An innovative harmonic radar prototype for miniaturized lightweight passive tags tracking

Harmonic radars can be generally used to track very small (1.5 cm) and lightweight (15 mg) passive tags; as an example, they have been adopted to track various insects for almost 30 years now. In most of the cases, their usage was motivated by the entomological interest in better knowing the habits of the observed insect; in fewer applications, like ours, prevailed the need of protecting the environment from invasive species. However, despite the purpose of the research involving entomological radars, not a lot of engineering resources have been invested during the last decades with the aim of improving what was basically considered a mere tool in the hands of entomologists. The goal of this paper is to show how modern radar techniques, the progresses in the available hardware and a three years long design effort helped us to build and test an harmonic radar system with considerably improved performances. The prototype herein described is able to detect the flight of tagged insects in real time, up to 500 meters with a quite large field of view in elevation, and can be therefore adopted also in harsh environments.