Radiometry system with an aperture synthesis type antenna and its application to hyper-frequency imaging

• US 6,307,502 B1
• Filed: 12/29/1999
• Issued: 10/23/2001
• Est. Priority Date: 12/30/1998
• Status: Expired due to Fees

• Current Assignee: Agence Spatiale Europeenne
• Original Assignee: Agence Spatiale Europeenne
• Inventors: Iversen, Per Olav, Martin-Neira, Manuel, Marti-Canales, Javier
• Primary Examiner(s): PHAN, DAO LINDA
• Application Number:
  US09/473,948
• Time in Patent Office: 664 Days
• Field of Search: 342/351, 342/361, 342/362, 342/363-366
• US Class Current: 342/351
• CPC Class Codes: G01K 11/006 using measurement of the effect of a material on microwaves or longer electromagnetic waves, e.g. measuring temperature via microwaves emitted by the object G01K17/003, G01J5/00 take precedence; measuring the effect of a material on X-, gamma- or particle radiation G01K11/30
• CPC Class Codes: G01S 13/9023 combined with interferometric techniques
• CPC Class Codes: H01Q 1/288 Satellite antennas
• CPC Class Codes: H01Q 21/064 using horn or slot aerials slotted waveguides arrays H01Q21/005
• CPC Class Codes: H01Q 3/10 to produce a conical or spiral scan
• CPC Class Codes: H01Q 9/0428 radiating a circular polarised wave
• CPC Class Codes: H01Q 9/0435 using two feed points

Abstract

A radiometry system including an aperture synthesis antenna array type, including plural antenna elements, distributed in an antenna plane relative to at least one axis, according to a determined law. Each antenna element includes first and second coupling probes sensitive to hyper-frequency electromagnetic signals with dual linear polarization in quadrature (arbitrarily referred to as horizontal and vertical polarizations). The probes are connected two by two with electric receiving circuits to create a synthetic aperture. The horizontal (f_H1-f_H4) and vertical (f_V1-f_V4) coupling probes of successive antenna elements (e_A1-e_A4) are oriented in the antenna plane (At′), along each of the axes (Δ), such that at least one of the horizontal or vertical probes (f_H1-f_H4, f_V1-f₄) presents a 180° phase shift from one antenna element to the other (e_A1-e_A4), with the phase shift obtained by a sequential 90° rotation of those probes (f_H1-f_H4, f_V1-f_V4). Further, 180° phase shifts (Φ_H2, Φ_V3, Φ_H4, Φ_V4) are applied onto the outputs of the horizontal (f_H1-f_H4) and vertical (f_V1-f_V4) coupling probes, when one of the orientations of an antenna element (e_A1) is taken as the phase origin reference, in order to compensate for the 180° phase shifts with respect to the corresponding coupling probes (f_H1-f_V1) of the reference antenna element (e_A1).

Claims

1. A radiometry system comprising an antenna array of the aperture synthesis type having a plurality of antenna elements, distributed in an antenna plane relative to at least one axis, according to a determined law, each of said antenna elements comprising first and second coupling probes sensitive to hyper-frequency electromagnetic signals with dual linear horizontal and vertical polarizations, in quadrature, said probes being connected two by two with electric receiving circuits so as to create said synthetic aperture, wherein said horizontal (f_H1-f₄) and vertical (f_V1-f_V4) coupling probes of successive antenna elements (e_A1-e_A4) are oriented in said antenna plane (At′

), along each of said axes (Δ

), in such a manner that at least one of said horizontal or vertical probes (f_H1-f_H4, f_V1-f_V4) presents a 180 degrees phase shift from one antenna element to the other (e_A1-e_A4), with said phase shift being obtained by a sequential 90 degrees rotation of those probes (f_H1-f_H4, f_V1-f_V4), and wherein means are provided to apply 180 degrees phase shifts (Φ

_H2, Φ

_V3, Φ

_H4, Φ

_V4) onto the outputs of said horizontal (f_H1-f_H4) and vertical (f_V1-f_V4) coupling probes, when one of said orientations of an antenna element (e_A1) is taken as the phase origin reference, in order to compensate for said 180 degrees phase shifts with respect to the corresponding coupling probes (f_H1-f_V1) of said reference antenna element (e_A1).

2. A radiometry system according to claim 1, wherein said antenna elements (e_A1-e_A4) are aligned on a single axis (Δ

), so as to form an array antenna with a uni-dimensional aperture synthesis (At′

).

3. A radiometry system according to claim 1, wherein said antenna elements (e_A0, e_A11-e_A34) are aligned on at least two axis (Δ

₁-Δ

₃) so as to form an array antenna with a bi-dimensional aperture synthesis (At″

) and said sequential rotation is performed along each of said axes (Δ

₁-Δ

₃.

4. A radiometry system according to claim 3, wherein said antenna elements (e_A11-e_A34) are distributed into three subsets each of which is arranged on a support arm (11-13), with such arms being aligned on three axes, with equiangular spacing (i.e. 120 degrees), and an additional antenna element (e_A0) is arranged at the intersection of said three axes (Δ

₁-Δ

₃), said antenna being of “

Y”

shape thereby.

5. A radiometry system according to claim 2 or 3, wherein said antenna elements (e_A0, e_A11-e_A34) are equally distributed along said axes (Δ

₁-Δ

₃).

6. A radiometry system according to claim 4, wherein said antenna elements are equally distributed along said axes (Δ

₁-Δ

₃).

7. A radiometry system according to claim 1, as used for hyper-frequency imaging, said antenna (At″

) being aboard a satellite rotating on an earth orbit and senses the energetic flux emitted by at least one zone (SO) on the earth globe (GT) in the hyper-frequency range, wherein all possible combinations of signal pairs (VeA_i, VeA_j) delivered on the outputs of said coupling probes (f_H1-f_H4, f_V1-f_V4) horizontal polarization are transmitted, two by two, as entries to electronic receiving circuits, and each of said electronic receiving circuits processes said received signals (VeA_i, VeA_j), so as to calculate a point of a visibility function of said zone (SO) on the earth globe (GT).

8. A radiometry system according to claim 7, wherein the output signals of said horizontal coupling probes (f_H1-f_H4) and the output signals of said vertical coupling probes (f_V1-f_V4) are sequentially transmitted, via an electronic switch, (K) to said electronic receiving circuits.

9. A radiometry system according to claim 1, wherein said electromagnetic signals are included in the “

L”

band and are centered on a 21 cm wavelength.