Author Topic: Constellation diagram on rigol ds1054z  (Read 1841 times)

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Offline freebil

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Constellation diagram on rigol ds1054z
« on: August 17, 2016, 07:42:06 PM »
Hello. Is it possible to see constellation diagram on rigol? I read here that it requires X-Y display, external sampling clock and a persistence display. Does rigol have them?
 

Offline borjam

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Re: Constellation diagram on rigol ds1054z
« Reply #1 on: August 17, 2016, 08:06:52 PM »
Hello. Is it possible to see constellation diagram on rigol? I read here that it requires X-Y display, external sampling clock and a persistence display. Does rigol have them?

Yes, it does have all the features although I haven't tried. You need the I+Q signals separated (which would feed the X-Y display) and one more channel as a trigger. As it has four channels it's not a problem.

I haven't tried but it should work. The X-Y mode has been improved in the latest firmware version, by the way. With the previous versions it wasn's full screen.
 

Offline freebil

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Re: Constellation diagram on rigol ds1054z
« Reply #2 on: August 17, 2016, 08:09:05 PM »
Thanks for the answer. I understand the inputs for the 2 channels but I dont understand what the input must be for the third channel? Thanks.
 

Offline borjam

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Re: Constellation diagram on rigol ds1054z
« Reply #3 on: August 17, 2016, 08:11:59 PM »
Thanks for the answer. I understand the inputs for the 2 channels but I dont understand what the input must be for the third channel?
A clock. What signal are you trying to display?

 

Offline freebil

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Re: Constellation diagram on rigol ds1054z
« Reply #4 on: August 17, 2016, 08:13:19 PM »
I would like to buy a usrp and try digital transmissions..
 

Offline borjam

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Re: Constellation diagram on rigol ds1054z
« Reply #5 on: August 17, 2016, 08:28:15 PM »
I would like to buy a usrp and try digital transmissions..
Nice. And won't you have a word clock available?
 

Offline freebil

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Re: Constellation diagram on rigol ds1054z
« Reply #6 on: August 17, 2016, 08:40:52 PM »
As far as I understand I have to use usrp internal clock or an external clock which I have to connect it on both usrp and oscilloscope?
 

Offline borjam

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Re: Constellation diagram on rigol ds1054z
« Reply #7 on: August 17, 2016, 08:45:39 PM »
As far as I understand I have to use usrp internal clock or an external clock which I have to connect it on both usrp and oscilloscope?
It depends on what you are doing.

If you are doing a transmission yourself and you want to check the results, you will have a symbol clock you can use. It´s the clock that will mark the transmission of each symbol, as its name says.

If you are just receiving a signal someone else is transmitting, you need to derive that clock yourself. Doing a Google search for terms such as QAM QPSK I+Q clock reconstruction should yield some useful answers, there are several lab notebooks from universities available.

 
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Offline alsetalokin4017

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Re: Constellation diagram on rigol ds1054z
« Reply #8 on: August 18, 2016, 07:10:05 AM »
Hello. Is it possible to see constellation diagram on rigol? I read here that it requires X-Y display, external sampling clock and a persistence display. Does rigol have them?

Yes, it does have all the features although I haven't tried. You need the I+Q signals separated (which would feed the X-Y display) and one more channel as a trigger. As it has four channels it's not a problem.

I haven't tried but it should work. The X-Y mode has been improved in the latest firmware version, by the way. With the previous versions it wasn's full screen.

Well... perhaps you _should_ try it. You will find out that you cannot turn on other channels when the X-Y mode is in use, nor is Persistence available, so it _does not_ have all the features required for a constellation display.

Or maybe you could just read what the User Manual says:

The easiest person to fool is yourself. -- Richard Feynman
 

Offline borjam

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Re: Constellation diagram on rigol ds1054z
« Reply #9 on: August 18, 2016, 05:08:27 PM »
Well... perhaps you _should_ try it. You will find out that you cannot turn on other channels when the X-Y mode is in use, nor is Persistence available, so it _does not_ have all the features required for a constellation display.

Or maybe you could just read what the User Manual says:
Oops I stand corrected. I wrongly assumed that it could trigger on another channel while in X-Y mode, which would make sense.

And, curiously, the manual says "setting persistence" rather than just "persistence". I'll check.


 

Offline ebastler

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Re: Constellation diagram on rigol ds1054z
« Reply #10 on: August 19, 2016, 01:49:31 AM »
I am missing something here. Why would a trigger be needed in (any) X/Y mode display? What would it trigger? (Not the start of the horizontal sweep, obviously, so what else?)

Thanks for educating me!
 

Online Fungus

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Re: Constellation diagram on rigol ds1054z
« Reply #11 on: August 19, 2016, 05:53:08 AM »
I am missing something here. Why would a trigger be needed in (any) X/Y mode display? What would it trigger? (Not the start of the horizontal sweep, obviously, so what else?)

It wouldn't. The DS1054Z disables trigger for a reason.

I think the "Constellation diagram" in the original question needs another input to turn the bean on/off or something like that. It's not very clear.

 


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