JP6464124B2 - Antenna device - Google Patents

Description

  The present invention relates to an antenna device formed using a dielectric substrate.

  An antenna formed on a dielectric substrate is used in, for example, a radar that monitors the periphery of a moving body such as a vehicle or an aircraft. In this type of antenna, it is known that radiation different from the main antenna radiation is generated at the substrate edge or the like by surface waves propagating on the substrate surface, and the directivity is disturbed.

  On the other hand, for example, Patent Document 1 discloses that the directivity is disturbed by forming a structure (hereinafter referred to as EBG) having a band gap that prevents surface wave propagation at a specific frequency used in an antenna on a substrate. A technique for suppressing the above is disclosed.

JP 2003-304113 A

  By the way, EBG has a structure in which hexagonal metal platelets are periodically arranged two-dimensionally on the surface of a substrate and are connected by a metal plate formed on the back surface of the substrate and a through hole formed of metal. In other words, when EBG is used, there is a problem that the structure of the substrate becomes complicated because it is necessary to form a through hole in the substrate. In addition, the EBG prevents the propagation of surface waves that cause the directivity to be disturbed by using LC resonance in principle. For this reason, there is a problem that the frequency band that can be blocked is narrow and it is difficult to apply to a broadband antenna.

  An object of this invention is to provide the technique which suppresses the influence of a surface wave by simple structure.

  The antenna device (1, 1a, 1b) of the present invention includes a dielectric substrate (2), a ground plane (3), an antenna unit (4), and additional function units (5, 5a, 5b). The ground plane is formed on one surface of the dielectric substrate and acts as an antenna ground plane. The antenna portion is formed on the other surface of the dielectric substrate and has an antenna pattern that functions as a radiating element. The additional function unit includes a plurality of conductor patches arranged around the antenna unit and formed with a size smaller than the wavelength at a preset operating frequency. Further, the plurality of conductor patches constituting the additional function unit form a plurality of blocks arranged along a preset block arrangement direction. In the antenna characteristics when the additional function part is removed, the radiated wave from the conductor patch by the surface wave propagating on the surface of the dielectric substrate is radiated toward the compensation azimuth with the direction where the gain becomes minimum as the compensation azimuth. Thus, the phase difference of the radiation wave between the blocks is set.

  According to such a configuration, the antenna characteristics when the additional function unit is removed by using a surface reflected wave from the additional function unit configured by a plurality of conductor patches with a simple configuration compared to the EBG. In this case, the gain in the compensation direction where the gain becomes minimum can be improved, and in particular, the bandwidth can be widened.

  In addition, the code | symbol in the parenthesis described in this column and a claim shows the correspondence with the specific means as described in embodiment mentioned later as one aspect, Comprising: The technical scope of this invention is shown. It is not limited.

It is xy top view used as the front view of an antenna apparatus. It is xz top view used as the side view of an antenna apparatus. It is the graph which changed the dimension of the electrically conductive patch about the frequency characteristic which calculated | required the phase of the reflected wave in an electrically conductive patch. It is a table | surface which shows the phase difference of the surface radiation wave which arises between the blocks of an Example and Comparative Examples 1 and 2. It is a graph which shows the simulation result which calculated | required the radiation characteristic of the whole antenna apparatus by changing the radiation phase difference of the surface current between the presence or absence of an additional function part, and the antenna elements which comprise an additional function part. It is a graph which shows the simulation result which calculated | required the radiation | emission characteristic of the additional function part formed in the one side of an antenna. It is a graph which shows the simulation result which calculated | required the radiation characteristic of the whole antenna apparatus about the presence or absence of an additional function part, and what provided EBG instead of the additional function part. It is explanatory drawing which shows the modification of the shape of the conductor patch which comprises an additional function part. It is explanatory drawing which shows the modification of the shape of the conductor patch which comprises an additional function part. It is the graph which changed the dimension of the gap between patches about the frequency characteristic which calculated | required the phase of the reflected wave in an electrically conductive patch.

Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings.
[1. Constitution]
The antenna device 1 is used, for example, in a millimeter wave radar that is mounted on a vehicle and detects various targets existing around the vehicle.

