A frequency-independent equivalent circuit model for planar symmetric balun in CMOS RFICs

In this paper, a new model for interleaved planar symmetric balun in CMOS radio frequency integrated circuits (RFICs) is developed. The model uses a “2-Π” sub-circuit to represent each inductor coil in the balun, and a novel substrate inductance is introduced to describe the substrate eddy-current effect. Verification with the measured data from a CMOS process demonstrates the model´s accurate performance prediction up to self-resonant frequency (SRF).