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 transmitter 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 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]. In preliminary results, we have demonstrated both a novel voltage controlled oscillator operating between 402-405MHz and a low power second stage buffer to drive an antenna. These circuits utilize our patented MESFET transistors, operate with less than 1mA and are the backbone circuitry of a transmitter. SJT Micropower already has microfabricated MESFETs from other process runs on hand and they will be used for a prototype hardware demonstration. The main project objectives are to: Objective 1) Design and simulate an ultra-low power voltage controlled oscillator (VCO) and a high efficiency output buffer using Cadence Design Software. Objective 2) Integrate the VCO and buffer together and optimize for ultra-low power operation and reliability using Cadence Design Software. Objective 3) Microfabrication layout of individual and integrated circuit components using Cadence CAD software tools to extract parasitics and optimize design. Objective 4) Build, characterize and document a hardware demonstration VCO and second stage buffer integrated together using pre-fabricated MESFETs. Our long-term goal is a fully integrated transceiver designed for operation in accordance with the MICS regulations. This device will be implanted within the human body and will improve patients' quality of life. The specific aims of this project will be to provide the circuit components necessary for the transmitter portion of the MICS transceiver. 7. Project Narrative currently, it is very 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 novel components for a 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, 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].