Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
2000-09-18
2002-01-01
Le, Hoanganh (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S846000
Reexamination Certificate
active
06335704
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an antenna device for use in an indoor type radio base station.
2. Description of the Related Art
FIGS. 12A and 12B
are illustrations showing the positional configuration of a plurality of flat antennas mounted in a conventional antenna device, wherein
FIG. 12A
is a front view and
FIG. 12B
is a side view.
FIGS. 13A and 13B
are magnified views respectively of the antenna device of FIG.
12
A and
FIG. 12B
showing one of the flat antennas mounted therein, wherein
FIG. 13A
is a sectional view observed from the line cut along I—I of
FIG. 12A
, and
FIG. 13B
is a plain view of that flat antenna. Further,
FIG. 14
is a block diagram showing a configuration of the conventional antenna device.
In these figures, reference numeral
100
denotes a rectangular ground plate, which is fixed along a wall surface within a house and supporting each of the flat antennas, the detail of which is explained later, numerals
101
to
106
are flat antennas which are supplied with electric power, and disposed on the ground plate
100
with a predetermined distance from one another, and numeral
107
denotes a covering stuff, which is 3.0 mm thick and made of a resin material such as ABS resin or the like.
In close proximity to the upper corners of the ground plate
100
, a flat antenna
101
and another flat antenna
102
, which are used for signal transmission, are disposed at a predetermined distance away from the edge surface of the ground plate
100
so as to prevent reduction of the gains of these flat antennas
101
and
102
. On the other hand, in close proximity to the lower corners of the ground plate
100
, a flat antenna
103
and another flat antenna
104
, which are used for signal reception, are disposed at a predetermined distance away from the edge surface of the ground plate
100
or from each other so as to prevent reduction of the gain of these flat antennas
103
and
104
, and also to eliminate the mutual effect on each other. Specially, the flat antennas
103
and
104
provided as the signal reception antennas are disposed at a predetermined distance away from each other for eliminating the mutual effects, in order that they function together as a diversity antenna. Further, flat antennas
106
and
105
are disposed between the flat antennas
101
and
102
and also between the flat antennas
103
and
104
respectively, each as an interference detection antenna for searching for a radio wave that can be an interference for communications of the base station.
Since the flat antennas
101
to
106
have more or less the same configuration except their exact dimensions, the flat antenna
104
is taken up here as an example for explaining the construction thereof.
The flat antenna
104
is schematically composed of, as shown in
FIGS. 13A and 13B
, a radiation conductor portion
104
a
disposed in parallel to the surface of the ground plate
100
at a predetermined distance therebetween, a ground conductor portion
104
b
in contact with the surface of the ground plate
100
, and a bent portion
104
c
connecting these conductor portions
104
a
and
104
b
. The radiation conductor portion
104
a
is configured in such a manner as to be supplied with electric power by way of a supporting member
111
having an RF connector
110
, whereas an insulation spacer
112
for maintaining the distance H between the radiation conductor portion
104
a
and the ground plate
100
is provided at the far end of the radiation conductor portion
104
a
. The ground conductor portion
104
b
is fixed to the ground plate
100
in a rather easy way by a rivet
113
. Note that only one side of the ground plate
100
is formed with a conductor pattern (not shown).
The length L
1
of the radiation conductor portion
104
a
shown in
FIG. 13A
is determined in accordance with the frequency that the antenna uses, whereas the length L
2
between the bent portion
104
c
and the power feeding point P is set in such a manner that the impedance becomes 50 ohm. The width W of the ground conductor portion
104
b
is determined by the gain of the antenna.
As shown in
FIG. 14
, the flat antennas (TX1)
101
and (TX2)
102
are transmission antennas, which are connected respectively to a first transmitter
120
and a second transmitter
121
. The flat antenna (RX1)
103
is connected in a branched manner to a first receiver
123
and also to a third receiver
124
by way of an amplifier (AMP)
122
, the flat antenna (RX2)
104
is connected in a branched manner to a second receiver
126
and also to a fourth receiver
127
by way of an amplifier (AMP)
125
. The flat antenna (MX1)
105
is connected in a branched manner to the first receiver
123
and the second receiver
126
by way of an element
128
provided with the function of an amplifier and that of a frequency converter, and these first receiver
123
and second receiver
126
are connected to a first signal combiner
129
. Further, the flat antenna (MX2)
106
is connected in a branched manner to the third receiver
124
and the fourth receiver
127
by way of an element
130
provided with the function of an amplifier and that of a frequency converter, and these third receiver
124
and fourth receiver
127
are connected to a second signal combiner
131
.
In the antenna device configured as mentioned above, the first transmitter
120
and the second transmitter
121
use different frequencies from each other, which are different also from those of the receivers
123
,
124
,
126
and
127
.
The operation of the conventional antenna device is as follows.
First of all, when a signal transmitted from the nearby area of the radio base station (hereinafter may be referred to as a radio station or just as a base station) is received by the flat antenna
105
that is an interference detection antenna, the thus received signal is amplified at the element
128
where a frequency conversion is processed, and thereafter sent to the first receiver
123
and the second receiver
126
, wherein if the frequency of the thus received signal is same as that of the signals transmitted from the first transmitter
120
and the second transmitter
121
, then the transmission of signals of the corresponding frequencies is prohibited in order to prevent a possible interference.
After the above procedure by use of the interference detection antenna, a signal transmission at a usable frequency is started. In this case, the TDMA (Time Division Multiple Access) communication is enabled by dividing one cycle of a transmitted signal into three portions, and also by allocating one frequency to three communication lines. In this antenna device, two transmitters
120
and
121
are used, wherein if the both frequencies are usable; each transmitter can hold three communication lines, so that communications of 6 lines can be assured in parallel by the whole antenna device. The communication using this time-division method can be applied even in the signal receiving case.
Next, in the case of signal receiving, the same one signal is received simultaneously by two different antennas; namely the flat antennas
103
and
104
, and thereafter the thus received signals are amplified by the amplifiers
122
and
125
, respectively, and the amplified signals are then fed through the first receiver
123
and the second receiver
126
to a first signal combiner
129
where these signals are combined after synchronizing the phase of each signal. This can be done by use of the diversity technique for improving the strength of signal reception.
It is to be noted here that the radiation pattern made of one flat antenna in the vertical direction is excellent not only about the directivity in the frontward direction, but also that in the upward and downward directions as well, as shown in FIG.
15
.
It is also to be noted that since this kind of antenna device is used in a base station
133
mounted at the upper side of an inner wall surface inside a building
132
as shown in
FIG. 16
, there is a c
Mitsubishi Denki & Kabushiki Kaisha
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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