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The Spectrum Application

R&S

FPC

79User Manual 1178.4130.02 ─ 07

Defining the number of harmonics

The R&S FPC supports measurements on up to six harmonics.

By default, the R&S FPC shows the signal's fundamental and its first harmonic. The

fundamental and its harmonics are indicated by a marker that the R&S FPC places on

the detected peaks. Note that all markers that have been set are normal markers that

show the absolute frequency of the harmonic.

At the same time, the R&S FPC also calculates the values for the total harmonic distor-

tion (THD) and shows the results in a box above the trace diagram. The values are

output in % and in dB.

1. If you want to analyze more than one harmonic, press the "Meas" key to open the

measurement menu.

2. Select the "Harmonics" menu item.

3. Enter the number of harmonics you would like to see.

The R&S FPC updates the measurement accordingly.

Optimizing measurement settings

1. Press the "Meas" key to open the measurement menu.

2. Select the "Adjust Settings" menu item.

The R&S FPC adjusts the reference level, frequency and span to display all har-

monics in the best way.

14.2.5 Measuring the AM Modulation Depth

Access: "Meas" > "Measurement Mode" > "AM Modulation Depth"

Remote commands required to configure AM modulation depth measurements:

●

Chapter 19.12.1.7, "AM Modulation Depth", on page 244

Amplitude modulation (AM) is a modulation scheme that varies the amplitude of the

carrier based on the waveform of the transmitted signal.

The AM modulation depth measurement analyzes amplitude modulated signals and

shows the spectral signal characteristics. It also analyzes the modulation depth of the

signal using the measurement results. The AM modulation depth indicates how much

the modulated signal varies around the carrier amplitude. The AM modulation depth m

is calculated as follows.

m = peak signal amplitude / unmodulated carrier amplitude

For example, for m = 0.5, the carrier amplitude varies by 50 % above and below its

unmodulated level.

For m = 1, it varies by 100 %.

Note that the measurement works properly only if you apply an AM modulated signal.

Measurements and Result Displays

R&S FPC Series User Manual

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