Antenna element, antenna array, and antenna module

Abstract

[Problem] To provide an antenna element, an antenna array, and an antenna module capable of achieving miniaturization and a wider bandwidth with a simple structure. [Solution] An antenna element according to one aspect of the present technology is provided with: a first conductor layer having a planar element shape; a second conductor layer; a dielectric layer; a first interlayer connection part; and a second interlayer connection part. The second conductor layer is connected to a ground potential. The dielectric layer is provided between the first conductor layer and the second conductor layer. The first interlayer connection part penetrates the dielectric layer, and connects the first conductor layer to a power supply part. The second interlayer connection part penetrates the dielectric layer, and connects the first conductor layer and the second conductor layer.

Description

Antenna element, antenna array and antenna module

[0001] The present technology relates to an antenna element, an antenna array, and an antenna module capable of transmitting or receiving electromagnetic waves, for example, millimeter waves.

[0002] In antennas used in the high frequency range, the short wavelength allows for miniaturization of the elements, and so pattern antennas formed of conductive materials on an electronic substrate are common. In particular, in recent years, for small antennas in the millimeter wave range used for cellular and radar applications, there has been a demand for antenna structures that are cheaper, smaller, have high gain, and are broadband and highly directional within limited spaces. The patch antenna, which is a planar antenna, is widely known as the antenna structure that is highly mass-producible and has been most widely used as a directional antenna (see, for example, Patent Document 1).

[0003] JP 2022-51890 A

[0004] However, with patch antennas, the fractional bandwidth that can be covered by a single element is only a few percent, and to widen the bandwidth, more complex structures are required, such as an array of multiple elements or a resonant structure between elements arranged across the stack, which imposes constraints in terms of space and cost.

[0005] In view of the above circumstances, an object of the present technology is to provide an antenna element, an antenna array, and an antenna module that can achieve miniaturization and broadband with a simple structure.

[0006] An antenna element according to one embodiment of the present technology includes a first conductor layer having a planar element shape, a second conductor layer, a dielectric layer, a first inter-layer connection portion, and a second inter-layer connection portion. The second conductor layer is connected to a ground potential. The dielectric layer is provided between the first conductor layer and the second conductor layer. The first inter-layer connection portion penetrates the dielectric layer and connects the first conductor layer to a power supply portion. The second inter-layer connection portion penetrates the dielectric layer and connects the first conductor layer and the second conductor layer.

[0007] In the antenna element, the first conductor layer functions as a radiating element, the second conductor layer functions as a ground plane, and the first interlayer connection portion, the first conductor layer, and the second interlayer connection portion form a loop antenna, which allows for a simple structure to be made smaller and have a wider bandwidth.

[0008] The first conductor layer is typically formed to have a smaller area than the second conductor layer, thereby achieving stable resonance in a target frequency band.

[0009] The length of the loop formed by the first interlayer connection portion, the first conductor layer, and the second interlayer connection portion may be equal to or less than one wavelength of the radio wave in use, for example, a half wavelength, which allows further miniaturization of the antenna element.

[0010] The first conductor layer may have a planar shape that is rectangular having long and short sides.

[0011] The first conductor layer may have a first region to which the first interlayer connector is connected and a second region to which the second interlayer connector is connected, and the first region and the second region may be disposed apart from a peripheral edge of the first conductor layer, thereby widening the directivity of radio waves.

[0012] The first region and the second region may be arranged in a direction parallel to the long sides, or may be arranged in a direction intersecting the direction parallel to the long sides.

[0013] The dielectric layer may be a dielectric substrate made of a dielectric material, the first conductor layer may be a metal layer formed on a first main surface of the dielectric substrate, and the second conductor layer may be a metal layer formed on a second main surface of the dielectric substrate opposite to the first main surface.

[0014] The second conductor layer may have an opening formed with a larger diameter than the first interlayer connection portion, thereby simplifying the electrical insulation structure between the first interlayer connection portion and the second conductor layer.

[0015] The first interlayer connection portion and the second interlayer connection portion may be through-hole plating or buried vias provided in the dielectric layer.

[0016] According to one aspect of the present technology, there is provided an antenna array including a plurality of antenna elements, each of which includes a first conductor layer having a planar element shape, a second conductor layer connected to a ground potential, a dielectric layer provided between the first conductor layer and the second conductor layer, a first inter-layer connector penetrating the dielectric layer and connecting the first conductor layer to a power feed portion, and a second inter-layer connector penetrating the dielectric layer and connecting the first conductor layer and the second conductor layer, wherein the first conductor layer of each of the plurality of antenna elements is arranged on one surface of the dielectric layer.

[0017] At least one of the plurality of antenna elements may be a transmitting antenna element, and at least one of the other antenna elements may be a receiving antenna element.

[0018] The plurality of antenna elements may be arranged in a matrix on the surface along a first axis direction and a second axis direction that are orthogonal to each other.

[0019] The first conductor layer has a rectangular planar shape with long sides parallel to the first axis direction and short sides parallel to the second axis direction, and the opposing short sides of two of the first conductor layers arranged in the first axis direction may have a notch portion that partially expands the spacing between the two first conductor layers.

[0020] The second conductor layer of each of the plurality of antenna elements may be formed from a common conductor layer.

[0021] According to one aspect of the present technology, there is provided an antenna module including a plurality of antenna elements and a signal processing circuit. Each of the plurality of antenna elements includes a first conductor layer having a planar element shape, a second conductor layer connected to a ground potential, a dielectric layer provided between the first conductor layer and the second conductor layer, a first inter-layer connector that penetrates the dielectric layer and connects the first conductor layer to a power supply portion, and a second inter-layer connector that penetrates the dielectric layer and connects the first conductor layer to the second conductor layer. The signal processing circuit is connected to the plurality of antenna elements.

