A Wireless Soil pH and Conductance Monitoring Chip Powered by Soil Microbial and Photovoltaic Energy Cells
Journal
IEEE Transactions on Biomedical Circuits and Systems
Journal Volume
16
Journal Issue
6
Pages
1008
Date Issued
2022-12-01
Author(s)
Lu, Ting Heng
Liu, Chi Wei
Wu, Chuan Yi
Huang, Cong Sheng
Chen, Jing Siang
Chen, Ling Chia
Huang, Yao Wei
Ou, I. Che
Lee, Sook Kuan
Chen, Yen Chi
Chen, Po Hung
CHI-TE LIU
Liao, Yu Te
Abstract
This paper presents an energy-autonomous wireless soil pH and electrical conductance measurement IC powered by soil microbial and photovoltaic energy. The chip integrates highly efficient dual-input, dual-output power management units, sensor readout circuits, a wireless receiver, and a transmitter. The design scavenges ambient energy with a maximal power point tracking mechanism while achieving a peak efficiency of 81.3% and the efficiency is more than 50% over the 0.05-14 mW load range. The sensor readout IC achieves a sensitivity of-8.8 kHz/pH and 6 kHz·m/S, a noise floor of 0.92 x 10-3 pH value, and 1.4 mS/m conductance. To avoid interference, a 433 MHz transceiver incorporates chirp modulation and on-off keying (OOK) modulation for data uplink and downlink communication. The receiver sensitivity is-80 dBm, and the output transmission power is-4 dBm. The uplink data rate is 100 kb/s using burst chirp modulation and gated Class E PA, while the downlink data rate is 10 kb/s with a self-frequency tracking mixer-first receiver.
Subjects
CMOS | energy harvesting | microbial energy cell | power-efficient | readout IC | soil monitoring
Publisher
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Type
journal article