Reconfigurable zonal beam forming system for an antenna on a satellite in orbit and method of optimizing reconfiguration

• US 5,929,804 A
• Filed: 06/24/1997
• Issued: 07/27/1999
• Est. Priority Date: 06/24/1996
• Status: Expired due to Term

• Current Assignee: Agence Spatiale Europeenne
• Original Assignee: Agence Spatiale Europeenne
• Inventors: Lambrecht, xavier Jean-Fran.cedilla.ois, Jones, Trevor Howar Price, Yarwood, Michael Philip, Folio, Benedicte
• Primary Examiner(s): Issing, Gregory C.
• Application Number:
  US08/881,134
• Time in Patent Office: 763 Days
• Field of Search: 342/354, 342/373, 342/353, 342/368, 342/374, 455/13.3
• US Class Current: 342/354
• CPC Class Codes: H01Q 3/40 with phasing matrix
• CPC Class Codes: H04B 7/18515 Transmission equipment in satellites or space-based relays
• CPC Class Codes: H04B 7/2041 Spot beam multiple access

Abstract

A reconfigurable zonal beam forming system for an antenna on a satellite in orbit includes, in cascade, a signal splitter applying signals of equal amplitude to each channel, first variable phase-shifters and amplifiers and a Butler matrix the outputs of which are connected via second variable phase-shifters to the radiating source elements of the antenna. Varying the phase-shifts introduced by the first and second phase-shifters reconfigures the transmitted beam optimally. A preferred variant of the system further includes variable attenuators. A control device is used to apply optimization parameters. A method of optimizing the resulting configuration uses a gradient search algorithm.

Claims

1. A reconfigurable zonal beam forming system for an antenna on a satellite in orbit having a particular number N of channels, comprising at least one input splitter dividing an input signal into N signals of equal amplitude applied to said N channels, a first set of input variable phase-shifters and a set of signal amplifiers, each channel comprising a phase-shifter and an amplifier in cascade, a first Butler matrix with N inputs and N outputs, and N radiating source elements, adjusting the phases of said N input phase-shifters to a particular phase value procuring said reconfiguration of the radiation pattern of the antenna, said system further comprising a second set of N output variable phase-shifters, one of these variable phase-shifters being disposed between each of said outputs of said Butler matrix and each of said radiating source elements, the relative adjustment of the phase-shifts introduced by said input phase-shifters and said output phase-shifters procuring a balanced distribution of the amplitudes of the excitation signals of said radiating source elements necessary for said reconfiguration.

2. The system claimed in claim 1 wherein each input channel includes a variable signal attenuator in cascade with said input phase-shifter.

3. A system as claimed in claim 1 further comprising means for computing optimization parameters and control means for applying to said input and output phase-shifters command signals adjusting their relative phase-shifts in such a manner as to obtain an optimum distribution of said excitation signals of said radiating source elements.

4. A system as claimed in claim 1 further comprising optimization parameter computation means and control means applying to said input and output phase-shifters and to said variable attenuators command signals adjusting their relative phase-shifts and their attenuation coefficient in such a manner as to obtain an optimum distribution of said excitation signals of said radiating source elements.

5. A method of optimizing the reconfiguration obtained by the system as claimed in claim 1, comprising at least the following phases:

a/ defining a global error function F_err =F₁ *F₂, where F₁ is the sum of the differences between the amplitudes to be obtained of said excitation signals of said radiating source elements, hereinafter referred to as target signals, and the amplitudes of the signals actually obtained, and F₂ represents the variation in the attenuation of said signals about the value 0 dB;

b/ replacing said input splitter dividing said input signal into N signals of equal amplitude applied to said N channels with substitute circuits comprising, in cascade on each of said N channels, an attenuator and an input phase-shifter, and a second Butler matrix;

said attenuators and phase-shifters being identical to said attenuators and phase-shifters of said beam forming system and said second Butler matrix being the inverse matrix of said first Butler matrix;

c/ applying to the inputs of said substitute circuit the phases and amplitudes of said target signals and acquiring the phases and amplitudes of said signals at the output of said substitute circuits as starting point parameters;

d/ launching a gradient algorithm to search for minimal values on the basis of said starting point values and acquiring these minima at the outputs of said substitute circuits; and

e/ withdrawing said substitute circuit and adjusting said attenuator and phase-shifter circuits of said beam forming system using the parameters determined in the preceding phase, corresponding to said minima;

in such a manner as to obtain a minimal global error for said reconfiguration.

6. A method as claimed in claim 5 including a step prior to said step d/ consisting in the random introduction of a slight disturbance, with a particular maximal amplitude, of the input signals of said first Butler matrix about the value 0 dB.

7. The method claimed in claim 5 wherein after said phase c/ said starting point values are compared to a particular range of reference values and if said starting point values are within a particular range said steps d/ and e/ are not carried out and said attenuator and input phase-shifter circuits of said beam forming system are adjusted directly to said starting point values.

8. A method as claimed in claim 5 including a preliminary phase consisting in searching for the combination of connections between said radiating source elements and said first Butler matrix procuring the lowest difference between the input signal amplitudes.

9. A method as claimed in claim 5 wherein, said radiating source elements being organized into groups, it includes an additional preliminary phase consisting in searching for the group of radiating source elements to be connected to said first Butler matrix procuring the best radiated power distribution.