Janus: A Combined Radar and Vibration Sensor for Beehive Monitoring
A novel beehive monitoring sensor with two faces is described. This sensor is attached to the outside of a hive, near the hive entrance. The outward-looking sensor is a 24-GHz continuous-wave Doppler radar for monitoring bee flying activity. The inward-looking sensor is a piezoelectric transducer. Unlike a conventional microphone that would pick up the sounds bees make, the piezoelectric transducer picks up the incidental vibrations transmitted by bee activity to the hive structure. The root-mean-square powers in concurrent radar and vibration measurements are shown to be highly correlated during honeybee swarming and robbing events. Principal component analysis was applied to radar, vibration, and environmental measurements to further reduce false alarms.