Inverse filter technique for high-precision ultrasonic pulsed wave range Doppler sensors

Ultrasonic pulsed wave range Doppler sensors provide application in various fields, e.g, intruder alarm systems or autonomous vehicle steering. The time-frequency methods commonly used in these sensors, however, inhere the problem that, due to the transducer's non-constant and direction-dependent transfer functions, the Doppler frequency cannot be determined with the high accuracy needed for such applications. The easiest way to improve the Doppler resolution is to reduce the signal bandwidth, but only at the expense of worse range resolution. A direction-dependent inverse filter technique is presented, which compensates the erroneous effects of the transfer function in the time-frequency analysis. An ultrasonic intruder alarm system determining location and velocity of persons in rooms serves as an example that the novel approach gives evidently better performance than conventional methods, resulting in both high velocity and range resolution.