6 Input/Output
6.2 Input
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 calibrated together. The probe calibration is done for a specific
channel (I or Q). If in Single-Ended mode, only the main port is calibrated. When in
Differential Input mode, the user is guided through calibrating both main and
complementary ports.
The front panel I/Q port LEDs indicate the current state of that port. On (green)
indicates it is active, and off (dark) indicates it is not in use. For example, the Cal Out
port LED is on if and only if there is signal coming out of that port.
The input is a context, and some parameters have separate values for each context.
The SCPI for these parameters has an optional "[:RF|IQ]" node. If the specific context
is omitted, the command acts on the current input context's value. Here are the
parameters that are input context sensitive:
–
Center Frequency
–
Trigger Source
It is important to distinguish between the I and Q input ports and the displayed I and
Q data values. The I and Q input ports feed into a digital receiver that does digital
tuning and filtering. The I and Q data seen by the user (either on the display or
through SCPI) corresponds to the real ("I") and the imaginary ("Q") output from the
digital receiver. When the input path is I+jQ or I Only and the center frequency is 0
Hz the I input ends up in as the real output from the receiver and appears as "I" data.
Likewise, when the input path is I+jQ and the center frequency is 0 Hz, the Q input
ends up as the imaginary output from the receiver and appears as "Q" data.
However, when the input path is Q Only, the Q input is sent to the receiver as Q+j0,
so the receiver output has the Q input coming out on the real output, and so in Q
Only, the signal from the Q input port appears as the "I" data. Another situation
where the I and Q data do not necessarily correspond directly to the I and Q inputs is
when the center frequency is non-zero. The digital processing involved in the tuning
2033 Short Range Comms & IoT Mode User's &Programmer's Reference
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