Phase-equivalent interferometer arrays

• US 5,574,468 A
• Filed: 04/20/1995
• Issued: 11/12/1996
• Est. Priority Date: 04/20/1995
• Status: Expired due to Term

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Litton Systems Incorporated (Northrop Grumman Corporation)
• Inventors: Rose, Conrad M.
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US08/426,000
• Time in Patent Office: 572 Days
• Field of Search: 342/424, 342/442, 342/444, 342/445
• US Class Current: 342/442
• CPC Class Codes: G01S 3/043 Receivers

Abstract

A method is described modifying initially linear or planar interferometer arrays such that the arrays can be placed in conformal installations. The method commences with a conventional linear or planar array design and then using certain techniques and relationships allows for the possibility of antenna placement with materially reduced restrictions. A plurality of phase equivalent antenna locations obeying prescribed relationships are generated. These positions lie on the conformal surface on which the array is to be mounted. This permits an optimal set of antenna positions to be chosen based on operational requirements.

Claims

1. A method for modifying conventional linear and planar interferometer arrays for installation on a conformal surface, comprising the steps of:

designing a conventional linear or planar interferometer array,

choosing a dispersed set of baselines on the basis of said conventional linear or planar array design and in accordance with the particular conformal surface installation,

changing the value of phase measurement noise for the conventional linear or planar array design so that it is consistent with a value for said dispersed set of baselines, and

generating a multiplicity of phase equivalent antenna locations from the specific antenna positions of the conventional design which consists, for a particular baseline a₁ and arbitrary origin change a₀, of the set of all antenna positions a₀ and a₁ on a line with Pluecker coordinates (d_p d₀ ×

d_i) such that

space="preserve" listing-type="equation">|a.sub.1 -a.sub.0 |-|d.sub.1 |.

2.

2. The method described in claim 1 comprising the additional steps of:

generating the Pluecker coordinates for said dispersed baselines such that predetermined gross error and DOA accuracy criteria are met,

testing different sets of dispersed baselines such that an error variance R is varied according to ##EQU22## choosing the optimal phase equivalent set such that minimum gross error rate or maximum DOA accuracy are achieved.

3. The method described in claim 2 where a conventional linear or planar array is used as the basis for generating dispersed phase equivalent arrays, and hence the error variance used initially is that of the conventional linear or planar array.

4. The method described in claim 1 where additional antenna elements are used to form said dispersed array thereby forming an ambiguous long baseline interferometer suitable for use in long baseline interferometer, or LBI, passive ranging.

5. The method described in claim 2 where the DOA accuracy or the gross error rate is improved over the conventional linear or planar array comprising the additional steps of:

moving the interferometer baselines apart to form said dispersed baselines such that larger diameter antennas can be used, thus improving the gross phase error rate and

conformably mounting the antennas so that no radome is needed.

6. The method of claim 1 where the phase measured across a single baseline in the conventional linear or planar array is synthesized by adding two or more phase measurements across separate baselines in said dispersed array.