Solenoidal transformers for magnetic materials integration

This paper presents the design, fabrication and characterization of suspended solenoidal transformers fabricated using a low cost single step 3D copper electroplating process. The design and optimization of solenoidal transformers with and without magnetic core are performed using HFSS. After optimization, the suspended structures reveal good electrical performance. The addition of a magnetic core to these structures shows a significant improvement of its electrical properties. Thus, an increase of 10% on G_max, 20% on coupling coefficient k, 80% on the quality factor Q and 350% on the inductance is observed. Under probe measurements carried on the suspended structures without magnetic core exhibit a Gmax of -1.45 dB and a Q of 28.5 at 2.5 GHz. The enhanced performance coupled with the low cost 3D process makes these transformers excellent candidates for today´s RF applications.