An Energy-Efficient Antenna Impedance Detection Using Electrical Balance for Single-Step On-Chip Tunable Matching in Wearable/Implantable Applications

A low-power impedance detection method using a hybrid transformer and its analysis are presented. A balun is reused for the hybrid transformer to achieve area-efficiency. The complex impedance detection enables faster optimization on a tunable matching network and its calibration technique increases the detection accuracy. The proposed impedance detection method fabricated in a 40-nm CMOS process consumes only 0.83 mW and demonstrates the accuracy of less than 18° and 0.1 on the Γ detection up to $\vert \Gamma _{{\rm{Ant}}}\vert $ of 0.5 in ISM2.4 GHz band. After single-step matching network tuning, PA power and RX noise figure are improved by up to 1.2 dB and 1.3 dB, respectively.