Antenna device

In an antenna device according to the present invention, a circular ring-shaped dielectric substrate has a radiation electrode formed on its one main surface and a ground electrode formed on its other main surface. In a vacant space portion of the dielectric substrate, a circular convex portion of a first base member is fitted, with an electronic circuit being fixed in the circular convex portion. The radiation electrode and the electronic circuit are connected to each other by a feeder line. Since the electronic circuit connected with the microstrip antenna is accommodated within the vacant space portion of the dielectric substrate, a compact and thin antenna device may be obtained.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention generally relates to an antenna device, and more 
particularly, to an improvement of a microstrip antenna incorporated with 
an electronic circuit. 
2. Description of the Related Art 
Conventionally, there has been known a microstrip antenna in which an 
electronic circuit such as an amplifier, filter or the like is 
incorporated (referred to as an antenna device hereinafter). 
In a known antenna device as shown in FIGS. 19 and 20 (referred to as a 
first prior art hereinafter), a microstrip antenna and an electronic 
circuit to be connected therewith are piled one upon another in a vertical 
direction. 
More specifically, the antenna device of the first prior art in FIGS. 19 
and 20 generally includes a dielectric substrate 1 in a circular flat 
plate-like configuration, a circular radiation electrode 2 formed at a 
central portion on one main surface of said dielectric substrate 1, a 
circular ground electrode 3 formed on an entire face of the other main 
surface of said dielectric substrate 1, and a feeder line 4 connected at 
its one end 4a to said radiation electrode 2 for supplying power thereto, 
and provided in a position somewhat deviated in a direction of diameter 
from a center of the radiation electrode 2. 
In the above arrangement, the so-called microstrip antenna is constituted 
by the dielectric substrate 1, radiation electrode 2, ground electrode 3, 
and feeder line 4. This microstrip antenna is fixedly placed on a base 5 
made, for example, of a metallic conductor. On an under surface of the 
base 5, an electronic circuit 6 having an amplifier, filter or the like is 
fixedly mounted. The electronic circuit 6 generally includes an insulative 
circuit substrate 6a, a ground electrode 6b formed on one main surface of 
the circuit substrate 6a, a circuit pattern 6c and electronic parts 
(capacitor, resistor, etc.) 6d formed on the other main surface thereof. 
The feeder line 4 referred to earlier extends through the radiation 
electrode 2, dielectric substrate 1, ground electrode 3, base 5, ground 
electrode 6b, and circuit substrate 6a, with the other end 4b thereof 
being connected to the circuit pattern 6c formed on the other main surface 
of the circuit substrate 6a. In other words, power is given to the feeder 
line 4 through the circuit pattern 6a. 
Moreover, on the under surface of the base 5, a cap member 7 is provided 
for protecting the electronic circuit 6, and preventing electromagnetic 
wave noises. 
In another example of conventional antenna devices as shown in FIGS. 21 and 
22 (referred to as a second prior art hereinafter), the microstrip antenna 
and the electronic circuit connected thereto are aligned laterally on the 
same dielectric substrate. 
More specifically, as shown in FIGS. 21 and 22, on one main surface of a 
dielectric substrate 11 in a rectangular flat plate-like shape, a circular 
radiation electrode 21 is formed at a central portion in the left half 
portion thereof, while an electronic circuit 61 is constituted at a 
central portion in its right half portion as shown, with the radiation 
electrode 21 and the electronic circuit 61 being connected to each other 
by a feeder line 41. Moreover, on the other main surface of the dielectric 
substrate 11, a ground electrode 31 is formed on its entire surface. 
In the antenna device of the first prior art as described earlier, since 
the microstrip antenna and the electronic circuit 6 are piled up 
vertically one upon another, the antenna device tends to be higher on the 
whole, and thus, the advantage of the microstrip antenna which is thin is 
undesirably lost. 
On the other hand, in the antenna device of the second prior art technique 
also referred to above, although the arrangement may be formed to be thin, 
since the microstrip antenna and the electronic circuit 61 are disposed on 
the same plane, there is involved another problem that the planner shape 
tends to be large. 
