ARRAY ANTENNA DEVICE

In adjacent two of linear array antennas, respective first element antennas and respective second element antennas are arranged so that positions of the first element antennas in the arrangement direction are shifted from each other by a half an arrangement interval and positions of the second element antennas in the arrangement direction are shifted from each other by a half the arrangement interval, the arrangement interval being an interval between the element antennas. In two of the linear array antennas, the first element antennas of one of the two and the second element antennas of the other one of the two are arranged at the same positions, and the second element antennas of the one of the two and the first element antennas of the other one of the two are arranged at the same positions, the two being located two linear array antennas away from each other.

TECHNICAL FIELD

The present invention relates to an array antenna device used in radars or wireless communication.

BACKGROUND ART

In the design of array antenna devices, it is necessary not to generate grating lobes that are unwanted radiation other than the main lobe. Whether or not a grating lobe occurs depends on the arrangement of element antennas included in an array antenna device. In order to prevent generation of grating lobes, it is only required to arrange element antennas at intervals of less than or equal to a predetermined distance with respect to the wavelength of the operating frequency. However, there are cases where it is difficult to arrange element antennas at narrow intervals due to physical factors such as the size of the element antennas.

Meanwhile, for example, Patent Literature 1 discloses a method that can reduce occurrence of grating lobes even in a case where it is difficult to arrange element antennas at narrow intervals. In this method, in a slotted waveguide array antenna device, multiple slotted waveguide array antennas are arranged on a plane, slotted waveguide array antennas adjacent to each other in a direction perpendicular to the tube axis of a rectangular waveguide are grouped, and groups of slotted waveguide array antennas, the groups being adjacent to each other in a direction of the tube axis, are arranged in a mutually zigzag shape in an offsetting manner by a distance of substantially a half of a free space wavelength of the operating frequency in the direction perpendicular to the tube axis. With this arrangement, phases of radio waves radiated in the direction perpendicular to the tube axis of the waveguide by adjacent groups of slotted waveguide array antennas become reverse phases, and as a result, grating lobes can be canceled.

CITATION LIST

Patent Literature

Patent Literature 1: JP 2007-259047 A

SUMMARY OF INVENTION

Technical Problem

In the conventional array antenna device described in Patent Literature 1, the case where the number of polarization types of the antennas is only one is considered. Meanwhile, in recent years, polarization division multiplexing technology has been used to increase the amount of information transmitted and received in communication applications. This technology is to double the amount of transmitted information by transmitting and receiving information without interfering nor being interfered with each other, for example, by giving different information to each of two waves having respective polarization planes perpendicular to each other. However, in the conventional array antenna device as described in Patent Literature 1, no consideration is made for the polarization division multiplexing, and there is no clear method for arranging array antennas having distinct polarization types in the same antenna aperture.

The present invention has been made to solve the problem as described above, and an object of the invention is to provide an array antenna device capable of suppressing grating lobes even in a case where the array antenna device has two polarization types.

Solution to Problem

An array antenna device according to the present invention includes: linear array antennas in each of which a first element antenna and a second element antenna are alternately arranged linearly, the first and second element antennas having respective polarization planes perpendicular to each other, in which the linear array antennas are arranged in a direction perpendicular to an arrangement direction of the first and second element antennas, in adjacent two of the linear array antennas, respective first element antennas each of which is the first element antenna and respective second element antennas each of which is the second element antenna are arranged so that positions of the respective first element antennas in the arrangement direction are shifted from each other by a half an arrangement interval and positions of the respective second element antennas in the arrangement direction are shifted from each other by a half the arrangement interval, the arrangement interval being an interval between the first element antenna and the second element antenna, and in two of the linear array antennas, the first element antenna of one of the two and the second element antenna of the other one of the two are arranged at the same position, and the second element antenna of the one of the two and the first element antenna of the other one of the two are arranged at the same position, the two being located two linear array antennas away from each other.

