Transmission/reception sources of electromagnetic waves for multireflector antenna

• US 6,861,998 B2
• Filed: 10/11/2001
• Issued: 03/01/2005
• Est. Priority Date: 10/12/2000
• Status: Expired due to Fees

• Current Assignee: Thomson Licensing SA (Vantiva SA)
• Original Assignee: Thomson Licensing SA (Vantiva SA)
• Inventors: Pintos, Jean-François, Louzir, Ali, Minard, Philippe, Thudor, Franck
• Primary Examiner(s): Wong, Don
• Assistant Examiner(s): A, MINH D
• Application Number:
  US10/398,834
• Publication Number:
  US 20040021612A1
• Time in Patent Office: 1,237 Days
• Field of Search: 343/781.P, 343/781.CA, 343/783.CA, 343/783, 343/840
• US Class Current: 343/781.00P
• 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 operating in a first frequency band and an array of n radiating elements 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 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 source for a multireflector antenna of the Cassegrain type comprising longitudinal-radiation means operating in a first frequency band and an array of n radiating elements 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, wherein the array of n radiating elements is excited by a waveguide forming a cavity in the shape of a slice of pineapple of polygonal cross section.

2. Source according to claim 1, wherein in that the array of n radiating elements is a circular array.

3. Source according to claim 1, wherein the waveguide 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>−

1/2</sup>, where λ

_c is the cut-off wavelength of the 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)^1/2, where a is the width of the rectangular waveguide.

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

1.3k_o<

D<

1.92,0.

5. Source according to claim 1, wherein the waveguide is filled with a dielectric of permittivity <

1.

6. Source according to claim 1, wherein the radiating elements of the traveling-wave type are helices.

7. Source according to claim 1, wherein the longitudinal-radiation means consist of a longitudinal-radiation dielectric rod or “

polyrod”

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

8. Source according to claim 1, wherein the longitudinal-radiation means consist of a device 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 claim 7, wherein the longitudinal-radiation means are surrounded by a cavity that reduces the side lobes.

10. Source according to claim 8, wherein the longitudinal radiation means are surrounded by a cavity that reduces the side lobes.

11. Electromagnetic wave transmission/reception source for a multireflector antenna of the Cassegrain type comprising longitudinal-radiation means operating in a first frequency band and an array of n radiating elements 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 of polygonal cross section,

wherein the waveguide has dimensions such that, D being the mean diameter of the 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>−

1/2</sup>, where λ

_c is the cut-off wavelength 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)^1/2, where a is the width of the rectangular waveguide.

12. Source according to claim 11, wherein D is chosen such that:

1.3λ

<sub>0<

D <

1.9</sub>λ

₀.