Communications: radio wave antennas – Antennas – Within conductive apertured wall
Reexamination Certificate
2002-01-30
2004-01-20
Le, Hoanganh (Department: 2821)
Communications: radio wave antennas
Antennas
Within conductive apertured wall
C343S7000MS
Reexamination Certificate
active
06680712
ABSTRACT:
DETAILED DESCRIPTION OF THE INVENTION
1. Field of the Invention
The present invention relates to an antenna having bidirectional characteristic
2. Related Art of the Invention
A conventional technique will be discussed in accordance with
FIGS. 21
to
24
.
FIG. 21
shows an example of an antenna having bidirectional radiation patterns on a horizontal surface, and
FIG. 22
shows an example of a prototype antenna. Further,
FIG. 23
shows input impedance characteristics of the prototype antenna, and
FIG. 24
shows radiating directivity of the prototype antenna.
In
FIG. 21
, reference number
111
denotes a feeding section, reference numeral
112
denotes an antenna element, reference numeral
113
denotes a cavity, reference numeral
114
denotes a linear conductor, and reference numerals
115
and
116
denote openings. The feeding section
111
is positioned at the center of the bottom of the cavity
113
, one of the ends of the antenna element
112
is connected to the feeding section
111
and the other end is electrically connected to the linear conductor
114
.
The following configuration is shown as an example: the cavity
113
forms a rectangular parallelepiped symmetric with respect to ZY surface and ZX surface, the two rectangular openings
115
and
116
, which are identical in form with the linear conductor
114
being sandwiched therebetween, are disposed on the upper surface of the cavity
113
so as to be symmetric with respect to ZY surface, the feeding section
111
is disposed on the origin of the XY surface, the antenna element
112
is composed of a conductor line perpendicular to XY surface, and the linear conductor
114
and the antenna element
112
are mechanically and electrically connected to each other by soldering and the like.
Here, a space surrounded by the cavity
113
is referred to as the interior of the antenna, and a space opposite to the interior of the antenna relative to the cavity
113
is referred to as the exterior of the antenna.
FIG. 22
shows the prototype antenna. As an example, the bottom of the cavity
113
is a square having a side of 0.835×&lgr;0 (&lgr;0:free space wavelength) and a height of 0.0835×&lgr;0 relative to a free space wavelength &lgr;0 of a center frequency f
0
. The linear conductor
114
is disposed on ZY surface in parallel with Y axis with a length of 0.835×&lgr;0, and both ends of the linear conductor
114
are electrically connected to the sides of the cavity
113
. And the two openings
115
and
116
are rectangular, each having a side of 0.209×&lgr;0 in parallel with X axis and a side of 0.835×&lgr;0 in parallel with Y axis. The two openings
115
and
116
are disposed so as to be adjacent to each other with the linear conductor
114
being sandwiched therebetween at the center of the ceiling of the antenna. The above-mentioned antenna has a symmetric structure with respect to ZX surface and ZY surface. At this moment, the antenna element
112
is composed of a conductor line and is 0.0835×&lgr;0 in length. The protruding end of the antenna element
112
is electrically connected to the linear conductor
114
on the ceiling of the antenna.
FIG. 23
shows VSWR (Voltage Standing Wave Ratio) characteristics relative to a 50-ohm feeding line regarding input impedance characteristics of the prototype antenna. The lateral axis is standardized at a center frequency of f
0
). f
1
of
FIG. 23
is a minimum frequency where VSWR satisfies 2 or less. f
2
is a maximum frequency where VSWR satisfies 2 or less. As shown in
FIG. 23
, a band where VSWR is 2 or less accounts for 18.2% in a fractional bandwidth ((f
2
−f
1
)/f
0
). It is found that fine impedance characteristics are shown over a broad band with small reflection loss.
FIG. 24
shows as an example the radiating directivity at a center frequency to regarding the antenna having the above configuration. The radiating directivity is marked in 10 dB, and the unit is dBi, which is based on radiant power of a point wave source. As shown in
FIG. 24
, the above-mentioned antenna suppresses radiation of radio waves in Y direction and obtains bidirectional radiation patterns in X direction. Therefore, the above example shows excellent characteristics in a narrow interior space such as a corridor.
Moreover, the antenna element
112
is 0.0835×&lgr;0 in height and is shorter than a typical ¼ wavelength antenna element. As described above, according to the configuration of the above-mentioned antenna, the antenna element
112
can be smaller in height. When the antenna cannot be embedded into the ceiling of a room, it is possible to realize an antenna having a preferable appearance with a small protruding part being out of a person's sight on the ceiling.
In addition, in the above-mentioned conventional technique, the antenna is symmetric with respect to ZY surface and ZX surface. In this case, the directivity of radiant radio waves from the antenna is symmetric with respect to ZY surface and ZX surface.
As described above, it is possible to realize a small and excellent antenna that has desired bidirectional radiation patterns with a simple configuration.
However, in the conventional example of
FIG. 21
is disadvantageous as follows: although the above-described configuration can achieve broadband impedance characteristics, it is not possible to have fine impedance characteristics and bidirectional radiation patterns on a broader band. For this reason, when a frequency bandwidth used by a plurality of applications is a broad band, a plurality of antennas is necessary.
However, a wider space is necessary for setting a plurality of antennas, and a plurality of signal transmission lines is further required, which is conspicuous and is undesirable in appearance. Also, the cost is increased.
Therefore, in order to achieve preferable appearance with low cost, when a frequency bandwidth used by a plurality of applications is a broad band, the configuration of the conventional example is inevitably unsuitable because it cannot obtain bidirectional radiation patterns over a broad band.
When a frequency bandwidth used by a plurality of applications is a broad band, it is necessary to obtain fine impedance characteristics and bidirectional radiation patterns at frequencies over a band broader than that of the conventional antenna.
SUMMARY OF THE INVENTION
Hence, in view of the above-mentioned problem, the present invention aims to provide an antenna which is small in size particularly on the upper side and obtains bidirectional radiation patterns over a broad band.
One aspect of the present invention is an antenna, comprising:
a box conductive case having at least a single opening on an upper part,
an internal conductor which is stored in said case, is disposed at a bottom, and is shaped like a letter “
” which is one of Japanese katakana letters, a letter “u”, a letter “U”, a cramp, a horseshoe or an arc, and
a feeding element which is stored in said conductive case and is connected to a feeding section disposed on said bottom of said conductive case,
wherein said internal conductor other than parts disposed on said conductive case is not connected to said case.
Another aspect of the present invention is the antenna, wherein said feeding element is connected to a ceiling of said internal conductor.
Still another aspect of the present invention is the antenna, further comprising a gap for electrically opening said feeding element from a feeding section of said internal conductor, said gap being provided between said feeding element and a ceiling of said internal conductor.
Yet still another aspect of the present invention is the antenna, further comprising at least one or more matching conductors being electrically connected to said conductive case.
Still yet another aspect of the present invention is the antenna, wherein at least one or more of said matching conductors are electrically connected to said feeding element.
A further aspect of the present invention is the antenna, wherein at least one or more of said
Iwai Hiroshi
Ogawa Koichi
Yamamoto Atsushi
LandOfFree
Antenna having a conductive case with an opening does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Antenna having a conductive case with an opening, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Antenna having a conductive case with an opening will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3235985