A Low Duty Cycle Burst-Mode Telemeter Signal Generation Technique for VHF Insect Tracking and Its CMOS Implementation

Abstract

This brief presents a new circuit design for very high-frequency (VHF) radio telemetry, to miniaturize active RFID tags for tracking small insects and bees. It reports the first CMOS insect tag implementation for generating 150-MHz burst-mode telemeter signals using employing digital approach. This design is vastly different from the present PCB-based analog VHF tag which uses bipolar transistors and large passive components. The new telemeter circuit uses a 150-MHz voltage-controlled ring-oscillator (VCRO) feeding into a cascade of frequency dividers whose outputs are combined (without requiring control logic) to generate extremely low duty cycle burst-mode transmission signal to save power. In addition, it is the first advancement of the VHF telemeter that incorporates digital code for insect tag identification, compared with the present state-of-the-art analog methods which use small frequency shifts from a reference fo (150 MHz) to fo+Δf MHz for individual tag identification. In the proposed design, the strength of the modulated carrier signal is used to track the tagged insect location through the triangulation technique. A DRC and pattern-density clean chip-tag was designed for an 8-bit code at a throughput of 576 b/s, on a 28-nm CMOS process. It occupies an active layout area of 1600μ m2 and consumes 8.2μ W.