Recommendations For Port Setup When Using ADS Momentum And Modelithics Models

With the increased complexity of today’s circuits, designers are increasingly dependent on EM simulations during the design phase.  With the trend towards smaller circuits and multiple layered circuit boards, EM simulations are needed to accurately model internal circuit interactions.  The use of discrete components helps to reduce a circuit’s overall footprint but introduces a level of complexity to the design process when performing co-simulations.  A good understanding of the proper EM port configurations and calibration types is required to ensure accurate co-simulation results.  

This application note is intended to help users of Agilent’s Advanced Design System (ADS) and Modelithics models accurately and efficiently simulate RF and microwave circuits.  The focus is on finding the optimum port setup for electromagnetic (EM) simulation of circuit layouts that include surface mount devices.  Starting with the ADS 2011 release, several new features and improvements were introduced to Momentum, the 3D planar EM simulator in ADS.  Of particular interest are the new port calibration types and their impact on co-simulations when using Modelithics models.  This application note explains the port nomenclature in ADS, presents multiple co-simulations between Momentum and Modelithics models, shows the impact of the various port shapes and calibration types, and provides recommendations based upon comparisons to measured data.  The content is organized in three main areas.  The first area provides detailed information concerning Momentum port types and calibration definitions. Following the calibration definitions is the results section, which includes examples that provide insight into port and calibration performance.  The final section contains the recommended calibration type and the recommended port configurations.