MSU Technologies

Harmonic RF Tag for Wireless Measurement of Multiple Products

VALUE PROPOSITION

It is desirable to remotely detect and measure the motions of objects in living spaces for applications such as human-computer interaction and connected homes. Furthermore, home health and remote diagnostic applications have seen dramatically increased demand as people look for solutions to health care that do not require leaving the home. While optical systems can track the motions of people and objects, privacy concerns related to devices obtaining images in the home have been a concern. Harmonic Doppler radar presents a solution that not only mitigates such privacy concerns, but also requires less data processing, and can differentiate between human motions and the motions of tagged objects. Passive harmonic tags can furthermore be made cheaply, enabling the detection and tracking of low-cost objects that otherwise would not include electronics. A challenge involved in harmonic Doppler measurements is the ability to discriminate tags in the environment. This technology is a narrowband harmonic tag that uses a microstrip antenna based on a ring resonator design capacitively coupled to the signal feed to discriminate objects in real time.

DESCRIPTION OF TECHNOLOGY

By tuning the ring radius and coupling capacitance, the operational bandwidth of the tag can be minimized, enabling better discrimination of separate tags. The tag captures an incident signal and generates a harmonic signal that is retransmitted back to the interrogating device. The principal impedance parameters were the feedline capacitance and the line-to-ground impedances which are dependent on the width of the microstrip line and the radius of the ring. The bandwidth of the antenna yields a favorable fractional bandwidth. The antenna accepts a wireless signal from the interrogating system at a frequency f and inputs it to the diode. The diode generates a harmonic signal at frequency 2f which is radiated back to the interrogating device using the antenna. The ring antenna is designed for narrow bandwidth operation, thus multiple tags at adjacent narrowband frequencies can exist in the environment simultaneously and be measured simultaneously without interfering with one another.

BENEFITS