Array antenna, antenna device with the array antenna and antenna system employing the antenna device

An array antenna includes a plurality of patches arrayed on a first surface of a base board and a plurality of feeders connected to the respective patches so as to radiate or receive an electromagnetic wave via the patches. The patches include a plurality of first patches and a plurality of second patches. The feeders connected to the first patches are formed on the first surface of the base board, while the feeders connected to the second patches are formed on a second surface of the base board. Further, first and second transmitting and receiving circuits are provided on the first and second surfaces, respectively, of the base board, so as to provide an antenna device. The first transmitting and receiving circuit feeds or receives electrical signals to or from the first patches, while the second transmitting and receiving circuit feeds or receives electrical signals to or from the second patches. The first and second transmitting and receiving circuits are both positioned on the same side of the arrayed patches. With such arrangements, the directivities of a first antenna unit with the first patches and of a second antenna unit with the second patches can be made different from each other, and the overall size of the antenna device can be reduced to a considerable degree.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an improved array antenna, and also 
relates to an antenna device including the improved array antenna and an 
antenna system employing such an antenna device. 
2. Description of the Related Art 
Japanese Patent Laid-Open Publication No. HEI-5-251928 discloses an antenna 
device, which includes an IC board with a transmitting and receiving 
circuit mounted thereon and a horn-type primary radiator. Further, 
Japanese Patent Laid-Open Publication No. HEI-8-97620 discloses an array 
antenna which includes a plurality of patch antennas arrayed on a 
dielectric substrate, a feed and feed lines or feeders connecting between 
the feed and the individual patch antennas. The feeders, in the form of 
microstrips, are formed on the dielectric substrate together with the 
patch antennas. 
Among various known examples of the array antenna is a phased array 
antenna, which is designed to vary a phase difference between adjacent 
antenna elements to change the direction of radiated beams, to thereby 
switch the direction of the main lobe. The array antennas, which comprise 
an array of planar antennas of same structure, can be used as a phased 
array antenna by just varying a phase difference between adjacent antenna 
elements; however, it is difficult to vary their directivity of the array 
antenna depending on, for example, the size and distance (from the 
antenna) of objects that are to be detected. Further, the array antennas, 
having patches of individual planar antenna elements and associated 
feeders formed on a same planar surface, present the problem that their 
directivities would considerably deteriorate due to unwanted radiation of 
electromagnetic waves from the feeders, although they provide a very 
simple feeding scheme. 
SUMMARY OF THE INVENTION 
Therefore, it is a primary object of the present invention to provide an 
array antenna capable of varying its directivity as desired. 
It is another object of the present invention to provide a small-size 
antenna device including the directivity-variable array antenna. 
It is yet another object of the present invention to provide an antenna 
system which employs the small-size antenna device including the 
directivity-variable array antenna. 
According to a first aspect of the present invention, there is provided an 
array antenna, which comprises a plurality of patches arrayed on a first 
surface of a base board and a plurality of feeders connected to respective 
ones of the patches so as to radiate or receive an electromagnetic wave 
via the patches. The plurality of patches comprises a plurality of first 
patches and a plurality of second patches. The feeders connected to the 
first patches are formed on the first surface of the base board, while the 
feeders connected to the second patches are formed on a second surface of 
the base board opposite to the first surface. 
Because the feeders connected to the first and second patches are formed on 
the first and second surfaces, respectively, of the base board and thus 
they differ in geographical position and form of electrical connection, 
the directivities of a first antenna unit with the first patches and of a 
second antenna unit with the second patches can be made different from 
each other. By simultaneously using a combination of optionally selected 
first and second patches (e.g., by simultaneously radiating 
electromagnetic waves via selected first and second patches) and varying 
phase differences between the selected patches, the directivities of the 
first and second antenna units can be varied. Further, because the feeders 
for the first and second patches are formed on the different surfaces of 
the base board, the interval between adjacent feeders on each of the 
surfaces can be made greater than where they are all formed on a single 
surface of the base board. The greater interval between the feeders can 
effectively reduce undesirable noise that would result from mutual 
radiation between the feeders. 