Advantageous Effects of Invention

In an array antenna device of the present invention, in adjacent two linear array antennas, first element antennas and second element antennas are arranged so that positions of the first element antennas in the arrangement direction are shifted from each other by a half an arrangement interval between the element antennas and positions of the second element antennas in the arrangement direction are shifted from each other by a half the arrangement interval. In addition, in two linear array antennas, first element antennas of one of the two and second element antennas of the other one of the two are arranged at the same positions, and second element antennas of the one of the two and first element antennas of the other one of the two are arranged at the same positions, the two being located two linear array antennas away from each other. As a result, grating lobes can be suppressed even in an array antenna device having two polarization types.

DESCRIPTION OF EMBODIMENTS

To describe the present invention further in detail, embodiments for carrying out the present invention will be described below with reference to the accompanying drawings.

First Embodiment

FIG. 1is a configuration diagram of an array antenna device according to the present embodiment.

The array antenna device illustrated inFIG. 1includes a linear array antenna10including first element antennas11ato14aand second element antennas11bto14b, a linear array antenna20including first element antennas21ato24aand second element antennas21bto24b, a linear array antenna30including first element antennas31ato34aand second element antennas31bto34b, a linear array antenna40including first element antennas41ato44aand second element antennas41bto44b, a linear array antenna50including first element antennas51ato54aand second element antennas51bto54b, a linear array antenna60including first element antennas61ato64aand second element antennas61bto64b, a linear array antenna70including first element antennas71ato74aand second element antennas71bto74b, and a linear array antenna80including first element antennas81ato84aand second element antennas81bto84b.

Here, the first element antennas11ato84aand the second element antennas11bto84bare element antennas included in an array antenna. Each of the first element antennas11ato84aand the second element antennas11bto84bschematically represents an element antenna such as a dipole antenna, and has polarization of the longitudinal direction of the rectangle. That is to say, the first element antennas11ato84aand the second element antennas11bto84bare perpendicular to each other. In the following, a component assigned with symbol a is distinguished as a first element antenna, and a component assigned with symbol b is distinguished as a second element antenna. In addition, a two-digit number assigned with the symbol represents the position of the element in the arrangement. For example, the first element antenna31arepresents the first element antenna located in the third row and the first column.

For example in the linear array antenna10, the first element antenna11aand the second element antenna11b, the first element antenna12aand the second element antenna12b, the first element antenna13aand the second element antenna13b, and the first element antenna14aand the second element antenna14bare arranged linearly and alternately at element intervals dx in the x-axis direction in the drawing. The element interval dx may be constant within the linear array antenna, or may differ for each element interval. Other linear array antennas20to80are similarly configured.

These linear array antennas10to80are arranged in multiple rows at element intervals dy in a direction perpendicular to the arrangement direction of the first element antennas11ato84aand the second element antennas11bto84b, that is, in the y-axis direction in the drawing. These linear array antennas10to80form an array antenna. The element interval dy may be constant between the linear array antennas or may differ for each linear array antenna.

In adjacent two of the linear array antennas10to80, the first element antennas11ato84aand the second element antennas11bto84bare arranged so that the positions of the first element antennas11ato84ain the arrangement direction are shifted from each other by a half an arrangement interval of the first element antennas11ato84aand the second element antennas11bto84b, that is, by dx/2, and so that the positions of the second element antennas11bto84bin the arrangement direction are shifted from each other by a half the arrangement interval, that is, by dx/2. For example, as illustrated inFIG. 1, the position of the first element antenna11aof the linear array antenna10and the position of the first element antenna21aof the linear array antenna20are shifted from each other by dx/2.

Furthermore, in two of the linear array antennas10to80located two linear array antennas away from each other, namely for example in the linear array antenna10and the linear array antenna30, the positions of the first element antennas11ato14aof the linear array antenna10in the arrangement direction (positions in the x direction) and the positions of the second element antennas31bto34bof the linear array antenna30in the arrangement direction are the same, and the positions of the second element antennas11bto14bof the linear array antenna10in the arrangement direction (positions in the x direction) and the positions of the first element antennas31ato34aof the linear array antenna30in the arrangement direction are the same. The positional relationship between the first element antennas11ato84aand the second element antennas11bto84bin other linear array antennas10to80is also similar.

Note that although four of the first element antennas11ato84aand four of the second element antennas11bto84bare included as element antennas in each of the linear array antennas10to80in the illustrated example, the number of element antennas included in a linear array antenna is not limited thereto. Likewise, although eight linear array antennas10to80are included, the number of linear array antennas may be another number.

