Jacobian Error while linearising a PLL

Hello,

I am trying to linearise a PLL with the mixed signal blockset, but I always get the following error :

"Error:'pll_filtre/Lowpass Resampler' implements a Jacobian method, but failed to configure its Jacobian dimensions in the DoPostPropagationTasks function."

That error comes from the LowPass Resampler in the second order loop filter. What I don't understand is that my blocks are configured the same as the one in the subsystem "Integer N PLL Single Modulus Prescaler". When using this subsystem I can linearise via the analysis tab and see the closed-loop bode etc... But not when placing the blocks by myself like in the attached picture.

Does someone know where this error comes from and how to fix it so that I can see the stability of my PLL ?

Thanks

Answer 1

[Kautuk Raj]

I see that you are encountering a Jacobian configuration error in the "Lowpass Resampler" while attempting to linearize a PLL.

I was also facing a similar issue in one of my workflows.

After some investigation, I found that the error occurs when the Bode Plot block tries to linearize the nonlinear PLL system. In order to obtain the frequency response, I conducted a frequency response estimation using the "Estimation" tab in the "Model Linearizer" app. You can refer to the following post in the MATLAB Answers forum to get more details about this: https://www.mathworks.com/matlabcentral/answers/684813-is-it-possible-to-linearize-a-phase-lock-loop-using-the-linear-analysis-gui

I hope the above resource helps you with your workflow to linearize the model and obtain the frequency response.