Correlated microwave-ultrasonic multi-sensor for reliable measurements of velocity and range

The potential of the combination of ultrasound and microwaves to improve existing sensors in terms of sensitivity and reliability is demonstrated. While noise and disturbances affect both waves differently, signal returns form target reflectors will be coherent. With data fusion performed on the signal level, the applicability is significantly improved compared with multisensors based on complementary sensor outputs. A compact low-cost sensor for the robust measurement of presence, velocity and distance of objects, using 24 GHz microwaves and 40 kHz ultrasound, has been designed. Key issues for a smart sensor design, inherently exploited by the multisensor approach, are the adaptation to the environment, self calibration and function monitoring. The design and operating parameters of the multisensor system are discussed and evidence for the satisfactory performance is given.