[0022] 1 is a transparent perspective view of an antenna element according to a first embodiment of the present technology. FIG. 2 is a side cross-sectional view of the antenna element. FIG. 3 is a simulation result showing an example of a voltage standing wave ratio of the antenna element. FIG. 4 is a simulation result showing a radiation characteristic of the antenna element in an azimuth plane at 60 GHz. FIG. 5 is a simulation result showing a radiation characteristic of the antenna element in an elevation plane at 60 GHz. FIG. 6 is a transparent perspective view of an antenna element according to a first embodiment of the present technology. FIG. 7 is a side cross-sectional view of the antenna element according to the first embodiment. FIG. 8 is a simulation result showing an example of a voltage standing wave ratio of the antenna element in an azimuth plane at 60 GHz. FIG. 9 is a simulation result showing a radiation characteristic of the antenna element in an elevation plane at 60 GHz. FIG. 10 is a transparent perspective view of an antenna element according to a first embodiment of the present technology. FIG. 11 is a side view of the antenna element according to the second embodiment. FIG. 12 is a simulation result showing an example of a voltage standing wave ratio of the antenna element according to the second embodiment. FIG. 13 is a simulation result showing a radiation characteristic of the antenna element in an elevation plane at 60 GHz. 17 is a perspective view similar to FIG. 17 , showing the configuration of the antenna module to which isolation processing has not been applied. It is a simulation result showing the isolation characteristic of one receiving antenna with respect to a transmitting antenna in the antenna module. It is a simulation result showing the isolation characteristic of another receiving antenna with respect to a transmitting antenna in the antenna module. It is a simulation result showing the isolation characteristic of yet another receiving antenna with respect to a transmitting antenna in the antenna module. It is a simulation result showing the isolation characteristic of yet another receiving antenna with respect to a transmitting antenna in the antenna module. It is a simulation result showing an example of the isolation characteristic between receiving antennas in the antenna module.30 is a simulation result showing another example of isolation characteristics between receiving antennas in the antenna module. 31 is a simulation result showing yet another example of isolation characteristics between receiving antennas in the antenna module. 32 is an explanatory diagram showing another configuration example of the isolation processing. 33 is a perspective view showing another configuration example of the antenna element shown in FIG. 1. 34 is a simulation result showing the voltage standing wave ratio (VSWR) characteristic of the antenna element shown in FIG. 28 and the radiation characteristic in the azimuth plane and the elevation plane at 60 GHz. 35 is a perspective view showing another configuration example of the antenna element shown in FIG. 30. 36 is a simulation result showing the voltage standing wave ratio (VSWR) characteristic of the antenna element shown in FIG. 32 and the radiation characteristic in the azimuth plane and the elevation plane at 60 GHz. 37 is a perspective view showing another configuration example of the antenna element shown in FIG. 31. 38 is a diagram showing an example of an antenna module according to the second embodiment.

[0044] FIG. 40 is a diagram showing the isolation characteristics of the antenna module shown in FIG. 40.

[0045] FIG. 41 is a diagram showing the isolation characteristics of the antenna module according to the fourth embodiment.

[0046] FIG. 42 is a diagram showing the isolation characteristics of the antenna module according to the fourth embodiment.

[0047] FIG. 43 is a diagram showing the isolation characteristics of the antenna module according to the fourth embodiment.

[0048] FIG. 44 is a diagram showing the isolation characteristics of the antenna module according to the fourth embodiment.

[0049] FIG. 45 is a diagram showing the isolation characteristics of the antenna module according to the fourth embodiment.

[0050] FIG. 46 is a diagram showing the isolation characteristics of the antenna module according to the fourth embodiment.

[0051] FIG. 47 is a diagram showing the isolation characteristics of the antenna module according to the fourth embodiment.

[0052] FIG. 48 is a diagram showing the isolation characteristics of the antenna module according to the fourth embodiment.

[0053] FIG. 49 is a diagram showing the isolation characteristics of the antenna module according to the fourth embodiment.

[0054]

[0023] Hereinafter, embodiments of the present technology will be described with reference to the drawings.

[0024] <First embodiment> Fig. 1 is a transparent perspective view of an antenna element 100 according to a first embodiment of the present technology, and Fig. 2 is a side cross-sectional view thereof. In the drawings, the X-axis, Y-axis, and Z-axis indicate three axial directions that are orthogonal to each other, and correspond to the vertical direction (front-rear direction), horizontal direction (width direction), and thickness direction (height direction) of the antenna element 100, respectively.

[0025] [Basic Configuration of Antenna Element] The antenna element 100 of this embodiment is configured as a millimeter-wave antenna for transmission, reception, or transmission and reception. The antenna element 100 includes a dielectric layer 10, a first conductor layer 21, a second conductor layer 22, a first interlayer connection portion 31, and a second interlayer connection portion 32. The antenna element 100 is configured by a dielectric multilayer substrate (double-sided wiring substrate).

[0026] The dielectric layer 10 is provided between the first conductor layer 21 and the second conductor layer 22. The dielectric layer 10 is a rigid dielectric substrate and corresponds to an insulating layer constituting the dielectric multilayer substrate. The dielectric layer 10 has a rectangular planar shape, with vertical (X-axis direction) and horizontal (Y-axis direction) lengths of, for example, approximately 5 mm. The thickness (Z-axis direction) of the dielectric layer 10 is set depending on the dielectric constant of the dielectric material constituting the dielectric layer 10 and the wavelength of the radio waves used; in this embodiment, which uses radio waves in the 60 GHz band, the thickness is, for example, 0.65 mm.