Preferably, the base board comprises an earth plate made of an electrically 
conductive material and a pair of dielectric substrates sandwiching the 
earth plate therebetween. The feeders, earth plate and one of the 
dielectric plates disposed between the feeders and the earth plate 
together constitute microstrips, and the first patches, earth plate and 
the one dielectric substrate disposed between the first patches and the 
earth plate together constitute patch antennas. The second patches, earth 
plate and the other dielectric plate disposed between the second patches 
and the earth plate together constitute inductance-coupling patch antennas 
with a plurality of slots formed in the earth plate. 
With the inductance-coupling patch antenna arranged in the above-mentioned 
manner, it is possible to save the labor necessary to connect the second 
patches and the associated feeders on the second surface via conductor 
lines (which may for example be through-holes) extending across the 
thickness of the base board, by using the mutual induction to feed to the 
second patches. Because the feeding to a selected one of the second 
patches is effected through the slot of a non-resonating length that is 
formed in the earth plate, the impedance can be adjusted by varying the 
dimensions of the slot. Further, by the earth plate interposed between the 
second patches and the feeders, it is possible to enhance the directivity 
of the inductance-coupling patch antenna while avoiding unwanted radiation 
from the feeder to the first surface. 
Preferably, the first patches and second patches are arrayed alternately on 
the first surface of the base board. This alternate arrangement can 
increase the interval between adjacent feeders on each of the surfaces so 
that noise resulting from the mutual radiation between the feeders is 
minimized. 
In a preferred implementation, the array antenna comprises an additional 
dielectric substrate covering the second surface of the base board, or an 
additional dielectric substrate that includes an additional earth plate 
covering the second surface of the base board. The first-said additional 
dielectric substrate protects the feeders formed on the second surface of 
the base board and reinforces the base board. The second-said additional 
dielectric substrate, including the additional earth plate covering the 
second surface of the base board, can protect the feeders, reinforce the 
base board and also effectively reduces unwanted radiation to the reverse 
side of the base board. 
According to a second aspect of the present invention, there is provided an 
antenna device including the above-mentioned array antenna. This antenna 
device comprises a first transmitting and receiving circuit for feeding 
electrical signals to the first patches of the array antenna or receiving 
electrical signals from the first patches, and a second transmitting and 
receiving circuit for feeding electrical signals to the second patches of 
the array antenna or receiving electrical signals from the second patches. 
The first transmitting and receiving circuit is provided on the first 
surface of the base board, the second transmitting and receiving circuit 
is provided on the second surface of the base board, and the first and 
second transmitting and receiving circuits are both positioned on a same 
side of the patches. 
The mounting areas on the base board can be used very efficiently, so that 
the base board and hence the entire antenna device can be substantially 
reduced in size. Furthermore, by providing the transmitting and receiving 
circuits on one same side of the corresponding arrayed patches, the 
necessary length of connecting wires from an external circuit to the 
transmitting and receiving circuits can be reduced effectively. The 
reduced wire length results in a reduced transmission loss and also 
effectively reduces influences of unwanted radiation to and from the 
wires. 
Preferably, the first and second transmitting and receiving circuits are 
capable of selecting any of said patches to or from which electrical 
signals are to be fed or received and phases of the selected patches. This 
arrangement allows the directivity of the array antenna to be varied 
optionally, and also permits beam formation, beam scanning and generation 
of time-divisional multibeams. 
According to a third aspect of the present invention, there is provided an 
antenna system which comprises first and second radiators, and wherein the 
first radiator is the above-mentioned antenna device and the second 
radiator is a reflector or a lens. 
Because the antenna device can be of compact size, the reduced overall size 
of the base board can effectively avoid aperture blocking by the board. 
Thus, the reflector can be made greater in size so that the radiated beam 
from any of the patches is reflected at more points on the unblocked 
surface of the reflector to provide more reflected beams. Therefore, the 
antenna gain can be improved. 
The above and other objects, features and advantages of the present 
invention will become manifest to those versed in the art upon reference 
to the detailed description and accompanying drawings in which preferred 
structural embodiments incorporating the principles of the present 
invention are shown by way of illustrative examples.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The following description is merely exemplary in nature and is in no way 
intended to limit the invention or its application or uses. 
