Variable Integer delay block

Hi, I am not so familiar with Simulink so I hope someone can help. I have a signal that is an impulse, and I want to delay it; in particular, I want that the delayed version appears after 5ns. So far so good. I am looking into the block called "variable Integer Delay". What I did is to input as the delay "d" my 5 ns. But nothing happens. If I put, for example, "10" as "d", I do see a delayed version of the signal, but I am not sure how "10" is related to what I see.. Can someone explain me how does this block work? Hope I explained myself. Best

[Birdman]

Can you share your model(export to r2017a)

[Maria]

Could you explain to me how to share the model here? If I am in the Simulink model, file, export model to... which option shall I choose?

[Birdman]

Go to File->Export to->Previous version and choose R2017a. Also save the model in .mdl format.

[Maria]

Okay, here it is. I was making some tests also with the tapped delay block.

[Birdman]

What is time(end) value for Stop time of simulation?

[Maria]

These are the variables that I load in "Simulation -> Model Configuration Parameters -> Data Import/Export". I load them as [time',i1s']. In the Solver, under "Additional Parameters", I set the max step size to 1e-10 (otherwise, the signal was not correctly plotted). I attach the snapshots

[Birdman]

dt?

[Maria]

dt= 1e-12 (sorry forgot to mention it)

Answer 1

[Birdman]

Working with variable step solver for this situation is not recommended because there are some parameters which are set as auto and since you are working with too little time steps, it will not give you the desired result. I changed the solver to fixed-step and set the step size as dt. Also, I defined a fixed length of delay which is 5000, so when it is multiplied by 1e-12(dt), the length of delay will be 5e-9. When I run the simulation, I saw the desired result.

[Maria]

Thank you so much! I got now that I have to put the delay length in terms of dt, so (delay)/dt, but it would have taken for me a long time to understand how set-up the solver! So in general, when I work with small time steps, is it the fixed-step always the best option? Thanks

[Birdman]

More reliable option, let's say. Because you force solver to take that specific step.