# ADS Momentum Based on the method of moments ([Galerkin's Method](Galerkin's%20Method.md)). This is used to solve Maxwell's equations for planar structures inside a multilayered dielectric substrate. ## Quasi-Static Mode RF sims run alot faster since L and C only have to be calculated once. These are real and frequency independent. Typically used for structures smaller than half a wavelength. ## Method of Moments Maxwell's equations are turned into integral form (electric and magnetic Green's functions are derived for the multilayered substrate). Electric and magnetic interactions are modelled as capacitance to ground and inductances between adjacent cells.  ## Solution Process ### Substrate Green's Functions Spatial impulse responses of the subtrate are calculated for each pair of signal layers mapped to a substrate level. It is not necessary to know the patterns on these signal layers - meaning Green's functions can be pre-calculated and stored in a substrate database. *Computations performed over very wide frequency ranges can consume more CPU time and disk space to store the results. To increase speed, the RF mode uses quasi-static electromagnetic Green's functions based on low-frequency approximation and scales the quasi-static Green functions at higher frequencies.* ## Meshing ## Loading and Solving of the MoM Interaction Matrix Equation Iterative solver is at worst O(N^2) vs. Direct solver O(N^3). [^1] --- # References [^1]: [Theory of Operation for Momentum - ADS 2011 - Keysight Knowledge Center](https://edadocs.software.keysight.com/display/ads2011/Theory+of+Operation+for+Momentum)