Input Coupling; Direct Path; Ghz - R&S FSW-K7 User Manual

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R&S FSW-K7
Remote command:
INPut:SELect

Input Coupling

The RF input of the R&S FSW can be coupled by alternating current (AC) or direct cur-
rent (DC).
This function is not available for input from the optional Digital Baseband Interface or
from the optional Analog Baseband Interface.
AC coupling blocks any DC voltage from the input signal. This is the default setting to
prevent damage to the instrument. Very low frequencies in the input signal may be dis-
torted.
However, some specifications require DC coupling. In this case, you must protect the
instrument from damaging DC input voltages manually. For details, refer to the data
sheet.
Remote command:
INPut:COUPling

Direct Path

Enables or disables the use of the direct path for small frequencies.
In spectrum analyzers, passive analog mixers are used for the first conversion of the
input signal. In such mixers, the LO signal is coupled into the IF path due to its limited
isolation. The coupled LO signal becomes visible at the RF frequency 0 Hz. This effect
is referred to as LO feedthrough.
To avoid the LO feedthrough the spectrum analyzer provides an alternative signal path
to the A/D converter, referred to as the direct path. By default, the direct path is
selected automatically for RF frequencies close to zero. However, this behavior can be
deactivated. If "Direct Path" is set to "Off", the spectrum analyzer always uses the ana-
log mixer path.
"Auto"
"Off"
Remote command:
INPut:DPATh
High-Pass Filter 1...3 GHz
Activates an additional internal high-pass filter for RF input signals from 1 GHz to
3 GHz. This filter is used to remove the harmonics of the analyzer to measure the har-
monics for a DUT, for example.
This function requires an additional hardware option.
(Note: for RF input signals outside the specified range, the high-pass filter has no
effect. For signals with a frequency of approximately 4 GHz upwards, the harmonics
are suppressed sufficiently by the YIG-preselector, if available.)
Remote command:
INPut:FILTer:HPASs[:STATe]
User Manual 1173.9240.02 ─ 23
on page 191
on page 189
(Default) The direct path is used automatically for frequencies close
to zero.
The analog mixer path is always used.
on page 190
on page 190
Configuration
Input and Frontend Settings
54