Measurement and Analysis of Coplanar MMIC Four-Port Spiral Transformers

Coplanar spiral transformers of small dimensions and broadband characteristics are designed and fabricated on Gallium Arsenide substrate. Their propertis are investigated using an accurate circuit model. The equivalent circuit parameters are calculated using a three - dimensional finite difference method. A full four-port time-domain measurement method is used to obtain the scattering parameters of the transformers. Comparison of calculated and measured reslts shows a good agreement up to the λ/4 -resonance frequency of the structures presented here.