A Compact Wireless Passive Harmonic Sensor for Packaged Food Quality Monitoring
Robin Raju, Greg E. Bridges
Abstract
There is currently a need to monitor food products while preserving quality and safety during long-term storage. In this article, a compact low-cost quasi-chipless sensor for monitoring the quality of high-value food items, such as milk and meat products, is presented. The sensor utilizes a dual-band dual-polarized annular ring antenna with an integrated harmonic generator and sensor to receive, modulate, and retransmit the interrogator signal. The resonant frequency of the receiving mode of the antenna is sensitized to the parameter being sensed using a varactor—pH electrode-based transduction scheme. The received signal is doubled using a diode frequency doubler circuit to minimize the clutter from the environment before retransmission. One application of the sensor for monitoring pH is presented. The sensor was shown to be able to successfully monitor the milk souring process.