SUMMARY OF THE INVENTION 
Accordingly, an essential object of the present invention is to provide a 
compact antenna device of a thin type, with a substantial elimination of 
the disadvantages inherent in the conventional antenna devices of this 
kind. 
Another object of the present invention is to provide an antenna device of 
the above described type, which is simple in construction and stable in 
functioning with high reliability, and which can be readily manufactured 
at low cost. 
In accomplishing these and other objects, according to one preferred 
embodiment of the present invention, there is provided an antenna device 
which includes a microstrip antenna and an electronic circuit connected to 
said microstrip antenna. 
The microstrip antenna comprises a dielectric substrate having first and 
second main surfaces, an outer peripheral face and an inner peripheral 
face, and is formed with a vacant space portion, defined by said inner 
peripheral face at a central portion of said dielectric substrate, a 
radiation electrode formed on said first main surface of said dielectric 
substrate so as to extend over at lest said vacant space portion, a ground 
electrode formed at least on the second main surface of said dielectric 
substrate, and a feeder line for connecting said electrode and said 
electronic circuit. The electronic circuit is disposed within said vacant 
space portion of said dielectric substrate. 
In the above arrangement of the present invention, by accommodating the 
electronic circuit connected to the microstrip antenna in the vacant space 
disposed at the central portion of the dielectric substrate, it is 
intended to reduce the size and thickness of the antenna device.

DETAILED DESCRIPTION OF THE INVENTION 
Before the description of the present invention proceeds, it is to be noted 
that like parts are designated by like reference numerals throughout the 
accompanying drawings. 
(1) First Embodiment 
Referring now to the drawings, there is shown in FIGS. 1 and 2, an antenna 
device A1 according to a first embodiment of the present invention which 
includes a microstrip antenna and an electronic circuit 6 connected to 
said microstrip antenna. The microstrip antenna comprises a dielectric 
substrate 12 having first and second main surfaces, an outer peripheral 
face and an inner peripheral face, and formed with a vacant space portion 
defined by said inner peripheral face at a central portion of said 
dielectric substrate 12, a radiation electrode 2 formed on the first main 
surface of said dielectric substrate 12 so as to cover or extend over at 
least the vacant space portion 12b, a ground electrode 31 formed at least 
on the second main surface of said dielectric substrate 12, and a feeder 
line 4 for connecting said electrode 2 and said electronic circuit 6. The 
electronic circuit 6 is disposed within said vacant space portion 12b of 
said dielectric substrate 12. 
More specifically, as shown in FIGS. 1 and 2, on one main surface of the 
circular ring-shaped dielectric substrate 12, the circular radiation 
electrode 2 is formed at a central portion of said substrate 12, and the 
diameter of this radiation electrode 2 is selected to be of a value larger 
than an inner diameter of said dielectric substrate 12. Accordingly, the 
radiation electrode 2 covers the entire circular opening at the one main 
surface of the dielectric substrate 12, and also, contacts, at part of its 
under surface, said one main surface of the dielectric substrate 12 (FIG. 
2). The other main surface of said dielectric substrate 12 is entirely 
formed with the ground electrode 31 having the circular ring-like shape 
similar to the other main surface of the substrate 12. Moreover, one end 
4a of the feeder line 4 for supplying power to the radiation electrode 2 
is connected to the radiation electrode 2. The feeder line 4 is provided 
in a position slightly deviated from a center of the radiation electrode 2 
in a direction of diameter. 
The microstrip antenna is constituted by the radiation electrode 2, 
dielectric substrate 12, ground electrode 31, and feeder line 4, and is 
fixedly placed on a circular first base member 81. At a central portion of 
said first base member 81, a hollow circular convex portion 81a is formed. 
This circular convex portion 81a is fitted in the vacant space 12b defined 
by the inner peripheral face 12a of the dielectric substrate 12. On the 
under surface of the first base member 81 and at a ceiling portion of the 
circular convex portion 81a, the electronic circuit 6 is fixedly provided. 