[0027] Examples of dielectric materials constituting the dielectric layer 10 include insulating organic materials such as FR4, BT resin, and polytetrafluoroethylene, and insulating inorganic materials such as ceramics. The dielectric constant of the dielectric layer 10 is not particularly limited and can be set arbitrarily depending on the frequency of the radio waves transmitted or received by the antenna element 100. For example, in the case of applications involving transmission and reception of electromagnetic waves in the 60 GHz band, a material with a dielectric constant of, for example, 3.6 is used for the dielectric substrate 10.

[0028] The first conductor layer 21 corresponds to a conductor layer formed on one surface side of the dielectric multilayer substrate, and in this embodiment is a metal layer formed on the first main surface 10a (the upper surface in FIGS. 1 and 2 ) of the dielectric layer 10. The first conductor layer 21 is configured as a radiating element of the antenna element 100.

[0029] The first conductor layer 21 is formed with a smaller area than the second conductor layer 22 and is formed into a planar pattern having a rectangular planar element shape, for example. The planar element shape refers to the planar shape (patch shape) of a conductor portion that forms a radiating element such as a patch antenna. The size (length of each side) of the first conductor layer 21 is not particularly limited and can be set arbitrarily depending on the frequency band of the radio waves used. In this embodiment, the length of the long side 21L along the X-axis direction is approximately 1.6 mm, and the length of the short side 21S along the Y-axis direction is approximately 1.0 mm.

[0030] The planar shape of the first conductor layer 21 is not limited to a rectangle, and may be a polygon other than a rectangle, a circle, an ellipse, or a combination thereof. Furthermore, at least a part of the rectangle (for example, a side or a vertex) may be deformed into any shape.

[0031] The second conductor layer 22 corresponds to a conductor layer formed on the other surface side of the dielectric multilayer substrate, and in this embodiment is a metal layer formed on the second main surface 10b (the bottom surface in FIGS. 1 and 2 ) opposite to the first main surface 10a of the dielectric layer 10. The second conductor layer 22 is configured as a ground conductor plate of the antenna element 100. By being electrically connected to the ground potential G, the second conductor layer 22 is formed over the entire back surface 10b of the dielectric layer 10, but of course, is not limited to this.

[0032] There are no particular limitations on the metals constituting the first conductor layer 21 and the second conductor layer 22, and examples thereof include copper, aluminum, etc. There are no particular limitations on the thicknesses of the first conductor layer 21 and the second conductor layer 22, and the first conductor layer 21 and the second conductor layer 22 may be formed to have the same thickness or different thicknesses.

[0033] The first interlayer connection portion 31 penetrates the dielectric layer 10 in its thickness direction (Z-axis direction) and connects the first conductor layer 21 to the power supply portion F. The first interlayer connection portion 31 is a cylindrical conductor electrically connected to the first conductor layer 21, and in this embodiment is formed by a through-hole plating provided in the dielectric layer 10 or a buried via filled with a conductive material. The second conductor layer 22 has an opening 22a formed with an opening diameter larger than the outer diameter of the first interlayer connection portion 31. The first interlayer connection portion 31 is housed within the opening 22a without contacting the periphery of the opening 22a, thereby being electrically insulated from the second conductor layer 22. The annular region between the opening 22a and the first interlayer connection portion 31 may be filled with the same material as the dielectric layer 10 or a different dielectric material.

[0034] The second interlayer connection portion 32 penetrates the dielectric layer 10 in its thickness direction (Z-axis direction) and electrically connects between the first conductor layer 21 and the second conductor layer 22. The second interlayer connection portion 32 is a cylindrical conductor like the first interlayer connection portion 31, and in this embodiment is formed by through-hole plating provided in the dielectric layer 10 or by a buried via filled with a conductive material. The second interlayer connection portion 32 is formed to have the same diameter and height as the first interlayer connection portion 31.

[0035] The first interlayer connection portion 31 and the second interlayer connection portion 32 are connected perpendicularly to the first conductor layer 21. Therefore, the length (height) of the first interlayer connection portion 31 and the second interlayer connection portion 32 corresponds to the thickness (0.65 mm) of the dielectric layer 10. As shown in FIG. 1 , the first conductor layer 21 has a first region 211 to which the first interlayer connection portion 31 is connected and a second region 212 to which the second interlayer connection portion 32 is connected. The first region 211 and the second region 212 are both located within the plane of the first conductor layer 21 and spaced apart from the peripheral edge of the first conductor layer 21.

[0036] In this embodiment, the first region 211 and the second region 212 are arranged in a direction parallel to the long side 21L (X-axis direction) at positions symmetrical with respect to the center of the first conductor layer 21. However, the first region 211 and the second region 212 may be arranged in a direction intersecting the direction parallel to the long side 21L (X-axis direction), as will be described later (see FIG. 38 ).

[0037] The antenna element 100 of this embodiment configured as described above is configured as a loop antenna having an axis parallel to the width direction (Y-axis direction) by the first conductor layer 21, the first interlayer connection portion 31 and the second interlayer connection portion 32.

[0038] In the antenna element 100 of this embodiment, the length of each side (long side 21L, short side 21S) of the first conductor layer 21 is set so that the frequency band of the radio waves used is 60 GHz (for example, 57 GHz to 64 GHz). That is, since the first conductor layer 21 is formed in the shape of a planar element with a length and width greater than the axial diameter and arrangement interval of the interlayer connectors 31, 32, current density is concentrated on the periphery of the first conductor layer 21, and therefore the relative bandwidth can be increased by setting the length of each side of the first conductor layer 21.

