A 2 MHz Wireless CMOS Transceiver for Implantable Biosignal Sensing Systems
An implementation of an implantable sensing biosystem composes of a readout circuit, a power management block, an embedded microcontroller unit (MCU), an implantable drug delivery section and a wireless uplink transceiver system. This paper describes a bi-directional wireless transceiver system for implantable sensing systems. The transceiver system is composed of an external and implantable transceiver, communicating through an inductive link. Half duplex communication between transceivers at a 10Kbps data rate was achieved at a maximum distance of 4cm. Command and data will be supplied to the implantable module by radio frequency (RF) telemetry utilizing an amplitude shift keying (ASK) modulated 2 MHz carrier frequency. A capacitor-less amplitude demodulation receiver architecture was produced in the research with implantable receiver core area measuring at 113.2m by 171.8m with average power dissipation at 815.1W at a 3.3V single rail power supply. An active uplink transceiver utilizing load shift keying (LSK) as backward data telemetry was designed. Implantable transmitter core area measures 251.7m by 139.3m, consuming 103.62mW while driving an RF ferrite core antenna at maximum reading range. Integrating both circuits, implantable transceiver, measuring 355.3m by 171.8m, was designed and implemented using TSMC 0.35m mixed-signal 2P4M 3.3V standard CMOS process. The integrated circuit solution addressed solutions for many of the problems associated with implanted devices and introduces circuits which improve in several ways over previously published designs, in functionality and integration level. In addition to being fully integrated in plain CMOS technology, not relying at least partly on available specialized elements and expensive technologies, these building blocks improve on previous designs in performance and/or power consumption. This work succeeded in implementing building blocks for an implantable transceiver, which depends only on the absolute minimum off-chip components. A complete implantable chip is presented, which highlight the design tradeoffs and optimizations applied to the design of CMOS implantable system chips.
biosignal sensing bi-directional wireless transceivers inductive link load shift keying implantable systems