Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
1999-10-18
2001-03-27
Phan, Tho G. (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
Reexamination Certificate
active
06208298
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a planar array antenna which can be applied to a transmit/receive antenna used for a WLL (wireless local loop) terminal.
FIGS. 5A
to
5
C illustrate one example of a prior art planar array antenna of the above type. Referring to these figures, a plurality of (two in this example) patch antenna elements
101
and
102
are arrayed on a rectangular dielectric substrate
100
. The elements
101
and
102
are coupled to each other by a feed line
103
, while the element
102
is coupled to a feeding point
105
by a feed line
104
. The feed lines
103
and
104
are each constituted of a strip line adhered onto the dielectric substrate
100
.
In the prior art planar array antenna, an electric power is applied, as a series feed, from the feeding point
105
to the patch antenna elements
101
and
102
through the feed lines
103
and
104
.
The planar array antenna so constituted is miniaturized as a whole by the dielectric effect of the dielectric substrate
100
. Since, however, the antenna is decreased in gain due to a dielectric loss, a usable bandwidth of VSWR (voltage standing-wave ratio) is narrowed. Since, moreover, the plurality of patch antenna elements
101
and
102
are arrayed and an electric power is applied to these elements as a series feed, the following problem arises. The patch antenna elements
101
and
102
are difficult to arrange at the optimum interval under the influence of a so-called contraction rate due to the dielectric of the dielectric substrate
100
. This problem will be described more specifically.
As illustrated in
FIGS. 5A and 5B
, the electrical length of the antenna is determined such that the length of each of the patch antenna elements
101
and
102
and the interval between them are both &lgr;/2 when the wavelength of transmitted/received wave is &lgr;. In
FIGS. 5A and 5B
, it is &lgr;/2 and P=&lgr; that correspond to the electrical length. The contraction rate, which is one of dielectric effects of the dielectric substrate
100
, is taken into consideration in order to set the electrical length.
Assuming that Teflon (known under the trade name of du Pont) is employed as the dielectric substrate
100
and its effective permittivity is &egr;e, an actual physical distance R between the patch antenna elements
101
and
102
is given by the following equation:
R=&lgr;/
2(&egr;
e
)
½
≈0.7&lgr;/2
If, as shown in
FIG. 5C
, the energy area of the patch antenna element
101
is S
101
and that of the patch antenna element
102
is S
102
, these areas overlap each other to cause a region S
103
shaded diagonally therein. The overlapped region S
103
reduces the antenna efficiency and accordingly the maximum gain cannot be obtained under the influence of a dielectric loss. When Teflon is used as the dielectric substrate
100
, the gain falls within a range from 8 dBi to 9 dBi, which is about 30% lower than the maximum gain in the ideal status or in air.
If an electric power is applied to the patch antenna elements
101
and
102
as a parallel feed, the foregoing problem does not arise, whereas the following drawback occurs: since the antenna necessitates an allotter, its structure is complicated and increased in size, and a loss is produced from the allotter.
BRIEF SUMMARY OF THE INVENTION
The object of the present invention is to provide a planer array antenna having the following advantages:
(a) Even though an electric power is applied to arrayed patch antenna elements as a series feed, the energy areas of adjacent antenna elements can be prevented from overlapping and the antenna elements can be arrayed at ideal intervals, when the length of each of the elements and the interval therebetween are both set to a predetermined electrical length;
(b) Since the ideal intervals can be secured and no dielectric loss occurs, the antenna efficiency is remarkably improved and the maximum antenna gain can be obtained; and
(c) The antenna can be simplified and miniaturized as a whole, and its costs can be lowered greatly.
In order to attain the above object, the planar array antenna of the present invention has the following feature in constitution. The other features will be clarified in the Description of the Invention.
A planar array antenna according to the present invention comprises a ground plate formed of metallic material, a plurality of patch antenna elements supported on the ground plate by insulation spacers, respectively, and arrayed at a predetermined pitch, and a feed line for coupling adjacent antenna elements of the plurality of patch antenna elements.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
REFERENCES:
patent: 5309164 (1994-05-01), Dienes et al.
patent: 5572222 (1996-11-01), Mailandt et al.
patent: 5892481 (1999-04-01), Andersson
patent: 5892482 (1999-04-01), Coleman et al.
patent: 5896107 (1999-04-01), Huynh
Kawasaki Moriyoshi
Uchino Shigeru
Harada Industry Co. Ltd.
Pennie & Edmonds LLP
Phan Tho G.
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