[0039] Furthermore, the loop length (effective length including wavelength shortening due to the dielectric constant of the dielectric layer 10) formed by the first interlayer connection portion 31, the second interlayer connection portion 32, and the first conductor layer 21 is set to be equal to or less than one wavelength of the radio wave being used, more preferably, a length equivalent to half the wavelength of the radio wave. In this embodiment, the effective length is 2.477 mm, which is a length equivalent to half the wavelength of a 60 GHz radio wave.

[0040] According to the antenna element 100 of this embodiment, since it has multiple resonant frequencies including a resonant frequency corresponding to the loop length and a resonant frequency corresponding to the circumferential length of the first conductor layer 21, it is possible to increase the fractional bandwidth (the value obtained by dividing the bandwidth by the center frequency) that can be covered by a single element.

[0041] Fig. 3 shows simulation results illustrating an example of the voltage standing wave ratio (VSWR) of the antenna element 100. Fig. 4 shows simulation results illustrating the radiation characteristics of the antenna element 100 in the azimuth plane (XZ plane) at 60 GHz, and Fig. 5 shows simulation results illustrating the radiation characteristics of the antenna element 100 in the elevation plane (YZ plane) at 60 GHz. In Figs. 4 and 5, the 0° direction (upward) corresponds to the ceiling direction (+Z direction).

[0042] As shown in Figure 3, the frequency band where the VSWR ratio was 1.5 or less was 59 GHz to 67 GHz, and the relative bandwidth was 12.7%. Also, as shown in Figures 4 and 5, a well-balanced directional characteristic was obtained over a wide range toward the ceiling.

[0043] As described above, according to this embodiment, it is possible to obtain antenna characteristics that resonate over a wide band despite having a single element structure.

[0044] Comparative Examples Next, the radiation characteristics of the antenna element 100 of this embodiment will be described in comparison with antenna structures according to comparative examples 1 and 2 described below.

[0045] Comparative Example 1 Fig. 6 is a see-through perspective view of an antenna element 101 according to Comparative Example 1, and Fig. 7 is its side cross-sectional view. This antenna element 101 shows a typical structure of a back-feed type patch antenna.

[0046] That is, the antenna element 101 has a dielectric layer 110, a first conductor layer 121 serving as a radiating element formed on the surface of the dielectric layer 110, a second conductor layer 122 serving as a ground conductor plate formed on the back surface of the dielectric layer 110, and an interlayer connection portion 131 that penetrates the dielectric layer 110 and connects the first conductor layer 121 to a feed point. The interlayer connection portion 131 is electrically insulated from the second conductor layer 122. Here, the shape of the first conductor layer 121 is rectangular with long sides of 1.2 mm and short sides of 1.0 mm.

[0047] Fig. 8 shows simulation results illustrating an example of the voltage standing wave ratio (VSWR) of the antenna element 101. Fig. 9 shows simulation results illustrating the radiation characteristics of the antenna element 101 in the azimuth plane (XZ plane) at 60 GHz, and Fig. 10 shows simulation results illustrating the radiation characteristics of the antenna element 101 in the elevation plane (YZ plane) at 60 GHz. In Figs. 9 and 10, the 0° direction (upward direction) corresponds to the ceiling direction (+Z direction).

[0048] As shown in Fig. 8, the frequency band in which the VSWR ratio is 1.5 or less for the antenna element 101 of Comparative Example 1 is 57 GHz to 61 GHz, and the fractional bandwidth is 6.7%. In contrast, with the antenna element 100 of this embodiment, the fractional bandwidth is 12.7% as described above (see Fig. 3), and therefore the fractional bandwidth can be increased by approximately two times compared to Comparative Example 1. This makes it possible to achieve a wider frequency band than the antenna element 101 of Comparative Example 1.

[0049] The antenna directivity was almost the same as that of the antenna element 101 of Comparative Example 1 shown in Figures 9 and 10. Therefore, according to this embodiment, it is possible to expand the frequency band while maintaining antenna directivity equivalent to that of a patch antenna structure.

[0050] (Comparative Example 2) Fig. 11 is a perspective view of an antenna element 102 according to Comparative Example 2, and Fig. 12 is a side view thereof. This antenna element 102 includes a loop-shaped antenna structure 123 formed perpendicular to a ground conductor plate 124. One end of the antenna structure is connected to the feed point, and the other end is connected to the ground conductor plate 124. The loop length was set to a size equivalent to half the wavelength of a 60 GHz radio wave.

[0051] Fig. 13 shows simulation results illustrating an example of the voltage standing wave ratio (VSWR) of the antenna element 102. Fig. 14 shows simulation results illustrating the radiation characteristics of the antenna element 102 in the azimuth plane (XZ plane) at 60 GHz, and Fig. 15 shows simulation results illustrating the radiation characteristics of the antenna element 102 in the elevation plane (YZ plane) at 60 GHz. In Figs. 14 and 15, the 0° direction (upward direction) corresponds to the ceiling direction (+Z direction).

[0052] As shown in Fig. 13, for the antenna element 102 of Comparative Example 2, the frequency band in which the VSWR ratio is 1.5 or less is 58 GHz to 60 GHz, and the fractional bandwidth is 6.6%. In contrast, with the antenna element 100 of this embodiment, the fractional bandwidth is 12.7% as described above (see Fig. 3), so the fractional bandwidth can be increased by approximately two times compared to Comparative Example 2. This makes it possible to achieve a wider frequency band than the antenna element 101 of Comparative Example 1.

