Patent ID: 6958951

Claim:
In a system configured to generate: a reference time signal; m free-running frequencies having corresponding fractional frequency errors y 1 . . . m and fractional frequency rate errors d 1 . . . m , from which are derived m corresponding free-running times having corresponding time errors x 1 . . . m ; a controlled frequency responsive to a responsive to a control signal Uk, the controlled frequency having a fractional frequency error y 0 , from which is derived a controlled time having time error x 0 ; and a difference measurement vector representing time differences between the controlled time and each of the free-running times, and the reference time; wherein: the fractional frequency errors are represented as functions of weighting parameters alpha 1 . . . m and beta 0, 1 . . . m ; and the time errors are represented as functions of the fractional frequency errors, a method of adaptively estimating the alpha 1 . . . m and beta 0, 1 . . . m parameters, comprising: (a) initializing a system state vector including a priori estimates of the time, fractional frequency, and fractional frequency rate errors, a corresponding covariance matrix of estimation errors, the alpha 1 . . . m and beta 0, 1 . . . m parameters, and a corresponding set of partial derivative matrices; (b) performing a Kalman Measurement Update based on the time difference measurement vector, to produce current time a posteriori state vector estimates of the time errors x 0, 1 . . . m , the fractional frequency errors y 0, 1 . . . m , and the fractional frequency rate errors d 1 . . . m , and a current time a posteriori covariance matrix; (c) updating the partial derivative matrices relative to the current time difference measurement vector; and (d) updating, based on the updated partial derivative matrices, the alpha 1 . . . m and beta 0, 1 . . . m parameters.