Matching and pattern control for dual band concentric antenna feed

Patent metadata

Field	Value
Publication number	US-9300042-B2
Application number	US-201414163351-A
Country	US
Kind code	B2
Filing date	Jan 24, 2014
Priority date	Jan 24, 2014
Publication date	Mar 29, 2016
Grant date	Mar 29, 2016

Abstract

A dual band concentric antenna feed is provided. The dual band concentric antenna feed includes an outer conductive tube and an inner conductive tube. The inner conductive tube is positioned inside the outer conductive tube and is coaxially aligned to a shared axis. A coaxial waveguide formed between the inner surface of the outer conductive tube and the outer surface of the inner conductive tube supports a first frequency band. A circular waveguide formed within of the inner conductive tube supports a second frequency band. The dual band concentric antenna feed also includes at least one transformer, a filter, and a plug in the coaxial waveguide. An impedance locus associated with the filter is high-frequency capacitive within the first frequency band and low-frequency inductive within the first frequency band. The plug is positioned near an aperture end of the concentric antenna feed.

First claim

What is claimed is:

1. A dual band concentric antenna feed comprising:
an outer conductive tube having an inner surface;
an inner conductive tube having an outer surface, the inner conductive tube positioned inside the outer conductive tube and coaxially aligned to a shared axis that extends a length of the outer conductive tube and the inner conductive tube, wherein a coaxial waveguide formed in a space between the inner surface of the outer conductive tube and the outer surface of the inner conductive tube supports a first frequency band, and wherein a circular waveguide formed within an inner surface of the inner conductive tube supports a second frequency band;
at least one transformer in the coaxial waveguide;
a filter in the coaxial waveguide, the filter being offset from the at least one transformer, the filter designed so that, when the filter is evaluated independently over a first frequency band, with respect to an input port of the filter and with respect an output port of the filter, the filter is inductive at frequency f 1 , capacitive at frequency f 2 , and is well matched near frequency (f 1 +f 2 )/2; and
a dielectric plug in the coaxial waveguide, the plug being offset from the at least one transformer and the filter and positioned near an aperture end of the concentric antenna feed.

2. The dual band concentric antenna feed of claim 1 , further comprising a dielectric material filling the inner conductive tube.

3. The dual band concentric antenna feed of claim 2 , wherein a portion of the dielectric material filling the inner conductive tube extends beyond the aperture plane to form a dielectric tip.

4. The dual band concentric antenna feed of claim 1 , wherein the at least one transformer in the coaxial waveguide comprises:
a first transformer in series with the plug; and
a second transformer in series with the first transformer and the plug, wherein an input impedance looking into an equivalent circuit of the first transformer, the second transformer, the plug, and a shunt coaxial aperture impedance is low-frequency capacitive in the first frequency band and is high-frequency inductive in the first frequency band.

5. The dual band concentric antenna feed of claim 4 , wherein the first transformer is positioned between the plug and the second transformer, and wherein the second transformer is positioned between the filter and the first transformer.

6. The dual band concentric antenna feed of claim 5 , wherein the plug has a length of a quarter of a guide wavelength at (f 1 +f 2 )/2, and wherein the shunt coaxial aperture impedance is matched across the first frequency band.

7. The dual band concentric antenna feed of claim 4 , wherein the first transformer is formed from a dielectric ring and the second transformer is formed in the coaxial waveguide as a protrusion of the outer surface of the inner conductive tube.

8. The dual band concentric antenna feed of claim 4 , wherein the first transformer is formed in the coaxial waveguide as a first protrusion on the outer surface of the inner conductive tube and the second transformer is formed in the coaxial waveguide as a second protrusion on the outer surface of the inner conductive tube, wherein a first gap is between the first protrusion and the inner surface of the outer conductive tube, and wherein a second gap is between the second protrusion and the inner surface of the outer conductive tube.

