High frequency modeling of SMD resistors

Abstract

Passive components, including resistors, capacitors, and inductors, are fundamental in electrical circuit design. Surface mount devices (SMDs) are extensively used in microwave hardware development at high frequencies and precise simulations of SMD components are crucial. This thesis highlights the unpredictability of SMD resistors and underscores the importance of accurate simulations for achieving expected performance and creates a 3D and equivalent circuit models of 0402 and 0201 SMD resistors to do this. 3D models are created and verified using real measurements of a SMD resistor up to 32 GHz, while the target is for the model to be valid in 42 GHz. This model is used to create an equivalent circuit model and a scalable model for ADS that can scale the substrate height, relative permittivity and the resistance of the resistor which can be used when developing microwave circuits such as attenuators. The film that is the resistive element of the SMD component is shown to be the biggest contributing factor to parasitics. The thickness and width of the film were studied, and it was concluded that the width affected the parasitics the most. Results show very good agreement between 3D model and real measurement as well as agreement between equivalent circuit models and 3D models. The scalability ranges between 0-500 Ohm with relative permittivity being adjustable between 2.6-5 and 4.7-13 Mil substrate height. Through optimization using the scalable model, a T-attenuator is created and compared with a 3D simulation which shows very good agreement in S11 with less agreement in S21 in terms of a small frequency shift. The methods of this thesis can be extended to creating models of SMD inductors and conductors.