FIGS. 1A and 1B show an antenna device 10 according to a preferred 
embodiment of the present invention, which comprises an array antenna as 
will be described in detail below. Specifically, FIG. 1A is a schematic 
top plan view of the antenna device 10, and FIG. 1B is a schematic bottom 
plan view of the antenna device shown in FIG. 1A. The array antenna 12 
includes a base board 14, on a first surface (obverse side) 14a of which 
are provided an array of patches 16 and a plurality of feeders 18 
connected to the respective patches 16. Via these patches 16, the antenna 
device 10 radiates and receives an electromagnetic wave. 
The patches 16 comprise a plurality of first and second patches 16a and 
16b, and the feeders 18a connected to the first patches 16a are formed on 
the first surface 14a of the base board 14 while the feeders 18b connected 
to the second patches 16b are formed on a second surface (reverse side) 
14b of the base board 14. 
The base board 14 comprises an earth plate 20 made of an electrically 
conductive material, and a pair of dielectric substrates 22a and 22b 
sandwiching the earth plate 20 therebetween. The feeders 18a connected to 
the first patches 16a and earth plate 20, as well as the dielectric 
substrate 22a located between the feeders 18a and the earth plate 20, 
together constitute microstrips 24. Similarly, the feeders 18b connected 
to the second patches 16b and earth plate 20, as well as the dielectric 
substrate 22b located between the feeders 18b and the earth plate 20, 
together constitute microstrips 24. 
The first patches 16a, earth plate 20, dielectric substrate 22a located 
between the feeders 18a and the earth plate 20 together constitute patch 
antennas (microstrip antennas) 12a. The feeders 18b connected to the 
second patches 16b, earth plate 20 and dielectric substrate 22b located 
between the feeders 18b and the earth plate 20 together constitute 
inductance-coupling patch antennas 12b with a plurality of slots 26 in the 
earth plate 20. Each of the slots 26 is elongated in the direction where 
the patches are arrayed. The array of the first patches 16a form an array 
of patch antennas 12a, and a time-divisional scanning antenna assembly or 
a phased array antenna can be provided by selecting any of the patches 16a 
and a phase of each selected patch 16a. Similarly, the array of the second 
patches 16b form an array of the inductance-coupling patch antennas 12b, 
and a time-divisional scanning antenna assembly or a phased array antenna 
can be provided by selecting any of the patches 16b and a phase of each 
selected patch 16b. 
As noted above, the feeders 18a and 18b connected to the first and second 
patches 16a and 16b are formed on the first and second surfaces 14a and 
14b, respectively, of the base board 14. Thus, the feeders 18a and 18b of 
the first and second patches 16a and 16b differ in geographical position 
and form of electrical connection, so that the patch antennas 12a and 
inductance-coupling patch antennas 12b can have different directivities. 
Thus, the respective directivities of the patch antennas 12a and 
inductance-coupling patch antennas 12b can be varied, by simultaneously 
using a combination of optionally selected first and second patches 16a 
and 16b (e.g., by simultaneously radiating electromagnetic waves via 
selected first and second patches 16a and 16b) and varying phase 
differences between the selected patches 16a and 16b. Because the 
directivities of the patch antennas 12a and inductance-coupling patch 
antennas 12b can be varied variously in the above-mentioned manner, the 
array antenna 12 can also be used as an "adaptive" array antenna which is 
capable of lowering the directivity in a specific direction when a jamming 
electromagnetic wave arrives from that specific direction. 
Further, because the feeders 18a and 18b are formed on the different 
surfaces 14a and 14b of the base board 14, the interval between adjacent 
feeders 18a or 18b on each of surfaces 14a or 14b can be made greater than 
where they are all formed on a single surface of the base board 14. The 
greater interval between the feeders 18a or 18b can effectively reduce 
unwanted noise that would result from the mutual radiation between the 
feeders 18a or 18b. 
Furthermore, the microstrips 24, which are formed by the feeders 18a, earth 
plate 20 and dielectric substrate 22a, can minimize a transmission loss. 
