Spectrum Measurements
R&S
®
ESR
442
User Manual 1175.7068.02 ─ 12
The noise of an oscillator is determined by phase noise near the oscillator frequency
and by thermal noise of the active elements far from the oscillator frequency. Phase
noise can mask weak signals near the oscillator frequency and make them impossible
to detect.
6.4.5.1
Measuring Noise Power Density
To measure noise power referred to a bandwidth of 1 Hz at a certain frequency, the
R&S
ESR provides marker function. This marker function calculates the noise power
density from the measured marker level.
Measurement Example – Measuring the Intrinsic Noise Power Density of the
R&S
ESR at 1 GHz and Calculating the R&S
ESR's Noise Figure
Test setup:
► Connect no signal to the RF input; terminate RF input with 50 Ω.
Procedure:
1. Set the R&S
ESR to its default state by pressing the PRESET key.
The R&S
ESR is in its default state.
2. Set the center frequency to 1.234 GHz and the span to 1 MHz.
a) Press the FREQ key and enter "1.234 GHz".
b) Press the SPAN key and enter "1 MHz".
3. Switch on the marker and set the marker frequency to 1.234 GHz by pressing the
MKR key and entering "1.234 GHz".
4. Switch on the noise marker function by switching on the "Noise Meas" softkey.
a) Press the MKR FUNC key.
b) Switch the "Noise Meas" softkey to "On"
The R&S
ESR displays the noise power at 1.234 GHz in dBm (1Hz).
Note:
Since noise is random, a sufficiently long measurement time has to be
selected to obtain stable measurement results. This can be achieved by averaging
the trace or by selecting a very small video bandwidth relative to the resolution
bandwidth.
5. The measurement result is stabilized by averaging the trace.
a) Press the TRACE key.
b) Press the "Trace Wizard" softkey.
The Trace Wizard dialog box opens.
c) Select "Average" in the "Trace Mode" drop-down menu of the selected trace.
The R&S
ESR performs sliding averaging over 10 traces from consecutive sweeps.
The measurement result becomes more stable.
Advanced Measurement Examples
