A New CMOS Implementation for Miniaturized Active RFID Insect Tag and VHF Insect Tracking

Abstract

This paper proposes a new circuit design for Very High Frequency (VHF) radio telemetry, in order to miniaturize active RFID tags for tracking small insects and bees. It presents a CMOS insect-tag implementation for generating 150 MHz burst-mode signaling scheme by employing digital approach which was not reported before. This design is vastly different from many presently available VHF tags which employs analog signal generation and discrete components. The new telemeter circuit employs a 150MHz voltage-controlled ring oscillator (VCRO) feeding into a cascade of frequency-dividers whose outputs are combined to generate an extremely low duty-cycle (LDC) burst-mode transmission signal to conserve power. In addition, it also incorporates digital-code for insect-tag identification, compared to analog methods which employs small frequency shifts from a reference f (~150MHz) to $\text{f}+{\boldsymbol{\Delta }}\text{f}$ MHz for individual tag identification. In the proposed design the strength of the modulated carrier signal is employed to track the tagged insect location through the triangulation technique. A design-rule-check (DRC) and pattern-density clean chip-tag was designed for an 8-bit identification code at a throughput of 576b/s, on a 28-nm CMOS process. It occupies an active layout area of 1600- $\mu \text{m}^{2}$ and consumes 8.2- $\mu \text{W}$ . The core transmitter employs supply-voltage of 0.6V to conserve power while the output drivers uses 1.2V for high transmitted signal strength. In addition, the new LDC burst-mode signal generation method was verified on silicon through measurements on a fabricated test chip using a 130nm CMOS process. This test circuit consumed a measured average power of only 7.07- $\mu \text{W}$ . This novel design enables the smallest tag-size (5mm $\times$ 5mm $\times$ 2.5 mm) and tag-weight (< 95mg) compared to many recent VHF tags.