# Help with defining an induced voltage in LTspice and setting frequency dependent parameters

I am trying to set up a similar circuit in LTspice and making necessary modifications to change it to a bandpass filter. I have a couple of questions regarding this model and was hoping someone could help me with it:

Where do I call the "skin effect" and "radiation" resistance from the library? it appears to be non-existent

How is the magnetic field being set up as a parameter based voltage source? Basically I am stuck at defining the voltage equation for the loop

How to make certain components frequency dependent? I guess by using the command Laplace but I have never used it before in form of an equation

• Where did you get this from? Is this your screenshot or someone else's? Jun 15, 2023 at 18:54
• Hi, no this is not my own work, I got the picture of the schematics from a website. Jun 20, 2023 at 14:07
• There is information (more commonly than not) within an LTspice schematic that is not visible so recreating those from an image can be next to impossible. In this case, it looks to me like Rrad and Rac are custom symbols which call custom .subckt's most likely contained within .lib files originally packed together with the schematic (.asc) file. If that website doesn't provide the text defining those subcircuits, then you would need to understand all the underlying theories/calculations and recreate them yourself. Or start from scratch from a completely different approach. Jun 20, 2023 at 17:16
• Thanks for the reply, I reached to the same conclusion as the information provided by the image is insufficient to replicate the exact design. However, I do poses the mathematical expression to define the corresponding resistance of 'Rac' and 'Rskin' as a function of frequency. My question right now is, how I can define a component as a "frequency dependent" component. I tried using 'Laplace( A*s/sqrt(-1))' for one of the components where A is numerical constant. But when I want to initiate the frequency analysis LTspice gives me an error not recognizing 'laplace()' Jun 22, 2023 at 15:17
• OK. Cool. Then I would check out the following questions and their answers. I would opt for using Laplace over FREQ wherever you can: electronics.stackexchange.com/questions/657820 electronics.stackexchange.com/questions/664313 Jun 22, 2023 at 15:22