FDTD Method Program for Computing Capacitance and Inductance Parameters of Parallel Coupled Microstrip Lines

The Finite-Difference Time-Domain (FDTD) method is a classical numerical approach for solving electromagnetic field problems, particularly well-suited for analyzing distributed parameter characteristics of microwave structures like microstrip lines. For parallel coupled microstrip lines, extracting capacitance and inductance parameters requires electromagnetic field simulation combined with post-processing.

The core computational logic consists of three steps: First, establish a 3D computational model containing the dual microstrip lines, setting appropriate mesh sizes to capture edge fields (implemented through grid generation algorithms like Yee's cell discretization). Second, during FDTD simulation, excite one microstrip line port while recording the time-domain response on the other transmission line (using waveform excitation functions and field monitoring modules). Finally, convert time-domain signals to frequency-domain parameters via Fourier transform (using FFT algorithms), then solve for distributed parameters using the mathematical relationship between impedance matrices and capacitance/inductance matrices.

The method's key aspects involve boundary condition handling (such as PML absorbing boundaries implemented through specialized update equations) and the frequency band coverage of excitation signals. Practical implementation requires careful attention to material parameter settings for the microstrip dielectric substrate (defined through material property arrays), and port calibration to eliminate numerical errors (achieved through reference plane adjustment algorithms). Compared to static field methods, FDTD more accurately captures high-frequency coupling effects, including parasitic capacitance and proximity effects.

In engineering applications, such programs typically integrate parameter scanning functionality (implemented via loop structures that systematically vary geometric parameters), enabling analysis of how geometric variations like line spacing and dielectric thickness affect coupling parameter curves.