Slotted bow tie antenna with parasitic element, and slotted...

Details Slotted bow tie antenna with parasitic element, and slotted... Slotted bow tie antenna with parasitic element, and slotted...

2002-08-30

2004-07-13

Ho, Tan (Department: 2821)

Communications: radio wave antennas

Antennas

Slot type

C343S7000MS, C343S815000

Reexamination Certificate

active

06762729

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an antenna for transmitting and receiving radio waves of a megacycle (MHz) or gigacycle (GHz), and particularly to an antenna device which can be structured in a thin shape, has a broad tuning frequency band, directivity, high gain, and which can be manufactured inexpensively.
2. Prior Art Statement
FIG. 1A
is a side view showing a prior art example of a planar antenna with a reflector, and
FIG. 1B
is the perspective view thereof.
Reference numeral
6
refers to an emission plate and reference numeral
5
refers to a reflector (see both FIG.
1
A and FIG.
1
B).
Reference numeral
6
a
is the center portion of the emission plate
6
, and at this point the impedance is 0, the current value is maximum and the voltage value is 0.
The impedance changes continuously from the center portion
6
a
to the end portion
6
b
. Point
7
of the impedance of 50 &OHgr; during such change is the feeding point, and a center conductor
8
a
of a coaxial cable
8
is connected thereto. The outside conductor
8
b
of the coaxial cable
8
is connected to the reflector
5
.
The aforementioned reflector
5
and emission plate
6
are supported in parallel with the connection conductor
9
at an interval measurement of L.
In this planar antenna example, the radio wave reflected at the reflector
5
is emitted in the arrow Z direction at a maximum of 3 dBd. In terms of bandwidth ratio, the areas of VSWR 2.0 or less are 3 to 5% or less.
FIG. 2A
is a side view of a prior art example in which the planar antenna of
FIG. 1A
was improved in order to obtain broad band characteristics, and
FIG. 2B
is the perspective view thereof.
Reference numeral
11
refers to an inverted-F antenna element,
11
a
refers to the grounding point thereof, and
11
b
refers to the open end thereof.
The open end
11
b
of this inverted-F antenna element
11
forms the static coupling capacity c by facing and being distanced from the reflector
10
. At this open end
11
b
, the impedance is infinite, the current value is 0, and the voltage value is maximum.
At the grounding point
11
a
, the voltage value is 0 and the current value is maximum, and these values change continuously between the open end
11
b
and the grounding point
11
a
. Point
11
c
having an impedance of 50 &OHgr; during such change is the feeding point, and a center conductor
8
a
of a coaxial cable
8
is connected thereto.
The electrical length between the end portion
6
b
and end portion
6
c
of the emission plate is a half wavelength, and the supporting body
10
supporting the center portion
6
a
thereof may be either a conductor or an insulator.
The bandwidth ratio of the prior art example shown in FIG.
2
A and
FIG. 2B
is slightly lower than 10%. The gain is approximately the same as the previous example (FIG.
1
A and FIG.
1
B), but shows a slight increase.
The thickness measurement (measurement in the Z axis direction) of the antennae of the prior art examples illustrated in
FIG. 1A
,
FIG. 1B
,
FIG. 2A
, and
FIG. 2B
is comparatively large, and, for instance, will be roughly 20 to 30 mm when designed and manufactured for use at 2.45 GHz. When designed and manufactured for a lower frequency, the thickness will be even larger.
FIG. 3
is a two-view diagram of a publicly known patch antenna. The basic structure of this patch antenna is the same as the prior art examples depicted in FIG.
1
A and
FIG. 1B
, and, therefore, the antenna characteristics are also approximately the same.
The patch antenna is structured from a two-layer substrate shown with reference numerals
21
and
22
, a ground plate
26
is formed on one of the faces of this two-layer substrate and a circular antenna element
23
is formed on the other face thereof, respectively with a conduction pattern, and are mutually connected and conducted with a short pin
25
passing through the two-layer substrate.
And, a contact pin
27
is bonded to the feeding point of the foregoing circular antenna element
23
with solder
28
and thereby connected to the strip line
24
.
This conventional example, as evident from the structure illustrated in
FIG. 3
, is structured to have a thickness measurement of two substrates worth of thickness.
Although it is advantageous in that the structure is simple, there is no room for any other improvement in the antenna performance.
Thus, an object of the present invention is to “provide an antenna device suitable in transmitting and receiving radio waves in megacycles or gigacycles, capable of being structured in an extremely thin shape, having a simple structure and low manufacturing cost, yielding superior antenna characteristics (particularly broad band, high gain, directivity), and capable of being structured to have dual band or triple band capability.
As described in detail later, the present invention is an improvement of the slotted bow tie antenna.
Thus, background art relating to a “bow tie antenna” and slotted antenna is described briefly below.
FIG. 4A
is a publicly known dipole antenna. (For ease of reading, the conductive portions are shown with spots in
FIG. 4A
to
FIG. 4E.
)
The dipole antenna is of the most basic structure, and
FIG. 4B
shows a modification thereof which is a “bow tie antenna with two triangular metal plates facing each other”. As a modification of
FIG. 4B
, “a wire bent into a triangle” may be used instead of the triangular metal plate.
Reference numeral
12
refers to a high frequency power source, and the two points (
1
a
,
1
b
), (
2
a
,
2
b
) connected to such high frequency power source in the drawings are feeding points.
Reference numeral
3
in
FIG. 4C
is a slotted version of the dipole antenna
1
, and a part of the metal plate
13
has been cut out.
Similarly, as shown in
FIG. 4D
, if the metal plate
13
is cut out in a form of a bow tie, a slotted bow tie antenna
14
can be obtained.
For the sake of explanation, the axis x—x illustrated in
FIG. 4D
will be referred to as the longitudinal symmetrical axis. In the basic form, the longitudinal symmetrical axis x—x is the perpendicular bisector of two sides which are parallel within the hexagon forming the bow tie shape.
The slotted bow tie antenna
14
is drawn in more detail and schematically in FIG.
5
.
Reference numeral
14
a
is the right side,
14
b
is the left side,
14
c
is the upper right side,
14
d
is the upper left side,
14
e
is the lower right side, and
14
f
is the lower left side.
The center conductor
8
a
of the coaxial cable
8
connected to the high frequency power source
12
is connected to the feeding point
15
a
, and the outside conductor
8
b
is connected to the feeding point
15
b
, respectively. However, the outside conductor
8
b
may be connected to an arbitrary location of the metal plate
13
.
SUMMARY OF THE INVENTION
The slotted bow tie antenna of the present invention is an improvement of the publicly known slotted bow tie antenna (prior art shown in
FIG. 5
for example), and, with the longitudinal symmetrical axis of the bow tie shaped slot (
14
) set as x, and the symmetrical axis perpendicular thereto set as y, “a narrow and long parasitic element insulated electrically” is placed over and across the slot (cut out portion) in the y axis direction. This is the basic structure of the present invention.
As a result of adding the aforementioned parasitic element, the present invention is able to broaden the tuning frequency band width without hindering the advantages of conventional slotted bow tie antennae such as “super thin shape,” “simple structure,” “directivity”, “low cost,” and so on.
Moreover, the performance is further improved as a result of establishing two parasitic elements and structuring an array antenna by arranging a plurality of slotted bow tie antennae with parasitic elements.


REFERENCES:
patent: 5442367 (1995-08-01), Naito et al.
patent: 6208311 (2001-03-01), Reece et al.
patent: 6421018 (2002-07-01), Zeilinger et al.
patent: 6424309 (2002-07-01), Johnston et al.
patent: 6429819 (2002-0

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