Similarly, the microstrips 24, which are formed by the feeders 18b, earth 
plate 20 and dielectric substrate 22b, can minimize a transmission loss. 
Moreover, with the first patches 16a, earth plate 20 and dielectric 
substrate 22a forming the patch antennas (microstrip antennas) 12a, these 
antennas 12a can be readily connected to the microstrips 24 formed by the 
feeders 18a, earth plate 20 and dielectric substrate 22a. 
In the array antenna 12 shown in FIGS. 1A and 1B, the first and second 
patches 16a and 16b are arranged alternately at equal intervals on the 
first surface 14a of the base board 14. Because of the alternate 
arrangement of the first and second patches 16a and 16b, the feeders 18a 
or 18b on each of the surfaces 14a or 14b can be disposed at greater 
intervals than where the first and second feeders 18a and 18b are formed 
in succession on a single surface of the base board 14, with the result 
that it is possible to avoid noise resulting from the mutual radiation 
between the feeders 18a or 18b. Alternatively, the first and second 
patches 16a and 16b may be arranged at non-equal intervals, and the 
radiating characteristics may be controlled by varying the number of the 
patches and phase differences among the patches. 
FIG. 2 is a perspective view of one of the above-mentioned 
inductance-coupling patch antennas 12, showing one of the patches 16b and 
various elements provided around the patch 16b described earlier in 
relation to FIG. 1A. Each of the patches 16b is sized to cause resonance, 
and the slot 26 provided in corresponding relation to the patch 16b is 
smaller in length than one-half the wavelength. With the 
inductance-coupling patch antenna 12b, it is possible to save the labor 
necessary to connect the second patch 16b and the associated feeder 18b on 
the second surface 18b via a conductor line (such as a through-hole) 
extending across the thickness of the base board 14, by using the mutual 
induction to feed to the second patch 16b. Because the feeding to the 
second patch 16b is effected through the slot 26 of a non-resonating 
length formed in the earth plate 20, the impedance can be adjusted by 
varying the dimensions of the slot 26. Further, by the earth plate 26 
interposed between the second patch 16b and the feeder 18b, it is possible 
to enhance the directivity of the inductance-coupling patch antenna 12b 
while effectively avoiding unwanted radiation from the feeder 18b to the 
first surface 14a. 
The antenna device 10 shown in FIGS. 1A and 1B further includes a first 
transmitting and receiving circuit 28 (FIG. 1A) which feeds (i.e., sends 
electrical signals) to the first patches 16a of the above-mentioned array 
antenna 12 and receives input electrical signals from the first patches 
16a. The antenna device 10 also includes a second transmitting and 
receiving circuit 30 (FIG. 1B) which feeds (i.e., sends electrical 
signals) to the second patches 16b of the above-mentioned array antenna 12 
and receives input electrical signals from the second patches 16b. The 
first transmitting and receiving circuit 28 is provided on the first 
surface 14a of the base board 14, while the second transmitting and 
receiving circuit 30 is provided on the second surface 14b. Further, the 
first and second transmitting and receiving circuits 28 and 30 are both 
provided on one same side of the corresponding arrayed patches 16a and 16b 
to be located near one same side edge of the board 14. 
By providing the first and second transmitting and receiving circuits 28 
and 30 on the opposite surfaces 14a and 14b of the base board 14 as 
mentioned, the base board 14 allows various component elements to be 
mounted thereon to a higher density (increased mounting density). 
Therefore, the mounting areas on the base board 14 can be used very 
efficiently, and the board 14 and hence the entire antenna device can be 
substantially reduced in size. Further, by thus providing each of the 
first and second transmitting and receiving circuits 28 or 30 on only one 
of the surfaces 14a or 14b separately from the other circuit 30 or 28, the 
area occupied by the transmitting and receiving circuit 28 or 30 on each 
of the surfaces can be reduced or halved relative to a case where the 
circuits 28 and 30 are both provided together only on one of the surfaces 
14a or 14b, which can also contribute to the size reduction of the base 
board 14. 