[0053] Furthermore, with regard to directivity, unlike Comparative Example 1, the antenna has a figure-8 shaped characteristic like a dipole antenna, and it can be said that this structure is not suitable for a directional antenna toward the radiation surface (top surface) used in the millimeter wave region. Therefore, according to this embodiment, compared to a typical loop antenna structure, it is possible to achieve a well-balanced directional characteristic over a wide range toward the top surface while also widening the frequency band.

[0054] 16 shows the results of a simulation comparing the antenna characteristics and directivity of the antenna element 100 of this embodiment with the antenna element 101 of Comparative Example 1. Here, each element was formed to the same size at a resonant frequency of 60 GHz, and the antenna characteristics and directivity from 50 to 65 GHz were measured at 5 GHz intervals.

[0055] As shown in Fig. 16, the antenna element 100 of this embodiment obtained directional characteristics similar to those of the antenna element 101 of Comparative Example 1. On the other hand, according to this embodiment, the antenna gain in the direction of the top surface was greater than that of Comparative Example 1 in the frequency range of 55 GHz to 65 GHz. Up until now, methods have been used to broaden the bandwidth and increase the gain of an antenna, such as using an array shape requiring multiple antenna elements, or increasing the number of layers in a laminated substrate and adding a reflection / broadband pattern in between, but according to this embodiment, a broadband can be achieved using an inexpensive and simple method.

[0056] Second Embodiment Fig. 17 is a see-through perspective view of an antenna module 300 according to a second embodiment of the present technology, Fig. 18 is a plan view thereof, and Fig. 19 is a block diagram showing a circuit configuration of the antenna module 300. In the drawings, parts corresponding to those in the above-described first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

[0057] The antenna module 300 of this embodiment includes the antenna array 200 and a signal processing circuit 301 (FIG. 19). The antenna array 200 and the signal processing circuit 301 are formed on or mounted on a common dielectric multilayer substrate 1.

[0058] [Antenna Array] The antenna array 200 has a plurality of antenna elements 100. The plurality of antenna elements 100 includes one transmitting antenna Tx and three receiving antennas Rx1, Rx2, and Rx3. Each antenna element 100 has the same configuration, and is configured similarly to the antenna element described in the first embodiment. The number of transmitting antennas is not limited to one, and may be two or more. Furthermore, the number of receiving antennas is not limited to three, and may be two or four or more.

[0059] The first conductor layers 21 of each antenna element 100 are arranged independently on the first main surface 10a of the dielectric layer 10. Each first conductor layer 21 is formed in a similar planar element shape, and in this embodiment, is formed in a roughly rectangular shape with its long side in the X-axis direction and its short side in the Y-axis direction. These antenna elements 100 are arranged in a matrix along the X-axis direction and the Y-axis direction on the first main surface 10a of the dielectric layer 10, as shown in Fig. 18 .

[0060] On the other hand, the second conductor layer 22 of each antenna element 100 is formed of a common conductor layer connected to ground potential. An opening 22a is provided in the second conductor layer 22 in an area where the first inter-layer connection 31 of each antenna element 100 is formed, thereby electrically insulating the second conductor layer 22 from each first inter-layer connection 31. The first inter-layer connection 31 of each antenna element 100 is connected to the signal processing circuit 301 via a signal transmission line (not shown) formed on the second main surface 10b of the dielectric layer 10. Various signal lines such as a microstrip line, a strip line, and a coplanar waveguide line can be used as the signal transmission line.

[0061] [Signal Processing Circuit] The signal processing circuit 301 is a millimeter-wave radar IC that generates a millimeter-wave signal to be transmitted to the transmitting antenna Tx and processes the millimeter-wave signals received by the receiving antennas Rx1 to Rx3 to calculate the angle of arrival, and corresponds to a power supply unit. As shown in Figure 19, the dielectric multilayer substrate 1 is further equipped with a regulator 302 that adjusts the voltage supplied to the signal processing circuit 301, a memory 303 that stores driving parameters for the signal processing circuit 301, and a connector 304 that electrically connects the signal processing circuit, regulator 302, and memory 303 to an external device (not shown).

[0062] The antenna module 300 of this embodiment is configured as a MIMO (Multi-Input Multi-Output) radar antenna. According to this embodiment, since transmitting and receiving antennas are mounted on the same substrate, the same effects as those of the first embodiment can be obtained, and the antenna device can be made smaller and thinner.

[0063] [Improvement of isolation characteristics] As described above, the first conductor layer 21 of each antenna element 100 constituting the antenna array 200 has a rectangular planar shape with long sides parallel to the X-axis direction and short sides parallel to the Y-axis direction. Therefore, when the antenna elements 100 are arranged on the first main surface 10a of the square-shaped dielectric layer 10, the distance between adjacent antenna elements 100 in the X-axis direction is smaller than the distance between adjacent antenna elements 100 in the Y-axis direction.

[0064] Therefore, in this embodiment, a notch 210 that partially expands the gap between two first conductor layers 21 is provided on the opposing short sides 21s of two first conductor layers 21 arranged in the X-axis direction. This makes it possible to improve the isolation characteristics between two antenna elements 100 adjacent in the X-axis direction (between the transmitting antenna Tx and the receiving antenna Rx1, and between the two receiving antennas Rx2 and Rx3) compared to an antenna array 200 that does not have the notch 210, as shown in Fig. 20 for example.

[0065] The shape of the notch 210 is not particularly limited, and in this embodiment, it is formed in an arc shape. Alternatively, as shown in FIG. 27 , the notch 210 may be formed in a triangular, rectangular, or trapezoidal shape. By providing the notch 210 in a portion of the short side 21S of the first conductor layer 21 in this manner, it is possible to prevent the circumferential length of the first conductor layer 21 from changing significantly. This makes it possible to improve isolation characteristics while ensuring a wide bandwidth.

