Communications: radio wave antennas – Antennas – Fractional – multiple – or full wave length linear type
Reexamination Certificate
2002-03-22
2003-07-29
Le, Hoanganh (Department: 2821)
Communications: radio wave antennas
Antennas
Fractional, multiple, or full wave length linear type
C343S826000
Reexamination Certificate
active
06600455
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an M-shaped antenna apparatus, and in particular, to an M-shaped antenna apparatus provided with at least two M-shaped antennas.
2. Description of the Related Art
FIG. 24
is a perspective view showing a construction of a prior art antenna apparatus capable of operating at a plurality of frequencies, and
FIG. 25
is an enlarged plan view showing a detailed construction of an antenna element
113
and its peripheries of FIG.
24
.
Referring to
FIG. 24
, the prior art antenna apparatus has a rectangular equipment body which is constituted by a grounding conductor
111
provided on a bottom surface located on an X-Y plane, three rectangular top surface conductors
115
a
,
115
b
and
115
c
provided on a top surface and four side surface conductors
114
. On the top surface thereof, a rectangular aperture
116
is formed between the top surface conductor
115
a
located in an approximate center portion and the top surface conductor
115
b
, and a rectangular aperture
117
is formed between the top surface conductor
115
a
and the top surface conductor
115
c
. In this case, a circular feeding point
118
is provided in an approximate center portion of the top surface conductor
115
a
. On the other hand, a feeding portion
112
is provided on the grounding conductor
111
just below the feeding point
118
, and a center conductor of the feeding portion
112
is connected to the lower end of the antenna element
113
. The antenna element
113
is extended in the vertical direction, and its upper end is located at the feeding point
118
.
Referring to
FIG. 25
, at the circular feeding point
118
, a gap
120
is formed between the top surface conductor
115
a
and the upper end of the antenna element
113
, and a frequency selection circuit
119
is connected between them. In this prior art antenna apparatus, the grounding conductor
111
, the top surface conductors
115
a
,
115
b
and
115
c
and the four side surface conductors
114
are electrically connected to each other, forming a rectangular parallelepiped symmetrically with respect to a Z-Y plane and a Z-X plane. On the top surface, two rectangular apertures
116
and
117
of the same shape are arranged symmetrically with respect to the Z-Y plane, the feeding portion
112
is arranged at the origin of the X-Y plane, and the antenna element
113
is constructed of a conductor line perpendicular to the X-Y plane.
The operation of the antenna apparatus shown in
FIGS. 24 and 25
will be described next in detail. According to this antenna apparatus, an antenna formed when the gap
120
is short-circuited by replacing the frequency selection circuit
119
with a conductor is referred to as a first antenna element, and the resonance frequency of the first antenna is denoted by f1. Moreover, an antenna formed when the gap
120
is opened by removing the frequency selection circuit
119
is referred to as a second antenna element, and the resonance frequency of the antenna is denoted by f2. Therefore, the first antenna has a structure in which the antenna element
113
and the top surface conductor
115
a
are short-circuited to each other, while the second antenna has a structure in which an electric capacity provided by the gap
120
is connected in series between the antenna element
113
and the top surface conductor
115
a
. With this arrangement, the first and second antennas have different resonance frequencies.
The frequency selection circuit
119
has such a characteristic that it has low impedance at the frequency f1 and high impedance at the frequency f2. If the antenna element
113
and the top surface conductor
115
a
are connected to each other by means of the frequency selection circuit
119
, then the frequency selection circuit
119
is put into a low-impedance state, i.e., almost short-circuited at the frequency f1, and the antenna operates as the first antenna. The circuit is put into a high-impedance state, i.e., almost opened at the frequency f2, and the antenna operates as the second antenna. As described above, this antenna apparatus becomes an antenna apparatus that operates at the two frequencies of the first and second antennas with one antenna structure.
FIG. 26
is a perspective view showing a construction of one implemental example (prototype) of the antenna apparatus of FIG.
24
. In this implemental example, a relation between the frequency f1 and the frequency f2 is expressed by the following equation (1).
f
2=2.6×
f
1 (1)
In this case, the free space wavelength of the frequency f1 is denoted by &lgr;1, and the free space wavelength of the frequency f2 is denoted by &lgr;2. In this case, the grounding conductor
111
has a rectangular shape constructed of two sides that have a length of 0.72×&lgr;1 and a length of 0.56×&lgr;1, and the side surface conductors
114
have a height of 0.06×&lgr;1. The top surface conductor
115
a
located in the approximate center portion has a rectangular shape of which the side parallel to the X-axis has a length of 0.26×&lgr;1 and the side parallel to the Y-axis has a length of 0.56×&lgr;1. The top surface conductors
115
b
and
115
c
located at both ends have a rectangular shape of which the side parallel to the X-axis has a length of 0.08×&lgr;1 and the side parallel to the Y-axis has a length of 0.56×&lgr;1. The two rectangular apertures are the rectangles of which the side parallel to the X-axis has a length of 0.15×&lgr;1 and the side parallel to the Y-axis has a length of 56×&lgr;1. The electric characteristics of this antenna apparatus when the antenna apparatus has a structure symmetrical with respect to the Z-X plane and the Z-Y plane are as follows.
Further, the antenna element
113
is a conductor line that has a diameter of 0.015×&lgr;1 and an element length of 0.06×&lgr;1. The frequency selection circuit
119
is constructed of an LC parallel circuit, whose resonance frequency is the frequency f2. As shown in the Smith chart of
FIG. 30
, this frequency selection circuit
119
becomes a low impedance at the frequency f1 and becomes a high impedance at the frequency f2. Citing one example in which the frequency f2 is 2.14 GHz, a combination of the inductance L and the electrostatic capacity C of the LC parallel circuit is provided as one example in which L=11 nH and C=0.5 pF.
FIG. 27A
is a graph showing a voltage standing wave ratio (VSWR) characteristic with respect to a normalized frequency f/f1 of the first antenna element when the frequency selection circuit
119
is replaced by a short-circuit conductor in the antenna apparatus of the implemental example of FIG.
26
.
FIG. 27B
is a graph showing a voltage standing wave ratio (VSWR) characteristic with respect to a normalized frequency f/f2 of the second antenna element when the frequency selection circuit
119
is put in an open state in the antenna apparatus of the implemental example of FIG.
26
.
FIG. 27C
is a graph showing a voltage standing wave ratio (VSWR) characteristic with respect to the frequency of the antenna apparatus provided with the frequency selection circuit
119
in the antenna apparatus of the implemental example of FIG.
26
. In this case, the characteristic impedance of the feeding cable connected to the feeding portion
112
of the antenna apparatus is assumed to be 50 &OHgr;.
FIG. 27A
shows an impedance characteristic of the first antenna in which the frequency selection circuit
119
is replaced by a conductor, and it can be understood that resonance occurs at the center frequency f1.
FIG. 27B
shows an impedance characteristic of the second antenna from which the frequency selection circuit
119
is removed, and it can be understood that resonance occurs at the center frequency f2. In either one of the antennas, the frequency band whose VSWR is equal to or smaller than two occupies 10% or more in a band width ratio, and a satisfactory characteristic of small loss thro
Iwai Hiroshi
Ogawa Koichi
Yamamoto Atsushi
Le Hoang-anh
Matsushita Electric - Industrial Co., Ltd.
LandOfFree
M-shaped antenna apparatus provided with at least two... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with M-shaped antenna apparatus provided with at least two..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and M-shaped antenna apparatus provided with at least two... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3017835