An Orthogonal Bidirectional Antenna Radar Sensing System for Smart Toilets

Human presence detection and water-level detection are two essential functions of smart toilets, making smart toilets more intelligent and hygienic. Traditional solutions require different sensors for each of these functions. Furthermore, existing detection methods in smart toilets have some limitations, such as sensor size, the undesirable effect of environment on detection results, etc. Millimeter-wave (mmWave) radars offer better performance in terms of ranging accuracy and environmental stability. If the mmWave radar is used to achieve the above two functions, the radar system is required to radiate toward the Region of Interest (RoI). The RoI for presence detection is the front of the toilet, while RoI for water-level detection is the toilet bowl. Therefore, the radar needs to radiate signals forward and downward radiation simultaneously, which requires the radar to achieve an orthogonal bidirectional radiation. In this article, we innovatively propose a low-cost radar system with orthogonal bidirectional radiation with good antenna gain and isolation performance by using Vivaldi antennas and wideband high-efficiency electromagnetic structure (WHEMS) antennas. Additionally, appropriate antenna selection gives the antenna system the characteristics of wide bandwidth to match different toilet installation environments with higher reliability. The system can achieve presence detection and water-level detection well, and has the advantages of low cost, small size, and practical application value.