Circularly polarized cross dipole antenna

Details Circularly polarized cross dipole antenna Circularly polarized cross dipole antenna

2000-04-05

2001-08-07

Wimer, Michael C. (Department: 2821)

Communications: radio wave antennas

Antennas

Balanced doublet - centerfed

C343S805000

Reexamination Certificate

active

06271800

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-292460, filed Oct. 14, 1999, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a circularly polarized cross dipole antenna which is favorably used as a mobile communication antenna for a GPS wave receiving system, a transmitting/receiving system of a satellite communications cellular phone, and the like.
FIGS. 10A and 10B
are illustrations for describing an overview of a prior art circularly polarized cross dipole antenna.
FIG. 10A
illustrates a dipole antenna, while
FIG. 10B
does a cross dipole antenna. The dipole antenna shown in
FIG. 10A
is assembled by forming a single dipole antenna element
101
on a ground plate
100
, whereas the cross dipole antenna shown in
FIG. 10B
is assembled by forming a pair of dipole antennas
101
and
102
on the ground plate
100
so as to cross each other. The cross dipole antenna excites a circularly polarized wave by shifting its phase 90 degrees.
An axial ratio characteristic is important to an antenna for exciting a circularly polarized wave. In the cross dipole antenna illustrated in
FIG. 10B
, the axial ratio characteristic of each of the dipole antenna elements
101
and
102
crossing each other is a problem. The axial ratio characteristic becomes good when a gain characteristic of E plane (where an electric field is generated) in each of the dipole antenna elements
101
and
102
is equal to that of H plane (where a magnetic field is generated) therein. When these gain characteristics differ from each other, the axial ratio characteristic becomes worse by an amount corresponding to the difference.
FIG. 11
is a chart of the comparison of a gain characteristic of E plane (C
1
indicated by the solid line) and that of H plane (C
2
indicated by the broken line) in the single dipole antenna element
101
shown in FIG.
10
A. It is seen from
FIG. 11
that the gain characteristics C
1
and C
2
are different very widely.
If a cross dipole antenna is assembled by simply crossing two dipole antenna elements having the above characteristics, an axial ratio of them is satisfactory in the vicinity of 0° but it is unsatisfactory at the other angles. It is thus difficult to obtain a circularly polarized cross dipole antenna having a wide-angle axial ratio characteristic even though it is assembled by simply combining two dipole antenna elements having a conventional structure.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a circularly polarized cross dipole antenna having an excellent axial ratio characteristic across a wide angle though its structure is simple.
To attain the above object, the circularly polarized cross dipole antenna according to the present invention has the following features in structure. The other features of the present invention will be clarified later in the Description of the Invention.
The circularly polarized cross dipole antenna according to the present invention comprises a cross dipole antenna element formed of two pairs of inverted-V-shaped dipole antenna elements, which are bent like an inverted “V” at a set angle, so as to cross each other on a ground plane; and a feeding mechanism provided to perform a single-point feed through a feeding section common to the inverted-V-shaped dipole antenna elements of the cross dipole antenna element.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.


REFERENCES:
patent: 3045240 (1962-07-01), Raynor
patent: 4062019 (1977-12-01), Woodward et al.
patent: 4446465 (1984-05-01), Donovan
patent: 0 936 693 A1 (1999-08-01), None

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