In this paper, a technology based on thin flexible polyimide substrate (Kapton) to develop antennas for millimeter wave wireless power transmission is presented. Firstly, we characterize the Kapton polyimide (relative permittivity and loss tangent) using a ring resonator method up to V band. A 60 GHz patch antenna is designed, fabricated, and measured to validate our technology. Crossed-dipoles array antennas at Ku band and K band for energy harvesting are also designed, fabricated, and measured. Then a prototype of crossed-slot dipole antenna at V band is proposed. Finally, a resistivity characterization of Au bump used in flip-chip packaging is done, which leads us one step further toward aheterogeneous integration on flexible substrate of different components for Wireless Sensor Network nodes.

Performance comparison is made between on-chip spiral inductor in flip-chip versus wirebond package technology. Full-wave electromagnetic simulation and on-strip measurement techniques were used to study the performance fluctuations of inductor within flip-chip environment. Results show that the performance of a flipped silicon-based spiral inductor is affected by the radio frequency (RF) current return path differences. The RF current return path for flip-chip is concentrated on the surface of silicon layer exclusively because back side ground under silicon is floating in flip-chip technology. In addition, the bump proximity effect is also considered. On-chip inductors in flip-chip environment must be optimized by reducing the eddy current in the silicon substrate and parasitic affects by adjusting design parameters. The equivalent circuit model of the flipped on-chip spiral inductor is verified with measured results over broadband frequencies. Also, the RF flip-chip characterization technique using on-strip measurement method is presented.