Vsg25a multiple signals

Hello,

Curious if its possible to generate multiple qpsk signals within the VSG25a’s bandwidth using the arbitrary plugin or add signals to the tab to generate more of them?

The challenge with the VSG25A is keeping your signal to <=2048 repeating I/Q samples. There's no reason you couldn't have 2 to 8 QPSK channels if they're ideally spaced and playing a short repeating sequence (Maybe 16-64 symbols would be a maximum). The VSG60 or VSG200 could handle much more complex (and arbitrarily longer) sequences, but 40 MHz of bandwidth is all you get.

Does anyone have an example arbitrary file to do this?
Or a better explanation than I can find?

What exactly are you looking to do? Basically anything custom is going to require some DSP tools, like Matlab or our VSG60 software.

For the VSG25 you’ll need to choose your I/Q sample rate and pattern length so the sequence can repeat perfectly, e.g. 4 MSPS, upsample by 32 for a 128 MHz sample clock. Use a repeating pattern of e.g. 32 symbols for 1024 sample pattern length. Then you can shift the center frequency in units of 128/1024 MHz, repeat for each QPSK signal, add and scale.
You can generate a sequence twice as long, then use the middle portion, to remove any edge artifacts.

Note that the VSG60 does not have the same limitations, and is generally the preferred tool for applications like this.

I have vsg60s as well. But those can be controlled via 3db labs sceptre.
This is for SATCOM signal emulation, which we want to have multiple qpsk signals spread a few MHz spart. The iq pattern doesn’t matter much

[Justin Crooks]

Our latest VSG60 software allows you to export waveforms. If you email me the details I might be able to throw a waveform together, as long as you’re ok with me rounding to easy offsets. justin at signalhound dot com

I’d need to know symbol rate, root raised cosine filtering unless otherwise specified, channel count and spacing

• This reply was modified 2 weeks, 3 days ago by Justin Crooks.

Essentially I’d just make a QPSK waveform, apply N rotations, probably in excel, maybe stagger them for a more realistic envelope, add them together and scale.

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