Three-solenoid windings transformer baluns on CMOS-grade silicon substrate

Several novel on-chip three-solenoid windings transformer baluns were designed and fabricated using post-CMOS compatible concave-suspending micromachining process, which are applicable in the design of radio-frequency integrated circuits (RFICs). A generalized lumped-element circuit model (LECM) is developed to accurately characterize input and output characteristics of these three-port signal conversion devices, with the partial element equivalent circuit (PEEC) method implemented for capturing skin and proximity effects in them. Satisfactory agreements are obtained among the measured, simulated, and modeled S-parameters of the fabricated baluns over the frequency range of 500 MHz–10 GHz. Measurements show that these baluns exhibit less than 1 dB amplitude imbalance and less than 1° phase imbalance up to 6 GHz. Their power transfer and impedance matching are also examined in details.