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ni5660 Configure for IQ VI Sets Incorrect RF and IF Attenuation Values on NI PXI-5660 RF Signal Analyzer

Primary Software: Driver Software>>NI-RFSA
Primary Software Version: 2.0
Primary Software Fixed Version: 2.0.1
Secondary Software: N/A
Hardware: Modular Instruments>>RF Measurement Devices>>PXI-5660

Problem: The version of the ni5660 VI titled 'ni5660 Configure for IQ' that is installed by NI-RFSA 2.0 sets incorrect attenuation on the NI PXI-5660 RF vector signal analyzer.

This issue only occurs when using the LabVIEW ni5660 Configure for IQ VI to configure an IQ data acquisition on an NI PXI-5660, which is composed of the NI PXI-5600 downconverter interconnected with NI PXI-5620 IF digitizer. Users programming other NI RF vector signal analyzers using NI-RFSA driver calls are unaffected. Users programming the NI PXI-5660 in other ADEs, such as LabWindows/CVI are also unaffected.

The NI PXI-5660 (or more specifically the NI PXI-5600 RF downconverter) contains both RF attenuators and IF attenuators. A change in the ni5660 Configure for IQ VI implemented in the NI-RFSA 2.0 installation package causes incorrect RF and IF attenuation values to be set when users configure the reference level (dBm) parameter to be greater than -20. If a reference level input of -20 dBm or below is configured, the attenuators are set correctly.

The effects of the incorrect attenuator values on the NI PXI-5660 are higher distortion products (i.e. spurs) and thermal noise (i.e. noise floor) than are listed in the specifications. In addition, warnings regarding ADC overload and longer than expected settling times are also indicative of this issue.

Solution: The solution for this issue is to install NI-RFSA 2.0.1 or later. NI-RFSA 2.0.1 contains a fix for the issue described in this document. Future releases will also contain this fix. See the Related Links section for a link to the latest versions of National Instruments RF products available for download.

Related Links: http://digital.ni.com/softlib.nsf/webcategories/86256C220055D6BC86256C24002C4ACF?opendocument&node=132060_US

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Report Date: 10/17/2006
Last Updated: 10/23/2006
Document ID: 42GFJCY5

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