CONSTELLATION DIAGRAM

[Idahor Emmanuel]

Hi,

Please how do i add and view the constellation diagram into my system of the attached direct OFDM system. without using project browser. I want the block added to my system.

[alistu]

Hi Idahor,

Choose constellation visualizer component from the visualizers library. Then use forks at each of the two outputs of the ODFM demodulator. Connect one of each of the forks outputs to the PSK decoder and the other to an electrical pulse generator. And finally connect the output of the electrical pulse generator to either of the inputs of the constellation visualizer.

Regards

[Idahor Emmanuel]

Thank you so much for your reply… I used two forks at the output of my ofdm demodulator. and one of the forks connected to the input of my PSK decoder as mentioned by you but the other fork which has two outputs can’t be connected to a pulse generator (NRZ pulse generator) that has only one input and one output, and the Electrical constellation visualizer has 2 inputs. where do i connect the other input of the second fork been connected to a pulse generator?
The connection is attached

[alistu]

maybe my explanation was not clear enough, so I have attached your file in which I have implemented the constellation diagram connected to the OFDM demodulator. (The constellation could have also been used diagram after the PSK coder in the transmitter instead of before OFDM demodulator though).

Regards

[Idahor Emmanuel]

Thank you alitsu for your prompt reply. I didnt get the explanation earlier, thanks for explaining better. I simulated the system and it was giving me a calculated error with the NRZ pulse generator making the constellation not to work. I have also tried using the constellation on the transmiter side and it gives the same error. Any reason to why this is happening?

[alistu]

I believe I should have been more specific in my previous comments about the type of electrical pulse generator in the first place… Sorry if it took you some time. The component “M-ary pulse generator” must be used for this purpose. By simply replacing the current pulse generators by them, the problem is solved. Please see the attachment.

[Idahor Emmanuel]

Thank you so much alitsu for your support… you have really helped me in understanding the basic design on optisystem. Lastly I want to test a matlab file on the system. Is there any way of calling matlab on optisystem? I tried it by watching the tutorial video but not sure its working properly, because it says undefined matlab file.

[alistu]

You’re welcome Idahor. If you have written your Matlab program with regard to the points explained in OptiSystem tutorials and now you want to troubleshoot it, please upload the .osd file along with the .m file if it is possible. Otherwise, please attach a screen shot of the error you are facing.

Regards

[Idahor Emmanuel]

okay thanks.. yes i have written the Matlab code and it works fine. I’m attaching both files now.

[alistu]

Your program should work in Matlab, but you should change its format to make it work in OptiSystem. For example, in your currently written Matlab program, I cannot find where the input is received from OptiSystem (you are going to replace it with OFDM component, so the input should be the output of coder).

[Idahor Emmanuel]

Thank you so much for your reply.. How do i call the input to be received in optisystem? I am aware i have to change the ofdm modulator and demodulator and replace em with matlab components… calling it from optisystem is a bit tricky and i cant find my way around it. thanks

[alistu]

You should go through the tutorials that I have addressed on this very page. The most important thing is to understand the format of vectors generated in OptiSystem (to be able to make necessary changes to them using Matlab) and the tutorials are supposed to give you such information.

[Idahor Emmanuel]

HI,

I have tried co simulating my matlab code on optisystem, and it isnt co simulating… I have attached both files and tried to call it from optisystem and changed my matlab file but it isnt working. It pops an error from the matlab calculation saying undefind name ‘channel’.. The matlab code works fine and i do not know what next to do for am really confused. Thanks

[alistu]

Hi Idahor,

There are two Matlab components and one .m file. Can you please explain more about this? If you nhave written the program in the Matlab component (which I suggest you don’t), then you won’t need to address the place of the file unless it is a file that is called by the program you have written above.

Regards

[Idahor Emmanuel]

The two matlab components represent the OFDM modulator and demodulator…. Am trying to learn my way around optisystem so am just trying to understand how everything works, but i think i figured the early error out but there is a little issue.. the matlab workspace from the matlab component isnt producing any result from the matlab file even if the calculation was successful. So am not too sure the matlab component is working. I attached the working file … but the matlab workspace isnt producing any results. Can u help please?

[alistu]

I find a very fundamental issue with your implementation. Both OFDM modulator and demodulator address the same Matlab file, so the file is either for modulator or demodulator. If the file contains both modulation and demodulation programs (which is not helpful in practice), then there should be just one Matlab component instead of two. It it right?

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