Computer aided design of square spiral transformers and inductors (MIC application)

A simple, yet accurate, lumped-element model for four-port planar rectangular spiral structures has been developed. Closed-form expressions were used to generate frequency-dependent parameter values, resulting in an equivalent circuit which is easily incorporated into existing analysis packages. The method can easily be implemented in a commercial microwave computer-aided design program, allowing its use in the optimization of various types of active circuits. The technique was applied to standard and center-tapped transformer configurations, as well as to spiral inductors to 20 GHz. Comparison with measured results shows good agreement up to the first resonant frequency of the structures.<>