Microwave and high-speed digital circuit design utilizing the finite-difference time-domain method

The work presented here examines the use of the Finite-Difference Time-Domain (FDTD) method as a microwave and high speed digital circuit design tool. Extensions of the method are presented to increase its capabilities in these design areas. These extentions are divided into two distinct categories: (1) incorporating lumped circuit element devices in the FDTD simulation and (2) modeling frequency dependent conductor losses.;Incorporating lumped circuit element devices into the FDTD grid is accomplished in one of two ways. The first method introduced, the equivalent source method, uses the lumped element's circuit equations for its implementation. This method will be used in conjunction with the Curtice-Cubic model for a MESFET to model an NEC transistor. The S-parameters calculated using this model in FDTD will be compared to results using Hewlett-Packard's (HP) Microwave Design System (MDS) and to the manufacture's measured data. A three port oscillator using this model will also be examined. The second method of incorporating lumped elements into FDTD simulations uses the device's S-parameters to develop equivalent total current and voltage relationships. Simple structures based on this method will be discussed.;Efficient modeling of frequency dependent conductor loss in FDTD requires a special algorithm to perform the time convolution of the conductor's tangential magnetic fields and its surface impedance function. The method examined employs a rational approximation to the impedance function in a recursive convolution to form the surface impedance boundary condition (SIBC). The method will be presented and progress in this area as applied to microwave transmission lines and high speed digital interconnects will be discussed.