A low-power miniature transmitter using a low-loss silicon platform for biotelemetry

This paper describes the development of a low-power micro-transmitter using a low-loss silicon platform for biotelemetry applications. The transmitter is a Colpitts oscillator built by attaching a surface mount hybrid RF transistor (Motorola MMBR931LT1) on a silicon platform. 5/spl times/5 mm/sup 2/ in dimensions which supports: a dielectric suspended high-Q inductor, metal-polysilicon capacitors, and polysilicon resistor. The inductor high quality factor (/spl sim/22 at /spl sim/315 MHz for a 115 nH inductor) allows the use of Frequency Division Multiple Access (FDMA) for recording physiological parameters from multiple subjects. The transmitter operates from a 3 V battery and consumes 200 /spl mu/A when operated continuously and 100 /spl mu/A when amplitude modulated (on-off keying) at a rate of 1 Mbps (50% duty cycle). The transmitter has a range of /spl sim/3 feet and has a magnetic dipole radiation pattern associated with its loop antenna.