How to apply a frequency-domain transfer function to a time-domain signal in a Simulink MATLAB Function block?

I’m struggling a bit with how to correctly implement a frequency-domain transfer function inside Simulink.I have a MATLAB script that computes a transfer function H(f) over a range of frequencies for a micro-ring resonator model. What I want in Simulink is:

• Input: a time-domain sine wave (carrier) + some control voltages
• Apply the frequency-domain transfer function to this sine wave
• Output: the filtered time-domain signal

I have attached an image showing the relevant parts of this model

Where I’m stuck

1. In Simulink, the carrier signal is a scalar at each time step. Doing an fft on a single scalar sample doesn’t make sense – I’d need a full frame of samples to apply the transfer function in the frequency domain.
2. If I try to implement the script logic directly, the MATLAB Function block ends up outputting a vector (c_out) while the Scope and the rest of my model expect a scalar at each time step. Simulink complains about dimensions / frame handling.
3. I will also be adding some blocks after c_out to extract the pilot signal because it will then be used further for some different processes in my ultimate goal of this simulation, so I’m not sure what the correct structure is supposed to be.

What would the approach to solving this be? I am working on recreating a model from a reference paper, but I have unfortunately not been able to acquire the original model developed by the author of the reference

[Paul]

Hi Rishikesh,

If I understand correctly, H(f) represented as a list of samples of H(f_n) at a set of n frequency points f_n.

If so, I'm not aware of any block or method one could use in Simulink to implement such a filter in a time domain simulation. Will be curious to see if anyone else comes up with a solution.

What you can try are functions like tfest or tfestimate or ssest or invfreqs to estimate an LTI model from the data, and then that model can be implemented with standard Simulink blocks, or an LTI System block (if the Control System Toolbox is available).

Those functions will be easier (though not necessarily easy) to use if you have a good understanding of the dynamics of the micro-ring resonator that's being modeled, particularly if the number of poles and zeros are known from first principles.

[Mathieu NOE]

hello

From the TF data / model , why not create (identify) a FIR or IIR digital filter, with invfreqs or invfreqz, then use it (with the appropriate discrete filter simulink block)

[Mathieu NOE]

problem solved ?