A Two-Way Power Combined <italic>Ka</italic>-Band Rectifier for Low Input Power Energy Harvesting

In this letter, we propose an RF power combining approach for energy harvesting at <italic>Ka</italic>-band frequencies. A two-way 28-nm CMOS rectifier is presented, utilizing ultralow threshold voltage (ULVT) transistors for efficient rectification of low voltage swing input signals. The power combiner is a compact voltage summation design that minimizes the losses associated with transformer-based power combiners at mm-Wave frequencies. The rectifier achieves a record 13% power conversion efficiency (PCE) for <inline-formula> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula>20 dBm input power per port, and peak PCE of 24% for <inline-formula> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula>14 dBm input power per port.