N5161A/62A/81A/82A/83A MXG Signal Generators User's Guide

Basic Digital Operation (Option 651/652/654)Understanding Option 012 (LO In/Out for Phase Coherency) with Multiple Baseband Generator SynchronizationUnderstanding Option 012 (LO In/Out for Phase Coherency) with MultipleBaseband Generator SynchronizationNOTEThis section assumes that the previous section on Multiple Baseband GeneratorSynchronization has been read and understood. If not, refer to “Multiple Baseband GeneratorSynchronization” on page 218 before continuing.The MXG with Option 012, enables 2x2, 3x3, or 4x4 MIMO configurations to share a common externalLO signal to create a phase coherent system (refer also, to “Multiple Baseband GeneratorSynchronization” on page 218).RF phase coherency may not be needed for general STC/MIMO receiver testing, since a MIMO receiverperceives any phase differences between the sources as part of the channel conditions and correct forthem. But, RF phase coherency might be desirable for certain applications such as R&D onbeamforming systems.Configuring the Option 012 (LO In/Out for Phase Coherency) with MIMOThe Agilent BNC cable, part number 10502A, is the recommended cable for the standard multi–BBGsynchronization setup, and is recommended for Option 012 too (see also Figure 8- 29 on page 222).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 8- 5, Figure 8- 30 on page 227, and Figure 8- 31 onpage 228).NOTEAgilent 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, theinstrument 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 phase coherent configuration requires the following:• The recommended LO input drive level should be in the 0 to 6 dBm range.NOTEThe 0 to 6 dBm LO input drive level ensures the instruments will operate over the fullfrequency and over the full 0 to 55 ambient temperature range 1 .• The I/Q calibration and the self–test must be performed with the LO In/Out jumper cable inplace. Where the I/Q calibration cannot be run, the baseband offset can be manually adjusted tominimize the I/Q offsets.• The phase coherency feature only applies to the Dual ARB modulation mode.• All cables from the splitter output to the instrument inputs should be of equal lengths.1 LO input power requirements vary with temperature; power