Antenna Design of Millimeter Wave Radar for Smart Toilet

Presence detection, seating detection, and water level detection in smart toilets have received widespread attentions. This paper uses a low-cost, simple structured 24G millimeter-wave radar with one transmitter and two receivers to achieve these functions. Presence detection and seating detection require the antenna to radiate signals forward, while water level detection requires the antenna to radiate signals vertically down to the water surface. This paper proposes a new bidirectional radiating antenna of millimeter-wave radar. The transmitting antenna is a hybrid end-fire and broadside radiating antenna, composed of the Vivaldi antenna and the wideband high efficiency electromagnetic structure (WHEMS) antenna. The hybrid end-fire radiating antenna is used for presence detection and seating detection, and broadside radiating antenna is used for water level detection. With advantages of the antenna, we have achieved accurate tracking of toilet users, and the water level measurement accuracy can reach ±2 mm.