6 Input/Output
6.2 Input
bar together compose the Q channel. Each channel has two modes of operation,
Single-Ended (also called "unbalanced") and Differential Input (also called
"balanced"). When in Single-Ended operation, only the main port (I or Q) is used,
and the complementary port (I-bar or Q-bar) is ignored. When in Differential Input
mode, both main and complementary ports are used.
The input settings (range, attenuation, skew, impedance, external gain) apply to the
channels, not the individual ports.
The system supports a variety of 1 MΩ input passive probes as well as the Keysight
113x Series active differential probes using the Infinimax probe interface.
The Keysight 113x Series active probes 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 50Ω
single ended 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 higher attenuation is used at the probe interface.Higher attenuation 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. Most
Keysight passive probes can be automatically identified by the system, setting the
input impedance setting 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, with the attenuation and impedance settings configured manually.
For full differential measurements, the system supports probes on each of the four
inputs. The attenuation of the probes should be the same for good common mode
rejection and channel match.
Both active and passive probes in single ended and differential configurations can
be calibrated. This calibration uses the Cal Out BNC connection and a probe
connection accessory. The calibration achieves excellent absolute gain flatness in a
probed measurement. It matches both the gain and frequency response of the I and
Q channels as well as any delay skew, resulting in high accuracy in derived
measurements such as Error Vector Magnitude (EVM).
When a probe is connected a status message will be displayed. The message will
indicate if calibration data is available or not. Calibration data is saved for each type
of probe (including "none") for each port and will be reapplied whenever that type of
probe is re-connected to the same port. For probes with EEPROM identification, the
calibration data will be stored based on the unique probe identifier and will reapply
data for that particular probe if it is available. The data will not follow a probe from
one port to another. For probes without EEPROM identification, the instrument
Short Range Comms & IoT Mode User's &Programmer's Reference 2032
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