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Output Power Amplitude May Be Incorrect When Generating Signals Below 2.5 MHz With the PXI-5670 and PXI-5671

Primary Software: Driver Software>>NI-RFSG
Primary Software Version: 1.2
Primary Software Fixed Version: 1.3
Secondary Software: N/A

Problem:
A recently discovered issue within the NI-RFSG driver (specifically versions 1.2, 1.2.1, and 1.2.5) can cause the RF output power of the PXI-5670 and PXI-5671 Vector Signal Generators to be off by ~2-3 dB when generating signals below 2.5 MHz in frequency.

The PXI-5670 and PXI-5671 are composed of a baseband arbitrary waveform generator (the PXI-5421 and PXI-5441, respectively) combined with the PXI-5610 RF upconverter module. When a new output frequency is requested, the NI-RFSG driver determines the new required PXI-5610 center frequency (RF center frequency) and new arb center frequency (IF center frequency).

For frequency changes less than 5 MHz, the PXI-5610 upconverter stays fixed (RF center unchanged) while the PXI 54x1 arb changes (IF center frequency moves). It is this situation where the aforementioned issue becomes a consideration, as incorrect calibration corrections are applied. The design of the PXI-5610 is such that the change of these calibration correction factors over frequency will only create output power errors that may cause the generator to be out of spec below 2.5 MHz.

Potential applications that could be affected by this are frequency sweeps starting below 2.5 MHz with frequency steps < 5 MHz wide, as well as AM radio testing.

Solution:
The immediate solution to this problem currently is to use the attached, fixed NI-RFSG DLL. The fix for this issue will be included in NI-RFSG 1.3, so once NI-RFSG 1.3 is released the solution will be to simply install the latest driver.

Instructions for installing fixed NI-RFSG DLL (nitnr2u.dll):
These instructions require NI-RFSG 1.2.5 to be installed. If an NI-RFSG version earlier than 1.2.5 is installed, you will have to upgrade to version 1.2.5 before executing the following steps that update the NI-RFSG DLL. If the following steps are executed on a system with a NI-RFSG version earlier than 1.2.5, the driver will not operate properly.

To check your version of NI-RFSG, launch Measurement and Automation Explorer and expand My System ยป Software. Click on the entry for NI-RFSG and the version will be displayed on the right hand side of the MAX screen. Download NI-RFSG 1.2.5 if needed. (See link below)
  1. Go to Start -> Run on the Windows taskbar
  2. In the run prompt, type 'cmd' and hit enter to bring up a command prompt.
  3. In the command prompt, type 'net stop nidevldu' and hit enter. You should see a message stating the NI Device Loader service was stopped successfully. Leave the command prompt available.
  4. Back in Windows, rename nitnr2u.dll to nitnr2u.dll_bak in C:\Windows\System32
  5. Copy the fixed nitnr2u.dll attached to this article to C:\Windows\System32
  6. Back in the command prompt, type net start nidevldu and press enter. You should see a message stating the NI Device Loader service was started successfully.


Related Links:
NI-RFSG 1.2.5

Attachments:


nitnr2u.dll - nitnr2u.dll

Report Date: 04/25/2007
Last Updated: 04/25/2007
Document ID: 48OFP8D3

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