A comb generator is a
signal generator that produces multiple
harmonic
A harmonic is a wave with a frequency that is a positive integer multiple of the ''fundamental frequency'', the frequency of the original periodic signal, such as a sinusoidal wave. The original signal is also called the ''1st harmonic'', the ...
s of its input signal. The appearance of the output at the
spectrum analyzer screen, resembling teeth of a
comb, gave the device its name.
Comb generators find wide range of uses in
microwave technology. E.g., synchronous signals in wide frequency bandwidth can be produced by a comb generator. The most common use is in broadband
frequency synthesizers, where the high frequency signals act as stable references correlated to the lower energy references; the outputs can be used directly, or to synchronize
phase-locked loop oscillator
Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendulum ...
s. It may be also used to generate a complete set of substitution channels for testing, each of which carries the same baseband audio and video signal.
Comb generators are also used in
RFI testing of
consumer electronics, where their output is used as a simulated
RF emissions, as it is a stable broadband noise source with repeatable output. It is also used during compliance testing to various government requirements for products such as medical devices (FDA), military electronics (
MIL-STD-461), commercial avionics (Federal Aviation Administration), digital electronics (Federal Communications Commission), in the USA.
An optical comb generator can be used as generators of
terahertz radiation. Internally, it is a
resonant electro-optic modulator, with the capability of generating hundreds of
sidebands with total span of at least 3 terahertz (limited by the
optical dispersion of the
lithium niobate crystal) and frequency spacing of 17 GHz. Other construction can be based on erbium-doped
fiber laser
A fiber laser (or fibre laser in British English) is a laser in which the active gain medium is an optical fiber doped with rare-earth elements such as erbium, ytterbium, neodymium, dysprosium, praseodymium, thulium and holmium. They are related t ...
or
Ti-sapphire laser often in combination with
carrier envelope offset control In optics, a frequency comb is a laser source whose spectrum consists of a series of discrete, equally spaced frequency lines. Frequency combs can be generated by a number of mechanisms, including periodic modulation (in amplitude and/or phase) of a ...
.
See also
*
Comb filter
*
Frequency comb
References
{{Reflist
External links
Yet another comb generatorCom-Power Corporation
Laboratory equipment
Electronic test equipment
Signal processing
Terahertz technology