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Concepts
Baseband I/Q Inputs (Option BBA) Measurement Concepts
Probes without stored calibration
The following 115xA active probes may be used with the MXA’s baseband IQ inputs
and may use the same probe calibration utility software. However, the probe
calibration data is not stored in the MXA and will be lost if power is cycled. Use of
the E2655B de-skew and calibration kit, including the calibration fixture, is required
because of the different physical configuration of the probes. (The physical
connections are different mechanically, not electrically.)
Refer to the current Keysight probe data sheet for specific information regarding
frequency of operation and power supply requirements.
Baseband I/Q measurement views
Measurement result views made in the IQ Analyzer (Basic) mode are available for
baseband signals if they relate to the nature of the signal itself. Many measurements
which relate to the characteristics that baseband I and Q signals have when mixed
and upconverted to signals in the RF spectrum can be made as well. However,
measurements which relate to the characteristics of an upconverted signal that lie
beyond the bandwidth available to the Baseband I/Q Input circuits can not be
measured (the limit are dependent on the installed options: Standard – 10 Hz to 20
MHz, Option B25 – 10 Hz to 50 MHz, and Option S40 – 10 Hz to 80 MHz).
At RF frequencies, power measurements are conventionally displayed on a
logarithmic vertical scale in dBm units, whereas measurements of baseband signals
using Baseband I/Q inputs may be conveniently displayed as voltage using a linear
vertical scale as well as a log scale.
Spectrum views and 0 Hz center frequency
To view the Spectrum display of I only or Q only signals, use the Complex Spectrum
measurement capability in IQ Analyzer (Basic) Mode.
I only and Q only Spectrum views are conventional, displayed with 0 Hz at the left
side of the horizontal axis. When upconverted or multiplied, an I only or Q only
signal could ultimately lie above or below the carrier center frequency, but in either
case it will only occupy half the bandwidth.
a. Probe heads are necessary to attach to your device properly. Probe con-
nectivity kits such as the E2668A, E2669A or E2675A are needed. For
more details, refer to the Keysight probe configuration guide,
5968-7141EN and 5989-6162EN.
Probe Type Model Number Description
Active 1153A 200MHz differential probe
1156A Active probe, 1.5 GHz
1157A Active probe, 2.5 GHz
1158A Active probe, 4 GHz
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