Resonator

resonant cavityresonatorscavity resonatorresonant cavitiescavityresonating chamberresonator cavitycavitiescavity resonators 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.wikipedia
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Microwave cavity

microwave cavitiesRF cavitiescavity
In electronics and radio, microwave cavities consisting of hollow metal boxes are used in microwave transmitters, receivers and test equipment to control frequency, in place of the tuned circuits which are used at lower frequencies.
A microwave cavity or radio frequency (RF) cavity is a special type of resonator, consisting of a closed (or largely closed) metal structure that confines electromagnetic fields in the microwave region of the spectrum.

LC circuit

tuned circuitLCresonant circuit
In electronics and radio, microwave cavities consisting of hollow metal boxes are used in microwave transmitters, receivers and test equipment to control frequency, in place of the tuned circuits which are used at lower frequencies.
The circuit can act as an electrical resonator, an electrical analogue of a tuning fork, storing energy oscillating at the circuit's resonant frequency.

Quartz clock

quartz watchquartzquartz movement
Another example is quartz crystals used in electronic devices such as radio transmitters and quartz watches to produce oscillations of very precise frequency.
Since quartz can be directly driven (to flex) by an electric signal, no additional transducer is required to use it in a resonator.

Helmholtz resonance

Helmholtz resonatorHelmholtz resonatorsresonator
Acoustic cavity resonators, in which sound is produced by air vibrating in a cavity with one opening, are known as Helmholtz resonators.
The Helmholtz resonator, as it is now called, consists of a rigid container of a known volume, nearly spherical in shape, with a small neck and hole in one end and a larger hole in the other end to emit the sound.

Standing wave

standing wavesstationary wavestationary waves
The oppositely moving waves interfere with each other, and at its resonant frequencies reinforce each other to create a pattern of standing waves in the resonator.
The most common cause of standing waves is the phenomenon of resonance, in which standing waves occur inside a resonator due to interference between waves reflected back and forth at the resonator's resonant frequency.

Crystal oscillator

crystalquartz oscillatorquartz crystal
Another example is quartz crystals used in electronic devices such as radio transmitters and quartz watches to produce oscillations of very precise frequency.
The crystal oscillator circuit sustains oscillation by taking a voltage signal from the quartz resonator, amplifying it, and feeding it back to the resonator.

Harmonic

harmonicsflageoletharmonic frequencies
So the resonant frequencies of resonators, called normal modes, are equally spaced multiples (harmonics) of a lowest frequency called the fundamental frequency.
Oscillators that produce harmonic partials behave somewhat like one-dimensional resonators, and are often long and thin, such as a guitar string or a column of air open at both ends (as with the modern orchestral transverse flute).

Resonance

resonantresonant frequencyresonance frequency
The oppositely moving waves interfere with each other, and at its resonant frequencies reinforce each other to create a pattern of standing waves in the 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.
Acoustic resonance is an important consideration for instrument builders, as most acoustic instruments use resonators, such as the strings and body of a violin, the length of tube in a flute, and the shape of, and tension on, a drum membrane.

Q factor

quality factorQQ'' factor
Due to the low resistance of their conductive walls, cavity resonators have very high Q factors; that is their bandwidth, the range of frequencies around the resonant frequency at which they will resonate, is very narrow.
In physics and engineering the quality factor or Q factor is a dimensionless parameter that describes how underdamped an oscillator or resonator is, and characterizes a resonator's bandwidth relative to its centre frequency.

Cavity magnetron

magnetronmagnetronssplit-anode magnetron
The cavity magnetron is a vacuum tube with a filament in the center of an evacuated, lobed, circular cavity resonator.
The cavity magnetron is a high-powered vacuum tube that generates microwaves using the interaction of a stream of electrons with a magnetic field while moving past a series of open metal cavities (cavity resonators).

Microwave

microwavesmicrowave radiationmicrowave tube
Since the cavity's lowest resonant frequency, the fundamental frequency, is that at which the width of the cavity is equal to a half-wavelength (λ/2), cavity resonators are only used at microwave frequencies and above, where wavelengths are short enough that the cavity is conveniently small in size.
Open-wire and coaxial transmission lines used at lower frequencies are replaced by waveguides and stripline, and lumped-element tuned circuits are replaced by cavity resonators or resonant stubs.

