04-02-2015 08:46 AM
hi all
i need help to make waterfall like this
i found this foto on google
i have a fm signal and want to see it in time - frequency graph time on y- axe and freq in x-axe
plz help - me
04-02-2015 04:01 PM
Waterfall plots can be difficult to accomplish depending on what refresh rate you need. Also, what kind of instrument do you have? You can do a lot more on the VSTs and 5668 since they allow you to customize the FPGA.
You can start with something like this. I took the RFSA getting started with IQ example, looped the acquistion, and charted the overall measured power. In the attached VI, you'd want to set your center frequency and use the IQ rate to define your channel width.
This example will miss data between each measurement (during the data processing portion). If you need to catch absolutely everything, you might want to take a look here: https://decibel.ni.com/content/docs/DOC-41154
Somewhere in between might be the streaming examples for the VST. Instead of displaying the spectrum in that example, you could calculate the power and chart it.
04-03-2015 03:10 PM
thanx for your help
but the example not working
how can i put time on y-axe
04-03-2015 03:42 PM
How is the example not working? Is there an error? What kind of hardware are you using?
You can see an example of how to set the X-axis to time here:
04-03-2015 03:58 PM
pxi 5661
and i want time on y not on x
04-03-2015 05:58 PM
I don't think you can change the chart direction, and this code could use some optimization. (It was quickly stolen from the RTSA example up above, without his optimizations)
It uses the intensity graph instead of the chart. The chart would go left to right, and it's MUCH faster in this example. But this gets you in the ballpark, I think.
04-06-2015 01:11 PM
Just for completeness, here's a more optimized version of the last VI. It uses a queue to take advantage of parallel processing and the 'transpose array' option on the intensity graph to speed things up. You'll have to manually update the frequency axis offset and multiplier to make it correspond to the correct frequency. The same is true of the time axis. This one is MUCH faster than the previous VI.