Location and velocity measurement system using atomic clocks in moving

Abstract

A coherent signal generated at a precise frequency determined by an atomic clock is transmitted by a moveable object. A receiver station compares the frequency of the coherent signal received from the moving object with a second coherent signal generated at the same precise frequency by an atomic clock in the receiver to determine the radial component of the velocity of the moveable object relative to the receiver as a function of the doppler shift of the transmitted signal. Low cost, low power, miniature atomic clocks with an accuracy of 10.sup.-11 make possible accurate measurements of velocities of only centimeters per second. Such velocity measurement can be used to enhance radar tracking in air traffic control and collision avoidance systems. These velocity measurements can also be used to resolve tracking ambiguities in precision location systems, such as prisoner, geriatric and airport ground control systems, where three or more receiver stations each having an atomic clock measure time of flight of the transmitted coherent signal to triangulate moving object position.