![]() The instantaneous frequency of an electronic signal (e.g. However, a plot of instantaneous frequency versus time generally does not carry the same information. The time dependence of the instantaneous frequency can sometimes be estimated from a spectrogram. The relation between instantaneous frequency and Fourier frequency is substantially more subtle than that. (root mean squared) value of the instantaneous frequency. Note that the Fourier spectrum of an oscillating signal (in optics, the optical spectrum) does not represent the probability distribution of instantaneous frequencies, and that the linewidth measured from such a spectrum is not an r.m.s. The instantaneous frequency is also useful in the context of chirped optical pulses, where the instantaneous frequency varies during the pulse. In the context of lasers, the instantaneous frequency can be easily defined for single-frequency lasers, whereas for multimode lasers one would first have to separate the different frequency components (with some filtering technique) before retrieving their instantaneous frequencies. However, the concept can become problematic for complicated signals, e.g. ![]() ![]() in music: music scores essentially specify notes as time intervals for which the instantaneous frequency has a certain value (corresponding to the pitch of one voice, and disregarding overtones). The basic idea is intuitive, actually more than that of Fourier frequencies. The concept of the instantaneous frequency is particularly important in the context of frequency noise and phase noise, but it is also applied to chirped optical pulses (Figure 1), which have a time-dependent instantaneous frequency. Figure 1: Electric field of a strongly up-chirped pulse, where the instantaneous frequency increases with time. The instantaneous frequency of a sinusoidal signal is constant and equals the oscillation frequency, as expected. (Without the factor 1/2, one would have the instantaneous angular frequency.) In contrast to a Fourier frequency, the instantaneous frequency is generally a time-dependent frequency. essentially as the temporal derivative of the oscillation phase. The instantaneous frequency is a useful concept for describing non- monochromatic ( polychromatic) signals – not only in optics. How to cite the article suggest additional literature ![]() German: instantane Frequenz, Momentanfrequenz Encyclopedia > letter I > Instantaneous frequency Instantaneous FrequencyÄefinition: temporal derivative of the oscillation phase divided by ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |