Problems with Generating Sources on Zoomed Spans in VirtualBench-DSA 2.5Primary Software: Other NI Software>>VirtualBenchPrimary Software Version: 2.5 Primary Software Fixed Version: N/A Secondary Software:
Problem: I am using version 2.5 of VirtualBench-DSA. If I generate Periodic Random Noise (PRN) and I get the Zoomed Span back, I do not see a flat constant power level on the power spectrum. I see a constant power level on every other FFT bin, so it looks like a very noisy signal instead of a nice flat line. However, if I use BaseBand instead, I see a nice flat line. Solution: The problem is that VirtualBench 2.5 does not uses the same FFT size for the BaseBand and the Zoom, and does not provide any way to change this. Then the PRN is generated based on the BaseBand span. It will generate energy on every BaseBand span frequency bin. This means that the Zoom span will show the correct information, but the energy is in every frequency bin that was set with energy according to the BaseBand FFT size, not the Zoom span size. You might see this behavior in LabVIEW as well, but there you can fix it by setting the Size on BaseBand and Zoom to be the same. For 400 lines BaseBand will use 1K, and for 1K Zoom can give you up to 800 lines. If you set the number of lines that way, you will see constant power all over your span. VirtualBench 2.5 does not have a work around for this yet. The problem is in the source code and you cannot make BaseBand and Zoom have the same size, so it will be fixed on a future release of Virtual Bench . Related Links: Attachments:
Report Date: 12/14/1998 Last Updated: 12/05/2002 Document ID: 1GDE420O |
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