Similar to the electronic circuit referred to earlier with reference to 
the first prior art in FIGS. 19 and 20, this electronic circuit 6 includes 
the insulative circuit substrate 6a, the ground electrode 6b formed on one 
main surface of the circuit substrate 6a, the circuit pattern 6c formed on 
the other main surface of said circuit substrate 6a, and the electronic 
parts 6d (including capacitors, resistors, etc.). Moreover, to the circuit 
pattern 6c, one end of an input/output terminal 6e extending downwardly is 
connected. The electronic circuit 6 is connected to outer circuits (not 
shown) through said input/output terminal 6e. 
The feeder line 4 extends through the radiation electrode 2, the first base 
member 81, the ground electrode 6b and the circuit substrate 6a, and is 
connected, at its other end 4b, to the circuit pattern 6c formed on the 
other main surface of the circuit substrate 6a. Namely, the microstrip 
antenna is connected to the electronic circuit 6 through the feeder line 
4, whereby power for transmission is supplied from the electronic circuit 
6 to the microstrip antenna, and the signal received by the microstrip 
antenna is given to the electronic circuit 6. It is to be noted here that 
the diameters of holes formed in the first base member 81, ground 
electrode 6b and circuit substrate 6a for extending the feeder line 4 
therethrough respectively are set to be larger than the diameter in the 
cross section of the feeder line 4. Accordingly, the feeder line 4 does 
not contact the first base member 81, and the ground electrode 6b for 
electrical insulation therefrom. 
Furthermore, to the under surface of the first base member 81, a second 
base member 82 is fixed for protection of the electronic circuit 6, and 
also for prevention of electromagnetic wave noises. Additionally, on the 
second base member 82, a porcelain insulator 81b is provided for leading 
the input/output terminal 6e outside in an insulated state. 
As described so far, according to the first embodiment of the present 
invention, since the electronic circuit 6 is accommodated in the vacant 
space 12b provided at the central portion of the dielectric substrate 12, 
the thickness and flat face configuration of the entire antenna device 
becomes generally equal to those of the dielectric substrate 12, and thus, 
a compact and thin type antenna device may be advantageously obtained. 
(2) Second Embodiment 
FIG. 3 shows an antenna device A2 according to a second embodiment of the 
present invention, in which the input/output terminal 6e described as 
extended downwardly in the first embodiment of FIGS. 1 and 2 is modified 
to be led out laterally as illustrated. More specifically, at the other 
main surface side of the dielectric substrate 12, a concave groove 12c for 
leading out the input/output terminal 6e is formed to extend in a radial 
direction, with a hollow convex groove 81c which fits in said concave 
groove 12c being formed in the first base member 81. The input/output 
terminal 6e is drawn outside through the porcelain insulator 81b provided 
within the convex groove 81c. In other words, the input/output terminal 6e 
is led outside in a state where it is insulated from the first and second 
base members 81 and 82. 
Since other constructions and functions of the antenna device A2 for the 
second embodiment as described above are generally similar to those of the 
antenna device A1 for the first embodiment described earlier with 
reference to FIGS. 1 and 2, detailed descriptions thereof have been 
abbreviated here for brevity of explanation, with like parts being 
designated by like reference numerals. 
(3) Third Embodiment 
Referring further to FIG. 4, there is shown an antenna device A3 according 
to a third embodiment of the present invention, in which the dielectric 
substrate 12 is formed to have a uniform thickness, and the concave groove 
12c described as provided in the antenna device A2 of FIG. 3 is dispensed 
with. Meanwhile, in the first base member 81, a stepped portion 81e is 
formed at a position confronting the other main surface of the dielectric 
substrate 12, and the input/output terminal 6e is led out of the device 
extending through the porcelain insulator 81b provided in said stepped 
portion 81e. 
Since other constructions and functions of the antenna device A3 of the 
third embodiment as described above are generally similar to those of the 
antenna device A1 for the first embodiment described earlier with 
reference to FIGS. 1 and 2, detailed description thereof has been 
abbreviated here for brevity of explanation, with like parts being 
designated by like reference numerals. 
(4) Fourth Embodiment 
FIGS. 5 and 6 show an antenna device A4 according to a fourth embodiment of 
the present invention, respectively representing the cross sections of 
said antenna device taken along directions intersecting at right angles to 
each other. 
