Transformer topologies for mmW integrated circuits

Layout topologies for millimeter-wave transformers are presented. Transformers whose windings present different shapes and relative position are compared in terms of inductance, quality-factors, coupling coefficient and minimum insertion loss. We present measurement results of transformers implemented in a 65 nm CMOS technology. It is observed that octagonal transformers present better Q-factors than square transformers, and that transformers whose primary is rotated by 180 degrees present a partial resonance.