US 7,068,233 B2Granted

Integrated multipath limiting ground based antenna

Assigneedb Systems Ltd.

InventorsD. Bryce Thornberg, Dean S. Thornberg

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Abstract

An integrated dual antenna system for Global Positioning System (GPS), Local Area Augmentation System (LAAS), ground based subsystem surface mounted (pole/tower/platform/other) and coaxially stacked (over and under). The dual antenna and receiver system is specifically designed and tuned to receive only the direct GPS satellite ranging signals while highly rejecting the ground multipath (indirect) signals. The upper antenna is a Right Hand Circularly Polarized (RHCP) omni-directional High Zenith Antenna (HZA) with dual obstruction lights and dual air terminals. The lower antenna is an electrically long vertically polarized omni-directional linear phased array having a very sharp horizon cut off and is a Multipath Limiting Antenna (MLA). When the two antennas (MLA and HZA) are mounted together they become the Integrated Multipath Limiting Antenna (IMLA). Interoperability is assured by high RF isolation between antennas. Both antennas are broad-band and have precisely controlled vertical and horizontal radiation patterns. Together the radiation patterns cover the complete upper hemisphere where satellites are visible.

Claims6

Dependent claims

An integrated dual antenna system having broadband elements and nearly constant group delay that provides complete upper hemispherical coverage, comprising (a) an MLA antenna having both active and RE choke large diameter cylindrical dipole elements and coaxial feed lines each of which is connected to an active cylindrical dipole element, each of said feed lines having line lengths which vary in length plus or minus only the length required to achieve a desired phase variation across the antenna aperture;

and (b) an HZA antenna having a broad-band cross-V-dipole, so that together the HZA and MLA antennas provide a large bandwidth with radiation characteristics that are not sensitive as a function of relative element geometries between the HZA and MLA antennas, and wherein said system implemer is a multiplicity of techniques to achieve high D/U ratio, S/N ratio, low sidelob:
levels and gain flatness, minimum phase and group delay in its coverage area which has in combination:
a) a flat, conductive, counterpoise oriented orthogonal to the vertical axis of the antenna system;
b) a shaped concave reflector and associated counterpoise electrically connected to a second conductive counterpoise which electrically and mechanically connects the cross-V-dipole to a beam forming network;
c) a vertically oriented, quarter wave, RF choke which suppresses the surface wave traveling along the surface of a microwave absorbing material;
d) a precisely shaped piece of RF absorbing material with specific carbon fill factor having a shaped inside surface to control a positive angle radiation pattern and whose shaped outside surface helps control the broadside and negative angle portions of the radiation pattern;
e) a highly symmetric cross-V-dipole having RHCP output polarization which produces a symmetry and ellipticity ratio over the service volume;
and
f) a specifically defined geometry between each mutually interactive element of the HZA antenna.

6 more elements

An integrated dual antenna system having broadband elements and nearly constant group delay that provides complete upper hemispherical coverage, comprising (a) an MLA antenna having both active and RF choke large diameter cylindrical dipole elements and coaxial feed lines each of which is connected to an active cylindrical dipole element, each of said feed lines having line lengths which vary in length plus or minus only the length required to achieve a desired phase variation across the antenna aperture;

and (b) an HZA antenna having a broad-band cross-V-dipole, so that together the HZA and MLA antennas provide a large bandwidth with radiation characteristics that are not sensitive as a function of relative element geometries between the HZA and MLA antennas;
such that a large, hollow, thick wall, multi-purpose, metal, center support tube in conjunction with said MLA cylindrical dipole elements such that the ratio of the diameter of the central metal support tube (2) to the diameter of the upper dipole half (7) and lower dipole half (13) can be as large as to 0.9 and so that the radius of the upper dipole half (7) and lower dipole half (13) is allowed to be smaller than one quarter wavelength and can be as small as 0.1 wavelengths as long as the central metal support tube (2) diameter is adjusted accordingly to allow for a gap between the central metal support tube (2) and the upper dipole half (7) and lower dipole half (13) so that said gap is at least 0.01 wavelengths and where said diameter ratio provides a maximization of the volume within the central metal support tube (2) for an RF power/phase coax transmission line system (1) along with other cables to be installed within the central metal support tube (2), where said transmission line system (1) and other cables are contained completely within the central metal support tube (2) and do not degrade or affect the radiation patterns of the MLA or other antennas or other antennas located above the MLA and where said diameter ratio provides a circumference of the upper dipole half (7) and lower dipole half (13) such that when fed with a multiplicity of feed wires consisting of at least one of an RF Feed wire (6) and symmetric feed crossbar (16) and feed coupler (15), the phase variation in the azimuth plane is reduced to less than 10 electrical degrees over the entire 360 physical degrees of azimuth angle.

Dependencies are inferred from the claim text.

Facts

Application: 10/430,959Filed 5 May 2003 · us provisional application
Priority: 6 May 2002
Published: US 2003/0206140 A16 Nov 2003
Granted: 27 Jun 2006
Term ends: Not estimatedThe source records don’t support an estimate.

Classification7 codes

H01Q 1/1242
Supports; Mounting means: rigid masts specially adapted for supporting an aerial
H01Q 1/06
Details of, or arrangements associated with, antennas: means for the lighting or illuminating of antennas, e.g. for purpose of warning
H01Q 9/0464
Substantially flat resonant element parallel to ground plane, e.g. patch antenna: annular ring patch
H01Q 19/00
Combinations of primary active antenna elements and units with secondary devices