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The Spectrum Application
R&S
®
FPC
78
User Manual 1178.4130.02 ─ 07
2. Press the "Sweep" key to open the sweep menu.
3. Select the "Trigger" menu item to open the trigger menu.
4. Select the trigger source ("Video" or "External Rise / Fall"
5. Select either the "External Rise" or "External Fall" menu item (rising or falling
edge).
The R&S
FPC activates the trigger and shows the results of the measurement.
14.2.4
Measuring the Harmonic Distortion
Access
: "Meas" > "Measurement Mode" > "Harmonic distortion"
Remote commands required to configure harmonic distortion measurements:
●
Chapter 19.12.1.6, "Harmonic Distortion"
Available with the optional "Advanced Measurements" application.
The harmonic distortion measurement is an easy way to identify the harmonics of a
signal and their characteristics.
Ideally, a signal would show as a single peak in the spectrum. In the real world, how-
ever, systems contain imperfections, like nonlinearities, which add spectral compo-
nents to the initial signal (the fundamental, corresponding to the center frequency of
the analyzer). Among these additional spectral components are harmonics (also called
overtones), signals with higher frequencies than the fundamental, which show as
whole number multiples of the fundamental in the spectrum. Each harmonic has a
lower level than the fundamental, but they still affect the signal as a whole.
The harmonic distortion is designed to detect the harmonics of the signal you are mea-
suring. When you start a measurement, the R&S
FPC looks for the first harmonic of
the signal (= the highest signal) in the frequency range you have defined. The number
of harmonics it looks for depends on the number of harmonics you have defined. It
then adjusts the frequency axis so that all harmonics are visible.
In addition, the R&S
FPC also calculates the total harmonic distortion (THD). The THD
is the root mean square of all harmonics in relation to the power of the fundamental
frequency.
Selecting the harmonic distortion measurement
1. Press the "Meas" key to open the measurement menu.
2. Select the "Measurement Mode" menu item to select the measurement.
3. Select the "Harmonic Distortion" menu item.
The R&S
FPC starts to measure the harmonic distortion and position a marker on
each harmonic it has detected.
It also calculates the THD and shows the result in the diagram header.
Measurements and Result Displays