An energy harvesting circuit for GHz on-chip antenna measurement

A novel and improved measurement technique for on-chip antenna using energy harvesting circuit is reported. The IC consists of (a) a full-wave rectifier for power measurement and self-powering, and (b) an inverter-based ring oscillator to transform rectifier DC output to frequency domain to improve measurement accuracy. Compared with the conventional direct probing method, the energy harvesting circuit provides the necessary isolation to minimize the radiation measurement error contributed from the relatively larger external measurement components such as wafer probes and bond wires. As demonstration, a 5-GHz differential loop antenna together with the self-powered IC are implemented in a 0.13-μm CMOS technology in a standard digital substrate (15 ohm-cm). The measurement shows within 2-dB accuracy compared with simulation and consistent results over various external loadings. The self-powered IC occupies area of 40-μm², and this method can be employed to measure antenna 60-GHz and beyond pending on the device f_T.