Communications: radio wave antennas – Antennas – Slot type
Reexamination Certificate
1999-12-20
2001-04-17
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
Slot type
C343S768000, C343S770000
Reexamination Certificate
active
06219001
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a tapered slot antenna for use in high-frequency transmission, and more particularly, to a tapered slot antenna provided with a corrugated structure, having an improved directivity, for use in mobile communication equipment, small information terminals, etc.
2. Description of the Background
Tapered slot antennas have a number of potential applications as single elements and focal plane arrays. They have important advantages such as being light in weight, less expensively manufactured with printed circuit board techniques that are capable of accurate replication from unit to unit.
FIG. 10
is a perspective view for exemplifying such a known tapered slot antenna. Referring to
FIG. 10
, the tapered slot antenna
100
includes a substrate
120
and a metal layer
130
disposed thereon.
The substrate
120
is made of a dielectric material such as polyimide, having a thickness of 10 to 100 microns. In addition, the metal layer
130
preferably made of copper has a thickness of 2 to 20 microns, with a tapered portion
14
etched away to expose a portion of the dielectric substrate
120
. This tapered portion
14
extends outward toward the aperture
15
of the slot antenna
100
.
The tapered slot antenna radiates the electromagnetic wave to the direction parallel to the antenna plane (that is, along a slot line). Since the tapered slot antenna has a structure similar to that of a slot line without requirements for a grounded conductor on the backside thereof unlike the micro strip line, it can be integrated more easily with various components such as, for example, feeder lines and matching circuits in a uniplanar structure.
In addition, since the tapered slot antenna has a broad band of transmission frequency and a high antenna gain, it is adequately used in mobile communication equipment, small information terminal and other wireless communication apparatuses.
For the known tapered slot antenna
100
, it is found that the D-plane cross-polarized component generally has a magnitude of as large as −6 dB to −9 dB. Referring to
FIG. 11
, the E- and H-planes of the tapered slot antenna are defined, respectively, as the planes which each includes the direction of radiation, and which is in parallel and in perpendicular to the surface plane of the antenna substrate
120
. In addition, the D-plane is defined as that which makes a 45° angle between both the E- and H-planes. Further, a cross-polarized wave is the electromagnetic wave which is polarized perpendicular to the polarization direction of the antenna.
A method of reducing the magnitude of a D-plane cross-polarized component is described by P. R. Acharya, J. Johansson and E. L. Kollberg, entitled SLOTLINE ANTENNA FOR MILLIMETER AND SUB-MILLIMETER WAVELENGTH, Proc. 20th Euro. Microwave Conf., Budapest, Hungary, pp. 353-358, September, 1990.
According to this publication, the magnitude of D-plane cross-polarized component can be reduced to −11 dB by fabricating a broken linearly tapered slot antenna (BLTSA). The tapered portion of this slot antenna has the shape composed of three compositional linear portions, each having consecutively different gradient.
This publication, however, does not detail further concerning the reasons why and how the D-plane cross-polarized component can be reduced. It is difficult, therefore, to fabricate such a slot antenna as above according to the description.
As indicated above, the D-plane cross-polarized component is large for the known tapered slot antenna. This gives rise to disadvantages for use in receiving more than one component, as exemplified hereinbelow: An antenna system is consisted of two tapered slot antennas with each slot line directed to the same direction and each antenna plane in perpendicular to each other to receive two polarized components separately. Because of the above-mentioned large intensity of D-plane cross-polarized component, one antenna in this system is sensitive not only to the component parallel to its own plane but also to the component perpendicular to its plane. Therefore, two polarized components can not be satisfactorily separated with the above antenna system.
In addition, the reasons for the aforementioned large magnitude of the D-plane cross-polarized component are yet to be clarified.
SUMMARY OF THE INVENTION
It is therefore an object of the present disclosure to provide an improved tapered slot antenna, which overcomes the above-noted difficulties.
It is another object of the present disclosure to provide a tapered slot antenna, having a reduced magnitude of its D-plane cross-polarized component and an improved directivity, with clarifying the reasons for a large magnitude of the D-plane component.
To achieve the foregoing and other objects, and to overcome the shortcomings discussed above, a tapered slot antenna is provided including a substrate and a metal layer which is disposed on the substrate and removed in a region to form a tapered slot portion having a closed narrow end and extending outward toward a relatively wider end that is open. The tapered slot portion radiates the electromagnetic wave from the wider end. In addition, the tapered slot antenna also includes an electric field generating means for generating an electric field which counteracts a field component radiated from the end portion of the tapered slot perpendicular to the substrate. The electric field generating means is formed in outside edge portions of the substrate, having the distances of within 0.65 wavelengths between the edge of the wide end and an outside edge of the substrate.
According to one aspect disclosed herein, the electric field generating means in the tapered slot antenna comprises a corrugated structure which includes a plurality of slits formed periodically in opposing outer edge portions of the metal layer parallel to the direction of the radiation, having a slit depth ranging from 0.04 wavelengths to 0.12 wavelengths.
According to another aspect disclosed herein, the electric field generating means in the tapered slot antenna comprises a corrugated structure and a plurality of linear slits. The corrugated structure includes a plurality of slits formed periodically positioned in opposing outer edge portions of the metal layer parallel to the direction of the radiation, having a slit depth of the corrugate structure of at least 0.15 wavelengths. In addition, the linear slits are additionally formed in the metal layer between the tapered portion and the corrugate structure parallel to the direction of the radiation.
With these structures of the tapered slot antenna disclosed herein including the corrugated structure, an electric field component can adequately be generated so as to reduce the cross-polarized D-plane component and the electric field intensity at the substrate edge portions as well.
REFERENCES:
patent: 6008770 (1999-12-01), Sugawara
patent: 6075493 (2000-06-01), Sugawara et al.
Satoru Sugawara et al, “Characteristics of a MM-Wave Tapered Slot Antenna With Corrugated Edges,” Digest of IEEE MTT-S International Microwave Symposium, 1998, pp. 533-536.
Pranay R. Acharya, et al, “Slotline Antennas for Millimeter and Submillimeter Wavelengths”, Proc. 20thEuro. Microwave Conf., Budapest, Hungary, Sep., 1990, pp. 353-358.
Mizuno Koji
Sugawara Satoru
Nguyen Hoang
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
Wong Don
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