method and device for radarmessung a ball in play

摘要

A system for continuously and precisely measuring the positions of a generally symmetrical object, e.g., a tennis ball, in motion in a predefined three-dimensional region, e.g., a tennis court, which transmits multiple radar signals from first, second, and third, spaced antenna devices, respectively, into the three-dimensional region. Multiple return signals are sensed and are compared with the transmitted signals to determine the phases of the return signals, to thereby obtain ambiguous ranges of the object. Ambiguities are removed by using the Chinese Remainder Theorem to obtain less-ambiguous ranges. Time-of-arrival range information is used in conjuction with the less-ambiguous ranges to provide unambiguous ranges over the range of interest. The unambiguous ranges are used to compute three-dimensional coordinates of the object that are accurate to within approximately 0.1 inches. A mathematical model defining boundaries of the three-dimensional region is completed by placing signal reflector devices on various boundary points of the three-dimensional region, and transmitting the radar signals when the object is not in the three-dimensional region. Coordinates of a projected trajectory are computed and compared with the actual coordinatres of the object, and certain characteristics are computed therefrom. Calibration of the system is maintained by placing signal reflector devices at various fixed locations within the region of interest and the return signals are processed to obtain an initial survey of the region and then to periodically resurvey the region.