Eberhardt, John E.; Garay, Oscar M.; Tay, Yew S.;

Sleeved monopole antenna

An antenna (100) includes a quarter-wave monopole radiating element (110, 110') having a signal feed point end (110A). The antenna (100) further includes a reactive element (150) in the form of a conductive sleeve. The sleeve (150) includes a grounding end (150A) and is coaxially positioned around a portion of the monopole radiating element (110, 110'). A spacer (140) is coaxially situated between the monopole radiating element (110, 110') and the reactive element (150), for electrically insulating the monopole radiating element (110, 110') from the reactive element (150). The spacer (140) is sufficiently dimensioned such that the monopole radiating element is tightly coupled to the reactive element (150) at substantially around the feed point end (150A).

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What is claimed is:

1. An antenna, comprising:

a quarter-wave monopole helical radiating element having an enclosed portion and an open portion, said portions having the same helical diameter, and said enclosed portion including a signal feed-point end; and

a reactive element comprising a conductive sleeve for covering said enclosed portion of said helical radiating element, said conductive sleeve including a grounding end and an open end, said sleeve being coaxially positioned around said enclosed portion above said feed point end of said monopole radiating element, and said grounding end being at the same end as the feed-point end of the radiating element

said conductive sleeve is insulated from and situated proximate said radiating element such that said monopole radiating element is tightly coupled to said reactive element around said feed-point end, so as to broaden the frequency response exhibited by said monopole radiating element.

2. The antenna of claim 1 wherein said reactive element is cylindrically configured.

3. The antenna of claim 1 wherein said reactive element is geometrically configured to surround said radiating element.

4. The antenna of claim 1 wherein said reactive element comprises a metallic sleeve.

5. The antenna of claim 1 wherein said reactive element is constructed from a conductive mesh.

6. The antenna of claim 1 further comprising a feed port including a signal feed portion and a ground portion, said signal feed portion being coupled to said signal feed-point end of said monopole radiating element and said ground portion being coupled to said grounding end of said conductive sleeve.

7. The antenna of claim 1 further comprising

spacer means, coaxially situated between said helical monopole radiating element and said reactive element, for electrically insulating said monopole radiating element from said reactive element, said spacer means being sufficiently dimensioned such that said monopole radiating element is tightly coupled to said reactive element substantially around said feed-point end, so as to broaden the frequency response exhibited by said monopole radiating element.

8. The antenna of claim 7 wherein said spacer means comprises air.

9. The antenna of claim 7 wherein said spacer means comprises a dielectric material.

10. A radio antenna, comprising:

a feed port including a signal feed portion and a ground portion;

a quarter-wave monopole helical radiating element having an enclosed portion and an open portion, said portions having the same helical diameter, and said enclosed portion having one end being coupled to said signal feed portion of said feed port;

a reactive element comprising a conductive sleeve, said sleeve having opposed ends, a grounding end and an open end, said sleeve having a certain length which covers a certain length portion of said radiating element, said sleeve being coaxially positioned around said enclosed portion above said feed portion of said monopole radiating element, and said grounding end being at the same end as the feed portion of the radiating element, and said grounding end of said sleeve being coupled to said ground portion of said feed port; and

spacer means having a minimum thickness and a dielectric constant, coaxially situated between said monopole radiating element and said reactive element to separate said radiating and reactive elements by a minimum distance, for electrically insulating said monopole radiating element from said reactive element, said spacer means being sufficiently dimensioned, in said minimum thickness at said dielectric constant, at said minimum distance, and with said certain length of said reactive element, such that said monopole radiating element is tightly coupled to said reactive element around said feed portion, so as to broaden the frequency response exhibited by said monopole radiating element.

11. The antenna of claim 10 wherein said feed port comprises a coaxial connector having the same diameter as the diameter of the sleeve, whereby it is integral with said sleeve.

12. An antenna in a communication device, comprising:

a feed port including a signal feed portion and a ground portion;

a monopole radiating helical radiating element said radiating element having an enclosed portion and an open portion, said portions having the same helical diameter, and said enclosed portion having one end, comprising a feed-point end, being coupled to said signal feed portion of said feed port;

a reactive element comprising a cylindrically configured conductive sleeve, said sleeve having a certain length which covers a certain length portion of said radiating element, said sleeve having opposed ends, a grounding end and an open end, said sleeve being concentrically positioned around said enclosed portion above said feed-point end of said monopole radiating element, said grounding end being at the same end as the feed-point end of the radiating element, and said grounding end of said sleeve being coupled to said ground portion of said feed port; and

spacer means having a minimum thickness and a dielectric constant, coaxially situated between said monopole radiating element and reactive element to separate said radiating and reactive elements by a minimum distance, for electrically insulating said monopole radiating element from said reactive element, said spacer means being sufficiently dimensioned, in said minimum thickness at said dielectric constant, at said minimum distance, and with said certain length of said reactive element, such that said monopole radiating element is tightly coupled to said reactive element around said feed portion to form a quarter-wave broadbanded antenna, whereby said monopole radiating element is tightly coupled to said reactive element.

13. The antenna of claim 12 wherein said reactive element comprises a parasitic radiator.

14. The antenna of claim 12 wherein said monopole radiating element comprises a quarter-wavelength element having an electrical length of a quarter-wavelength.

15. The antenna of claim 12 wherein said feed port comprises a coaxial connector.