[0066] 21 shows the results of a simulation showing the isolation characteristics of the receiving antenna Rx1 relative to the transmitting antenna Tx. The solid line in the figure shows the characteristics when the cutout 210 is present (hereinafter also referred to as with isolation processing), and the dashed line shows the characteristics when the cutout 210 is not present (hereinafter also referred to as without isolation processing). As shown in the figure, with isolation processing, an improvement of approximately 1 dB is observed compared to without isolation processing.

[0067] Figure 22 shows the results of a simulation showing the isolation characteristics of the receiving antenna Rx2 relative to the transmitting antenna Tx. The solid line in the figure shows the characteristics with isolation processing, and the dashed line shows the characteristics without isolation processing. As shown in the figure, in this experiment, no significant difference was observed between the cases with and without isolation processing. This is thought to be because the transmitting antenna Tx and receiving antenna Rx2 are located diagonally opposite each other, and there is a large physical distance between them.

[0068] Figure 23 shows the results of a simulation showing the isolation characteristics of the receiving antenna Rx3 relative to the transmitting antenna Tx. The solid line in the figure shows the characteristics with isolation processing, and the dashed line shows the characteristics without isolation processing. As shown in the figure, with isolation processing, a significant improvement is observed in the 60 GHz to 64 GHz band compared to without isolation processing. This is thought to be because, since the long sides of the first conductor layer 21 of the transmitting antenna Tx and the receiving antenna Rx3 face each other, there is no effect from the formation of the notch 210. However, since the current density is high at the peripheral portion of the first conductor layer 21, the shape effect of the notch 210 provides a filter-like function at a specific frequency.

[0069] 24 shows the results of a simulation showing the isolation characteristics between receiving antennas Rx2 and Rx3. The solid line in the figure shows the characteristics with isolation processing, and the dashed line shows the characteristics without isolation processing. As shown in the figure, with isolation processing, an improvement of approximately 2 dB is observed compared to without isolation processing.

[0070] Figure 25 shows the results of a simulation showing the isolation characteristics between receiving antennas Rx1 and Rx3. The solid line in the figure shows the characteristics with isolation processing, and the dashed line shows the characteristics without isolation processing. As shown in the figure, in this experiment, no significant difference was observed between cases with and without isolation processing. This is thought to be because receiving antennas Rx1 and Rx3 are located diagonally opposite each other, and there is a large physical distance between them.

[0071] Figure 26 shows the results of a simulation showing the isolation characteristics between receiving antennas Rx1 and Rx2. The solid line in the figure shows the characteristics with isolation processing, and the dashed line shows the characteristics without isolation processing. As shown in the figure, with isolation processing, a significant improvement is observed in the 60 GHz to 64 GHz band compared to without isolation processing. This is thought to be due to the shape effect of the cutout portion 210, which provides a filter-like function at a specific frequency, similar to the results shown in Figure 23.

[0072] Third Embodiment [Another Configuration Example of Antenna Element] Next, another configuration example of an antenna element according to the present technology will be described. Note that in each drawing, parts corresponding to those in FIG. 1 are given the same reference numerals, and detailed description thereof will be omitted.

[0073] The antenna element 151 shown in Fig. 28 differs from the antenna element 100 shown in Fig. 1 in that the first conductor layer 21 serving as the radiating element is formed with the same area as the second conductor layer 22 serving as the ground conductor plate. Here, the length of each side of the first conductor layer 21 and the second conductor layer 22 is set to 3 mm.

[0074] 29 shows simulation results showing the voltage standing wave ratio (VSWR) characteristics of the antenna element 151 and the radiation characteristics in the azimuth plane (XZ plane) and elevation plane (YZ plane) at 60 GHz. As shown in the figure, if the area of ​​the first conductor layer 21 is too large, the resonance state changes, making it difficult to use as an antenna for the 60 GHz band. For this reason, the first conductor layer 21 must be formed with an area at least smaller than that of the second conductor layer 22, and it is preferable to optimize the circuit length of the first conductor layer 21 depending on the frequency band being used.

[0075] 30 differs from the antenna element 100 shown in Fig. 1 in that, when viewed from the Z-axis direction, the peripheral edge (long side and short side) of the first conductor layer 21 serving as a radiating element is formed in a band shape that contacts the outer periphery of the first interlayer connection portion 31 (first region 211) and the second interlayer connection portion 32 (second region 212). Here, the length of the short side of the first conductor layer 21 is 0.3 mm, and the length of the long side is 1.1 mm.

[0076] 31 shows the simulation results showing the voltage standing wave ratio (VSWR) characteristics of the antenna element 152 and the radiation characteristics in the azimuth plane (XZ plane) and elevation plane (YZ plane) at 60 GHz. As shown in the figure, resonance occurs in the 60 GHz band, but the radiation characteristics of the antenna remain the directionality of a loop antenna.

[0077] On the other hand, the antenna element 153 shown in Fig. 32 differs from the antenna element 152 shown in Fig. 30 in that, when viewed from the Z-axis direction, the antenna element 153 is formed in a band shape in which the outer peripheries of the first interlayer connection portion 31 (first region 211) and the second interlayer connection portion 32 (second region 212) are located inside the peripheral edge portion (long side and short side) of the first conductor layer 21 serving as a radiating element. Here, the length of the short side of the first conductor layer 21 is 0.5 mm, and the length of the long side is 1.3 mm.