In the fourth embodiment of FIGS. 5 and 6, two concave grooves 12c and 12d 
are formed in positions confronting through 180.degree. in the under 
surface of the dielectric substrate 12, while in the first base member 81, 
corresponding two hollow convex grooves 81c and 81d, which are fitted with 
said concave grooves 12c and 12d, are formed in said first base member 81. 
The input/output terminal 6e is drawn out of the device through the 
porcelain insulator 81b provided in the convex groove 81c. 
Since other constructions and functions of the antenna device A4 for the 
fourth embodiment as described above are generally similar to those of the 
antenna device A2 for the second embodiment described earlier with 
reference to FIG. 3, detailed description thereof has been abbreviated 
here for brevity of explanation, with like parts being designated by like 
reference numerals. 
(5) Fifth Embodiment 
FIG. 7 shows an antenna device A5 according to a fifth embodiment of the 
present invention, which differs from the antenna device A2 for the second 
embodiment as described earlier with reference to FIG. 3 in the following 
points. In the second embodiment of FIG. 3, although the input/output 
terminal 6e is disposed between the first base member 81 and the second 
base member 82, such input/output terminal 6e in the fifth embodiment of 
FIG. 7 is disposed between the dielectric substrate 12 and the first base 
member 81. More specifically, in the antenna device A5 of FIG. 7, in the 
side face of the circular convex portion 81a of the first base member 81, 
a bore 81f is formed in a position confronting the concave groove 12c of 
the dielectric substrate 12. The input/output terminal 6e is led outside 
extending through the bore 81f and the porcelain insulator 81b provided in 
the concave groove 12c of the dielectric substrate 12. 
Since other construction and functions of the antenna device A5 for the 
fifth embodiment as described above are generally similar to those of the 
antenna device A2 for the second embodiment described earlier with 
reference to FIG. 3, detailed description thereof has been abbreviated 
here for brevity of explanation, with like parts being designated by like 
reference numerals. 
(6) Sixth Embodiment 
FIG. 8 shows an antenna device A6 according to a sixth embodiment of the 
present invention. 
In this sixth embodiment, the construction at the lead-out portion of the 
input/output terminal 6e in the third embodiment of FIG. 4 has been 
replaced by that of the fifth embodiment as described above with reference 
to FIG. 7. 
In the antenna device A6 for the sixth embodiment of FIG. 8, like parts in 
the third embodiment of FIG. 4 or the fifth embodiment of FIG. 7 are 
designated by like reference numerals, with detailed description thereof 
being abbreviated for brevity of explanation. 
(7) Seventh Embodiment 
Shown in FIG. 9 is an antenna device A7 according to a seventh embodiment 
of the present invention, which is so arranged that the ground electrode 
31 is eliminated from the portion of the concave groove 12c of the 
dielectric substrate 12 in the antenna device A5 for the fifth embodiment 
of FIG. 7. 
Since other constructions and functions of the antenna device A7 for the 
seventh embodiment as described above are generally similar to those of 
the antenna device A5 for the fifth embodiment described earlier with 
reference to FIG. 7, detailed description thereof has been abbreviated 
here for brevity of explanation, with like parts being designated by like 
reference numerals. 
(8) Eighth Embodiment 
Referring further to FIG. 10, there is shown an antenna device A8 for an 
eighth embodiment according to the present invention, in which, in the 
seventh embodiment of FIG. 9, there is also formed another concave groove 
12d in a position confronting the concave groove 12c through 180.degree. 
in the other main surface of the dielectric substrate 12. 
Since other constructions and functions of the antenna device A8 for the 
eighth embodiment as described above are generally similar to those of the 
antenna device A7 for the seventh embodiment, detailed description thereof 
has been abbreviated here for brevity of explanation, with like parts 
being designated by like reference numerals. 
(9) Ninth Embodiment 
FIGS. 11 and 12 show construction of an antenna device A9 for a ninth 
embodiment according to the present invention. 
