Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION
ANTENNA FOR A RADIO BASE STATION
BACKGXOUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates to an antenna for a
radio base station as in a mobile radio communication.
DISCUSSION OF BACKGROUND
Figure 11 designates a construction diagram showing
an example of a conventional antenna for a radio base
station. In Figure 11, notations 4a to 4c designate
antennae having an omni-directionality with respect to a
hori~ontal plane, which are connected to power feeding
circuits 5a to 5c for exciting the antennae. Notations
lS 6a to 6c designate phase shifters, for varying excitation
phases of the respective antennae 4a to 4c, which are
connected to the power feeding circuits 5a to 5c and to a
connecting and distributing circuit 7 which performs
connection and distribution of RF (radio frequency
carrier wave) signalsO A phase controlling circuit 8
controls the phases of the signals to be fed to the
respective antennae 4a to 4c, which is connected to the
respective phase shifters 6a to 6c.
The operation is as follows. In Figure 11, the
antennae 4a to 4c are excited by the respective feeding
circuits Sa to Sc. As shown in Figure 12, two pieces of
antennae ~aving the same characteristic, are arranged at
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an interval of A/2 (m) in a phase relationship under
which the respective antennae are excited~ A figure-8
type characteristic can be obtained by feeding powers of
the same phase to the respective antennae. As shown in
an Example of Figure 12, the antennae 4a and 4b having
the same characteristic are arranged at a pertinent
interval, for instance, A/2 (m), the phase relationship
of the signals to be fed to the respective antennae 4a
and 4b to provide an aimed directivity, is varied by the
phase shifters thereby obtaining various directivities.
In Figure 11, the phaae shifters 6a to 6c are installed
in accordance with the respective antennae 4a to 4c, the
phase shifting amounts of the phase shifters 6a to 6c are
controlled by the phase controlling ~ircuit 8, thereby
obtaining various directivities. The connecting and
distributing circuit 7 is a distributor for connecting
powers received by the antennae 4a to 4c, or conversely,
supplying a transmitting radio carrier wave to the
antennae 4a to 4c, which may include switching portions
for selecting the antennae in accordance with the
necessity.
Since the conventional antennae for a radio base
station is constructed as above, in case of providing a
directivity to the antennae in a desired single direction
or a plurality of directions, it is necessary to install
the phase shifters 6a to 6c, the power feeding circuits
5a to 5c and the phase controlling circuit 8 respectively
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to the antennae 4a to 4c for excitation. Therefore,
there is a hazard against the downsizingr the price
reduction and the low power consumption of equipments~
SUMMARY OF THE INVENTION
It is an o~ject of the present invention to solve the
above problems and to provide an antenna for a radio base
station capable of providing desired various
directivities and realizing the downsizingr the price
reduction and the low power consumption of equipments.
According to a first aspect of the present invention,
there is provided an antenna for a radio base station
compri 5 ing:
a base plate having a limited length;
attaching portions provided in the base plate and
arran9ed in a longitudinal direction and a transverse
direction of the base plate at intervals of approximately
a ~uarter of a wavelength of an electromagnetic wave;
radiation elements provided at first selected ones of
the attaching portions; and
stick-like non-power-feeding reflectors or directors
attached to second selected ones of the attaching
portions surrounding the radiation elements, thereby
providing a desired directivity thereof.
According to a second aspect of the present
invention, there is provided the antenna for a radio base
station according to the first aspect, wherein the
attaching portions are formed in a sleeve antenna.
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According to the antenna for a radio base station of
the first aspect, by setting the attaching portions of
the non-power-feeding reflectors 9 or the directors 10
surrounding the radiation elements at predetermined
positions, a directivity in accordance with the
positions, can be provided.
