Transmission/reception sources of electromagnetic waves for multireflector antenna

• US 20040021612A1
• Filed: 04/09/2003
• Published: 02/05/2004
• Est. Priority Date: 10/12/2000
• Status: Active Grant

• Current Assignee: Thomson Licensing SA (Vantiva SA)
• Original Assignee: Thomson Licensing SA (Vantiva SA)
• Inventors: Louzir, Ali, Pintos, Jean-Francois, Minard, Philippe, Thudor, Franck
• Granted Patent: US 6,861,998 B2
• Time in Patent Office: Days
• US Class Current: 343/781CA
• CPC Class Codes: H01Q 11/08 Helical antennas
• CPC Class Codes: H01Q 13/24 constituted by a dielectric or ferromagnetic rod or pipe H01Q13/28 takes precedence
• CPC Class Codes: H01Q 21/28 Combinations of substantially independent non-interacting antenna units or systems multiple beam H01Q25/00
• CPC Class Codes: H01Q 5/45 using two or more feeds in association with a common reflecting, diffracting or refracting device
• CPC Class Codes: H01Q 5/47 with a coaxial arrangement of the feeds

Abstract

The present invention relates to an electromagnetic wave transmission/reception source for a multireflector antenna of the Cassegrain type comprising longitudinal-radiation means (12) operating in a first frequency band and an array of n radiating elements (11) of the travelling-wave type operating in a second frequency band with the n radiating elements arranged symmetrically around the longitudinal-radiation means, the array and the longitudinal-radiation means having an approximately common phase centre, the array of n radiating elements being excited by a waveguide (15) of polygonal cross section.

The invention applies especially in satellite communication systems operating in the C-, Ku- or Ka-bands.

Claims

1. Electromagnetic wave transmission/reception (T/R) source for a multireflector antenna of the Cassegrain type comprising longitudinal-radiation means (12, 12′

) operating in a first frequency band and an array of n radiating elements (11) of the travelling-wave type operating in a second frequency band with the n radiating elements arranged symmetrically around the longitudinal-radiation means, the array and the longitudinal-radiation means having an approximately common phase centre, characterized in that the array of n radiating elements is excited by a waveguide (15) of polygonal cross section.

2. Source according to claim 1, characterized in that the array of n radiating elements is a circular array and the waveguide forms a cavity in the shape of a “

slice of pineapple”

.

3. Source according to claims 1 and 2, characterized in that the waveguide (15) has dimensions such that, D being the mean diameter of the circular array:

D=nλ

_g/2 where n represents the number of radiating elements and λ

_g represents the wavelength of the guided wave at the operating frequency;

λ

_g=λ

₀[ε

_r−

(λ

₀/λ

_c)²]<sup>−

½</sup>

, where λ

_c is the cut-off wavelength of the reactangular waveguide for the TE₀₁ fundamental mode, λ

₀ is the wavelength in vacuo and ε

_r is the permittivity of the dielectric filling the waveguide; and

λ

_c=2a(ε

_r)^½

, where a is the width of the rectangular waveguide.

4. Source according to claim 3, characterized in that D is chosen such that:

1.3λ

₀<

D<

1.9λ

₀.

5. Source according to any one of claims 1 to 4, characterized in that the waveguide is filled with a dielectric of permittivity ≧

1.

6. Source according to any one of claims 1 to 5, characterized in that the radiating elements of the travelling-wave type are helices (11).

7. Source according to any one of claims 1 to 3, characterized in that the longitudinal-radiation means consist of a longitudinal-radiation dielectric rod or “

polyrod”

(12) whose axis is coincident with the radiation axis, the said rod being excited by means comprising a waveguide.

8. Source according to any one of claims 1 to 3, characterized in that the longitudinal-radiation means consist of a device (12′

) in the form of a helix whose axis is coincident with the radiation axis, the said device being excited by means comprising a coaxial line.

9. Source according to either of claims 7 and 8, characterized in that the longitudinal-radiation means are surrounded by a cavity (14) that reduces the side lobes.