Microwave performance of monolithic silicon passive transformers

This paper presents a comparative study between three transformer layout styles, namely the Frlan style, the planar shunt style and the three-dimensional series style, in terms of their minimum insertion loss, gain bandwidth, and transformation ratio over a broad frequency range. A new performance metric, the frequency dependant 1 dB insertion loss bandwidth is presented. Measured insertion loss as low as 2 dB at 20 GHz has been observed. Furthermore, it is shown that with proper layout, a transformation ratio as high as 40:1 is possible over a bandwidth of 40 %.