Communications: radio wave antennas – Antennas – Balanced doublet - centerfed
Reexamination Certificate
1999-07-21
2001-03-13
Phan, Tho (Department: 2821)
Communications: radio wave antennas
Antennas
Balanced doublet - centerfed
C343S797000, C343S798000, C343S803000, C343S810000, C343S814000, C343S891000
Reexamination Certificate
active
06201510
ABSTRACT:
RELATED APPLICATIONS
(Not Applicable)
FEDERALLY SPONSORED RESEARCH
(Not Applicable)
BACKGROUND OF THE INVENTION
This invention relates to antennas to receive signals from Global Positioning System (GPS) satellites and, more generally, to self-contained progressive-phase-omnidirectional elements and antennas utilizing a linear vertical array of such elements.
Antenna systems providing a circular polarization characteristic in all directions horizontally and upward from the horizon, with a sharp cut-off characteristic below the horizon are described in U.S. Pat. No. 5,534,882, issued to A. R. Lopez on Jul. 9, 1996. Antennas having such characteristics are particularly suited to reception of signals from GPS satellites.
As described in that patent, application of the GPS for aircraft precision approach and landing guidance is subject to various local and other errors limiting accuracy. Proposed implementation of Differential GPS (DGPS) would provide local corrections to improve accuracy at one or more airports in a localized geographical area. A DGPS ground installation would provide corrections for errors, such as ionospheric, tropospheric and satellite clock and ephemeris errors, effective for local use. The ground station would use one or more GPS reception antennas having suitable antenna pattern characteristics. Of particular significance is the desirability of antennas having the characteristic of a unitary phase center of accurately determined position, to permit precision determinations of phase of received signals and avoid introduction of phase discrepancies. Antenna systems having the desired characteristics are described and illustrated in U.S. Pat. No. 5,534,882, which is hereby incorporated herein by reference.
Objects of the present invention are to provide new and improved elements and antennas, and elements and antennas having one or more of the following characteristics and advantages:
progressive-phase-omnidirectional elements;
self-contained elements providing a progressive-phase-omnidirectional pattern via a single signal port;
simplified progressive-phase excitation network includable within a self-contained antenna element;
self-contained four-dipole elements usable in stacked configurations;
antennas using a stack of identical individually-excited progressive-phase-omnidirectional elements;
antennas including a stack of such elements with excitation of different amplitude or phase, or both; and
antennas utilizing a stack of such elements, including directly excited and indirectly excited elements.
SUMMARY OF THE INVENTION
In accordance with the invention, a four-dipole element, double tuned for reception at two GPS frequencies, incorporates a progressive-phase-omnidirectional excitation network. The element includes a signal port and first, second, third and fourth dipoles successively spaced around a vertical axis and each having two opposed arms. The progressive-phase-omnidirectional (PPO) excitation network is coupled between the signal port and the four dipoles and includes
(a) a first quadrature coupler coupled between the first and second dipoles to provide first dipole excitation of a first phase and to provide second dipole excitation of a quadrature phase,
(b) a second quadrature coupler coupled between the third and fourth dipoles to provide third dipole excitation of a phase differing by 180 degrees from the first phase and to provide fourth dipole excitation of a quadrature phase differing by 180 degrees from the second dipole excitation, and
(c) first and second transmission line sections respectively coupled between the signal port and the first and second quadrature couplers; and
four resonant circuits, one coupled to each dipole to provide double tuning for signal reception at two GPS frequencies.
In the context of each dipole of the above-described four-dipole element having a left arm and a right arm when viewed from the vertical axis, the element may be configured so that: the first quadrature coupler has a port coupled to the left arm of the first dipole and a quadrature port coupled to the left arm of the second dipole; and the second quadrature coupler has a port coupled to the right arm of the third dipole and a quadrature port coupled to the right arm of the fourth dipole.
Also in accordance with the invention, a GPS antenna with progressive-phase-omnidirectional excitation includes a four-dipole first element incorporating a PPO excitation network having first and second quadrature couplers as described above, and a plurality of four-dipole additional elements each substantially the same as the first element. The additional elements include upper elements positioned above and lower elements positioned below the first element along the vertical axis. The antenna also includes a signal distribution network coupled between an antenna output port and the signal ports of the first element and a plurality of the additional elements. Typically, the signal distribution network is arranged to provide excitation signals to the upper elements which lags excitation signals provided to the first (middle) element by a 90 degree phase differential, and excitation signals to the lower elements which leads excitation signals provided to the first (middle) element by a 90 degree phase differential. As a result, PPO excitation of the upper elements and lower elements will respectively lag and lead the PPO excitation of the first (middle) element by a 90 degree phase differential.
For a better understanding of the invention, together with other and further objects, reference is made to the accompanying drawings and the scope of the invention will be pointed out in the accompanying claims.
REFERENCES:
patent: 2688081 (1954-08-01), Laport
patent: 3375524 (1968-03-01), Kunemund et al.
patent: 3887925 (1975-06-01), Ranghelli et al.
patent: 4038662 (1977-07-01), Turner
patent: 4193077 (1980-03-01), Greenberg et al.
patent: 4446465 (1984-05-01), Donovan
patent: 5534882 (1996-07-01), Lopez
patent: 5936590 (1999-08-01), Funder
Kumpfbeck Richard J.
Lopez Alfred R.
Newman Edward M.
BAE Systems Advanced Systems
Onders Edward A.
Phan Tho
Robinson Kenneth P.
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