Sandquist 2004 Design of a wireless power and data link for a cranially-implanted neural prosthesis 10 Mbps- contracted from NASA's Jet Propulsion Laboratory?? - May I ask just why JPL is wanting 10 Mbps from the brain? Wireless (inductive) transmission of 15 mW for circuitry operations Main functionality allowed by "inductive coupling." Absorption of energy by tissue will increase with frequency. `Several articles have been published (e.g.[2], [3]) with details on the design of inductively coupled coils for implanted devices.` [2] W. H. Ko, “Design of Radio-Frequency Powered Coils for Implant Instruments,” Medical & Biological Engineering & Computing, vol. 15, pp. 634-640, Nov. 1977. [3] N. Donaldson, et al., “Analysis of Resonant Coupled Coils in the Design of Radio Frequency Transcutaneous Links,” Medical & Biological Engineering & Computing, vol. 21, pp. 612-627, Sep. 1983. [4] M. Ghovanloo, et al., “A BiCMOS Wireless Interface Chip for Micromachined Stimulating Microprobes,” 2nd Annual International IEEE-EMBS Special Topic Conference on Microtechnologies in Medicine & Biology, pp. 277 – 282, May 2002. `Ghovanloo et al. documented in [4] the development of a transcutaneous power and forward data link intended for wirelessly transmitting power and data to an implant that would be responsible for stimulating the brain in the visual cortex area.` ` In [6], Von Arx and Najafi documented the development of a fully-integrated (including the receiving coil) implantable micro-stimulator capable of providing 20mW to implants at depths up to 3cm. The external transmitter inductively couples a 4MHz RF power carrier into an on-chip coil. The on-chip coil is electroplated after the standard BiCMOS fabrication. The inductor is a 17-turn 2x8.7mm2 coil resulting in a 2.9uH inductance and a Q of 2.6 at 4MHz. Data is transmitted to the chip at 8.3kb/s by pulse-width encoded amplitude modulation of the power carrier.` [6] J. Von Arx and K. Najafi, “A Wireless Single-Chip Telemetry-Powered Neural Stimulation System,” IEEE International Solid-State Circuits Conference, pp. 214- 215, 1999. ` In [7], R. J. Betancourt-Zamora developed the BioLink Implantable Telemetry System (BITS) which is a low-power bi-directional data link for recording bio-signals in lab animals. The system is suitable for short range biosensor and implantable use. This digital RF transmitter operates at 100kbps, using QPSK modulation in the 174-216MHz ISM band. Command and control of the unit is achieved through a 433MHz downlink. The implant uses a battery for power and is therefore only for short-term use.` [7] R. J. Betancourt-Zamora, “The Biolink Implantable Telemetry System,” Stanford University, 1999. inductive link `The main effect of non-ionizing radiation is the heating of tissues due to the absorption of electromagnetic energy. This heating of tissues has been known to have side-effects including the inductions of opacities of the lens of the eye, possible effects on development and male fertility, various physiological and thermoregulatory responses to heat, and decreased ability to perform mental tasks ([12]).` [12] “Health Issues Related to the use of Hand-Held Radiotelephones and Base Transmitters” Health Physics Society, vol. 70, no. 4, pp. 587-593, 1996. `Poynting’s Theorem tells us that when a mass is exposed to an electromagnetic field, energy from the field is either stored in the mass in the form of an electric or magnetic field or dissipated via conduction losses.` Maxwell's curl equations Finite-Difference Time-Domain (FDTD) method magnetic flux density rectifier reflected impedance modulation load impedance modulation "For the data-receiving coil, a large capture area is desired to capture a large amount of flux." ??? flux density pg 54 - photographs of the circuit boards, with onboard coils. Kapton (thin film substance?) spectrum analyzer Platinum may be more biocompatible than copper [11] A. Drossos, et al., “The Dependence of Electromagnetic Energy Absorption Upon Human Head Tissue Composition in the Frequency Range of 300-3000MHz,” IEEE Transactions on Microwave Theory and Techniques, vol. 48, no. 11, pp. 1988-1995, Nov. 2000. [17] F. W. Grover, Inductance Calculations: Working Formulas and Tables, New York, NY: D. Van Nostrand Company Inc., 1946. [20] K. Henney, Radio Engineering Handbook, New York, NY: McGraw-Hill Book Company, Inc., 1950. [21] Francis A. Duck, Physical Properties of Tissue: A Comprehensive Reverence Book, San Diego, CA: Academic Press Inc., 1990.