High-power microwave sources use specialized vacuum tubes to generate microwaves. These devices operate on different principles from low-frequency vacuum tubes, using the ballistic motion of electrons in a vacuum under the influence of controlling electric or magnetic fields, and include the magnetron (used in microwave ovens), klystron, traveling-wave tube (TWT), and gyrotron. These devices work in the density modulated mode, rather than the current modulated mode. This means that they work on the basis of clumps of electrons flying ballistically through them, rather than using a continuous stream of electrons.
Low-power microwave sources use solid-state devices such as the field-effect transistor (at least at lower frequencies), tunnel diodes, Gunn diodes, and IMPATT diodes. Low-power sources are available as benchtop instruments, rackmount instruments, embeddable modules and in card-level formats.
A maser is a device similar to a laser, which amplifies light energy by stimulating photons. The maser, rather than amplifying visible light energy, amplifies the lower-frequency, longer-wavelength microwaves and radio frequency emissions.
The sun also emits microwave radiation, although most of it is blocked by Earth's atmosphere.
The Cosmic Microwave Background Radiation (CMBR) is a source of microwaves that supports the science of cosmology's Big Bang theory of the origin of the Universe.
Read more about this topic: Microwave
Famous quotes containing the words sources and/or microwave:
“Even healthy families need outside sources of moral guidance to keep those tensions from implodingand this means, among other things, a public philosophy of gender equality and concern for child welfare. When instead the larger culture aggrandizes wife beaters, degrades women or nods approvingly at child slappers, the family gets a little more dangerous for everyone, and so, inevitably, does the larger world.”
—Barbara Ehrenreich (20th century)
“The New Age? Its just the old age stuck in a microwave oven for fifteen seconds.”
—James Randi (b. 1928)