According to the antenna for a radio base station of
the second aspect, by setting the attaching positions of
the non-power-feeding reflectors or the directors
arranged ~round the radiation elements in the sleeve
antenna, to predetermined positions a directivity of the
sleeve antenna in accordance with the positions, can be
obtained~
BRI~F DESCRIPTION OF THE DRAWINGS
Figure l is a construction diagram showing an
embodiment of an antenna for a radio base station
according to the present invent.ion;
Figure 2 is a sectional diagram showing an example of
an attaching portion according to the present invention;
Figure 3 i5 a diagram for explaining operations of a
non-power-feeding reflector and a director according to
the present invention;
Figure 4 is a plane showing an example of a single
lobe directivity;
Figure 5 is a plane showing an example of a figure-8
type characteristic;
Figure 6 is a plane showing an example of a petal
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like characteristic;
Figure 7 is a diagram for explaining an installation
place of a radio base station of this kind;
Figure 8 is a plane showing another embodiment of an
antenna for a radio base station according to the present
invention;
Figure 9 is a sectional diagram showing another
example of an antenna for a radio base station according
to the present invention;
Figure 10 is a sectional diagram showing another
example oE an attaching portion according to the present
invention;
Figure 11 is an outline construction diagram showing
an example of a conventional antenna for a radio base
lS station; and
Figure 12 is a diagram for explainin~ operation of
the conventional antenna for a radio base station~
~ E~TT.~n DESCRIPrTION OF THE PREFERRED EMBODIMENT~
Figure 1 shows an embodiment of an antenna for a
radio base station according to the present invention.
In Figure 1, a reference numeral 1 designates a radiation
element, which is connected to a power feeding circuit 3.
A numeral 2 designates a tapped hole as an attachiny ;
portionr which .is formed in a base plate 33, as shown in
Figure 2. By these tapped holes, non-power-feeding
reflectors 9 or directors 10 can arbitrarily be f.ixed to
positions for providing an aimed directivity.
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Furthermore, these tapped holes 2 are arranged in the
longitudinal direction and in the transverse direction of
the base plate at intervals of about A/4 (m). The non-
power-feeding reflectors 9 and the directors 10 are
provided with male screws 29 as fixing portions to be
screwed in the tapped holes 2. Furthermore, the base
plate 33 is provided with a size of a limited length.
Furthermore, the radiation element 1 is also provided
with the male screw 29 which is to be screwed in the
attaching poxtion 2. ~owever, the radiation element 1
may be welded to the base plate 33.
The operation is as ~ollows. Explanation will be
given to the operations of the reflector 9 such as the
non-power-feeding reflector and the director 10 by
referring to ~igure 3. Generally, the reflector 9 is
provided with a length having an inductive reactance (for
instance, about A/2. The electromagnetic wave is
radiated from the radiation element 1 in the radial
direction~ A distance between the radiation element 1
and the reflector 9 is A/4. Therefore, the radiated
electromagnetic wave proceeds by A/4, and xeaches the
reflector 9 while the phase angle thereof lags by 90~.
Furthermore, a voltage of which phase lags by 90~, is
induced at the reflector 9 by the arriving
electromagnetic wave. The phase of a current induced by
the voltage further lags by 90~. Accordingly, the
electromagnetic wave, the phase of which lags by 270~
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compared with that radiated from the radiation element 1,
is radiated from the reflector 9. Since the phases of
the electromagnetic waves in a range between of the
radlation element 1 and the reflector 9 are mutually
reversed, they cancel each other. The elect~omagnetic
wave which is reflected by the reflector, is added to
that radiated from the radiation element both in the same
phase with respect to the right hand side direction of
the radiation element. Furthermore, the director 10 is
provided with a length having a capacitative reactance
(for instance, not more than A/2). Therefore, a voltage
of which phase angle lags by 180~ is induced in the
director 10 as above, by the electromagnetic wave
radiated from the radiation element 1. Since the
director 10 is capacitative, the phase of the flowing
current advances by 90~ (A/4-)~ Accordingly, since the
electromagneti~ wave radiated from the director 10 shares ~:
the same phase with the electromagnetic wave radiated
from the radiation element 1, the electromagnetic wave is
strengthened in the right hand side direction. As stated
above, when the single reflector 9 and the single
director 10 are arranged respectively at the right hand
side and the left hand side of the radiation element 1,
the electromagnetic wave i9 provided with a single lobe
characteristic as shown in Figure 4. When the number of
the directors 10 is increased, a sharper directivity can
be provided. As shown in Figure 5, when the directors 10
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are arranged on the left hand side and the right hand
side of the radiation element 1, and the reflectors 9 are
arranged on the top side and on the bottom side thereof
the figure-8 type characteristic can be obtained~ As
S shown in Figure 6, when the directors 10 are arranged on
the top side, on the bottom side, on the left hand side,
and on the right hand side of the radiation element and
the reflectors 9 are arran~ed between the respective
directors, a petal-like characteristic can be obtained.
