A fast frequency-domain calculation method for electromagnetic fields based on the time-domain finite element method

Traditional frequency-domain finite element methods (FEM) require independent solutions of system matrix equations for each frequency point in multi-frequency electromagnetic field analysis, leading to low computational efficiency, high resource consumption, and challenges in balancing accuracy and speed. This paper proposes a fast frequency-domain electromagnetic field calculation method based on time-domain FEM. By introducing a unit step function as the excitation source, solving the time-domain fundamental solution, and leveraging the superposition principle to rapidly synthesize frequency-domain responses at arbitrary frequencies, the method captures full-frequency domain information through a single time-domain simulation, significantly reducing computational time while employing an adaptive time-step selection strategy based on the CFL condition and local error estimation to enhance accuracy. Simulation results demonstrate that the proposed method achieves an 8 times improvement in computational efficiency compared to traditional frequency-domain FEM, with relative errors controlled within 0.5% across the evaluated frequency spectrum. It is suitable for multi-frequency analysis in linear systems and has broad engineering applications in antenna design, power system optimization, and electromagnetic compatibility analysis.