Abstract: This invention relates to a frequency modulation of continuous wave (“FMCW”) radar altimeter capable of controlled linear sweep modes. The FMCW radar altimeter is characterized by the following functions: (1) adopts sweep up frequency and sweep down frequency to solve problems of distance and doppler signal mixture; (2) injects a random generated variable time delay in between sweep intervals to overcome interferences among different altimeters; and (3) switches different sweep frequency bands in accordance with different altitudes.

Abstract: A position detector is provided for use on a spin-drying machine employed in integrated circuit (IC) fabrication to detect whether the spin-drying machine has shifted in position during operation. If the spin-drying machine is positioned incorrectly, the position detector is capable of stopping the operation of robot arms used to grab and position wafers on the spin-drying machine so that the robot arms will not be damaged or crash into the wafers on the spin-drying machine due to the incorrect positioning of the spin-drying machine. The position detector is designed for use on a spin-drying machine having a spinning unit, a fixed platform surrounding the spinning unit, and at least one robot arm mounted on the fixed unit. The position detector comprises a pair of emitters mounted on the spinning unit and a pair of oppositely arranged receivers on the fixed platform.