R&S FSMR, Operating Manual

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R&S FSMR MKR – Analyzer
1166.3363.12 4.13-3 E-1
Frequency Measurement with the Frequency Counter
In order to accurately determine the frequency of a signal, R&S FSMR is equipped with a frequency
counter which measures the frequency of the RF signal at the intermediate frequency. Using the meas-
ured IF, R&S FSMR calculates the frequency of the RF input signal by applying the known frequency
conversion factors.
The frequency measurement error depends only upon the accuracy of the frequency standard used
(external or internal reference). Although R&S FSMR always operates synchronously irrespective of the
set span, the frequency counter delivers a more exact result than a measurement performed with a
marker. This is due to the following:
•
The marker measures only the position of the pixel on the trace and infers the frequency of the sig-
nal from this value. The trace, however, contains only a limited number of pixels. Depending upon
the selected span, each pixel may contain many measurement values, which therefore limits the
frequency resolution.
•
The resolution with which the frequency can be measured is proportional to the measurement time.
For this reason, the bandwidth is normally made as wide as possible and the sweep time as short as
possible. This results in a loss of frequency resolution.
For the measurement with the frequency counter, the sweep is stopped at the reference marker, the
frequency is counted with the desired resolution and then the sweep is allowed to continue.
SIGNAL
COUNT
The SIGNAL COUNT softkey switches the frequency counter on/off.
The frequency is counted at the position of the reference marker ( MARKER
1). The sweep stops at the reference marker until the frequency counter has
delivered a result. The time required for a frequency measurement depends
on the selected frequency resolution. The resolution is set in the side menu.
If no marker is enabled when the SIGNAL COUNT softkey is pressed,
MARKER 1 is switched on and set at the largest signal.
In addition, the SIGNAL COUNT function is displayed in the marker info field
on the screen with [Tx CNT].
MARKER 1 [T1 CNT]
23.4567891 MHz
-27.5 dBm
Switching the SIGNAL COUNT function off is accomplished by pressing the
softkey again.
IEC/IEEE-bus command:
CALC:MARK1:COUN ON;
CALC:MARK:COUN:FREQ?