Can I Phase Synchronize Multiple RF Devices?Hardware: PXI/CompactPCI>>Controllers
Problem: Is it possible to phase synchronize any two or more of the following RF devices: NI PXI-5660, NI PXI-5661, NI PXIe-5663, NI PXI-5670, NI PXI-5671, NI PXIe-5672, or NI PXIe-5673? Solution: The short answer is no for the 5660, 5661, 5670, 5671 and 5672. Although you can reference all the devices to the same 10 MHz reference clock and synchronize their start triggers, each device has its own local oscillator (LO) that cannot be shared between multiple devices. Each LO is susceptible to inherent phase drift and noise that affects each individual device. The result is that any two devices requiring an LO cannot be accurately synchronized. The following diagram shows how an LO is used to mix a signal from an intermediate frequency (IF) to a radio frequency (RF). In reality, the NI 5600 and the NI 5610 use three of these mixers to convert the signal.  The architecture of the PXIe-5673 and PXIe-5663 allows for phase coherent applications between multiple generators or multiple analyzers. Each PXIe-5673 and PXIe-5663 uses an external source for the LO, which by default is provided by a PXI-5652 RF Source. Because the LO is external, you can split the signal between several generators or several analyzers. Furthermore, the PXIe-5601 downconverter and PXIe-5611 IQ modulator are cable of repeating the LO signal for a daisy chain configuration. Here is an example on how to configure this in your PXI chassis:
Please see the NI RF Signal Generators or RF Vector Signal Analyzer help files on how to setup and associate multiple 5673s and 5663s. NOTE: The PXIe-5673 and PXIe-5663 cannot be phase synchronized together due to the fundamental difference in architecture. The PXIe-5673 is a direct to RF upconversion system, while the PXIe-5663 is super heterodyne downconversion using a dedicated IF frequency. This difference requires two different LO frequencies when generating and analyzer at the same RF frequency. Related Links: Attachments:  - rfmixer.gif
Report Date: 11/09/2006 Last Updated: 03/08/2009 Document ID: 438G2PQ7 |
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