[0078] 33 shows the simulation results showing the voltage standing wave ratio (VSWR) characteristics of the antenna element 153 and the radiation characteristics in the azimuth plane (XZ plane) and elevation plane (YZ plane) at 60 GHz. As shown in the figure, the band begins to widen around the 60 GHz band, and the radiation characteristics toward the ceiling as an antenna also become larger.

[0079] Also, the antenna element 154 shown in FIG. 34 differs from the antenna element 153 shown in FIG. 32 in that the length of the short side of the first conductor layer 21 serving as the radiating element is 1.0 mm and the length of the long side is 1.3 mm.

[0080] 35 shows the simulation results showing the voltage standing wave ratio (VSWR) characteristics of the antenna element 154 and the radiation characteristics in the azimuth plane (XZ plane) and elevation plane (YZ plane) at 60 GHz. As shown in the figure, the band is further expanded and the antenna radiation pattern is optimized toward the ceiling.

[0081] Furthermore, the antenna element 155 shown in FIG. 36 differs from the antenna element 154 shown in FIG. 34 in that the length of the short side of the first conductor layer 21 serving as the radiating element is 0.5 mm and the length of the long side is 1.6 mm.

[0082] 37 shows the simulation results showing the voltage standing wave ratio (VSWR) characteristics of the antenna element 155 and the radiation characteristics in the azimuth plane (XZ plane) and elevation plane (YZ plane) at 60 GHz. As shown in the figure, multiple resonances are also generated in the Y-axis direction, widening the band and making the antenna radiation pattern stronger toward the ceiling.

[0083] 38 differ from the antenna element 100 shown in Fig. 1 in that the first interlayer connection portion 31 and the second interlayer connection portion 32 connected to the first conductor layer 21 as a radiating element are arranged in a direction intersecting with the direction parallel to the long side (X-axis direction). Here, an example is shown in which the second interlayer connection portion 32 is arranged at a corner of the first conductor layer 21.

[0084] 39 shows simulation results showing the voltage standing wave ratio (VSWR) characteristics and radiation characteristics in the azimuth plane (XZ plane) and elevation plane (YZ plane) at 60 GHz of the antenna element 156. As shown in the figure, simulation results similar to the VSWR characteristics (FIG. 3) and radiation characteristics (FIGS. 4 and 5) of the antenna element 100 shown in FIG. 1 are obtained, and therefore, this configuration example can also achieve the same effects as the first embodiment.

[0085] Fourth Embodiment Another Example of Improvement in Isolation Characteristics Next, a fourth embodiment of the present technology will be described. In this fourth embodiment, another example of improvement in the isolation characteristics described in the second embodiment will be described.

[0086] In the second embodiment, the isolation characteristics are improved by providing the notches 210 on the short sides of each first conductor layer 21 that face each other in the X-axis direction. In the fourth embodiment, the isolation characteristics are further improved by making improvements in other respects in addition to the notches 210.

[0087] In the following description, an example of a configuration corresponding to the above-described second embodiment will first be described. Fig. 40 is a diagram showing an example of an antenna module 300 corresponding to the above-described second embodiment.

[0088] 40 , the antenna module 300 (antenna array 200) has a plurality of antenna elements 100, which include one transmitting antenna Tx and three receiving antennas Rx1, Rx2, and Rx3. The first conductor layers 21 of the transmitting antenna Tx and the receiving antennas Rx1, Rx2, and Rx each have a notch 210 on the short sides that face each other in the X-axis direction.

[0089] The antenna module 300 has a rectangular shape in the planar direction, and in this example, the length in the X-axis direction is 5.0 mm, and the width in the Y-axis direction is 5.0 mm.

[0090] In the Y-axis direction, the distance between the center position of receiving antenna Rx1 and the center position of receiving antenna Rx2, and the distance between the center position of receiving antenna Rx1 and the center position of receiving antenna Rx3, are 2.5 mm. In the X-axis direction, the distance between the center position of receiving antenna Rx2 and the center position of receiving antenna Rx3, and the distance between the center position of receiving antenna Rx1 and the center position of receiving antenna Rx3, are 2.5 mm.

[0091] The distance D between the center of the transmitting antenna Tx and the centers of the three receiving antennas Rx1, Rx3, and Rx3 in the X and Y directions (planar directions) is 2 mm. The center positions of the three receiving antennas Rx1, Rx3, and Rx3 in the planar direction are the midpoint between the centers of the receiving antenna Rx1 and Rx2 in the Y-axis direction, and the midpoint between the centers of the receiving antenna Rx2 and Rx3 in the X-axis direction.

[0092] Fig. 41 is a diagram showing the isolation characteristics of the antenna module 300 shown in Fig. 40. In Fig. 41, the horizontal axis represents the frequency [GHz] of the radio waves used in the antenna element 100, and the vertical axis represents the isolation characteristics [dB]. Note that a lower value [dB] on the vertical axis means higher isolation characteristics.

[0093] Also, in Figure 41, three graphs respectively show the isolation characteristics of receiving antenna Rx1 relative to transmitting antenna Tx (Tx → Rx1), the isolation characteristics of receiving antenna Rx2 relative to transmitting antenna Tx (Tx → Rx2), and the isolation characteristics of receiving antenna Rx3 relative to transmitting antenna Tx (Tx → Rx3).

[0094] Also, in the upper right corner of FIG. 41, a map (in thermography format) is shown for visualizing the influence of the transmitting antenna Tx on the receiving antennas Rx1, Rx2, and Rx3.

[0095] As described above in the second embodiment, in the configuration shown in FIG. 40, the first conductor layer 21 has the notch 210, and therefore the isolation characteristics are improved compared to a configuration without the notch 210.

