Time transfer method and system

#The present application is related to U.S. patent application Ser. No. 12/948,841, filed on Nov. 18, 2010.

#The invention is directed to a method and system for synchronizing a clock employing time transfer with a time reverse mirror, and more particularly, to computing a delay between a return signal and an imaginary time-reversed signal and applying the computed delay to a clock input calibration for a desired signal such as a multistatic radar signal.

#A bistatic radar is a radar with transmit and receive antennas separated by a considerable distance with respect to target range. In recent years, these bistatic and multistatic radars are gaining more and more attention because they can provide low-cost, ECCM capabilities against stealth targets.

#FIG. 1 is a schematic diagram illustrating the operational principle of time transfer using a time reversal mirror (TT TRM) according to the invention;

#FIG. 2 is a schematic diagram illustrating the time difference determination between two nodes being independent of various propagation delays according to the invention;

#FIG. 3 is a schematic diagram illustrating the compensation for signal distortion according to the invention;

#The operational principle of time transfer using a time reversal mirror (TT-TRM) is simple, as shown in FIG. 1. At first, Node A sends out a series of short pulses repeatedly at a period T. Node B receives, time reverses, and retransmits the incoming signals at the same period. At Node A, the returned signal is compared with the imaginary time-reversed version of the original signal (shown with a dotted red vertical line). The delay between the two pulses measured at Node A is twice the time difference between the two nodes. This amount of time is independent of various propagation delays due to the unique feature of time reversal, as explained below in detail.

#FIG. 2 explains how the amount of time delay between the transmitted and returned pulses measured at User node is solely dependent on the time difference between the two nodes—User and Reference nodes—and is independent of various propagation delays and multipath effects.

#In the example shown in the Figure, the following values are assumed: period T=30 sec, the time skew of the User node with respect to Reference node s=5 sec. and propagation delay between the two nodes p=15 sec. These numbers are exaggerated only for illustration. The time measured in User frame is shown on the top of the figure with vertical dotted lines.