Microwave technology Microwave technology A backward wave oscillator (BWO), also called carcinotron or backward wave tube, is a device that is used to generate microwaves and terahertz radiation. It consists of a vacuum tube that provides 1 mW to 50 mW of power. Some types can produce frequencies in a range of 200 GHz to 1.1 THz. It sustains the oscillations by reflecting the traveling wave backwards against the beam. It is derived from the traveling wave tube. It has two main subtypes, the M-type (M-BWO) and O-type (O-BWO). Carcinotrons are used as powerful and stable microwave sources. Due to the good quality wavefront they produce, they find use as illuminators in terahertz imaging. ...more on Wikipedia about "Backward wave oscillator"
A cavity magnetron is a high-powered vacuum tube that generates coherent microwaves. They are commonly found in the microwave oven, as well as various radar applications. ...more on Wikipedia about "Cavity magnetron"
A crossed-field amplifier (CFA) is a specialized vacuum tube, first introduced in the mid- 1950s and frequently used as a microwave amplifier in very-high-power transmitters. A CFA has lower gain and bandwidth than other microwave amplifier tubes (such as klystrons or traveling wave tubes); but it is more efficient and capable of much higher output power. Peak output powers of many megawatts and average power levels of tens of kilowatts can be achieved, with efficiency ratings in excess of 70 percent. ...more on Wikipedia about "Crossed-field amplifier"
A free electron laser, or FEL, generates tunable, coherent, high power radiation, currently ranging in wavelength from millimeters to the visible. While an FEL laser beam shares the same optical properties as conventional lasers such as coherent radiation, the operation of an FEL is quite different. Unlike gas or diode lasers which rely on bound atomic or molecular states, FELs use a relativistic electron beam as the lasing medium, hence the term free-electron. Free electron lasers can be used to generate terahertz radiation. ...more on Wikipedia about "Free electron laser"
A Gunn diode, also known as a transferred electron device (TED) is a form of diode used in high-frequency electronics. It is somewhat unusual in that it consists only of N-doped semiconductor material, whereas ordinary diodes consist of both P and N-doped regions. In the Gunn diode, three regions exist: two of them are heavily N-doped on each terminal, with a thin layer of lightly doped material in between. When a voltage is applied to the device, the electrical gradient will be largest across the thin middle layer. Eventually, this layer starts to conduct, reducing the gradient across it, preventing further conduction. In practice, this means a Gunn diode has a region of negative differential resistance. ...more on Wikipedia about "Gunn diode"
Gyrotrons are high powered electron tubes which emit a millimeter wave beam by bunching electrons with cyclotron motion in a strong magnetic field. Typical output powers range from 10s of kilowatts to 1-2 megawatts. Output frequencies range from about 20 to 250 GHz. Gyrotrons can be designed for pulsed or continuous operation. Gyrotron manufacturers include CPI (USA), Gycom (Russia), Thales Group (EU), and Toshiba (Japan). A prevalent application of gyrotrons is as a source of plasma heating in nuclear fusion research experiments. ...more on Wikipedia about "Gyrotron"
HEMT stands for High Electron Mobility Transistor, and is also called heterostructure FET (HFET). A HEMT is a Field effect transistor with a junction between two materials with different band gaps (i.e. a heterojunction) as the channel instead of an n-doped region. A commonly used combination is GaAs with AlGaAs. The effect of this junction is to create a very thin layer where the Fermi energy is above the conduction band, giving the channel very low resistance (or to put it another way, "high electron mobility"). This layer is sometimes called a two-dimensional electron gas. As with all the other types of FETs, a voltage applied to the gate alters the conductivity of this layer. ...more on Wikipedia about "HEMT"
The Heterojunction Bipolar Transistor (HBT) is an improvement of the bipolar junction transistor (BJT) that can handle signals of very high frequencies up to several hundred GHz. It is common nowadays in ultrafast circuits, mostly radio-frequency (RF) systems. ...more on Wikipedia about "Heterojunction bipolar transistor"
The inductive output tube or IOT is a variety of vacuum tube which evolved in the 1980s to meet increasing efficiency requirements for high-power RF amplifiers having their primary commercial use in UHF television transmitters, in which application they have mostly replaced klystrons. ...more on Wikipedia about "Inductive output tube"
A klystron is a specialized vacuum tube (evacuated electron tube) called a linear-beam tube. The pseudo- Greek word klystron comes from the stem form κλυσ- (klys) of a Greek verb referring to the action of waves breaking against a shore, and the end of the word electron. Klystrons are used as an oscillator or amplifier 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 linear accelerators. It has the advantage (over the magnetron) of coherently amplifying a reference signal and so its output may be precisely controlled in amplitude, frequency and phase. Many klystrons have a waveguide for coupling microwave energy into and out of the device, although it is also quite common for lower power and lower frequency klysrons to use coaxial couplings instead. In some cases a coupling probe is used to couple the microwave energy from a klystron into a separate external waveguide. ...more on Wikipedia about "Klystron tube"
A maser is a device that produces coherent electromagnetic waves through amplification due to stimulated emission. Historically the term came from the acronym "microwave amplification by stimulated emission of radiation", although modern masers emit over a broad portion of the electromagnetic spectrum. This has lead some to replace "microwave" with "molecular" in the acronym, as suggested by Townes ** . When optical coherent oscillators were first developed, they were called optical masers, but it has become more common to refer to these as lasers. See the section on terminology below for more on this. ...more on Wikipedia about "Maser"
A microwave oven, (or microwave), is a kitchen appliance employing microwave radiation primarily to cook or heat food. ...more on Wikipedia about "Microwave oven"
MMICs, or Monolithic Microwave Integrated Circuits, are integrated circuit (IC) devices that operate at microwave frequencies. They typically perform functions such as microwave mixing, amplification, and tuning. Inputs and outputs on MMIC devices are frequently matched to 50 ohms; this makes them easy to use, because an external matching network is not always necessary. ...more on Wikipedia about "MMIC"
Space charge is the electrical current that results when a metal object is heated to incandescence in a vacuum. ...more on Wikipedia about "Space charge" http://www.shortopedia.com, it's as simple as that!
A traveling wave tube (TWT) is an electronic device used to produce high-power radio frequency signals. The bandwidth of a broadband TWT can be as high as one octave, although tuned (narrowband) versions exist, and operating frequencies range from 300 MHz to 50 GHz. The voltage gain of the tube can be of the order of 40 decibels. ...more on Wikipedia about "Traveling wave tube"
In electromagnetics and communications engineering, a waveguide is any physical structure that guides electromagnetic waves. ...more on Wikipedia about "Waveguide"
The Wilkinson power divider, named after Ernest J. Wilkinson, is a lossy N-port network commonly used for power splitting and combining. The Wilkinson power divider is especially useful because the output ports are simultaneously isolated and matched. The S matrix for the common case of a 2-way equal-split Wilkinson power divider at the design frequency is given by ...more on Wikipedia about "Wilkinson power divider"
Yttrium iron garnet filter (YIG filter, YIGF) is a tunable electronic filter for microwave frequencies. It typically has a high Q factor. ...more on Wikipedia about "Yttrium iron garnet filter"
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