MER display in signal analysis

Is there a way of displaying the MER (in dB) value as well as
the EVM value when doing modulation analysis using Spike?
If not could it be added in a later version of the software.
It should be a relatively easy thing to do.

– Charles

Hello Charles,

There is not currently a way to display this number. To clarify as well, MER(dB) == SNR(dB) ?

You can find an equation for the EVM(%) -> SNR(dB) conversion here.
https://www.keysight.com/main/editorial.jspx?ckey=847674&id=847674&nid=-11143.0.00&lc=eng&cc=UG

I can look into adding this for a future release of Spike. I look forward to your response.

Regards,
Andrew

Hello Andrew,
I have been doing the calculations manually. I am
working on DVB and they seem to use MER rather than
EVM. I am only interested in QPSK and 8PSK as the
other constellations are not supported by Spike.
In my own receiver software I use
https://en.wikipedia.org/wiki/Modulation_error_ratio
calculating the RMS error and signal vectors from the
samples. Example here http://g4guo.blogspot.co.uk/

I hope you are able to add it as it would help me.

– Charles

Andrew while I am on the subject of ‘would be nice if’.
Could you please consider adding user defined constellations like those described in the R&S appnote
DVB-S2 Constellation definition

– Charles

Thanks for adding custom constellations. Would it be possible to remove the restriction of having constellations that are a power of 2? An option in DVB-S2 is to have preamble / pilot symbols that fall outside of the data constellation, so for example in the case of 32APSK I actually need 36 constellation points.

– Charles

Hi Charles,

Thanks for the feedback. I’ll look into this, or at least see if there is a quick way to add something to solve this. It may involve adding dummy or duplicate points. Unfortunately I can’t provide a timeline for this right now.

I appreciate the requests and feedback you have been giving us. I hope some of the added functionality has been of use to you.

Regards,
Andrew

Hi Andrew,
Yes it is most helpful, when I make changes to my software
I use it for making sure I have not done something silly.

I have also used it with screen capture software to do
a couple of presentations.

The software I was using before could only cope with QPSK
so having the ability to analyse more complex signals is very helpful.

I have created a set of CSV files for DVB-S2, they are currently
missing the preamble definitions and I will be happy to make them available if anyone needs them.

Keep up the good work.

– Charles

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