Agilent Technologies Signal Analyzer N9030a - Manual (Page 593)

6 RLC Swept SA Measurement Front-Panel & SCPI Reference
Input/Output
The Agilent 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 50 Ω 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 Agilent 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 cannot distinguish between different probes of the same type and it will use the
data from the last calibration for that probe type on that port.
When in differential mode, both the main and complementary probes are expected to be of the
same type.
In some situations, the I and Q channels should be configured identically. In other situations it is
convenient to control them independently. Some menus have a "Q Same as I" setting that will
cause the Q channel configuration to mirror the I channel configuration, avoiding the overhead of
double data entry when the channels should be the same.
The output port is for calibrating the I/Q input ports, although it can also be manually controlled.
There are two types of calibrations available: cable calibration and probe calibration. The cable
calibration will guide the user through connecting each input port in turn. All ports must be
Remote Language Compatibility Measurement Application Reference 593