Microwave Engineering
Encyclopedia
Microwave engineering pertains to the study and design of microwave
circuits, components, and systems. Fundamental principles are applied to analysis, design and measurement techniques in this field. The short wavelengths involved distinguish this discipline from Electronic engineering
. 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 antennae, radar
, transmission line
s, space based systems (remote sensing
), measurements, microwave radiation hazards and safety measures.
During World War II 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
and the work of Heinrich Hertz, William Thompson
's waveguide theory
, J.C. Bose, the klystron
from Russel and Varian Bross, as well as contributions from Perry Spencer, and others.
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 currents while microwave theory is based on electromagnetic fields.
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 lumped-element circuit theory
is inaccurate. As a consequence, practical microwave technique tends to move away from the discrete resistor
s, capacitor
s, and inductor
s used with lower frequency radio waves
. Instead, distributed circuit element
s and transmission-line theory are more useful methods for design and analysis. Open-wire and coaxial transmission line
s give way to waveguide
s and stripline
, and lumped-element tuned circuits are replaced by cavity resonator
s or resonant lines. Effects of reflection
, polarization, scattering
, diffraction
and atmospheric absorption
usually associated with visible light are of practical significance in the study of microwave propagation
. The same equations
of electromagnetic theory apply at all frequencies.
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
, wireless radio, optical communication
, faster computer circuits, and collision avoidance radar.
The University of Massachusetts Amherst
provides research and educational programs in microwave sensing 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, propagation, microwave remote sensing systems, image processing, and THz imaging.
Tufts University
offers a Microwave and Wireless Engineering certificate program as part of its graduate studies programs. It can be applied toward a Masters degree in electrical engineering. The student must have an appropriate bachelors degree to enroll in this program.
Auburn University
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
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.
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.
, IEEE Microwave and Wireless Components Letters
, Microwave Magazine, and IET Microwaves, Antennas & Propagation.
Microwave
Microwaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...
circuits, components, and systems. Fundamental principles are applied to analysis, design and measurement techniques in this field. The short wavelengths involved distinguish this discipline from Electronic engineering
Electronic engineering
Electronics engineering, also referred to as electronic engineering, is an engineering discipline where non-linear and active electrical components such as electron tubes, and semiconductor devices, especially transistors, diodes and integrated circuits, are utilized to design electronic...
. 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 antennae, radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
, transmission line
Transmission line
In communications and electronic engineering, a transmission line is a specialized cable designed to carry alternating current of radio frequency, that is, currents with a frequency high enough that its wave nature must be taken into account...
s, space based systems (remote sensing
Remote sensing
Remote sensing is the acquisition of information about an object or phenomenon, without making physical contact with the object. In modern usage, the term generally refers to the use of aerial sensor technologies to detect and classify objects on Earth by means of propagated signals Remote sensing...
), measurements, microwave radiation hazards and safety measures.
During World War II 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
Maxwell's equations are a set of partial differential equations that, together with the Lorentz force law, form the foundation of classical electrodynamics, classical optics, and electric circuits. These fields in turn underlie modern electrical and communications technologies.Maxwell's equations...
and the work of Heinrich Hertz, William Thompson
William Thompson
-Academics and scientists:* William Thompson , Irish ornithologist and botanist* William Thompson , Englishman who developed the Thompson Seedless grape...
's waveguide theory
Waveguide
A waveguide is a structure which guides waves, such as electromagnetic waves or sound waves. There are different types of waveguides for each type of wave...
, J.C. Bose, the klystron
Klystron
A klystron is a specialized linear-beam vacuum tube . Klystrons are used as amplifiers at microwave and radio frequencies to produce both low-power reference signals for superheterodyne radar receivers and to produce high-power carrier waves for communications and the driving force for modern...
from Russel and Varian Bross, as well as contributions from Perry Spencer, and others.
The microwave domain
Microwave 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 wavelengthWavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
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 currents while microwave theory is based on electromagnetic fields.
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 lumped-element circuit theory
Lumped element model
The lumped element model simplifies the description of the behaviour of spatially distributed physical systems into a topology consisting of discrete entities that approximate the behaviour of the distributed system under certain assumptions...
is inaccurate. As a consequence, practical microwave technique tends to move away from the discrete resistor
Resistor
A linear resistor is a linear, passive two-terminal electrical component that implements electrical resistance as a circuit element.The current through a resistor is in direct proportion to the voltage across the resistor's terminals. Thus, the ratio of the voltage applied across a resistor's...
s, capacitor
Capacitor
A capacitor is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric ; for example, one common construction consists of metal foils separated...
s, and inductor
Inductor
An inductor is a passive two-terminal electrical component used to store energy in a magnetic field. An inductor's ability to store magnetic energy is measured by its inductance, in units of henries...
s used with lower frequency radio waves
Radio waves
Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Radio waves have frequencies from 300 GHz to as low as 3 kHz, and corresponding wavelengths from 1 millimeter to 100 kilometers. Like all other electromagnetic waves,...
