First Ever Lowest Duty Cycle for Periodic Burst Mode Signals for Insect Telemeter Package Design

Abstract

An extremely low duty cycle (LDC) generation digital circuit, for very high-frequency (VHF) radio telemetry application, is described in this article. This is done to miniaturize the package size for active radio frequency identification (RFID) tags, for tracking small insects and bees. This design is built on a silicon chip to prove the manufacturability of these LDC tags in high-volume manufacturing environments in a tiny package. The study was done to determine the total weight of this LDC tag, and it was estimated to be less than 15 mg, without battery and 95 mg with battery. This is much less compared to the existing tags that use many passive components for insect telemeter design. This kind of digital circuit is being built for the first time, where no passive components are used. Here, CMOS technology was used for generating a 132-MHz radio frequency signal at 0.0078 or less duty cycle, for saving power. The lowest duty cycle we found was close to $6.1 \times 10^{-5}$ at 132-MHz frequency. This signal comes in burst mode for about 485 ns and then remains silent until about $62.3~\mu \text{s}$ . In the new approach, for the first time, digital binary division and multiplication circuits are used for getting the lowest duty cycles. This design is different than the present printed circuit board (PCB)-based, analog VHF tags. These tags use bipolar transistors circuit and passive components. The new telemeter circuit generates about 3.2 MHz/132 MHz frequency, using a voltage-controlled ring oscillator, which then passes through multiple cascaded frequency dividers. The outputs of those frequency dividers are combined to form an LDC burst-mode transmission signal for saving the battery-operated tags, in order for the battery to last longer in the field. The chip designed in 130-nm CMOS technology was fabricated and tested using quad flat no-lead (QFN) package. It requires 0.028-mm2 active die area and consumes about 7.07- $\mu \text{W}$ power at 0.6-V power supply voltage while operating at 132 MHz.