A 160-GHz radar sniffer probe for honey bee detection

Abstract

The use of radar systems is limited in some applications by spatial constraints or special thermal and environmental conditions. The spatial separation of the sensitive electronics and the more robust antenna by a flexible connection therefore opens up new applications. A 160-GHz radar system with a mechanically flexible front end fulfilling these requirements is proposed in this paper. The flexible front end is an extremely low loss dielectric waveguide feeding a dielectric elliptical lens antenna (28 dBi gain). The dielectric waveguide has dielectric losses of 4.5 dB/m at 160 GHz and is very flexible, allowing bending radii of down to 1.5 cm with negligible losses. The dielectric waveguide is fed by a 160-GHz radar monolithic microwave integrated circuit (MMIC), which allows bandwidths of up to 20 GHz for a high range resolution. The transition between MMIC and dielectric waveguide is realized with a rectangular-waveguide interface. The radar back end consists of a phased-locked loop (PLL) with standard components, an intermediate frequency (IF) signal conditioning part, and a Xilinx Zynq 7030 System-On-Module (SOM) with an FPGA and an ARM-based processor. The sampled signal is processed directly on the FPGA with a 2D Fourier transform and is available as a UDP stream with an update rate of up to 15 Hz. In addition, a camera image is taken for each radar measurement. The presented system is used to detect and measure the flight behavior of honey bees. The electronics are housed in a building whereas the flexible dielectric waveguide allows the antenna to be placed anywhere around the beehive, where it is exposed to environmental conditions.