Next, the operation of the array antenna device of the first embodiment will be described.

As a comparative example,FIG. 2illustrates a configuration in which, in each of linear array antennas10to80, first element antennas11ato84aand second element antennas11bto84bhave the same arrangement.

InFIG. 2, when focusing on only the first element antennas or only the second element antennas with regard to the element antennas arranged in the x direction, the element intervals are unequal. For example, the x-direction distance between the first element antenna11aand the first element antenna21ais dx/2, whereas the distance between the first element antenna21aand the first element antenna32ais dx×3/2. That is to say, the element antennas are arranged with omissions in the x direction. In such an arrangement, there are cases where wavefronts are aligned in a direction other than the direction in which the main lobe is generated, and thereby unwanted lobes such as grating lobes or large side lobes equivalent thereto may be generated. On the other hand, when focusing on the element antennas arranged in the x direction inFIG. 1, since all the element antennas are arranged at equal intervals of dx/2, it is possible to suppress generation of unwanted lobes.

InFIG. 3, relative radiation patterns of the array antenna device of the first embodiment and the comparative example ofFIG. 2are illustrated. Here, the vertical axis represents the relative gain, and the horizontal axis represents the angle (deg.) in a half space of the xz plane. A solid line illustrates the characteristics of the array antenna device of the first embodiment, and a broken line illustrates the characteristics of the array antenna device of the comparative example. InFIG. 3, calculation results of the radiation pattern of the array antenna device of the first embodiment illustrated inFIG. 1and the radiation pattern of the array antenna device of the comparative example illustrated inFIG. 2are illustrated assuming that the directivity of each element is a cosine electric field directivity (cos θ). The element intervals dx and dy are set to half the wavelength of the calculation frequency. As is clear fromFIG. 3, the array antenna device according to the first embodiment can sufficiently suppress grating lobes appearing in wide angle directions.

Regarding the feeding of the first element antennas11ato84aand the second element antennas11bto84b, a circuit for supplying a high-frequency signal may be included in each of the element antennas. Alternatively, the multiple first element antennas11ato84aand the multiple second element antennas11bto84bmay be grouped as sub-arrays, and a circuit for supplying a high-frequency signal may be included in each of the sub-arrays.

As described above, the array antenna device of the first embodiment includes linear array antennas in each of which a first element antenna and a second element antenna alternately arranged linearly, the first and second element antennas having respective polarization planes perpendicular to each other. The linear array antennas are arranged in a direction perpendicular to the arrangement direction of the element antennas. In adjacent two of the linear array antennas, respective first element antennas and respective second element antennas are arranged so that positions of the first element antennas in the arrangement direction are shifted from each other by a half an arrangement interval and positions of the second element antennas in the arrangement direction are shifted from each other by a half the arrangement interval, the arrangement interval being an interval between the first element antenna and the second element antenna. In two of the linear array antennas, the first element antenna of one of the two and the second element antenna of the other one of the two are arranged at the same position, and the second element antenna of the one of the two and the first element antenna of the other one of the two are arranged at the same position, the two being located two linear array antennas away from each other. Therefore, grating lobes can be suppressed even in an array antenna device having two polarization types.

Moreover, according to the array antenna device of the first embodiment, the arrangement intervals of the first element antenna and the second element antenna in each of the linear array antennas are equal, and thus generation of unwanted lobes can be suppressed.

Moreover, according to the array antenna device of the first embodiment, the arrangement intervals of the linear array antennas are equal, and thus generation of unwanted lobes can be suppressed.

According to the array antenna device of the first embodiment, the polarization of the first element antennas is one of vertical polarization and horizontal polarization, and the polarization of the second element antennas is the other one of vertical polarization and horizontal polarization, and thus it is possible to implement an array antenna device having two perpendicular polarization types.

Second Embodiment

FIG. 4is a configuration diagram of an array antenna device of a second embodiment.