  As shown in FIGS. 1 and 2, the antenna device 1 includes a rectangular dielectric substrate 2 and a copper pattern formed on the dielectric substrate 2. Hereinafter, one surface of the dielectric substrate 2 is referred to as a substrate surface 2a, and the other surface is referred to as a substrate back surface 2b. The direction along one long side of the dielectric substrate 2 is the x-axis direction, the direction along the other short side perpendicular to the x-axis direction is the y-axis direction, and the normal direction of the substrate surface 2a is the normal direction. This is called the z-axis direction.

  On the back surface 2b of the substrate, a ground plate 3 made of a copper pattern covering the entire surface is formed. On the substrate surface 2a, an antenna portion 4 is formed near the center in the x-axis direction, and an additional function portion 5 is formed on both sides in the x-axis direction with the antenna portion 4 interposed therebetween. Hereinafter, the substrate surface 2a is also referred to as a radiation surface.

  The antenna unit 4 is formed of a copper pattern, and includes a rectangular patch antenna 41 and a ground plane pattern 42 formed around the patch antenna 41. The patch antenna 41 is fed so that the polarization direction of the radiated radio wave coincides with the x-axis direction.

  The additional function unit 5 is configured by two-dimensionally arranging rectangular conductor patches P formed of a copper pattern. The conductor patch P is formed in a square shape, and the size of one side thereof is set smaller than the wavelength λ at the operating frequency of the antenna device 1. More specifically, the size of one side of the conductor patch P is preferably 3/4 wavelength or less, and here, a size of about 1/5 to 1/3 wavelength is used.

  The conductor patches P constituting the additional function unit 5 are arranged in a line in the same size along the y-axis direction, and the conductor patches P of the same size arranged in the line form a block B. The blocks B are arranged along the x-axis direction, and the sizes of the conductor patches P constituting each block B are different. That is, the block arrangement direction coincides with the x-axis direction. However, the gap between the conductor patches P in the block B is set to a constant size that is different for each block. In addition, the gap between the conductor patches P straddling the block B is set to a constant size.

  The additional function unit 5 includes two parts 51 and 52 located on both sides of the antenna unit 4. Each of the blocks B constituting the two portions 51 and 52, and thus the conductor patch P, has a symmetrical structure with the antenna portion 4 interposed therebetween. In the following, the block closest to the antenna unit 4 among the portions 51 and 52 is represented by B1, and hereinafter, each block is represented by B2, B3,.

  In the additional function unit 5, the conductor patch P has an inductance component, and the gap between the conductor patches P has a capacitance component. That is, when the additional function unit 5 is represented by an equivalent circuit, as shown in FIG. 2, a series circuit composed of an inductance and a capacitance is connected in series by the number of blocks. The inductance component causes a phase lag and the capacitance component causes a phase advance with respect to a current flowing through the radiation surface 2a, that is, a surface wave propagating through the radiation surface 2a.

  Using this property, each block Bi constituting the additional function unit 5 is designed to have a structure that satisfies the following conditions (1) to (3). That is, (1) the phase characteristics of the reflected wave are line symmetric with respect to the block center. (2) The phase lag increases as the distance from the block center increases. (3) The directivity of the surface radiation wave radiated from the additional function unit 5 is directed in the compensation direction by the surface wave propagating along the x-axis direction on the radiation surface 2a. However, the direction in which the gain is minimized in the antenna characteristics (hereinafter referred to as basic characteristics) on a normal board that is a board that does not have the additional function unit 5 is defined as a compensation direction.

Here, it is designed by adjusting the size of the conductor patch P constituting each block Bi.
[2. design]
The additional function unit 5 of the antenna device 1 is designed as follows, for example.

  FIG. 3 is a graph showing reflection characteristics used for design. Specifically, the phase characteristic (hereinafter referred to as reflection characteristic) of the reflected wave at the conductor patch P with respect to the incoming wave coming from the front direction of the antenna is reflected on the normal board that is a board that does not have the additional function unit 5. It is shown on the basis of the phase. However, the gap between the conductor patches P is fixed to 1 mm, and the size of one side of the conductor patch P is changed between 2.5 mm and 3.3 mm. That is, when the size of the conductor patch P is constant, the phase delay increases as the operating frequency increases. When the operating frequency is constant, the phase delay increases as the size of the conductor patch P increases. However, in FIG. 3, since the phase difference is shown in the range of −180 deg to 180 deg, the phase difference −180 deg and 180 deg are regarded as the same.

