Monolithic RF Transformers on CMOS Technologies

Cátia Patrícia Rodrigues de

Key information

Authors:

Cátia Patrícia Rodrigues de (Cátia Patrícia Rodrigues de Almeida)

Supervisors:

João Manuel Torres Caldinhas Simões Vaz (João Manuel Torres Caldinhas Simões Vaz)

Published in

05/27/2010

Abstract

This dissertation presents a thorough study of square monolithic transformers on a 0.18µm CMOS technology, for radiofrequency applications. The structures are analyzed with Momentum, a 2.5-D electromagnetic simulator, in terms of dimensions and geometry, focusing in high performance design techniques, i.e., that are known to provide strong magnetic coupling with the least possible insertion losses. Planar transformers with a Metal 5 spiral connected to the spirals present the best behavior, since they generally present higher coupling factor and power gain. A complete model for planar transformers with metal 5 is presented and tuned, proving to be unfit for one-turn transformers. An alternative model for one-turn transformers is proposed. A simplified model for the calculation of the quality factor of primary and secondary windings is presented. An inductance calculation computer program for symmetric designs, based on Greenhouse?s method, is presented. This program computes the Greenhouse formula in each segment of a symmetric transformer, calculating the self-inductance of the primary and secondary windings. The results obtained were compared with the EM simulations results, and the error is almost negligible for the symmetric structures. This program also provides fairly accurate results for a type of quasi-symmetric transformers, although with higher error.