Rohde & Schwarz FSW13, User Manual

Page: 385 / 1150

Common Measurement Settings
R&S
®
FSW
385 User Manual 1173.9411.02 ─ 19
6.3.1 Impact of the Frequency and Span Settings
Some background knowledge on the impact of the described settings is provided here
for a better understanding of the required configuration.
● Defining the Scope of the Measurement - Frequency Range ...............................385
● Stepping Through the Frequency Range - Center Frequency Stepsize ............... 385
● Keeping the Center Frequency Stable - Signal Tracking ......................................385
● Coping with Large Frequency Ranges - Logarithmic Scaling ............................... 386
6.3.1.1 Defining the Scope of the Measurement - Frequency Range
The frequency range defines the scope of the signal and spectrum to be analyzed. It
can either be defined as a span around a center frequency, or as a range from a start
to a stop frequency. Furthermore, the full span comprising the entire possible fre-
quency range can be selected, or a zero span. The full span option allows you to per-
form an overview measurement over the entire span. Using the "Last Span" function
you can easily switch back to the detailed measurement of a specific frequency range.
For sinusoidal signals, the center frequency can be defined automatically by the
R&S
FSW as the highest frequency level in the frequency span (see "Adjusting the
Center Frequency Automatically (Auto Freq)" on page 438).
6.3.1.2 Stepping Through the Frequency Range - Center Frequency Stepsize
Using the arrow keys you can move the center frequency in discrete steps through the
available frequency range. The step size by which the center frequency is increased or
decreased is defined by the "Center Frequency Stepsize".
The "Center Frequency Stepsize" also defines the step size by which the value is
increased or decreased when you use the rotary knob to change the center frequency;
however, the
rotary knob moves in steps of only 1/10 of the "Center Frequency
Stepsize" to allow for a more precise setting.
By default, the step size is set in relation to the selected span or resolution bandwidth
(for zero span measurements). In some cases, however, it may be useful to set the
step size to other values.
For example, to analyze signal harmonics, you can define the step size to be equal to
the center frequency. In this case, each stroke of the arrow key selects the center fre-
quency of another harmonic. Similarly, you can define the step size to be equal to the
current marker frequency.
6.3.1.3 Keeping the Center Frequency Stable - Signal Tracking
If the signal drifts on the display but you want to keep the center frequency on the sig-
nal peak, the center frequency can be adjusted automatically using
signal tracking . In
this case, the signal trace is surveyed in a specified bandwidth around the expected
center frequency. After each sweep, the center frequency is set to the maximum signal
Frequency and Span Configuration