Configuration
R&S
®
VSE-K149
22
User Manual 1179.3315.02 ─ 01
Instrument
Specifies a configured instrument to be used for input.
Input 1 / Input 2
For instruments with two input connectors, you must define which input source is used
for each measurement channel.
Note that you cannot use both RF inputs simultaneously.
"Input 1"
R&S
FSW85: 1.00
mm RF input connector for frequencies up to
85
GHz (90
GHz with option R&S
FSW-B90G)
"Input2"
R&S
FSW85: 1.85
mm RF input connector for frequencies up to
67
GHz
Remote command:
Input Coupling
The RF input of the R&S
VSE can be coupled by alternating current (AC) or direct cur-
rent (DC).
The RF input of the connected instrument can be coupled by alternating current (AC)
or direct current (DC).
For an active external frontend, input coupling is always DC.
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:
Impedance
For some measurements, the reference impedance for the measured levels of the con-
nected instrument can be set to 50
Ω
or 75
Ω
.
Select 75
Ω
if the 50
Ω
input impedance is transformed to a higher impedance using a
75
Ω
adapter of the RAZ type. (That corresponds to 25
Ω
in series to the input impe-
dance of the instrument.) The correction value in this case is 1.76 dB = 10
log (75
Ω
/
50
Ω
).
Remote command:
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.
Input and Frontend Settings
