High-Performance Solenoidal RF Transformers on High-Resistivity Silicon Substrates for 3D Integrated Circuits

Soleniod-like transformers based on a traveling-wave design and using advanced through silicon via process technology are reported for operation at frequencies from 1 to 14 GHz. The symmetrical 1:1 transformers are designed as compact slow-wave transmission-line structures with well-defined signal return paths. One-, two-, three-, and four-turn transformers have 1-dB bandwidths ranging from 6 to 9.2 GHz, and midband insertion losses from 0.24 to 0.37 dB. The measured intrinsic loss is 0.46 dB or less up to 10 GHz, and 0.97 dB up to 14 GHz. Relatively simple and scalable physically based lumped-element circuit models accurately predict the performance of these low parasitic transformers.