Keysight EXG and MXG X-Series Signal Generators User’s Guide 241
Basic Digital Operation for N5172B/82B with Options 653/655/656/657
Understanding Option 012 (LO In/Out for Phase Coherency) with Multiple Baseband Generator
Synchronization
Understanding Option 012 (LO In/Out for Phase Coherency) with
Multiple Baseband Generator Synchronization
The MXG/EXG with Option 012, enables 2x2, 3x3, or 4x4 MIMO configurations to share a common
external LO signal to create a phase coherent system (refer also, to “Multiple Baseband Generator
Synchronization” on page 234).
RF phase coherency may not be needed for general STC/MIMO receiver testing, since a MIMO
receiver perceives any phase differences between the sources as part of the channel conditions and
correct for them. But, RF phase coherency might be desirable for certain applications such as R&D
on beamforming systems.
Configuring the Option 012 (LO In/Out for Phase Coherency) with MIMO
The Keysight BNC cable, part number 10502A, is the recommended cable for the standard multi–
BBG synchronization setup, and is recommended for Option 012 too (see also Figure 8-29 on
page 237). Additionally, for the 2x2, 3x3, and 4x4 MIMO connections from the LO IN and LO OUT to
the splitter, additional cables are required (refer to Table , Figure 8-30 on page 243, and Figure
8-31 on page 244).
The phase coherent configuration requires the following:
— The recommended LO input drive level should be in the 0 to 6 dBm range.
— The I/Q calibration and the self–test must be performed with the LO In/Out jumper cable in
place. Where the I/Q calibration cannot be run, the baseband offset can be manually adjusted
to minimize the I/Q offsets.
This section assumes that the previous section on Multiple Baseband
Generator Synchronization has been read and understood. If not, refer to
“Multiple Baseband Generator Synchronization” on page 234 before
continuing.
Keysight recommends the LO Output be covered when not in use.
When the LO In/Out jumper cable is removed and the instrument is in
Dual ARB mode, the instrument is unleveled and the instrument displays
an Unlevel error message.
All test equipment requires a 12 hour warm–up period to ensure accurate
performance.
The 0 to 6 dBm LO input drive level ensures the instruments will operate
over the full frequency and over the full 0 to 55 ambient temperature
range
a
.
a. LO input power requirements vary with temperature; power <0 dBm may work at 20–30 degree
ambient temperature conditions. Refer to the Data Sheet.
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