic forms of optical communication date ...
, faster computer circuits, and collision avoidance radar.


Education

Many colleges and universities offer microwave engineering. A few examples follow. The
University of Massachusetts Amherst The University of Massachusetts Amherst (UMass Amherst, UMass) is a public research university in Amherst, Massachusetts and the sole public land-grant university in Commonwealth of Massachusetts. Founded in 1863 as an agricultural college, ...
provides research and educational programs in microwave remote sensing, antenna design and communications systems. Courses and project work are offered leading toward graduate degrees. Specialties include microwave and RF integrated circuit design, antenna engineering, computational electromagnetics, radiowave propagation, radar and remote sensing systems, image processing, and THz imaging.
Tufts University Tufts University is a private research university on the border of Medford and Somerville, Massachusetts. It was founded in 1852 as Tufts College by Christian universalists who sought to provide a nonsectarian institution of higher learning. ...
offers a ''Microwave and Wireless Engineering'' certificate program as part of its graduate studies programs. It can be applied toward a master's degree in electrical engineering. The student must have an appropriate bachelor's degree to enroll in this program.
Auburn University Auburn University (AU or Auburn) is a public land-grant research university in Auburn, Alabama. With more than 24,600 undergraduate students and a total enrollment of more than 30,000 with 1,330 faculty members, Auburn is the second largest ...
offers research for the microwave arena. Wireless Engineering Research and Education Center is one of three research centers. The university also offers a Bachelor of Wireless Engineering degree with a Wireless Electrical Engineering major.
Bradley University Bradley University is a private university in Peoria, Illinois. Founded in 1897, Bradley University enrolls 5,400 students who are pursuing degrees in more than 100 undergraduate programs and more than 30 graduate programs in five colleges. Th ...
offers an undergraduate and a graduate degree in its Microwave and Wireless Engineering Program. It has an Advanced Microwave Laboratory, a Wireless Communication Laboratory and other facilities related to research.


Societies

There are professional societies pertinent to this discipline: The IEEE Microwave Theory and Techniques Society (MTT-S) "promotes the advancement of microwave theory and its applications...". The society also publishes peer reviewed journals, and one magazine.


Journals and other scholarly periodicals

There are peer reviewed journals and other scholarly periodicals that cover topics that pertains to microwave engineering. Some of these are
IEEE Transactions on Microwave Theory and Techniques ''IEEE Transactions on Microwave Theory and Techniques'' (T-MTT) is a monthly peer-reviewed scientific journal with a focus on that part of engineering and theory associated with microwave/millimeter-wave technology and components, electronic devi ...
,
IEEE Microwave and Wireless Components Letters ''IEEE Microwave and Wireless Components Letters'' is a monthly peer-reviewed scientific journal published by the IEEE Microwave Theory and Techniques Society. The editor-in-chief is Roberto Gómez García ( University of Alcala). The journal cove ...
, Microwave Magazine, IET Microwaves, Antennas & Propagation, and Microwave Journal.


See also

*
Artificial dielectrics Artificial dielectrics are fabricated composite materials, often consisting of arrays of conductive shapes or particles in a nonconductive support matrix, designed to have specific electromagnetic properties similar to dielectrics. As long as the ...
*
Microwave transmission Microwave transmission is the transmission of information by electromagnetic waves with wavelengths in the microwave frequency range of 300MHz to 300GHz(1 m - 1 mm wavelength) of the electromagnetic spectrum. Microwave signals are normally limi ...
*
Radio-frequency engineering Radio-frequency (RF) engineering is a subset of electronic engineering involving the application of transmission line, waveguide, antenna and electromagnetic field principles to the design and application of devices that produce or use sign ...
* Winston E. Kock


References


Further reading

* {{Engineering fields Microwave technology Electrical engineering