In the first embodiment, the polarization of the first element antennas11ato84ais the x-direction polarization, and the polarization of the second element antennas11bto84bis the y-direction polarization; however in the second embodiment, either the first element antennas11ato84aor the second element antennas11bto84bhave polarization of +45 degrees, and the other element antennas have polarization of −45 degrees. In the array antenna device illustrated inFIG. 4, an example is illustrated in which first element antennas11ato84ahave polarization of +45 degrees and second element antennas11bto84bhave polarization of −45 degrees. The arrangement of the first element antennas11ato84aand the second element antennas11bto84bin linear array antennas10to80is similar to that of the first embodiment. Furthermore, the combination of polarization of the first element antennas11ato84aand polarization of the second element antennas11bto84bis not limited to the illustrated example, and a similar combination may be used as long as polarization of the first element antennas11ato84aand polarization of the second element antennas11bto84bare perpendicular to each other.

As described above, according to the array antenna device of the second embodiment, the polarization of the first element antennas is either one of polarization of +45 degrees and polarization of −45 degrees, and the polarization of the second element antennas is the other one of the two. Thus, grating lobes can be suppressed even in an array antenna device having two polarization types.

Third Embodiment

In a third embodiment, each of the first element antennas11ato84aand the second element antenna11bto84bincludes multiple elements.

FIG. 5is a configuration diagram of an array antenna device of the third embodiment. In the illustrated array antenna device, a first element antenna11ais configured as a sub-array antenna in which two elements11a-1and11a-2are arranged in the arrangement direction of element antennas (x direction), and similarly, a second element antenna11bis configured as a sub-array antenna in which two elements11b-1and11b-2are arranged in the arrangement direction of element antennas (x direction). Note that inFIG. 5, although only the first element antenna11aand the second element antenna11bare denoted by the symbols in order to avoid complexity of the drawing, other first element antennas12ato84aand other second element antennas12bto84bare also configured similarly.

Furthermore, also in the third embodiment, a circuit for supplying a high-frequency signal may be included in each of the first element antennas11ato84aand the second element antennas11bto84blike in the first embodiment. Alternatively, the multiple first element antennas11ato84aand the multiple second element antennas11bto84bmay be each grouped, and a circuit for supplying a high-frequency signal may be included in each of the grouped units.

Furthermore, as illustrated inFIG. 6, a first element antenna11amay include two elements11a-1and11a-2arranged in they direction, and a second element antenna11bmay include two elements11b-1and11b-2arranged in they direction. Other first element antennas12ato84aand other second element antennas12bto84balso have similar configurations.

Further alternatively, one element antenna includes two elements in the examples ofFIGS. 5 and 6; however, three or more elements may be included. Moreover, as one element antenna, multiple elements may be arranged in each of the x direction and the y direction on a plane. Furthermore, although the polarization of two elements is the x-direction polarization or the y-direction polarization in the examples ofFIGS. 5 and 6, the polarization of two elements may be polarization of +45 degrees or polarization of −45 degrees as a configuration corresponding to the array antenna device of the second embodiment.

As described above, according to the array antenna device of the third embodiment, each of the first element antennas and the second element antennas includes a sub-array antenna in which multiple elements are linearly arranged in the arrangement direction of the first element antennas and the second element antennas in the linear array antenna. Thus, grating lobes can be suppressed even in an array antenna device having two polarization types.

In addition, according to the array antenna device of the third embodiment, each of the first element antennas and the second element antennas includes a sub-array antenna in which multiple elements are linearly arranged in the arrangement direction of the linear array antennas. Thus, grating lobes can be suppressed even in an array antenna device having two polarization types.

In addition, according to the array antenna device of the third embodiment, each of the first element antennas and the second element antennas includes a sub-array antenna in which multiple elements are arranged on a plane. Thus, grating lobes can be suppressed even in an array antenna device having two polarization types.

Note that the present invention may include a flexible combination of the embodiments, a modification of any component of the embodiments, or an omission of any component in the embodiments within the scope of the present invention.

INDUSTRIAL APPLICABILITY

As described above, an array antenna device according to the present invention relates to a configuration including linear array antennas in each of which a first element antenna and a second element antenna are alternately arranged linearly, the first and second element antennas having respective polarization planes perpendicular to each other, and the array antenna device is suitable for use as an array antenna device for radar or wireless communication.

REFERENCE SIGNS LIST