Spectrum Scope

Spectrum Scope is a specialization of the Perun Scope component custom-made for displaying and visualization of live spectra.

_images/scope_spectrum.png

Spectrum Scope with highlighted area for units selection.

The following functionality is specific for Spectrum Scope component:

  • Zooming and panning functionalities are horizontally constrained. It is impossible to zoom or pan outside the time-span of the shown signals.

  • It is possible to choose units for the horizontal (frequency) axis. The default frequency unit is Hertz (Hz), however, it is also possible to express frequencies as angular (in radians per second), as discrete frequencies (in radians) and as relative frequency. The last two options are specific for discrete-time analysis. Discrete frequency is obtained by multiplying angular frequency with the length of the sampling interval. Discrete frequency of \(\pi\) is equal to the Nyquist frequency, i.e. one half of the sampling frequency. Similarly, relative frequency of 1 is equal to the sampling frequency, etc.

  • It is also possible to choose units for the vertical (value) axis. Two options are supported, absolute units and decibel (dB) units. The connection is well-known, decibel value is 20 times logarithm with base 10 of the absolute value. Depending on the type of the spectrum one unit system may be preferred over another.

_images/scope_spectrum_db.png

Spectrum Scope with relative frequencies and amplitudes expressed in decibels.

Note. It is not possible to choose logarithmic scaling neither for the frequency nor for the value axis. These axes are always linear. Naturally, if decibels are chosen as the value unit, vertical axis will be linear in decibels, i.e. logarithmic in absolute values.