Mechanical tuning and modulation of battery-less semiconductor-free scatterers for small insect pollinator tracking

The number of pollinators across the world is decreasing rapidly in part due to human activity -tracking insects is a way to understand and curb this decrease. Historically valued for its range, harmonic RADAR is now rare. The technology's high power demands (typically 20 kW) and the inherently low, non-linear conversion efficiency of its tags make it impractical for most modern applications. This paper designs and provides proof-of-principle demonstration of a RADAR tag that can be detected with lower power. It proposes taking advantage of the insect's wingbeat to provide a frequency shift to stand out from reflections off clutter. This wingbeat approach also has the added benefit of enabling behavioural analysis and creating a battery-less and semiconductor-free design. The paper shows the design, fabrication and measurement of a mechanically tuning tag; mathematical modelling of the backscattered signal; dynamic testing of the tag with vibration to simulate wingbeats; and analysis of this data in comparison with harmonic RADAR. The measured tag has a conversion efficiency of 10%, and it has been predicted that it could provide a detection range of nearly 900 m with only 10 W transmit power using standard antennas and receiver sensitivity.