Fast Simulation of Interconnect Structures Using Adaptive Integral Method (AIM)

A full-wave technique is developed for fast analysis of high-frequency planar interconnects and microwave circuits. The proposed methodology is an extension of the adaptive integral method to the objects enclosed in a rectangular box with perfect electrically conducting walls. It can be used for simulation of both shielded and open structures. The only limiting condition for the open circuit analysis is that the substrate is to be electrically thin in the frequency range of interest. The advantage of the proposed method compared to the FFT based techniques adopted in the commercial tools such as Sonnet EM simulator is in the adaptive scheme allowing efficient FFT use for the circuits not fitting onto the FFT grids. The computational time per iteration and memory usage for the solver scale as (l og ) ON N and () ON respectively, where N is the number of unknowns in the discrete model. The accuracy and efficiency of the solver is demonstrated through its application to the modeling of a microwave filter. I. Introduction The growth of operating frequencies and on-board dense packaging make full electromagnetic simulation an essential part of modern high-frequency design. Under these conditions, traditional design schemes, based on the decomposition of the system into smaller components with independent analysis of each component, provides inadequate accuracy due to the strong near field coupling. Attempts to simulate systems without such a decomposition, however, often times result in the prohibitively large size of the discrete problem requiring CPU and memory resources unavailable to most designers. This situation motivates the development of new fast algorithms capable of accurate simulation of large scale problems using moderate computational resources. In this paper we discuss one such algorithm built specifically for the analysis of dense open integrated circuits. The presented technique is a modification of the adaptive integral method [1] for the case when the circuit is situated within a rectangular waveguide with proper termination loads. The presence of the perfectly conducting walls forming the guide is brought into the analysis by modeling of the circuit port excitation using a delta-gap voltage generator [2]. Such implementation of AIM for the shielded circuits exhibits specific features because of the modal structure of the electromagnetic field excited in the waveguide and is discussed in this paper. The new AIM algorithm has proven to be in the same order of complexity as its open media counterpart where computational time per iteration scales as (l og ) ON N instead of 2