EP1339132A1

EP1339132A1 - Patch antenna

Info

Publication number: EP1339132A1
Application number: EP03250910A
Authority: EP
Inventors: Yuanzhu c/o Alps Electric Co. Ltd. Dou
Original assignee: Alps Electric Co Ltd
Current assignee: Alps Alpine Co Ltd
Priority date: 2002-02-15
Filing date: 2003-02-14
Publication date: 2003-08-27
Also published as: JP2003243926A

Abstract

A patch antenna (11) includes a patch electrode (13) provided on one surface of a dielectric substrate (12) and a ground conductor (14) provided on the other surface of the dielectric substrate. The ground conductor has a planar shape substantially coinciding with that of the patch electrode. According to this arrangement, most radio waves radiated from the patch electrode toward the ground conductor are radiated forward from the ground conductor, allowing transmission and reception both in front and at the back of the patch electrode.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a patch antenna that is suitable for use, for example, in a wireless LAN (local area network).

2. Description of the Related Art

Recently, wireless LANs, which allow exchange of information by transmitting and receiving radio waves without using wired cables, are becoming common. In accordance with this trend, electronic apparatuses, such as personal computers, that allow antennas for transmission and reception of communication data to be mounted or that have such antennas pre-installed have come into practical use.
As antennas for such wireless LANs, linear antennas such as dipole antennas and monopole antennas are usually used. These antennas are non-directive, i.e., radiate radio waves with the same intensity in all directions, in a plane that is perpendicular to an antenna conductor, allowing reception of radio waves in an operating frequency range transmitted from any direction 360 degrees around the antennas.
If a patch antenna 1 shown in Fig. 5 is used as an antenna to be mounted or pre-installed on an electronic apparatus, such as a personal computer, circularly polarized waves as well as linearly polarized waves can be readily used as operating radio waves, allowing significant improvement in versatility. More specifically, in the patch antenna 1 commonly known, a patch electrode 3 is provided on one surface of a dielectric substrate 2, a ground conductor 4 is provided on the other surface of the dielectric substrate 2, and a high-frequency signal is fed to the patch electrode 3 via a feed pin 5. In the patch antenna 1 constructed as described above, transmission and reception of linearly polarized waves are allowed if the patch electrode 3, serving as a radiating element, is circular or square in shape, while transmission and reception of circularly polarized waves are allowed if degeneracy-breaking elements such as cutouts or protrusions are provided on the patch electrode 3.
However, the directivity of the patch antenna 1 described above is such that a substantially spherical main radiation pattern (main lobe) is formed in front of the patch electrode 3 (a space opposite to the dielectric substrate 2), as indicated by a double-dotted chain line in Fig. 5, allowing transmission and reception only in front of the patch antenna 3. Thus, the conventional patch antenna 1 is not suitable as an antenna that can be used even under an environment where the location of a target for transmission or reception cannot be specified.

