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Chapter 4 161
Making Measurements
Using Baseband I/Q Inputs (Option B7C)
Setting Up Baseband I/Q Inputs
Option B7C adds two keys that let you adjust the I/Q inputs; the I/Q
Setup key and the I/Q Range key. Both keys are located under the
Input/Output front panel key in the Input menu.
The
I/Q Range key lets you select one of four levels as an upper limit for
the signal being applied to the Baseband I/Q inputs. The level may be
selected in units of dBm, dBmv, dBuv, Volts, and Watts. The following
table shows the four-level selections available for each unit of measure:
The default is 1 Volt.
The
I/Q Range power levels in Table 4-8 are based on an I/Q Input Z of 50
Ω. I/Q Range voltage levels are independent of I/Q Input Z.
If I/Q Range is set below the default and the error message “Input
Overload
” is displayed, this value may be adjusted to its maximum.
Beyond that point, the signal must be attenuated to preserve the
measurement accuracy. Using a lower value than the default can
provide an increased dynamic measurement range.
I/Q Setup lets you adjust the following:
• I Offset - Use
I Offset to input a value in Volts to offset the measured I
value. The default value is 0.0000 Volts, the min/max values are
±
2.5600 Volts. The tuning increment depends on the I/Q Range setting
as shown in Table 4-9. This value only affects the displayed results,
and does not appear as a correcting voltage at the probe.
Table 4-8 I/Q Range Settings by Displayed Unit of Measure
Unit of
Measure
Highest
Setting
Lowest
Setting
dBm
13.0 dBm 7.0 dBm 1.0 dBm −5.1 dBm
dBmv
60 dBmv 54 dBmv 48 dBmv 41.9 dBmv
dBuv
120.0 dBuv 114.0 dBuv 108 dBuv 101.9 dBuv
Volts
1 Volt 500 mV 250 mV 125 mV
Watts
20.0 mW 5.0 mW 1.2 mW 310.0 uW