Patent ID: 10578748

Abstract:
The basic concept of satellite-free time transfer using time reversal (T3R) has been invented and successfully demonstrated over long distance (about 4,000 km) with an accuracy of approximately 200 ns rms. The current invention describes new methods to drastically improve performance up to <10 ns rms—better than the current differential GPS, without satellites. The new method employs the Vernier concept utilizing the unique p-independence property of T3R irrespective of carrier frequencies. Also, a histogram method to automatically filter out extraneous data and allow high accuracy and a new method to extend the timing range of T3R beyond the pulse repetition period by removing ambiguity are proposed. A systematic way to obviate the signal blockage caused by transmit/receive window mismatch, is also proposed. Issues and solutions associated with the ionosphere are proposed, including 24-7 operation in adverse ionospheric conditions, such as the constantly changing ionosphere, multiple hops, static asymmetry, and jamming and spoofing.