9. The dual band concentric antenna feed of claim 4 , wherein the first transformer is formed from a dielectric ring and the second transformer is formed from a dielectric ring.

10. The dual band concentric antenna feed of claim 1 , wherein the plug has a length of a quarter of a guide wavelength at (f 1 +f 2 )/2, and wherein a shunt coaxial aperture impedance is matched across the first frequency band.

11. The dual band concentric antenna feed of claim 1 , wherein the at least one transformer in the coaxial waveguide comprises:
a transformer, wherein the filter is positioned between the transformer and the plug, and wherein a length of the plug is optimized to increase a crossover gain in the second frequency band and decrease an axial ratio in the second frequency band.

12. The dual band concentric antenna feed of claim 11 , wherein the plug has a length of a quarter of a guide wavelength at (f 1 +f 2 )/2 in the first frequency band, wherein the input return loss across the first frequency band is less than −20 dB.

13. The dual band concentric antenna feed of claim 11 , wherein the plug has a length of 40 electrical degrees in the first frequency band.

14. An antenna system comprising:
at least one dual band concentric antenna feed including:
an outer conductive tube having an inner surface;
an inner conductive tube having an outer surface, the inner conductive tube positioned inside the outer conductive tube and coaxially aligned to a shared axis that extends a length of the outer conductive tube and the inner conductive tube, wherein a coaxial waveguide formed in a space between the inner surface of the outer conductive tube and the outer surface of the inner conductive tube supports a first frequency band, and wherein a circular waveguide formed within an inner surface of the inner conductive tube supports a second frequency band;
at least one transformer in the coaxial waveguide;
a filter in the coaxial waveguide, the filter being offset from the at least one transformer, wherein an impedance locus associated with the filter is high-frequency capacitive within the first frequency band and low-frequency inductive within the first frequency band; and
a dielectric plug in the coaxial waveguide, the plug being offset from the at least one transformer and the filter, the plug filling a space between the outer surface of the inner conductive tube and the inner surface of the outer conductive tube at an aperture plane, the antenna system further comprising:

a lens having a radius, wherein at least one distance between the respective at least one aperture plane of the at least one dual band concentric antenna feed and the lens is selected to provide a desired antenna beam pattern, and wherein an extension of the shared axis of the dual band concentric feed is parallel to and overlaps the radius of the lens.

15. The antenna system of claim 14 , further comprising a dielectric material filling the inner conductive tube.

16. The antenna system of claim 14 , wherein the at least one transformer in the coaxial waveguide comprises:
a first transformer in series with the plug; and
a second transformer in series with the first transform and the plug, wherein an input impedance looking into an equivalent circuit of the first transformer, the second transformer, the plug, and a shunt coaxial aperture impedance is low-frequency capacitive in the first frequency band and is high-frequency inductive in the first frequency band.

17. The antenna system of claim 16 , wherein the first transformer is formed from a dielectric ring and the second transformer is formed as a protrusion in the coaxial waveguide.

18. The antenna system of claim 16 , wherein the first transformer is formed from a protrusion in the coaxial waveguide and the second transformer is formed as a protrusion in the coaxial waveguide, wherein a first gap is between the first transformer and the inner surface of the outer conductive tube, and wherein a second gap is between the second transformer and the inner surface of the outer conductive tube.

19. The antenna system of claim 14 , wherein the at least one transformer

Assignees

• Honeywell Int Inc

Inventors

• Rogers Shawn D
• Ruiz Enrique J

Classifications

• H01Q13/08

  Radiating ends of two-conductor microwave transmission lines, e.g. of coaxial lines, of microstrip lines · CPC title

• H01Q5/321 Primary

  within a radiating element or between connected radiating elements · CPC title

• H01Q5/335

  at the feed, e.g. for impedance matching · CPC title

• H01Q13/0258

  Orthomode horns (orthomode transducers H01P1/161) · CPC title

• H01Q19/062

  for focusing · CPC title