Passive Backscatter Biotelemetry for Neural Interfacing

Wireless telemetry of low level biopotentials from bioelectrodes can be accomplished over decimeter-order distances by using the biopotential to directly modulate the characteristics of a simple passive resonant circuit consisting of two varactor diodes and an inductor. Backscattered radio frequency energy at or near the circuit resonance in the 300 MHz region is amplitude modulated by the biopotential and detected by a remote receiver. The varactor circuit exhibits a high input impedance suited to bioelectrodes and a sensitivity to submillivolt levels. The circuit is miniaturizable to several cubic millimeters and can be realized with conventional commercially available surface mount components.