Keysight EXG and MXG X-Series Signal Generators User’s Guide
249
Basic Digital Operation (Option 653/655/656/657)
I/Q Adjustments
I/Q Adjustments
Use the I/Q Adjustments to compensate for or add impairments to the I/Q signal.
I/Q
>
I/Q Adjustments
Available only when a
waveform is playing.
Adjusts the I signal amplitude relative to the Q
signal amplitude. Use this as an internal
impairment, or to compensate for differences in
signal path loss that occur due to path irregularities
in the external I and Q output cabling.
Offsets the phase of the Q signal
relative to the phase of the I signal.
The baseband quadrature
adjustment key is calibrated in units
of degrees. The external input
quadrature adjustment is not
calibrated.
The function provided by this key is
not the same as the function
provided by the
I/Q Skew
key.
Skew
is typically used either to create
impairments, or to reduce error vectors on large
bandwidth signals.
Provides a relative time delay correction between
the I and Q signals. The different signal paths
traveled by the I and Q signals result in time delay
differences that show up as an EVM error in large
bandwidth modulated signals.
Adding an equal and opposite time delay (skew) in
the I/Q signals during baseband generation
eliminates the time delay error, correcting for any
delays in signals that are generated in the internal
baseband generator.
Changes the absolute phase of
both the I and Q signals with
respect to triggers and markers.
Positive values add delay and
negative values advance the
signals. This value affects both
the baseband signal modulated
onto the RF and the external
output signals (I and Q). This
setting cannot be used with
constant envelope modulation
and it does not affect external I
and Q inputs.
Offsets
are typically used to either reduce carrier leakage, or to create an impairment that simulates carrier leakage.
Common Mode I/Q Offset Range
This changes the adjustment range of the Common Mode I/Q Offset from Coarse (Default) to fine or vice versa. The Coarse
range corresponds to the default value of
±
2.5V. The Fine range corresponds to a value of
±
100 mV.
Common Mode I/Q Offset
This adjusts the DC offset of both I and Q signals simultaneously.
Diff Mode I Offset
This adjusts the DC offset level of the I and I–bar output signal. I and I–bar cannot be adjusted independently.
Diff Mode Q Offset
This adjusts the DC offset level of the I and I–bar output signal. I and I–bar cannot be adjusted independently.
The DC offset values are calibrated relative to
the RMS waveform voltage being played out of
the ARB. See
.
The I/Q Attenuator softkey affects the I/Q signal to the
RF Output and the External I/Q Outputs.
This softkey is active when the I/Q optimized path is set
to
Ext I/Q Output
and a digital modulation personality
is on. This attenuation is also adjustable using the
Mod
Attenuator
key located in the Arb Setup menus in each
personality. This adjustment is not affected by the I/Q
Adjustments On/Off key.
When Auto mode is selected, the signal generator
automatically optimizes I/Q attenuation for the current
conditions. When the Manual mode is selected, I/Q
Attenuation is the active function. The value you enter
sets the attenuation level of the I/Q signal.
SCPI Commands (Refer to the commands for each
personality):
[:SOURce]:RADio:<personality>:IQ:MODulation:ATTen
This feature allows adjustment of the absolute phase of the internal I/Q channel by
rotating both I and Q, thus adjusting the relative phase of the RF carrier. For option
012, this is the only way to adjust the RF phase for a unit with an external LO.
Note: The I/Q signal will be
scaled down by 0.7071 for all
phase offsets except 0. Use
-360 or +360, if it is desirable
to maintain a constant power
level with the ALC off while
adjusting the I/Q phase.
