FDTD Analysis on Microwave Active Circuits with Lumped Device Characterized by S-parameters

Inverse Fourier transforms and complex convolution integral are adopted in traditional method to take S pa- rameters of active components into FDTD iteration steps. To avoid the complex convolution integral calculation, we firstly transform the measured S parameters into Y parameters, and then the Vector Fitting technique is used to obtain rational poly- nomial of Y parameters in s domain. Through difference technique or Z-transform method, the Y parameter is taken into FDTD iteration steps. To increase the computational efficiency and stability, FDTD is used to distill the time domain charac- ter model of distributing elements. An example of microwave FET amplifier circuit is analyzed, and validates the efficiency and precision of the method.