SUMMARY OF THE INVENTION

The present invention has been made in view of the situation of the conventional art described above, and an object thereof is to provide a patch antenna in which directivity is weakened so that a radiation pattern extending in multiple directions around is formed.
In order to achieve the above object, the present invention provides a patch antenna including a dielectric substrate; a patch electrode for receiving a feed of a high-frequency signal, provided on one surface of the dielectric substrate; and a ground conductor provided on the other surface of the dielectric substrate; wherein the ground conductor has a planar shape that substantially coincides with the patch electrode facing the ground conductor via the dielectric substrate.
In the patch antenna constructed as described above, most radio waves radiated from the patch electrode toward the ground conductor are radiated forward from the ground conductor (to a space opposite to the dielectric substrate). Thus, a radiation pattern shaped like a peanut hull is formed around the patch antenna. That is, directivity for radiating radio waves intensely in a particular direction is weakened, allowing transmission and reception both in front and at the back of the patch electrode. Accordingly, use of the patch antenna is allowed even under an environment where the location of a target for transmission or reception cannot be specified.
When the patch antenna is used for transmission and reception of circularly polarized waves, the arrangement may be such that one of the patch electrode and the ground conductor radiates forward a right-hand circularly polarized (RHCP) wave and the other radiates forward a left-hand circularly polarized (LHCP) wave. According to this arrangement, whether an operating radio wave is a right-hand circularly polarized wave or a left-hand circularly polarized wave, the radio wave whose direction of rotation of electric filed is reversed by reflection at a room wall or the like is efficiently transmitted or received.
Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which:
Fig. 1 is a front view of a patch antenna according to a first embodiment of the present invention;
Fig. 2 is a sectional view of the patch antenna;
Fig. 3 is a front view of a patch antenna according to a second embodiment of the present invention;
Fig. 4 is a rear view of the patch antenna; and
Fig. 5 is a sectional view of a conventional patch antenna.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will now be described with reference to the drawings. Fig. 1 is a front view of a patch antenna according to a first embodiment of the present invention, and Fig. 2 is a sectional view of the patch antenna.
A patch antenna 11 shown in Figs. 1 and 2 includes a dielectric substrate 12; a patch electrode 13 having a square shape in a plan view, provided on one surface of the dielectric substrate 12; and a ground conductor 14 having the same shape as that of the patch electrode 13, provided on the other surface of the dielectric substrate 12. The patch electrode 13 receives a feed of a high-frequency signal via a feed pin 15. Since the patch electrode 13, which functions as a radiating element, has a square shape, the patch antenna 11 allows transmission and reception of linearly polarized waves. As opposed to known patch antennas, in the patch antenna 11, the ground conductor 14 has a square shape of the same size as the patch electrode 13, and the planar shapes of the ground conductor 14 and the patch electrode 13 overlap with each other when viewed along a thickness direction of the dielectric substrate 12. Thus, most radio waves radiated from the patch electrode 13 toward the ground conductor 14 are radiated forward from the ground conductor 14 (to a space opposite to the dielectric substrate 12). Thus, the patch antenna 11 has a radiation pattern shaped like a peanut hull when viewed from a side, as indicated by a double-dotted chain line in Fig. 2.
As described above, in the patch antenna 11 according to this embodiment, the ground conductor 14 has a planar shape substantially coinciding with that of the patch electrode 13 facing the ground conductor 14 via the dielectric substrate 12. Thus, directivity for radiating radio waves intensely in a particular direction is weakened, allowing transmission and reception of linearly polarized waves both in front and at the back of the patch electrode 13. Accordingly, even under an environment where the location of a target for transmission or reception cannot be specified, for example, in a wireless LAN, use of the patch antenna 11 allows favorable transmission and reception in unspecified directions and readily allows improvement in gain.
When the patch antenna 11 is used as an antenna for transmission and reception of linearly polarized waves, as in this embodiment, the patch electrode 13 and the ground conductor 14 may be circular in planar shape.
Fig. 3 is a front view of a patch antenna according to a second embodiment of the present invention, and Fig. 4 is a rear view of the patch antenna.
A patch antenna 21 shown in Figs. 3 and 4 is used for transmission and reception of circularly polarized waves. In the patch antenna 21, a patch electrode 23 on a dielectric substrate 22 has cutouts 23a and 23b, which serve as degeneracy-breaking elements, and the patch electrode 23 receives a feed of a high-frequency signal via a feed pin 25. Furthermore, similarly to the first embodiment described earlier, a ground conductor 24 has a planar shape substantially coinciding with that of the patch electrode 23 facing the ground conductor 24 via the dielectric substrate 22, so that the ground conductor 24 has cutouts 24a and 24b. Note, however, since an image formed by projecting the patch electrode 23 onto the surface on the opposite side of the dielectric substrate 22 substantially coincides with the ground conductor 24, the positions of the cutouts 23a and 23b of the patch electrode 23 as viewed from the front (upper right and lower left in Fig. 3) are in left-right symmetry with the positions of the cutouts 24a and 24b of the ground conductor 24 as viewed from the front (upper left and lower right in Fig. 4).
Similarly to the first embodiment described earlier, the patch antenna 21 constructed as described above has a radiation pattern shaped like a peanut hull, allowing transmission and reception of circularly polarized waves both in front and at the back of the patch electrode 23. Furthermore, the patch electrode 23 is shaped so as to radiate forward a right-hand circularly polarized wave, as shown in Fig. 3, while the ground conductor 24 is shaped so as to radiate forward a left-hand circularly polarized wave, as shown in Fig. 4. Thus, whether an operating radio wave is a right-hand circularly polarized wave or a left-hand circularly polarized wave, the radio wave whose direction of rotation of electric filed is reversed by reflection at a room wall or the like is efficiently transmitted or received. Accordingly, use of the patch antenna 21 allows favorable transmission and reception in unspecified directions and readily allows improvement in gain under an environment where the location of a target for transmission or reception of a circularly polarized radio wave cannot be specified.
The degeneracy-breaking elements of the patch electrode 23 and the ground conductor 24 may be protrusions instead of cutouts, and may be formed at positions selected as desired. Furthermore, although the degeneracy-breaking elements are implemented by square-shaped conductors in this embodiment, the degeneracy-breaking elements may be implemented by circular-shaped or elliptical-shaped conductors.

Claims

A patch antenna comprising:

a dielectric substrate;

a patch electrode for receiving a feed of a high-frequency signal, provided on one surface of the dielectric substrate; and

a ground conductor provided on the other surface of the dielectric substrate;

wherein the ground conductor has a planar shape that substantially coincides with a planar shape of the patch electrode facing the ground conductor via the dielectric substrate.
A patch antenna according to Claim 1, wherein one of the patch electrode and the ground conductor radiates forward a right-hand circularly polarized wave and the other radiates forward a left-hand circularly polarized wave.