R&S FSMR, Operating Manual

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R&S FSMR Analyzer - MEAS
1166.3363.12 4.16-27 E-2
Measurement principle:
For example, the bandwidth containing 99% of the signal power is to be determined. The routine first
calculates the total power of all displayed points of the trace. In the next step, the points from the right
edge of the trace are summed up until 0.5% of the total power is reached. Auxiliary marker 1 is
positioned at the corresponding frequency. Then the R&S FSMR sums up the points from the left edge
of the trace until 0.5% of the power is reached. Auxiliary marker 2 is positioned at this point. 99% of the
power is now between the two markers. The distance between the two frequency markers is the
occupied bandwidth which is displayed in the marker info field.
A prerequisite for correct measurement is that only the signal to be measured is visible on the screen of
the R&S FSMR. An additional signal would invalidate the measurement.
To ensure correct power measurement especially for noise signals and to obtain the correct occupied
bandwidth, the following settings should be selected:
RBW
<< occupied bandwidth (approx. 1/20 of occupied bandwidth, for voice
communication type. 300 Hz or 1 kHz)
VBW 3 x RBW
Detector RMS or sample
Span 2 to 3 x occupied bandwidth
Some of the measurement specifications (e.g. PDC, RCR STD-27B) require measurement of the
occupied bandwidth using a peak detector. The detector setting of the R&S FSMR has to be changed
accordingly then.
Example :
Measurement of occupied bandwidth of a PDC signal at 800 MHz, level 0 dBm
[ PRESET ] Set the R&S FSMR to the default setting.
[ FREQ : CENTER : 800 MHz] Set the center frequency to 800 MHz.
[ AMPT : 0 dBm] Set the reference level to 0 dBm.
[ MEAS ] Call the menu for the measurement functions.
[ OCCUPIED BANDWIDTH ] Select measurement of the occupied bandwidth and open the submenu
for configuring the measurement.
[% POWER BANDWIDTH : Select 99% for the bandwidth to be measured.
99 % ]
[ CHANNEL BANDWIDTH : Enter the channel bandwidth of 21 kHz specified by PDC.
21 kHz ]
[ ADJUST SETTINGS ] Optimize the measurement parameters for the specified channel band-
width.
Allow for a complete frequency sweep so that the R&S FSMR can
determine the total signal power.
[ ADJUST REF LVL ] Adjust the reference level to the measured signal power.
[ TRACE : DETECTOR : PDC requires measurement of the occupied bandwidth using a
DETECTOR MAX PEAK ] peak detector. Therefore, switch on the peak detector instead of the
RMS detector selected by
ADJUST SETTINGS .