Communications: radio wave antennas – Antennas – Plural separate diverse type
Reexamination Certificate
2002-04-02
2003-09-16
Ho, Tan (Department: 2821)
Communications: radio wave antennas
Antennas
Plural separate diverse type
C343S7000MS, C343S895000
Reexamination Certificate
active
06621458
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
(not applicable)
FIELD OF THE INVENTION
The invention relates generally to a combination quadrifilar and linearly polarized antenna, and more particularly to a combination linearly polarized and quadrifilar antenna able to provide excellent performance for both antennas in a low profile arrangement.
BACKGROUND OF THE INVENTION
Charles D. McCarrick describes a combination monopole/quadrifilar helix antenna for S-band/Satellite applications on page 330 of the May 2001 edition of the Microwave Journal.
FIG. 1
illustrates the monopole/ quadrifilar antenna
10
discussed in the McCarrick article. The antenna
10
includes a monopole
15
whose reflective element is a quarter-wave choke
14
. Elements
14
and
15
form dipole antenna
13
. The antenna
10
comprises a coaxial line
12
with a section of the outer conductor removed to expose the center conductor
15
. The quarter-wave choke
14
is placed within a quadrifilar helix antenna shell
16
in an axially concentric fashion. The quadrifilar helix antenna is typically phased to produce circular polarization. Appropriate placement of the dipole antenna
14
within the quadrifilar antenna is critical for avoiding coupling between the two antennas and avoiding degradation of radiation patterns.
A combined antenna as described above has the disadvantages of having strict design requirements in terms of relative placement between antennas to avoid interference between the antennas and further requires a wider overall structure that may not necessarily be aesthetically pleasing. It is very difficult to optimize due to interactions between the dipole and quadrifilar helix. Furthermore, it is a mechanically-challenging structure and difficult to manufacture. The typical placement for such a combined antenna would be on the sloping back windshield of a vehicle. In this instance, for good satellite reception, care must be taken to ensure that most of the quadrifilar antenna “clears” the line of sight with the transmitting satellite that may be blocked by the roof of the vehicle.
A combination linearly polarized/quadrifilar helix antenna
40
is illustrated in
FIG. 2
as described in an application filed Jun. 6, 2001 and having application Ser. No. 09/875,728, now U.S. Pat. No. 6,483,47 which is incorporated by reference and assigned to the Assignee herein. It consists of a tubular dipole antenna
44
that is placed coaxially underneath the quadrifilar helix, but it should be noted that other types of dipole antennas, patches, or loop antennas (being linearly polarized) could easily replace the tubular dipole antenna. A (first) coaxial cable
46
is passed through the new tubular dipole with minimum effect on its performance. That coaxial cable
46
is connected to a feed network
48
of the quadrifilar helix antenna
49
and to a ground plane (residing behind the feed network
48
-not shown) of the quadrifilar helix antenna
49
. It should be noted that feed network
48
and quadrifilar shell
47
form the quadrifilar helix antenna
49
. A (second) coaxial cable
42
preferably couples to a quarter wave hollow metal tube coupled to an inner conductor of coaxial cable
42
forming the tubular dipole antenna
44
. The outer conductor of cable
42
(shield) is physically connected to the outer conductor (shield) of cable
46
and both are also connected to the shorted top section of tube
45
. This configuration results in excellent performance for both antennas. Coaxial cable
46
has a minimum effect on dipole
44
due to the dipoles tubular structure. Also, this configuration results in minimum interaction between quadrifilar antenna
49
and dipole
44
, but note that the dipole uses a separate tube to serve as a ground plane for the dipole antenna. Although helix antenna
40
does provide excellent performance and is simpler to construct than the antenna of
FIG. 1
, the quadrifilar antenna and the linearly polarized antenna of the combination do not share the same RF ground plane and is not fully integrated on a flexible substrate to provide further ease of assembly.
Thus, a need exists for a combined linearly polarized and quadrifilar antenna that will enable designers further freedom in the relative placement of the antennas while avoiding the detriments of coupling and interference between the antennas and further provide ease of assembly. Further, a need exists for a combined antenna that is esthetically pleasing that will be formed in a manner sharing a common ground plane.
SUMMARY
In a first aspect of the present invention, a combination linearly polarized antenna and quadrifilar helix antenna comprises a flexible substrate, a quadrifilar antenna with a feed network etched on a first portion of the flexible substrate, an antenna with linear polarization etched on a second portion of the flexible substrate and a ground plane for the quadrifilar antenna and the antenna with linear polarization etched on the flexible substrate.
In a second aspect of the present invention, a combination monopole and quadrifilar helix antenna comprises a quadrifilar antenna having a feed network and a monopole antenna arranged below the quadrifilar antenna, wherein the monopole and the feed network share a common ground plane and wherein the monopole is at least partially below the common ground plane.
In a third aspect of the present invention, a method of manufacturing a combination monopole and quadrifilar antenna comprises the steps of forming a quadrifilar antenna pattern with a feed network on at least a first plane of a flexible substrate, forming a monopole antenna pattern on at least the first plane of the flexible substrate, and forming a ground plane pattern on at least a substantial portion of a second plane of the flexible substrate.
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Helstrom Terry C.
Petros Argy
Akerman & Senterfitt
Ho Tan
XM Satellite Radio Inc.
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