Klystron

reflex klystronklystron tubeklystrons
The klystron, tube waveguide, is a beam tube including at least two apertured cavity resonators.
In a klystron, an electron beam interacts with radio waves as it passes through resonant cavities, metal boxes along the length of a tube.

Electronic oscillator

oscillatoroscillatorsaudio oscillator
Cavity resonators are widely used as the frequency determining element in microwave oscillators.
*In an LC oscillator circuit, the filter is a tuned circuit (often called a tank circuit; the tuned circuit is a resonator) consisting of an inductor (L) and capacitor (C) connected together.

Oscillation

oscillatorvibrationoscillators
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.
Resonator

Optical cavity

optical resonatorcavitylaser cavity
Thus an optical cavity, also known as a resonator, is a cavity with walls that reflect electromagnetic waves (i.e. light).
An optical cavity, resonating cavity or optical resonator is an arrangement of mirrors that forms a standing wave cavity resonator for light waves.

Tuning fork

tuning forkstuning-forkDiapasons
Common designs consist of electrodes attached to a piece of quartz, in the shape of a rectangular plate for high frequency applications, or in the shape of a tuning fork for low frequency applications.
A tuning fork is an acoustic resonator in the form of a two-pronged fork with the prongs (tines) formed from a U-shaped bar of elastic metal (usually steel).

Helical resonator

An example of this, much used in filtering, is the helical resonator.
Like cavity resonators, helical resonators can achieve Q factors in the 1000s.

Laser

laserslaser beamlaser light
In a laser, light is amplified in a cavity resonator that is usually composed of two or more mirrors.
The optical resonator is sometimes referred to as an "optical cavity", but this is a misnomer: lasers use open resonators as opposed to the literal cavity that would be employed at microwave frequencies in a maser.

Organ pipe

pipesorgan pipespipe
Organ pipes, the bodies of woodwinds, and the sound boxes of stringed instruments are examples of acoustic cavity resonators.
An organ pipe is a sound-producing element of the pipe organ that resonates at a specific pitch when pressurized air (commonly referred to as wind) is driven through it. Each pipe is tuned to a specific note of the musical scale.

Tesla coil

magnifying transmitterTeslaTesla Coils
A single layer coil (or solenoid) that is used as a secondary or tertiary winding in a Tesla coil or magnifying transmitter is also a distributed resonator.
A more complex version of a Tesla coil, termed a "magnifier" by Tesla, uses a more tightly coupled air-core resonance "driver" transformer (or "master oscillator") and a smaller, remotely located output coil (called the "extra coil" or simply the resonator) that has a large number of turns on a relatively small coil form.

Xylophone

xylophonesxylophonisttimbila
Some generate the sound directly, such as the wooden bars in a xylophone, the head of a drum, the strings in stringed instruments, and the pipes in an organ.
Concert xylophones have tube resonators below the bars to enhance the tone and sustain.

Acoustic resonance

resonanceresonatorresonant
In many keyboard percussion instruments, below the centre of each note is a tube, which is an acoustic cavity resonator.
Acoustic resonance is an important consideration for instrument builders, as most acoustic instruments use resonators, such as the strings and body of a violin, the length of tube in a flute, and the shape of a drum membrane.

Resonator guitar

resonatorresophonic guitarNational guitar
The term resonator, used by itself, may also refer to the resonator guitar.
A resonator guitar or resophonic guitar is an acoustic guitar that produces sound by conducting string vibrations through the bridge to one or more spun metal cones (resonators), instead of to the guitar's sounding board (top).

Particle accelerator

particle acceleratorsacceleratoraccelerators
It is a particle accelerator that works in conjunction with a specifically tuned cavity by the configuration of the structures.
Since high energy synchrotrons do most of their work on particles that are already traveling at nearly the speed of light c, the time to complete one orbit of the ring is nearly constant, as is the frequency of the RF cavity resonators used to drive the acceleration.

Coplanar waveguide

coplanarCPW
Planar transmission line resonators are commonly employed for coplanar, stripline, and microstrip transmission lines.
In particular the research field of circuit quantum electrodynamics was initiated with coplanar waveguide resonators as crucial elements that allow for high field strength and thus strong coupling to a superconducting qubit by confining a microwave photon to a volume that is much smaller than the cube of the wavelength.