Furthermore, by providing the transmitting and receiving circuits 28 and 30 
on one same side of the corresponding arrayed patches 16a or 16b to be 
located near one same side edge of the board 14 as mentioned above, the 
necessary length of connecting wires (not shown) from an external circuit 
(not shown) to the circuits 28 and 30 can be reduced. The reduced wire 
length permits a reduced transmission loss and also effectively reduces 
influences of unwanted radiation to and from the wires. 
Each of the first and second transmitting and receiving circuits 28 and 30 
may be a switchable transmitting and receiving circuit for radiating 
multibeams, or may include a combination of an amplifier circuit, a 
circulator and an antenna-switching PIN diode. Also, each of the first and 
second transmitting and receiving circuits 28 and 30 may include a FM 
signal generator, a directivity coupler and a mixer; for example, the 
transmitting and receiving circuit may be constructed as a radar module as 
shown in FIG. 3 of Japanese Patent Laid-Open Publication No. HEI-8-97620 
and may make a selection from among the patches 16a, 16b and perform phase 
control of each selected patch. The first and second transmitting and 
receiving circuits 28 and 30 may be provided on separate IC boards. 
FIG. 3 is a view showing an example of a conventional antenna device 40 to 
clarify useful features of the present invention. The conventional antenna 
device 40 includes an array antenna 42, which has a plurality of patches 
arrayed on a single surface of a base board 44, and a plurality of feeders 
48 connected to the respective patches 48. The antenna device 40 radiates 
and receives an electronic wave via the patches 46. The patches 46 
comprises a plurality of first patches 46a and a plurality of second 
patches 46b, and the feeders 48a and 48b connected to the first and second 
patches 46a and 46b are formed on the single surface 44a of the base board 
44. 
The illustrated conventional antenna device 40 further includes a first 
transmitting and receiving circuit 50 which feeds (i.e., sends electrical 
signals) to the first patches 46a of the above-mentioned array antenna 42 
and receives input electrical signals from the first patches 46a. The 
antenna device 40 also includes a second transmitting and receiving 
circuit 52 which feeds (i.e., sends electrical signals) to the second 
patches 46b of the above-mentioned array antenna 42 and receives input 
electrical signals from the second patches 46b. The first and second 
transmitting and receiving circuits 50 and 52 are both provided on the 
first surface 14a of the base board 14 in such a manner that the 
transmitting and receiving circuit 50 is located on one side of the 
arrayed patches 46a and 46b while the second transmitting and receiving 
circuit 52 is located on the other side of the patches 46a and 46b. 
The base board 44 comprises an earth plate 54 made of an electrically 
conductive material, and a pair of dielectric substrates 56a and 56b 
sandwiching the earth plate 54 therebetween. The feeders 48a connected to 
the first patches 46a, earth plate 54 and dielectric substrate 56a located 
between the feeders 48a and earth plate 54 together constitute microstrips 
58. Similarly, the feeders 48b connected to the second patches 46b, earth 
plate 54 and dielectric substrate 56b located between the feeders 48b and 
earth plate 54 together constitute microstrips 24. The first and second 
patches 46a and 46b, earth plate 20 and dielectric substrate 56a located 
between the patches and the earth plate together constitute patch 
antennas. The first and second transmitting and receiving circuits 50 and 
52 are of the same construction as the above-described counterparts 28 and 
30 shown in FIGS. 1A and 1B, respectively. The patches 46 are of the same 
construction as the above-described patches of FIG. 1A. Further, the 
number of antennas (antenna elements) in the array antenna 42 is the same 
as that in the array antenna 12 of FIG. 1A. 
FIG. 4 is a schematic view of an offset parabolic antenna system, where the 
conventional antenna device 40 of FIG. 3 is employed as a primary radiator 
and a parabolic reflector 60 is employed as a secondary radiator. 
Similarly, FIG. 5 is a schematic view of an offset parabolic antenna 
system, where the antenna device 10 of FIGS. 1A and 1B is employed as a 
primary radiator and a parabolic reflector 62 is employed as a secondary 
radiator. The two parabolic reflectors 60 and 62 are the same in focal 
length, and any one of the patches 42 or 12 is positioned at the focal 
point of each of the reflectors. 