A mobile radio base station mounted with the antenna
of this kind, is used in a cellular system of which
service area is provided with a size of 100 to 200 m. As
shown in Figure 7, a base station 34 is often installed
at a telegraph poles 35 or at an edge portion of a
building the height of which is about 3 to 5 m above the
ground. Therefore, the electromagnetic wave is apt to be
shielded by a building 36 or the like. The arriving
direction of the electromagnetic wave is more or less
limited by the positional environment. Therefore, when
the mobile radio base station is provided with a
directivity in accordance with the place thereof, a
directivity gain based on the directivity enlarges the
service area.
In the antenna for a radio base station according to
the first aspect of the present invention, various
directivities can be achieved by a combination of the
non-power-feeding reflectors 9 and the directors 10 in
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accordance with the installation place of the radio base
stationr by attaching the ends of the stick-like non-
power-feeding reflectors 9 or the directors 10 at
selected ones of the attaching portions 2 as shown in
Figure 1 and the enlarging of the service area in a fixed
area of the cellular system can be achieved. Compared
with the conventional example, the antenna of this
invention can be achieved, for instance, by a single
antenna having omni-directionality with respect to a
horizontal plane, as the radiation element 1 and a single
power-feeding circuit. Furthermore, the installation of
the phase shifters 6a to 6c, the phase controlling
circuit 8 or the like is not necessary, thereby achieving
the downsizing, the cost reduction and the low
consumption of power of the equipments.
Figures 8 and 9 show another embodiment of an antenna
for a radio base station according to the present
invention. In Figures 8 and 9, a reference numeral 24
designates a sleeve antenna haviny a skirt 24s. A
numeral 21 designates a radiation element which is
integrated with an electronic circuit 26. Numerals 22a
and 22b designate directors and 23a and 23b, non-power
feeding reflectors. A numeral 27 designates an interface
with a telephone network. A numeral 25 deslgnates an
inner conductive body of the sleeve antenna, which
achieves the weather resistance and the integration of
the antenna and the circuit by incorporating the
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electronic circuit 26. Around the radiation element 21
of the sleeve antenna 24, tapped holes 28 are formed as
attaching portions. As in the embodiment of Figure 1,
the non-power-feeding reflectors 23a and 23b and the
directors 22a and 22b are provided with male screws 29 as
fixing portions to be screwed in the tapped holes 28.
Since the operation of this embodiment i5 the same
with that in the embodiment of Figure 1, explanation
thereof will be omitted. By arranging the non-power-
feeding reflectors 23a and 23b and the directors 22a and22b as in Figure 8, the figure-8 type characteristic
shown in Figure 5, is provided. Furthermore, when the
tapped holes 28 as attaching portions are arranged on a
circle as in Figure 6, the petal-like characteristic
shown in Figure 6 ca~ be obtained.
An effect can be obtained in the above construction
which is the same as that in the embodiment of Figure 1.
Furthermore, as shown in Figure 10, the tapped hole
can be substituted by a through hole 30. Retaining
pieces 31a and 31b having hooks 32a and 32b provided at
ends of the non-power-feeding reflector 9 and the
director 10 may be inserted into the through hole 30, in
a single motion.
In the antenna for a radio base station of the first
aspect oE the present invention, since a desired
directivity can be obtained by attaching the stick like
non-power-feeding reflectors or directors to selected
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attaching portions, this antenna can be constructed by a
single radiation element and a single power-feeding
circuit. It is not necessary to provide the phase
shifter, the phase controlling circuit and the likeO The
invention can achieve the downsizin~, the cost reduction
and the low consumption of power of equipments, and
capable of providing various directivities in accordance
with the installation place of the radio base station and
enlarging the service area of the mobile radio base
station of a small cellular system, or the like.
In the antenna for a radio base station of the second
aspect of the present invention, since the attaching
portions are formed in the sleeve antenna, various
directivities can be provided also ~y the sleeve antenna,
and the service area of the mobile radio base station in
a small cellular system, or-the like can be enlarged.
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