Quality Factor Optimization of Inductive Antennas for Implantable Pressure Sensors

Inductive antenna 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 limits sensitivity to changes in capacitance at low-frequency operation. It is thus necessary to optimize the inductor for maximal sensitivity while satisfying tight area and low frequency constraints. Here, a design methodology is presented for planar circular spiral inductors used with capacitive pressure sensors to form a passive wireless implantable pressure sensor. Several analytical expressions are collected to find the optimal geometric parameters that maximize the quality factor and sensitivity of the sensor frequency response. The analysis is validated through comparison with field solvers and wireless measurements of fabricated devices.

[1]  Stephen P. Boyd,et al.  Simple accurate expressions for planar spiral inductances , 1999, IEEE J. Solid State Circuits.

[2]  Mohamad Sawan,et al.  Novel coils topology intended for biomedical implants with multiple carrier inductive link , 2009, 2009 IEEE International Symposium on Circuits and Systems.

[3]  C. Collins,et al.  Miniature passive pressure transensor for implanting in the eye. , 1967, IEEE transactions on bio-medical engineering.

[4]  K. Wise,et al.  A wireless microsensor for monitoring flow and pressure in a blood vessel utilizing a dual-inductor antenna stent and two pressure sensors , 2004, 17th IEEE International Conference on Micro Electro Mechanical Systems. Maastricht MEMS 2004 Technical Digest.

[5]  Y. Tsividis,et al.  Design techniques for automatically tuned integrated gigahertz-range active LC filters , 2002 .

[6]  Lars Rosengren,et al.  Passive silicon transensor intended for biomedical, remote pressure monitoring , 1990 .

[7]  L. Steiner,et al.  Monitoring the injured brain: ICP and CBF. , 2006, British journal of anaesthesia.

[8]  Ali Hajimiri,et al.  Concepts and methods in optimization of integrated LC VCOs , 2001, IEEE J. Solid State Circuits.

[9]  Shuvo Roy,et al.  An in vivo Biocompatibility Assessment of MEMS Materials for Spinal Fusion Monitoring , 2003 .

[10]  R. W. Lau,et al.  The dielectric properties of biological tissues: III. Parametric models for the dielectric spectrum of tissues. , 1996, Physics in medicine and biology.

[11]  Zewen Liu,et al.  The Enhancement of $Q$-Factor of Planar Spiral Inductor With Low-Temperature Annealing , 2008, IEEE Transactions on Electron Devices.

[12]  Douglass J. Wilde,et al.  Globally optimal design , 1978 .

[13]  Miko Elwenspoek,et al.  Characterization of a planar microcoil for implantable microsystems , 1997 .

[14]  S. N. Kundra,et al.  Microelectromechanical systems and neurosurgery: a new era in a new millennium. , 2002, Neurosurgery.

[15]  Thomas H. Lee,et al.  The Design of CMOS Radio-Frequency Integrated Circuits: RF CIRCUITS THROUGH THE AGES , 2003 .

[16]  Yvonne Schuhmacher,et al.  Rfid Handbook Fundamentals And Applications In Contactless Smart Cards And Identification , 2016 .

[17]  S. Wong,et al.  Physical modeling of spiral inductors on silicon , 2000 .

[18]  Shuvo Roy,et al.  Orthogonal-coil RF probe for implantable passive sensors , 2006, IEEE Transactions on Biomedical Engineering.

[19]  B.J. Hosticka,et al.  A programmable intraocular CMOS pressure sensor system implant , 2001, Proceedings of the 26th European Solid-State Circuits Conference.

[20]  Babak Ziaie,et al.  A hydrogel-based implantable micromachined transponder for wireless glucose measurement. , 2006, Diabetes technology & therapeutics.

[21]  S. Fandrey,et al.  Mechanical and electrical properties of electroplated copper for MR-imaging coils , 2006 .

[22]  K. Katuri,et al.  Intraocular Pressure Monitoring Sensors , 2008, IEEE Sensors Journal.