Ultra-Low Power Transceiver for the Medical Implant Communications Service

DESCRIPTION (provided by applicant): This proposal describes the research required to design, simulate and manufacture ultra-low power circuitries to be used in a complete transceiver implanted inside the human body. Currently, it is difficult to communicate with devices implanted within the human body and the present commercial technologies do not adequately fill this need. We have identified that circuits using SJT Micropower proprietary MESFET technologies will have a lower current draw resulting in longer lifetimes than conventional devices and will be more suited for implanted devices. In order to improve communication with implanted devices, the FCC implemented the Medical Implant Communications Service (MICS) which is an ultra-low power, unlicensed, mobile radio service for transmitting data in support of diagnostic or therapeutic functions associated with implanted medical devices [1]. The FCC rules require that devices operating in the MICS frequency band of 402-405 MHz are limited to a bandwidth of 300kHz and maximum effective isotropic radiated power (EIRP) of 25 microwatts [1]. During Phase 1 research, we have demonstrated a novel MESFET based output stage and an industry leading phase locked loop frequency synthesizer operating between 402-405MHz. These circuits utilize our patented MESFET transistors, operate with less than 2mA and are the backbone circuitry of a transmitter. SJT Micropower will microfabricate the transmitter circuits from Phase 1 along with additional circuitries for a complete transceiver design during Phase 2. The following Phase 2 objectives will lead to a complete transceiver prototype: Objective 1) Finalize Output Transmitter Section - Frequency Synthesizer and Buffer from Phase 1 Objective 2) Design and Fabricate Input Receiver Stage - LNA Front End Objective 3) Design and Fabricate Backend Receiver Circuitry Objective 4) Integrate all Transceiver Circuitries and Build Final Prototype This device will be implanted within the human body and will improve patients' quality of life. Our technology advantages include the ability to operate with high voltage swings which will decrease the current draw of the output buffer, the ability to provide easier bias circuitry which will reduce component count, the ability to match the impedance of the transceiver antenna without additional matching circuitry and a possibility for lower noise circuitry than conventional MOSFETs. These all result in lower current draw from an implanted battery during data transmission and directly increase the useful lifetime of both the battery and implanted transceiver. In addition, our technology is fabricated on radiation hard SOI processes and does not suffer from ionizing radiation effects which can cripple medical circuitry that must last for many years. We have obtained strong support from microfabrication foundries, design consultants, medical device manufacturers and end users. PUBLIC HEALTH RELEVANCE: Currently, it is difficult for medical devices implanted within the human body to communicate with medical professionals in the outside world. This research will utilize the Medical Implant Communications Service (MICS) to build a novel low power transceiver which will allow physicians the ability to use wireless technology to diagnose and treat their patients. The final devices will permit faster data transfer rates between medical implants and external monitoring/control equipment, consume less power than existing solutions therefore requiring fewer replacement procedures, allow for less patient trauma, have a lower cost per survival day, reduce the risk of infection to patients, enhance the comfort of patients, and expand the freedom of movement of medical personnel working with the equipment [2].