  First, the size of the conductor patch P of the reference block Bi is arbitrarily determined. Next, the size of the conductor patch of the block adjacent to the block whose size is determined is set so as to obtain a preset phase difference at a predetermined operating frequency using the relationship shown in FIG. As a result, the phase of the reflected wave that does not take the propagation delay of the surface wave into consideration is obtained. Therefore, in order to obtain the phase of the surface radiation wave, a correction in consideration of the propagation delay of the surface wave is required. Hereinafter, the size of the conductor patch P of all the blocks Bi is designed by sequentially repeating this.

[3. effect]
According to the first embodiment described in detail above, the following effects can be obtained.
(3A) In the antenna device 1, using the surface radiation wave radiated from the conductor patch P constituting the additional function unit 5 based on the surface wave propagating on the radiation surface 2a, the direction in which the gain is minimized in the basic characteristics Lifting the gain. As a result, the antenna characteristics of the entire antenna device 1 can be improved, and in particular, the bandwidth can be widened.

  (3B) In the antenna device 1, the additional function unit 5 is configured by the conductor patch P formed on the radiation surface 2a, and unlike the conventional technique using EBG, the ground plate 3 formed on the conductor patch P and the substrate back surface 2b. Since there is no need to provide a through hole for connecting the device, the device configuration can be simplified.

  (3C) In the antenna device 1, the radiation direction of the surface reflected wave is adjusted by using the phase difference between the blocks B configured by the plurality of conductor patches P. For this reason, a broadband antenna can be realized as compared with the prior art using EBG, in which the surface wave rejection bandwidth, and hence the use bandwidth of the antenna, is determined by LC resonance.

[4. Experiment]
Example in which phase difference of surface radiation wave between blocks B (hereinafter referred to as radiation phase difference) is set to 60 deg, Comparative Example 1 using a normal substrate without additional function unit 5, comparison in which radiation phase difference is set to 90 deg The result of having performed simulation about the comparative example 3 which provided the site | part which has an EBG structure instead of the example 2 and the additional function part 5 is demonstrated. However, the operating frequency was 24.15 GHz. FIG. 4 is a table showing the radiation phases of the respective blocks with respect to the block B1 for the comparative examples 1 and 2 and the examples.

  As shown in FIG. 5, Comparative Example 1 has an antenna characteristic (that is, a basic characteristic) at which the gain is minimized in the vicinity of the reflection azimuth 40 to 45 deg (hereinafter, compensation azimuth). In contrast, the embodiment has an antenna characteristic in which the gain of the compensation direction is improved and the bandwidth is widened and the side lobes are suppressed as compared with the comparative example 1. Further, in the comparative example 2 in which the radiation phase difference is set to a value different from that of the embodiment, even when compared with the comparative example 1, the antenna characteristics are narrow and the side lobes are not suppressed. That is, it can be seen that the radiation phase difference of the additional function unit 5 needs to be optimized appropriately according to the basic characteristics.

  FIG. 6 shows the result of the simulation of the single antenna characteristic of one of the parts 51 and 52 constituting the additional function unit 5. The example of FIG. 5 and the comparative example 2 are obtained by adding and synthesizing the graph of FIG.

  As shown in FIG. 7, in the embodiment having the additional function unit 5, compared with the comparative example 3 using the EBG structure that is more complicated than the additional function unit 5, the antenna characteristics that are equal to or higher in terms of gain and bandwidth are obtained. It turns out that it is obtained. That is, an effect equivalent to that of the antenna device using the EBG structure can be realized with a simpler configuration.

[5. Other Embodiments]
As mentioned above, although the form for implementing this invention was demonstrated, this invention is not limited to the above-mentioned embodiment, It can implement in various deformation | transformation.