As compared with the antenna device A1 of the first embodiment according to 
the present invention in FIGS. 1 and 2, it is so modified in the antenna 
device A9 for the ninth embodiment, that the electronic circuit 6 is 
fixedly provided on the second base member 82, and the input/output 
terminal 6e is led downwardly out of the device through the porcelain 
insulator 81b provided in the second base member 82, while the feeder line 
4 extends through the porcelain guide 81f provided in the first base 
member 81, and connects the radiation electrode 2 with the electronic 
circuit 6. 
Since other constructions and functions of the antenna device A9 for the 
ninth embodiment as described above are generally similar to those of the 
antenna device A1 for the first embodiment described earlier with 
reference to FIGS. 1 and 2, detailed description thereof has been 
abbreviated here for brevity of explanation, with like parts being 
designated by like reference numerals. 
(10) Tenth Embodiment 
FIGS. 13 and 14 show construction of an antenna device A10 according to a 
tenth embodiment of the present invention. 
As compared with the antenna device A1 for the first embodiment of FIGS. 1 
and 2, the ground electrode is also formed on the outer peripheral side 
face of the dielectric substrate 12 as well as on the other main surface 
of the dielectric substrate 12 in the tenth embodiment of FIGS. 13 and 14. 
Since other constructions and functions of the antenna device A10 for the 
tenth embodiment as described above are generally similar to those of the 
antenna device A1 for the first embodiment described earlier with 
reference to FIGS. 1 and 2, detailed description thereof has been 
abbreviated here for brevity of explanation, with like parts being 
designated by like reference numerals. 
(11) Eleventh Embodiment 
FIGS. 15 and 16 show an antenna device A11 for an eleventh embodiment 
according to the present invention. In this eleventh embodiment, the 
circular ring-shape dielectric substrate 12 described as employed in the 
first to tenth embodiments has been replaced by a circular flat plate-like 
dielectric substrate 13. At a central portion in the other main surface of 
said dielectric member 13, a circular concave portion 13a is formed so as 
to serve as a vacant space for accommodating the electronic circuit 6 
therein. More specifically, the circular convex portion 81a of the first 
base member 81 fits in the above circular concave portion 13a, and the 
electronic circuit 6 is secured to the ceiling portion of said circular 
convex portion 81a. In this embodiment, the ground electrode 31 is formed 
over the entire surface of the other main surface of the dielectric 
substrate 13 and the circular concave portion 13a as illustrated. 
Since other constructions and functions of the antenna device A11 for the 
eleventh embodiment as described above are generally similar to those of 
the antenna device A1 for the first embodiment described earlier with 
reference to FIGS. 1 and 2, detailed description thereof has been 
abbreviated here for brevity of explanation, with like parts being 
designated by like reference numerals. 
(12) Twelfth Embodiment 
FIGS. 17 and 18 show an antenna device A12 for a twelfth embodiment 
according to the present invention. 
In the twelfth embodiment of FIGS. 17 and 18, it is so modified that the 
ground electrode 31 described as formed on the other main surface of the 
dielectric substrate 13 and over the entire surface of the circular 
concave portion 13a in the eleventh embodiment of FIGS. 15 and 16 is 
formed only on the other main surface of the dielectric substrate 13, 
without formation thereof on the circular concave portion 13a. 
Since other constructions and functions of the antenna device A12 for the 
twelfth embodiment as described above are generally similar to those of 
the antenna device A11 for the eleventh embodiment described earlier with 
reference to FIGS. 15 and 16, detailed description thereof has been 
abbreviated here for brevity of explanation, with like parts being 
designated by like reference numerals. 
Although the foregoing description relates to the case where the present 
invention is applied to antennas for transmission, it is needless to say 
that the concept of the present invention is also applied to an antenna 
for reception or antenna which may be commonly used for transmission and 
reception. 
As is clear from the foregoing description, according to the present 
invention, since it is so arranged to accommodate the electronic circuit 
within a vacant space provided at the central portion of the dielectric 
substrate, an antenna device compact and thin in size can be 
advantageously provided through simple construction at low cost. 
Although the present invention has been fully described by way of example 
with reference to the accompanying drawings, it is to be noted here that 
various changes and modifications will be apparent to those skilled in the 
art. Therefore, unless otherwise such changes and modifications depart 
from the scope of the present invention, they should be construed as 
included therein.