ISOLATING ANTENNA ELEMENTS

• US 3,681,770 A
• Filed: 01/14/1970
• Issued: 08/01/1972
• Est. Priority Date: 01/14/1970
• Status: Expired due to Term

• Current Assignee: Andrew Alford
• Original Assignee: Andrew Alford
• Inventors: Alford, Andrew
• Primary Examiner(s): Saalbach, Herman Karl
• Assistant Examiner(s): Chatmon, Jr., Saxfield
• Application Number:
  US05/002,816
• Time in Patent Office: 930 Days
• Field of Search: 343/793,794,795,796,797,798,799,810,800,841,851 315/85
• US Class Current: 343/815
• CPC Class Codes: H01Q 1/521 reducing the coupling between adjacent antennas
• CPC Class Codes: H01Q 21/205 providing an omnidirectional coverage turnstile aerials H01Q21/26

Abstract

A conducting shelf is situated between adjacent levels of dipoles fed in the same or nearly the same phase. The shelf is dimensioned to reduce the intensity of the coupling between adjacent dipoles while adding partial images which tend to cancel the remaining coupling and thereby improve the SWR of each dipole over a relatively wide frequency range in the presence of other energized dipoles.

Claims

1. An antenna system comprising;

a tower having means defining at least one electrically conducting surface, an antenna array having dipole radiators mounted on the tower at spaced locations, adjacent dipoles of the array being parallel and being directly coupled, conducting means mounted on the tower intending in a perpendicular direction with relation to the conducting surface, the conducting means dispose, between adjacent dipoled, the dipoles extending parallel to the plane of the conducting means and the conducting means being dimensioned to reflect images of the dipoles while reducing the direct coupling between the dipoles to cause the image coupling effect to oppose the direct coupling effect.

2. An antenna system as set forth in claim 1 wherein said antenna array comprises, a first plurality of dipole radiators forming a line thereof, a second plurality of dipole radiators forming a line said conducting means being disposed between said lines of first and second pluralities of dipole radiators.

3. An antenna system as set forth in claim 2 and further comprising, second and third ones of said conducting means sandwiching said first and second pluralities of dipole radiators and said conducting means.

4. An antenna system as set forth in claim 1 wherein the separation between adjacent dipoles is slightly less than a wavelength.

5. An antenna system as set forth in claim 1 wherein said tower is of cylindrical cross-section,.

6. An antenna system as set forth in claim 1 wherein said tower is of triangular cross-section.

7. An antenna system as set forth in claim 1 wherein said means defining at least one electrically conducting surface is of square cross-section with the length of each square side substantially 0.85 wavelength at the center frequency of said array.

8. An antenna system as set forth in claim 1 wherein said means defining at least one electrically conducting surface is of triangular cross-section with the length of each triangle side substantially 0.53 wavelength at the center frequency of said array.

9. An antenna system as set forth in claim 1 wherein the separation between said conducting means and an adjacent dipole is substantially 0.45 wavelength and the width of said conducting means is substantially a quarter wavelength at the center frequency of said dipole.

10. An antenna system as set forth in claim 2 wherein said conducting means are midway between adjacent ones of said lines, the separation between adjacent ones of said lines being substantially 0.9 wavelength and the width of said conducting means is substantially a quarter wavelength at the center frequency of said array.

11. An antenna system as set forth in claim 10 wherein said means defining at least one electrically conducting surface is of square cross-section with the length of each square side substantially 0.85 wavelength at said center frequency.

12. An antenna system as set forth in claim 10 wherein said means defining at least one electrically conducting surface is of triangular cross-section with the length of each triangle side substantially 0.53 wavelength at said center frequency. 13. An antenna system as set forthin claim 4 wherein each of said conducting means includes generally symmetrical trapeqoIdal segments having a long parallel adjacent side spaced from said long parallel side substantially ky said quarter wavelength

14. An antenna system as set forth in claim 12 wherein each of said conducting means includes generally wherein each of said conducting means includes generally symmetrical trapeqoidal segments having a long parallel side adjacent to a triangle side and short parallel side spaced from said long parallel side substantially by said quarter wavelength.

15. An antenna system as set forth in claim 1 comprising a second of said conducting means wherein the separation between said conducting means is slightly less than a wavelength.

16. An antenna system as set forth in claim 4 wherein the conducting means has a long dimension in the direction o f the dipole radiator of at least 0.5 wavelength and a shorter dimension orthogonal to the longer dimension on the order of 0.1 to 0.4 wavelength.

17. An antenna system as set forth in claim 1 whereby the input impedances of the dipoles are mor nearly matched to the characteristic impedances of the transmission lines used to feed the dipoles.

18. An antenna system as set firth in claim 1 wherein said conducting means includes a conducting sheet or screen