SELF SURVEY OF RANDOM ARRAYS

Assignee

UNITED STATES, OF AMERICA AS REPRESENTED BY THE SECRETARY OF THE NAVY, THE

Filed

Jun 30, 1986

Granted

Dec 14, 1999

Location

San Diego CA (SAIC/General Dynamics)

Abstract

A method for determining the positions of the N array elements of a random array to an accuracy sufficient to accomplish beam forming is provided where the initial positions of the array elements are known to an accuracy of lambda min/2, and where lambda min is the wavelength of the highest frequency of any of the M cohering sources which are in the field of the array and where the relative directions are unknown. The method includes the steps of: identifying M cohering sources in the field of the array, each of which emits at least one narrowband frequency, each frequency differing from the adjacent frequency by 1/T, where T is the time period of the measurements; a device for measuring the true bearing of one of the M sources; receiving the M cohering signals at the N array elements; performing a Fast Fourier Transform (FFT) on each of the N element signals; examining the spectrum of each of the N received signals; and from the N spectra, selecting M (M>3) lowest angular frequencies, omega p with the strongest signals. The method also includes at each omega p forming the cross coherence matrix using the formula where Apn is the complex Fourier coefficient from element n, the symbol pair indicating time average for each of the M Frequencies, omega p; obtaining the equation GAMMA p,mn=exp J p/c[kp-(+E,rar r+EE m-+E,rar r+EE n)](2)where ri is the vector position of the ith element, c is the speed of propagation and +E,cir k+EE p is the unit length direction vector of the pth cohering source; testing and discarding data where Equation (2) is satisfied for all element pairs with the same +E,cir k+EE p; and solving the overdetermined set of Equations (2) for the unknown +E,rar r+EE i and +E,cir k+EE p.

Source: Google Patents