Aperiodic and Non-Planar Array of Electromagnetic Scatterers, and Reflectarray Antenna Comprising the Same

• US 20120268340A1
• Filed: 09/16/2010
• Published: 10/25/2012
• Est. Priority Date: 09/16/2009
• Status: Active Grant

• Current Assignee: Agence Spatiale Europeenne
• Original Assignee: Agence Spatiale Europeenne
• Inventors: Toso, Giovanni, Capozzoli, Amedeo, Curcio, Claudio, Liseno, Angelo, D'Elia, Giuseppe, Vinetti, Pietro
• Granted Patent: US 9,742,073 B2
• Time in Patent Office: Days
• US Class Current: 343/836
• CPC Class Codes: H01Q 15/14 Reflecting surfaces; Equivalent structures electromagnetic shields H01Q1/526
• CPC Class Codes: H01Q 19/10 using reflecting surfaces
• CPC Class Codes: H01Q 19/18 having two or more spaced reflecting surfaces H01Q19/20 takes precedence
• CPC Class Codes: H01Q 21/0018 Space- fed arrays

Abstract

The application discloses a one or two dimensional array of electromagnetic scatterers n scatterers (ED), whereby the aforementioned scatterers (ED) are arranged aperiodically on a curved line or surface (S). Further, the application describes a reflectarray antenna comprising at least one such array of electromagnetic scatters (ED) and at least one receiving and/or transmitting feed (F), cooperating with said array to generate an antenna beam A method for designing and manufacturing said array and said antenna is explained. The method optimizes in a several stages all degrees of freedom in order improve the performance of reflectarrays, increase the flexibility thereof and/or the conformity thereof with design specifications (radio pattern) and/or allowing said specifications to be satisfied with a smaller number of scatters.

Claims

1. Method for manufacturing a one- or two-dimensional aperiodic array of electromagnetic scatterers, or an aperiodic reflectarray antenna, that comprises:

a design phase, comprising identifying a set of physical and/or geometrical parameters of said array as a function of design specifications; and

a phase of physically making the array based on said parameters;

characterized in that said design phase uses a multi-stage synthesis algorithm to identify a set of said physical and/or geometrical parameters of the array which optimizes an appropriate cost function, wherein every stage except the first takes as initial values of said parameters those provided by the previous stage, wherein said synthesis algorithm comprises;

a first stage (I), based on a continuous electromagnetic modelling of the array, implementing the synthesis, in modulus and in phase, of an electromagnetic field on a pre-set reflecting line or surface, said surface being presumed to be continuous;

one or more intermediate stages (II, III, IV), based on a discrete phase-only electromagnetic modelling of the array, wherein each electromagnetic scatterer is only characterized by a phase factor; and

a final refinement stage (V) based on a more accurate electromagnetic modelling of the array.

2. Method according to claim 1, wherein the physical or geometrical parameters of the array identified by the synthesis algorithm comprise parameters that define the geometry of a curved surface or line on which said electromagnetic scatterers are arranged aperiodically.

4. Method according to claim 1, wherein in the stages of said synthesis algorithm, except at most in said final refinement stage, the parameters to be identified are the coefficients of modal representations of appropriate functions.

5. Method according to claim 1, wherein the stages of said synthesis algorithm implement a constrained optimization of the cost function, with unilateral or bilateral nonholonomic constraints intended to ensure array implementability.

6. Method according to claim 5, wherein said constraints comprise at least one of the following:

a maximum value and a minimum value of the module of the electromagnetic field identified by the first stage of the algorithm;

a maximum value of the variation or gradient of the phase of said electromagnetic field;

a maximum value and a minimum value of the spacing between two scatterers.

7. Method according to claim 1, wherein said or at least one of the intermediate stages is based on a calculation of the field radiated by the array, implemented by means of non-uniform fast Fourier transforms.

10. Method according to claim 1, wherein said synthesis algorithm comprises at least one first intermediate stage based on a phase-only model in which the electromagnetic field radiated by the array is approximated by the product of an element factor and an array factor.

11. Method according to claim 10 wherein said synthesis algorithm also comprises a final intermediate stage based on a phase-only model in which the electromagnetic field radiated by the array is not approximated by the product of an element factor and an array factor.

12. Method according to claim 1, wherein said synthesis algorithm is a five-stage algorithm which comprises three intermediate stages.

13. Method according to claim 12, wherein said synthesis algorithm comprises:

a first synthesis stage, in modulus and in phase, of an electromagnetic field on a pre-set surface, presumed to be continuous;

the identification of an initial positioning of the electromagnetic scatterers as a function of the modulus of the electromagnetic field obtained by said first stage, and of initial control phases of the electromagnetic scatterers as a function of the phase of the electromagnetic field obtained by said first stage;

a first intermediate stage of refinement of said control phases, based on a phase-only model in which the electromagnetic field radiated by the array is approximated by the product of an element factor and an array factor;

a second intermediate stage of refinement of said control phases and of the positioning of the electromagnetic scatterers, and of the surface on which said scatterers are arranged, also based on a phase-only model in which the electromagnetic field radiated by the array is approximated by the product of an element factor and an array factor;

a third intermediate stage of refinement of said control phases and of the positioning of the electromagnetic scatterers, and of the surface on which said scatterers are arranged, based on a phase-only model in which the electromagnetic field radiated by the array is not approximated by the product of an element factor and an array factor; and

a final stage of refining at least the positioning of the electromagnetic scatterers, as well as identifying the orientation thereof and the physical design parameters thereof.

14. Method according to claim 1, wherein the scatterers of said array are arranged aperiodically on a curved line or surface.

15. Method according to claim 1, wherein said synthesis algorithm is run by a computer.

20. Method according to claim 1, wherein the physical or geometrical parameters of the array identified by the synthesis algorithm comprise parameters that define the aperiodic arrangement of said electromagnetic scatterers on a supporting line or surface.

3. (canceled)

8. (canceled)

9. Method according to claim 8 wherein, before the intermediate stages of the synthesis algorithm are run, the initial positioning of the electromagnetic scatterers is identified as a function of the modulus of the electromagnetic field obtained by said first stage.

16. One- or two-dimensional array of electromagnetic scatterers (ED), characterized in that said scatterers are arranged aperiodically on a curved line or surface (S, S₁, S₂).

17. Reflectarray antenna comprising:

at least one array of electromagnetic scatterers (ED) according to claim 16; and

at least one receiving and/or transmitting feed (F), cooperating with said array to generate an antenna beam.

18. Reflectarray antenna according to claim 17, comprising a plurality of said arrays, arranged in cascade and cooperating with each other and with the feed to generate said antenna beam.

19. Reflectarray antenna according to claim 17, comprising a single feed.