Abstract: A flat antenna architecture for use in radio frequency monitoring systems including a patch antenna configured for use on a conductive surface of an object to be monitored. The patch antenna includes a conductive patch formed on a first surface of a dielectric base and an opposing surface on the dielectric base configured for attachment to the reflective surface of an object. This provides a patch antenna of relatively thin makeup having a lower cost and lower overall thickness and corresponding lower weight.

Abstract: A radio frequency identification system having a radio frequency transceiver for generating a continuous wave RF interrogation signal that impinges upon an RF identification tag. An oscillation circuit in the RF identification tag modulates the interrogation signal with a subcarrier of a predetermined frequency and modulates the frequency-modulated signal back to the transmitting interrogator. The interrogator recovers and analyzes the subcarrier signal and determines its frequency. The interrogator generates an output indicative of the frequency of the subcarrier frequency, thereby identifying the responding RFID tag as one of a “class” of RFID tags configured to respond with a subcarrier signal of a predetermined frequency.