Inductor design for passive wireless implantable use presents several challenges not currently addressed. A small form factor is desired for minimally invasive implantation and monitoring, and a low frequency is necessary for effective through-body power transfer. However a small inductor area limits effective power transfer and low-frequency operation. It is thus necessary to optimize the inductor for maximal power transfer while satisfying tight area and low frequency constraints. We present a design methodology for planar circular spiral inductors used with capacitive pressure sensors to form a passive wireless implantable pressure sensor. We collect several analytical expressions and find the optimal geometric parameters to maximize the quality factor of the sensor frequency response. We validate our analysis through comparison with field solvers, and wired and wireless measurements of fabricated devices.
Project end date: 08/17/11