  (5A) In the above embodiment, the gap between the conductor patches P straddling the block B is made constant, and the phases of the reflected wave and the radiated wave are adjusted by changing the size of the conductor patch P. However, the present invention is not limited to this. It is not something. For example, as in the antenna device 1a shown in FIG. 8, the size of the conductor patch P is the same in all the blocks B constituting the portions 51a, 52a of the additional function unit 5a, and the conductor patches P straddling the block B are between the conductor patches P. You may adjust the phase of a reflected wave and a radiation wave by changing a gap. Further, like the antenna device 1b shown in FIG. 9, the conductor patch P constituting each part 51b, 52b of the additional function unit 5b is configured in a spiral pattern, and the pattern width of this spiral pattern is set for each block B. The phase of the reflected wave and the radiated wave may be adjusted by changing the phase. Moreover, you may adjust the phase of a reflected wave and a radiation wave combining these methods.

  (3B) In the above embodiment, the additional function unit 5 is designed using the graph shown in FIG. 3, but the phase of the reflected wave or the radiated wave is adjusted by changing the gap between the conductor patches P. Instead of the graph shown in FIG. 3, the additional function unit 5 may be designed using the graph shown in FIG. In FIG. 10, the size of the conductor patch P is fixed to 2.9 mm × 2.9 mm, and the gap between the conductor patches is changed in the range of 0.16 mm to 0.2 mm with respect to the normal substrate. The frequency characteristics of the phase difference are obtained. As shown in the figure, it can be seen that the phase delay increases as the operating frequency is constant and the gap increases, and the operating frequency increases as the gap is constant.

  (3C) A plurality of functions of one constituent element in the above embodiment may be realized by a plurality of constituent elements, or a single function of one constituent element may be realized by a plurality of constituent elements. . Further, a plurality of functions possessed by a plurality of constituent elements may be realized by one constituent element, or one function realized by a plurality of constituent elements may be realized by one constituent element. Moreover, you may abbreviate | omit a part of structure of the said embodiment. In addition, at least a part of the configuration of the above embodiment may be added to or replaced with the configuration of the other embodiment. In addition, all the aspects included in the technical idea specified only by the wording described in the claim are embodiment of this invention.

  (3D) In addition to the antenna device described above, the present invention can be realized in various forms such as a system including the antenna device as a component.

  DESCRIPTION OF SYMBOLS 1, 1a, 1b ... Antenna apparatus, 2 ... Dielectric board | substrate, 2a ... Substrate surface / radiation surface, 2b ... Substrate back surface, 3 ... Ground plane, 4 ... Antenna part, 5, 5a, 5b ... Additional function part, 41 ... Patch Antenna, 42 ... ground plane pattern, B ... block, P ... conductor patch.

Claims (5)

A dielectric substrate (2);
A ground plane (3) formed on one surface of the dielectric substrate and acting as an antenna ground plane;
An antenna part (4) having an antenna pattern formed on the other surface of the dielectric substrate and acting as a radiating element;
An additional function part (5, 5a, 5b) having a plurality of conductor patches arranged around the antenna part and having a smaller size than the wavelength at a preset operating frequency;
With
The plurality of conductor patches constituting the additional function unit forms a plurality of blocks arranged along a preset block arrangement direction,
The additional function unit has a phase difference of the radiated wave between the blocks necessary for radiating the radiated wave from the conductor patch toward the compensation direction due to the surface wave propagating on the surface of the dielectric substrate. As realized, the size of the conductor patch is varied for each block, the interval between the adjacent conductor patches across the block is varied for each adjacent block, and the conductor The patch is configured in a spiral pattern, and by performing at least one of making the pattern width of the spiral pattern different for each block, the inductance component of the conductor patch and the gap between the conductor patches are reduced. A capacitance component having
The compensation azimuth is an azimuth in which gain is minimized in antenna characteristics when the additional function unit is removed.
Antenna device (1, 1a, 1b). The antenna device according to claim 1,
In the antenna device, the phase of the radiated wave becomes a lagging phase as the block moves away from the center of the block which is the center of the dielectric substrate in the block arrangement direction. In the antenna device according to claim 1 or 2 ,
The block is set such that the phase characteristics of the reflected wave are symmetrical with respect to the block center. The antenna device according to claim 3 , wherein
The antenna device in which the block arrangement direction and the polarization direction of the antenna unit coincide. In the antenna device according to any one of claims 1 to 4 ,
The size of the conductor patch is 3/4 wavelength or less. Antenna device.

Images