In the offset parabolic antenna system of FIG. 4 employing the conventional 
antenna device 40, the radiated beam is reflected off concave upper end, 
middle and lower end surface portions of the reflector 60 to provide 
reflected beams 1 to 3. In the offset parabolic antenna system of FIG. 5 
employing the antenna device 10 of the present invention, however, the 
radiated beam is reflected off concave upper end, middle, near-lower-end 
and lower end surface portions of the reflector 62 to provide reflected 
beams 1 to 4. As will be readily understood from a comparison between the 
two systems of FIGS. 4 and 5, the base board 14 of the antenna device 10 
of the present invention can be substantially reduced in size because the 
second transmitting and receiving circuit 30 is provided on the reverse 
side of the base board 14 separately from the first transmitting and 
receiving circuit 28 on the obverse side. The reduced size of the base 
board 14 can effectively eliminate aperture blocking by the board 14, and 
thus the reflector 62 can be made greater in size so that the radiated 
beam from the patch is reflected at more points on the unblocked concave 
surface of the reflector 62 to provide more reflected beams. Therefore, 
the offset parabolic antenna system of FIG. 5, as compared to that of FIG. 
4, can improve the antenna gain as well as effectively reducing electric 
power consumption by the antenna device. 
Note that the offset parabolic antenna system of FIG. 5 is capable of 
generating multibeams by defocused feeding for the individual patches and 
may be used as a multibeam antenna by varying the primary beam direction. 
Further, as shown in FIG. 6, the antenna device 10 of the present 
invention may be combined with a dielectric lens to provide another 
antenna system. The dielectric lens may be replaced with any other 
suitable lens, such as a path-length lens or waveguide-shaped metal lens. 
FIGS. 7 and 8 show modifications of the antenna device of the present 
invention. The modified antenna device 10' of FIG. 7 includes an 
additional dielectric substrate 22c that covers the surface of the 
dielectric substrate 22b, i.e., the second surface 14b of the base board 
14. The additional dielectric substrate 22c protects the feeders 18b on 
the second surface 14b of the base board 14 and reinforces the base board 
14. The modified antenna device 10" of FIG. 8 includes an additional 
dielectric substrate 22c having an additional earth plate 20a that covers 
the surface of the dielectric substrate 22b, i.e., the second surface 14b 
of the base board 14. The additional dielectric substrate 22c, having such 
an additional earth plate 20a covering the second surface 14b of the base 
board 14, can protect the feeders 18b, reinforce the base board 14 and 
also effectively reduce unwanted radiation to the reverse side of the base 
board 14. In particular, it is possible to effectively reduce influences 
of the unwanted radiation on any circuit provided on the reverse side 14b 
of the base board 14. The base board 14 may be reinforced by employing the 
earth plates 20 and 20a of increased thickness. 
The array antenna 12 and antenna device 10, 10' or 10" of the present 
invention may be applied to a vehicle-mounted radar device for detection 
of obstacles near the vehicle, or may be applied to an indoor wireless LAN 
system. 
The interval between adjacent antenna elements (patch antennas) of the 
array antenna 12 may be shorter than one wave length, or equivalent to or 
shorter than one-half the wavelength, or it may be equivalent to about 
one-fourth the wavelength. The array antenna 12 may be in a linear array 
where planar antennas are arranged linearly, or in a planar array where 
planar antennas are arranged on a same planar surface. Whereas all the 
patches 16 are shown in the drawings as square patches, either the first 
patches 16a or the second patches 16b may be in a circular shape. One side 
of each of the square patches may be chosen to equal about one-half of the 
wavelength. For example, the frequency of signals (FM signals) to be fed 
may be about 60 GHz, one side of each of the square patches may be about 
1.6-2.2 mm, and the interval between adjacent square patches may be about 
0.2-0.4 mm. The dielectric substrates 22a and 22b of the base board 14 may 
be of the same thickness. 
Obviously, various minor changes and modifications of the present invention 
are possible in the light of the above teaching. It is, therefore, to be 
understood that within the scope of the appended claims the invention may 
be practiced otherwise than as specifically described.