CAPABILITY OF PATCH ANTENNAS IN A PORTABLE HARMONIC RADAR SYSTEM TO TRACK INSECTS

Monitoring technologies are needed to track insects and gain a better understanding of their behavior, population, migration, and movement. A portable microwave harmonic-radar tracking system that utilizes antenna miniaturization techniques was investigated to achieve this goal. The system mainly consists of a compact radar unit, a hand-held transmitter/receiver (Tx/Rx) patch antenna array panel, and a passive radio frequency (RF) transponder. The system transmits a signal at 5.882 GHz and receives returned signals in the 11.764 GHz band. The RF transponder to be mounted on insects is a 9.63 mm × 9.63 mm flat plane weighing 6 mg. Tests were conducted to optimize the horizontal and vertical tracking ranges of the system by measurement of radio frequency signal strength from the transponder in open terrain, inside tree canopies, and underground at different tracking angles. In open terrain, a directional tracking range of over 60 m was achieved. However, obstructions from tree canopies and the high water content of leaves severely weakened the microwave signal strength and restricted the tracking range to below 20 m. To obtain maximum signal strength, the Tx/Rx antenna panel and the transponder must be in a mutually clear line of sight and their angles must be maintained within a 10° range. However, the use of harmonic radar technology to develop a portable tracking system with a small insect-borne transponder currently poses insurmountable challenges for antenna design due to the very stringent requirements to accommodate the tracking range, the transponder size and mass, and the methods used to attach the transponders to insects.

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