. Instead, distributed circuit element
Distributed element model
In electrical engineering, the distributed element model or transmission line model of electrical circuits assumes that the attributes of the circuit are distributed continuously throughout the material of the circuit...
s and transmission-line theory are more useful methods for design and analysis. Open-wire and coaxial transmission line
Transmission line
In communications and electronic engineering, a transmission line is a specialized cable designed to carry alternating current of radio frequency, that is, currents with a frequency high enough that its wave nature must be taken into account...
s give way to waveguide
Waveguide
A waveguide is a structure which guides waves, such as electromagnetic waves or sound waves. There are different types of waveguides for each type of wave...
s and stripline
Stripline
Stripline is a transverse electromagnetic transmission line medium, that was invented by Robert M. Barrett of the Air Force Cambridge Research Centre in the 1950s.- Description :...
, and lumped-element tuned circuits are replaced by cavity resonator
Resonator
A resonator is a device or system that exhibits resonance or resonant behavior, that is, it naturally oscillates at some frequencies, called its resonant frequencies, with greater amplitude than at others. The oscillations in a resonator can be either electromagnetic or mechanical...
s or resonant lines. Effects of reflection
Reflection (physics)
Reflection is the change in direction of a wavefront at an interface between two differentmedia so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves...
, polarization, scattering
Scattering
Scattering is a general physical process where some forms of radiation, such as light, sound, or moving particles, are forced to deviate from a straight trajectory by one or more localized non-uniformities in the medium through which they pass. In conventional use, this also includes deviation of...
, diffraction
Diffraction
Diffraction refers to various phenomena which occur when a wave encounters an obstacle. Italian scientist Francesco Maria Grimaldi coined the word "diffraction" and was the first to record accurate observations of the phenomenon in 1665...
and atmospheric absorption
Absorption (electromagnetic radiation)
In physics, absorption of electromagnetic radiation is the way by which the energy of a photon is taken up by matter, typically the electrons of an atom. Thus, the electromagnetic energy is transformed to other forms of energy for example, to heat. The absorption of light during wave propagation is...
usually associated with visible light are of practical significance in the study of microwave propagation
Radio propagation
Radio propagation is the behavior of radio waves when they are transmitted, or propagated from one point on the Earth to another, or into various parts of the atmosphere...
. The same equations
Maxwell's equations
Maxwell's equations are a set of partial differential equations that, together with the Lorentz force law, form the foundation of classical electrodynamics, classical optics, and electric circuits. These fields in turn underlie modern electrical and communications technologies.Maxwell's equations...
of electromagnetic theory apply at all frequencies.
Relevance
The microwave engineering discipline has become relevant as the microwaveMicrowave
Microwaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...
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
Satellite
In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....
, wireless radio, optical communication
Optical communication
Optical communication is any form of telecommunication that uses light as the transmission medium.An optical communication system consists of a transmitter, which encodes a message into an optical signal, a channel, which carries the signal to its destination, and a receiver, which reproduces the...
, faster computer circuits, and collision avoidance radar.
Education
Colleges and universities offer microwave engineering.The University of Massachusetts Amherst
University of Massachusetts Amherst
The University of Massachusetts Amherst is a public research and land-grant university in Amherst, Massachusetts, United States and the flagship of the University of Massachusetts system...
provides research and educational programs in microwave sensing 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, propagation, microwave remote sensing systems, image processing, and THz imaging.
Tufts University
Tufts University
Tufts University is a private research university located in Medford/Somerville, near Boston, Massachusetts. It is organized into ten schools, including two undergraduate programs and eight graduate divisions, on four campuses in Massachusetts and on the eastern border of France...
offers a Microwave and Wireless Engineering certificate program as part of its graduate studies programs. It can be applied toward a Masters degree in electrical engineering. The student must have an appropriate bachelors degree to enroll in this program.
Auburn University
Auburn University
Auburn University is a public university located in Auburn, Alabama, United States. With more than 25,000 students and 1,200 faculty members, it is one of the largest universities in the state. Auburn was chartered on February 7, 1856, as the East Alabama Male College, a private liberal arts...
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
Bradley University, founded in 1897, is a private, co-educational university located in Peoria, Illinois. It is a small institution with an enrollment of approximately 6,100 undergraduate and postgraduate students and a full-time faculty of approximately 350....
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
IEEE Microwave Theory and Techniques Society
The IEEE Microwave Theory and Techniques Society is the largest technical profession society for the promotion of the theory and applications of RF, microwave, millimeter-wave, and terahertz technologies. The MTT-S has over 10,000 worldwide professional members in academia, industry and...
(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 TechniquesIEEE Transactions on Microwave Theory and Techniques
IEEE Transactions on Microwave Theory and Techniques is a monthly peer-reviewed scientific journal covering microwave theory, techniques, and applications at various primary, intermediate, and completed integration levels of a structured microwave system. It is published by the IEEE Microwave...
, IEEE Microwave and Wireless Components Letters
IEEE Microwave and Wireless Components Letters
IEEE Microwave and Wireless Components Letters is a peer-reviewed scientific journal that is published monthly by the IEEE Microwave Theory and Techniques Society. The editor-in-chief is C.-K. Clive Tzuang. The focus of the journal is electromagnetic radiation and the relevant, physical components...
, Microwave Magazine, and IET Microwaves, Antennas & Propagation.