Resolution and synthetic aperture characterization of sparse radar arrays

The concept of radar satellite constellations, or clusters, for synthetic aperture radar (SAR), moving target indicator (MTI), and other radar modes has been proposed and is currently under research. These constellations form an array that is sparsely populated and irregularly spaced; therefore, traditional matched filtering is inadequate for dealing with the constellation's radiation pattern. To aid in the design, analysis, and signal processing of radar satellite constellations and sparse arrays in general, the characterization of the resolution and ambiguity functions of such systems is investigated. We project the radar's received phase history versus five sensor parameters: time, frequency, and three-dimensional position, into a phase history in terms of two eigensensors that can be interpreted as the dimensions of a two-dimensional synthetic aperture. Then, the synthetic aperture expression is used to derive resolution and the ambiguity function. Simulations are presented to verify the theory.

I. Introduction

As evidenced by recent literature [1]–[4] and by the theme of a recent radar conference, 2001: Radar's Odyssey into Space [5], there is currently much interest in moving radar technology onto spaceborne platforms. The advantages of moving radar into space are numerous [3], [6]–[7]. First, spaceborne radars provide global coverage, as opposed to airborne radars that are limited by airspace restrictions. Satellite radars may also reduce the amount of personnel needed to support surveillance operations, since no on-board crew is necessary. Furthermore, support personnel and the radar asset are not as vulnerable to military threats as they would be on an airborne platform.