INTERFERENCE CANCELLATION IN SELF-COHERING ARRAYS.

Format:

Book

Thesis/Dissertation

Author/Creator:

LU, CHUNG H.

Contributor:

University of Pennsylvania.

Subjects (All):

System theory.

0790.

Local Subjects:

0790.

Physical Description:

335 pages

Contained In:

Dissertation Abstracts International 41-10B.

System Details:

Mode of access: World Wide Web.

text file

Summary:

This dissertation is devoted to self-cohering of a large, random, nonrigid antenna array in the presence of interference. The techniques of self-cohering by self-survey and by adaptive beamforming are addressed. Both of these techniques make use of phase information from beacon signals. In such self-cohering techniques, interference must be cancelled locally at each array element where phase measurements are made. Three interference cancellation schemes which meet this local cancellation requirement are introduced: an element-pair approach, an approach focusing on single elements with injected reference, and an approach focusing on single elements (subarrays) with controllable radiation patterns.

Two issues which are not directly related to interference cancellation are also addressed. The essence of the phase center concept in an antenna array sheds light on the self-survey process. Two techniques, a multiple frequency method and a minimum least square method, are developed for resolution of the phase-measurement ambiguities associated with self-survey.

The self-survey process employs a radio navigation technique (i.e., phase multilateration) to accurately locate the flexible array elements and calibrate the cable delays, aiming at an application for wide-angle scanning with high angular resolution and accuracy. The self-survey system in effect determines a least-square phase-error fit for the relative phase centers of the array elements and therefore reduces the power gain loss of the array to a minimum value. The best-fit phase centers partially compensate for the actual phase profile of a nonideal radiator and also reduce the effect of phase perturbations; e.g., those caused by a turbulent transmission medium.

A least-mean-square (LMS) steepest descent method is used to derive a phase-shift control loop and a gain-phase-shift control loop. The control loops are applied throughout for interference cancellation. The control loops have similarities to a phase-locked loop (PLL), a squaring loop and a Costas loop. Each loop is a power inversion loop in principle. It is found that complex weight control and gain-phase-shift control have comparable transient performance and lead to equivalent error-free steady-state solutions. The interference residue associated with such (gain-) phase-shift control loops is shown to result in a tolerable beacon signal phase distortion.

The interference cancellation scheme using single elements (subarrays) with controllable radiation patterns is applied to an element-pair subarray, a linear subarray and a circular subarray. This scheme is essentially a spatial filtering technique (adaptive array processing) and is the most promising scheme for application in self-cohering arrays.

Notes:

Source: Dissertation Abstracts International, Volume: 41-10, Section: B, page: 3866.

Thesis (Ph.D.)--University of Pennsylvania, 1980.

Local Notes:

School code: 0175.

Access Restriction:

Restricted for use by site license.