Microcomb-injected, pulsed lasers as variable microwave gears

Low-noise microwave signals are of critical importance in numerous applications such as high-speed telecommunication and ultrafast data processing. Conventionally, such signals are generated with bulky and delicate microwave ...

The return of the spin echo

A research team from Garching and Vienna discovered a remarkable echo effect that offers exciting new possibilities for working with quantum information.

Plans underway for new polar ice and snow topography mission

Monitoring the cryosphere is essential to fully assess, predict and adapt to climate variability and change. Given the importance of this fragile component of the Earth system, today ESA, along with Airbus Defence and Space ...

Microwaving new materials

Microwave ovens are the mainstay of cooking appliances in our homes. Five years ago, when Reeja Jayan was a new professor at Carnegie Mellon University, she was intrigued by the idea of using microwaves to grow materials. ...

Cosmic tango between the very small and the very large

While Einstein's theory of general relativity can explain a large array of fascinating astrophysical and cosmological phenomena, some aspects of the properties of the universe at the largest-scales remain a mystery. A new ...

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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 (0.3 GHz) and 300 GHz. This broad definition includes both UHF and EHF (millimeter waves), and various sources use different boundaries. In all cases, microwave includes the entire SHF band (3 to 30 GHz, or 10 to 1 cm) at minimum, with RF engineering often putting the lower boundary at 1 GHz (30 cm), and the upper around 100 GHz (3 mm).

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 resistors, capacitors, and inductors used with lower-frequency radio waves. Instead, distributed circuit elements and transmission-line theory are more useful methods for design and analysis. Open-wire and coaxial transmission lines give way to waveguides and stripline, and lumped-element tuned circuits are replaced by cavity resonators 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.

The prefix "micro-" in "microwave" is not meant to suggest a wavelength in the micrometer range. It indicates that microwaves are "small" compared to waves used in typical radio broadcasting, in that they have shorter wavelengths. The boundaries between far infrared light, terahertz radiation, microwaves, and ultra-high-frequency radio waves are fairly arbitrary and are used variously between different fields of study.

Electromagnetic waves longer (lower frequency) than microwaves are called "radio waves". Electromagnetic radiation with shorter wavelengths may be called "millimeter waves", terahertz radiation or even T-rays. Definitions differ for millimeter wave band, which the IEEE defines as 110 GHz to 300 GHz.

Above 300 GHz, the absorption of electromagnetic radiation by Earth's atmosphere is so great that it is in effect opaque, until the atmosphere becomes transparent again in the so-called infrared and optical window frequency ranges.

This text uses material from Wikipedia, licensed under CC BY-SA