How can I combine a delay with an amplitude weighting in simulink?

Hello,

EDIT: ------------

Adding maths might help. I'd like to start with some sine:

*sin(2*π*F*t + )

And then split it into several, delayed, sine waves (here I'll use 2 for clarity):

*sin(2*π*F*t + )

*sin(2*π*F*t + )

Where and are the phase offsets caused by the delay, and A2, A3 are reduced amplitudes according to some distribution (say ). The phase delays and amplitudes are then, obv, assessed at the same time.

Original Message: -------

I am trying to build a Simulink system where I take a given input singal wave, split it and pass one branch through a delay. The amplitude of the delayed wave would then weighted, and where I can pick any weighting scheme. The output of this combined delay-and-weight would be a signal with some phase offset according to the delay and an amplitude modification from my scheme - e.g. an exponential decay with some time constant. I would then recombine these waves and check the effects of variation in weighting on the interference of the two waves.

I have been able to get a basic sine wave, and to get a manual (static) delay using the Transport Delay block and a static dB loss on that line to approximate this but it owuld be good to build the complete effect.

This might be excruciatingly simple, but I cannot think how to achieve it.

For context, I have a structured light input - sine with frequency F - hitting some fluorescent material, which responds with standard fluorescent lifetime decay physics. The fastest repsonse is effectively instant in my system, but the tail is long. I would like to model what I epxect to see as I, say, increase the frequncy of the input wave or change the decay lifetime of the material. Once I have it working for a simple sine input wave I can then worry about making that input more complicated.

Any help would be much appreciated.

Answer 1

[Renato SL]

I'm pretty sure my answer does not have a solid theoretical background since I basically do a trial & error, but I managed to make the attached file.

When you said about exponential decay, I can only think about defining my own function using MATLAB Function block and somehow incorporate the evolution of time there, hence the function decay.

This is definitely not a straightforward answer, but I hope this helps or at least inspires you to make something that suits your needs.

[Euan Cowie]

Hi Renato,

Thanks for the reply, that has helped clear a few things in my head. I don't think there is a way to do what I intend without creating a huge number of branches of the initial sine wave, or computing it all in a normal matlab function as you demosntrate here.

I'll mark your as an answer, because I don't think someone is going to be quickly able to answer it with a swift simulink example. I had hoped that some easy combination of blocks would have done the trick!

[Renato SL]

Regarding the number of branches, maybe you can have only 2 branches from the source of the signal.

The first one would be for the original, undisturbed signal.

The second one would go inside a subsystem. Inside this subsystem is where you define how many branches you have with different values of delay and gains. The number of output of the subsystem will follow accordingly.

[Euan Cowie]

Yea, i can picure the function I would write. Sadly I think that I understand too little in the context of how the simulink system works. I was hoping to modulate a couple of "sine" waves with a QAM amplitude, and combine it into a carrier wave but the output isn't coming out anything i expected so I think I'll try to get it working purely in scripted form.

Thank you muchly for your assistance :-) .