title: A 1.48-mW low-phase-noise analog frequency modulator for wireless biotelemetry.
abstract: This paper presents a low-phase-noise, hybrid LC-tank, analog frequency modulator for wireless biotelemetry employing on-chip NMOS varactors in the inversion region as the frequency tuning element. We demonstrate that a correct estimate for the destination signal-to-noise ratio, which quantifies the quality of the wirelessly received signal in a frequency-modulated biotelemetry system, is only achieved after taking into account the large-signal oscillation effect on the tank varactor. A prototype chip is fabricated using AMI 1.5-microm double-poly double-metal n-well CMOS process, and exhibits a measured gain factor of 1.21 MHz/V in the mid-range of the tuning voltage and a phase noise of -88.6 dBc/Hz at 10-kHz offset from the 95.1-MHz carrier while dissipating 1.48 mW from a 3 V power supply leading to a figure of merit (FOM) of -166.5 dBc/Hz. The VCO is successfully interfaced with a penetrating silicon microelectrode with 700 microm2 iridium recording sites for wireless in vitro recording of a 50 Hz simulated normal sinus rhythm signal from saline over a distance of approximately 0.25 m. Given a typical gain of approximately 40 dB for fully integrated front-end bioamplifiers, a wireless recording microsystem employing this VCO would be capable of detecting input biopotentials down to the submilivolt range.
authors.affiliation: Center for Wireless Integrated MicroSystems, Electrical Engineering and Computer Science Department, University of Michigan, Ann Arbor, MI 48109-2122, USA. pmohseni@umich.edu
authors.forename: Pedram
authors.initials: P
authors.lastname: Mohseni
authors.forename: Khalil
authors.initials: K
authors.lastname: Najafi
mesh_terms: D004582:Electronics, Medical; D004594:Electrophysiology / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008904:Miniaturization; D011846:Radio Waves; D013685:Telecommunications / Q000295:instrumentation*; D013686:Telemetry / Q000295:instrumentation* / Q000379:methods