| As the switching speed of digital integrated circuits (ICs) increases, detrimental effects such as signal crosstalk, propagation delay, attenuation, dispersion, and reflection become more important. At relatively low switching speeds, the signals have small bandwidth and thus quasi-static electromagnetic modeling methods are sufficient to analyze these effects. However, integrated circuits having high-speed, wide-bandwidth signals, where the signal wavelengths are comparable to the dimensions of the IC and package, must be analyzed with a full-wave electromagnetic field method.; A three-dimensional variable-mesh transmission line matrix (TLM) method is developed for the full-wave time-domain simulation of the electromagnetic properties of ICs. This is made more computationally efficient by rewriting the TLM scattering matrices in the form of finite-differences, yielding the finite-difference transmission line matrix (FD-TLM) method. Models for lumped circuit components, such as resistors, capacitors, diodes, and GaAs metal-semiconductor field-effect transistors (MESFETs) are derived and incorporated into the FD-TLM method, allowing the three-dimensional full-wave electromagnetic field simulation of complete active ICs.; Applications of the method are discussed, the main ones being as follows. (1) Three-dimensional simulations of parallel airbridges and parallel conductors on a substrate are compared for crosstalk and signal delay. (2) Three-dimensional electromagnetic field simulations of a direct-coupled FET logic (DCFL) inverter, a DCFL three-stage ring oscillator, and a divide-by-two dynamic frequency divider using the FD-TLM method agree well with another numerical method, verifying the success of implementing MESFETs in the variable-mesh FD-TLM method. (3) A picosecond pulse generator is simulated. The accuracy of the variable-mesh FD-TLM simulation is supported by the good agreement with experimental electro-optical measurements.; Although the research concentrates on digital ICs, the same FD-TLM method is applicable to analog and monolithic microwave ICs, as demonstrated by the three-dimensional simulation of a spiral inductor. |
