Selecting Input Probes For Baseband Measurements - Keysight X Series Measurement Manual

Selecting input probes for baseband measurements

The selection of baseband measurement probe(s) and measurement method is
primarily dependent on the location of the measurement point in the circuit. The
probe must sample voltages without imposing an inappropriate load on the circuit.
The system supports a variety of 1 MΩ impedance input passive probes as well as
the Keysight 1153A active differential probe using the InfiniMax probe interface.
The Keysight 1153A active probe can be used for both single-ended and differential
measurements. In either case a single connection is made for each channel (on either
the I or Q input). The input is automatically configured to 50 Ω single-ended type
measurement and the probe power is supplied through the InfiniMax interface. The
probe can be configured for a variety of input coupling and low frequency rejection
modes. In addition, a wide range of offset voltages and probe attenuation accessories
are supported at the probe interface. The active probe has the advantage that it does
not significantly load the circuit under test, even with unity gain probing.
With passive 1 MΩ probes, the probe will introduce a capacitive load on the circuit,
unless a higher attenuation is used at the probe interface. Higher attenuation helps
isolate the probe, however, it reduces the signal level and degrades the
signal-to-noise-ratio of the measurement. Passive probes are available with a variety
of attenuation values for a moderate cost. Many Keysight passive probes can be
automatically identified by the system, setting the input impedance required as well
as the nominal attenuation. For single-ended measurements a single probe is used for
each channel. Other passive probes can be used, after manually setting the
attenuation and probe impedance configurations.
For full differential measurements, the system supports probes on each of the four
inputs. The attenuation for each of the probes should be the same for good common
mode rejection and channel match.
Supported probes
The following table lists the probes currently supported by Option BBA:
Probe Type
Active
Passive
Baseband I/Q Inputs (Option BBA) Measurement Concepts
Model Number Description
1130A 1.5 GHz differential probe amp
(No probe head)
InfiniMax 3.5 GHz probe
a
1131A
InfiniMax 5 GHz probe
a
1132A
InfiniMax 7 GHz probe
a
1133A
1161A Miniature passive probe, 10:1, 10 MΩ, 1.5 m
223
Concepts