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In physics, acoustics, and telecommunications, a harmonic is a sinusoidal wave with a frequency that is a positive integer multiple of the fundamental frequency of a periodic signal. The fundamental frequency is also called the 1st harmonic; the other harmonics are known as higher harmonics.
Thus, the third harmonic is the third multiple of the fundamental frequency. Harmonics in power systems are generated by non-linear loads. Semiconductor devices like transistors, IGBTs, MOSFETs, diodes, etc. are all non-linear loads. Further examples of non-linear loads include common office equipment such as computers and printers, fluorescent ...
The same nonlinear system will produce both total harmonic distortion (with a solitary sine wave input) and IMD (with more complex tones). In music, for instance, IMD is intentionally applied to electric guitars using overdriven amplifiers or effects pedals to produce new tones at sub harmonics of the tones being played on the instrument.
Telecommunication systems strive to increase the ratio of signal level to noise level in order to effectively transfer data. Noise in telecommunication systems is a product of both internal and external sources to the system. Noise is a random process, characterized by stochastic properties such as its variance, distribution, and spectral density.
In some analog video formats frequency modulation is the standard method for recording the luminance part of the signal, and is used to record a composite video signal in direct color systems, e.g. Video 2000 and some Hi-band formats a pilot tone is added to the signal to detect and correct timebase errors.
The superior close-in phase noise performance of a DDS stems from the fact that it is a feed-forward system. In a traditional phase locked loop (PLL), the frequency divider in the feedback path acts to multiply the phase noise of the reference oscillator and, within the PLL loop bandwidth, impresses this excess noise onto the VCO output.
An exciter (also called a harmonic exciter or aural exciter) is an audio signal processing technique used to enhance a signal by dynamic equalization, phase manipulation, harmonic synthesis of (usually) high frequency signals, and through the addition of subtle harmonic distortion. Dynamic equalization involves variation of the equalizer ...
Harmonic oscillators occurring in a number of areas of engineering are equivalent in the sense that their mathematical models are identical (see universal oscillator equation above). Below is a table showing analogous quantities in four harmonic oscillator systems in mechanics and electronics.