Contact UsExpression input in the HFSS and Maxwell Fields Calculator lets you build field expressions using either the traditional stack-based method or an algebraic input mode. Introduced as a beta feature in the 2025 R1 release, this capability gives users more flexibility when working with the Fields Calculator. In the following example, we calculate the capacitance of a simple parallel plate structure using each method and compare the results with the solution data.
Enabling Expression Input in the Fields Calculator
To enable this feature, go to Tools > Options > General Options, and under General > Desktop Configuration, click the Beta Options button.
In the Beta Options window, check the box for HFSS/Maxwell Support Expression Input in Fields Calculator. Once enabled, you will be able to switch between the traditional stack-based method and the algebraic method.
2. Calculating Capacitance Using the Fields Calculator with Expression Input
In this example, we calculate the capacitance of parallel plates using both the stack-based and algebraic methods in the Fields Calculator.
After running the simulation, you can find the capacitance value in the results under Solution Data; in this case, it is approximately 14.941 pF.
To verify this result, we use the Fields Calculator. The capacitance formula is:
C = (ε₀ · εᵣ · A) / d
where ε₀ is the permittivity of free space, εr is the relative permittivity of the dielectric material between the plates, A is the area of the plates, and d is the distance separating them.
As shown below, the Fields Calculator returns a capacitance value of approximately 14.941 pF, which matches the simulation results.
Switching Between Stack and Algebraic Expression Input Methods
The Fields Calculator automatically converts the expression as you switch between the stack-based and algebraic methods.
The video below walks through this example in detail.
Working with the HFSS or Maxwell Fields Calculator or need help with electromagnetic post-processing? SimuTech Group’s electromagnetic simulation consultants work with Ansys HFSS, Maxwell, and the full AEDT platform. For more on HFSS workflows, see our article on antenna design using Ansys HFSS. Learn more about Ansys HFSS or contact us to discuss your project.
