A readout circuit for an intra-ocular pressure sensor

Abstract A readout circuit for a passive telemetric intra-ocular pressure (IOP) sensor is being developed. The intra-ocular sensor consists of a capacitive pressure sensor in parallel with a planar coil. This inductor–capacitor (LC) resonant circuit transduces the pressure into a shift of resonance frequency. A voltage controlled oscillator (VCO) is used to excite the sensor over a large frequency range (20–40 MHz), hereby detecting resonance of the internal sensor, and thus enabling the measurement of the intra-ocular pressure. This low power circuit is extremely compact, making it suitable for long-term ambulant patient monitoring. The circuit allows wireless readout of the smallest pressure transducers. Tests show promising results at mutual coil distances up to 7.5 mm.

[1]  Mattan Kamon,et al.  FASTHENRY: a multipole-accelerated 3-D inductance extraction program , 1994 .

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

[3]  K. Najafi,et al.  A wireless batch sealed absolute capacitive pressure sensor , 2001 .

[4]  Willy Sansen,et al.  A capacitive pressure sensor with low impedance output and active suppression of parasitic effects , 1990 .

[5]  Robert Puers,et al.  Electrodeposited copper inductors for intraocular pressure telemetry , 2000 .

[6]  Euisik Yoon,et al.  Hermetically Sealed Inductor-Capacitor (LC) Resonator for Remote Pressure Monitoring , 1998 .

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

[8]  C.M. Zierhofer,et al.  Geometric approach for coupling enhancement of magnetically coupled coils , 1996, IEEE Transactions on Biomedical Engineering.

[9]  田村 俊世,et al.  Biomedical Transducers and Instruments , 1997 .

[10]  Behzad Razavi,et al.  Design of Analog CMOS Integrated Circuits , 1999 .

[11]  Mani Soma,et al.  Radio-Frequency Coils in Implantable Devices: Misalignment Analysis and Design Procedure , 1987, IEEE Transactions on Biomedical Engineering.

[12]  R. Puers,et al.  Passive telemetry by harmonics detection , 1996, Proceedings of 18th Annual International Conference of the IEEE Engineering in Medicine and Biology Society.

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

[14]  Willy Sansen,et al.  Analog circuit design : (X)DSL and other communication systems, RF MOST models, integrated filters and oscillators , 1999 .