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R&S FSL
Measuring of AM–Modulated Signals
The spectrum analyzer rectifies the RF input signal and displays it as a magnitude spectrum.
The rectification also demodulates AM–modulated signals. The AF voltage can be displayed in
zero span if the modulation sidebands fall within the resolution bandwidth.
Displaying the AF of an AM–Modulated Signal (Zero Span)
Test setup:
Signal
R&S FSL
Generator
Signal generator settings (e.g. R&S SMU):
Frequency: 128 MHz
Level:
0 dBm
Modulation: 50 % AM, 1 kHz AF
Procedure:
1. Set the spectrum analyzer to the default state.
– Press the PRESET key.
The R&S FSL is set to its default state.
2. Set the center frequency to 128 MHz and the span to 0 Hz.
– Press the FREQ key and enter 128 MHz.
– Press the SPAN key and enter 0 Hz or press the Zero Span softkey.
3. Set the reference level to +6 dBm, the display range to linear and the unit to Volt.
– Press the AMPT key and enter 6 dBm.
– Press the Range Linear softkey.
– Press the More
– Press the Unit softkey and select Volt.
4. Triggering in response to the AF signal by using the video trigger to produce a static
image.
– Press the TRIG key.
– Press the Trg/Gate Source softkey and select Video using the arrow keys.
– Press the Trg/Gate Level softkey and enter 50%.
The trigger level is displayed as a horizontal line across the entire measurement
diagram. The R&S FSL displays the 1 kHz AF signal as a static image in zero span.
The AF can be listened to by using a headset.
1300.2519.62
Measuring Signal Spectra with Multiple Signals
softkey
5.15
E-10
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