[0096] On the other hand, further improvement in isolation characteristics is expected, and therefore, in the fourth embodiment, this isolation characteristic is further improved.

[0097] Fig. 42 is a see-through perspective view of an antenna module 400 according to a fourth embodiment. Fig. 43 is a plan view of the antenna module 400 according to the fourth embodiment. In the description of this fourth embodiment, differences from the second embodiment (and Figs. 40 and 41) will be mainly described.

[0098] Typically, in this fourth embodiment, the following three techniques (A) to (C) are mainly used to improve the isolation characteristics of the receiving antennas Rx1, Rx2, and Rx3 from the transmitting antenna Tx. (A) A notch 210 is provided in each first conductor layer 21 (similar to the second embodiment described above). (B) The distance between the transmitting antenna Tx and the receiving antennas Rx1, Rx2, and Rx3 is increased in the planar direction (X and Y directions). (C) A shielding layer 41 is provided to shield the electric field from the transmitting antenna Tx to the receiving antennas Rx1, Rx2, and Rx3. (c) A third interlayer connection 42 is provided to connect the shielding layer 41 and the second conductor layer 22, dropping the shielding layer 41 to ground potential.

[0099] 42 and 43 , an antenna module 400 (antenna array) has a plurality of antenna elements 100, which include one transmitting antenna Tx and three receiving antennas Rx1, Rx2, and Rx3. The first conductor layers 21 of the transmitting antenna Tx and the receiving antennas Rx1, Rx2, and Rx each have a notch 210 on the short sides that face each other in the X-axis direction.

[0100] The antenna module 400 has a rectangular shape in the planar direction that is long in the X-axis direction, and in this example, the length in the X-axis direction (direction parallel to the long sides of the first conductor layer 21) is 12.5 mm, and the width in the Y-axis direction (direction parallel to the short sides of the first conductor layer 21) is 7.5 mm (5 mm x 5 mm in Figure 40). Note that the specific numerical values ​​described in the fourth embodiment are merely examples and can be changed as appropriate.

[0101] In the Y-axis direction, the distance between the center position of receiving antenna Rx1 and the center position of receiving antenna Rx2, and the distance between the center position of receiving antenna Rx1 and the center position of receiving antenna Rx3, are 2.5 mm. In the X-axis direction, the distance between the center position of receiving antenna Rx2 and the center position of receiving antenna Rx3, and the distance between the center position of receiving antenna Rx1 and the center position of receiving antenna Rx3, are 2.5 mm.

[0102] The distance D between the center of the transmitting antenna Tx and the centers of the three receiving antennas Rx1, Rx3, and Rx3 in the X and Y directions (planar directions) is 5 mm. The center positions of the three receiving antennas Rx1, Rx3, and Rx3 in the planar direction are the midpoint between the centers of the receiving antenna Rx1 and Rx2 in the Y-axis direction, and the midpoint between the centers of the receiving antenna Rx2 and Rx3 in the X-axis direction.

[0103] Here, the relative positional relationship between the three receiving antennas Rx1, Rx2, and Rx3 is the same as in the example (and the second embodiment) shown in Fig. 40. Meanwhile, the distance D between the center position of the transmitting antenna Tx and the center positions of the three receiving antennas Rx1, Rx2, and Rx3 is 2 mm in the example shown in Fig. 40, but is 5 mm in this example, which is longer than the example shown in Fig. 40.

[0104] 40 (and the second example), the relative positional relationship between the three receiving antennas Rx1, Rx2, and R3 remains fixed, and the three receiving antennas Rx1, Rx2, and R3 are moved in the X-axis direction away from the transmitting antenna Tx. Note that the relative positional relationship between the three receiving antennas Rx1, Rx2, and R3 is fixed because the relative positional relationship between the three receiving antennas Rx1, Rx2, and R3 is roughly determined due to the use of MIMO in the present technology.

[0105] In this way, by moving the central positions of the three receiving antennas Rx1, Rx3, and Rx3 away from the central position of the transmitting antenna Tx, the isolation characteristics of the receiving antennas Rx1, Rx3, and Rx3 with respect to the transmitting antenna Tx can be improved.

[0106] Typically, the distance D in the X and Y directions (plane directions) between the center position of the transmitting antenna Tx and the centers of the three receiving antennas Rx1, Rx3, and Rx3 is set to be equal to or greater than half the wavelength (½λ) of the radio wave used. Experimental results have shown that by setting the distance D to a length equal to or greater than half the wavelength (½λ), the isolation characteristics of the receiving antennas Rx1, Rx3, and Rx3 from the transmitting antenna Tx are improved.

[0107] On the other hand, it may be thought that the isolation characteristics of the receiving antennas Rx1, Rx2, and Rx3 relative to the transmitting antenna Tx will improve as the distance D increases, but experimental results have shown that this tendency for improvement plateaus once the distance D exceeds a certain distance. Naturally, the larger the distance D, the larger the antenna module 400 will become. If the antenna module 400 becomes larger, transmission loss will occur between the millimeter-wave radar IC 301 and the receiving antenna Tx and the receiving antennas Rx1, Rx2, and Rx2, deteriorating the performance of the entire system.

[0108] For this reason, typically, the distance D in the XY directions (planar direction) between the center position of the transmitting antenna Tx and the centers of the three receiving antennas Rx1, Rx2, and Rx3 is set to 1.5 times the wavelength of the radio wave used (1.5λ) or less. This makes it possible to appropriately improve the isolation characteristics without increasing the size of the antenna module 400.

[0109] The antenna module 400 (antenna array) also has a shielding layer 41 provided on the surface 10a of the dielectric layer 10 between the first conductor layer 21 of the transmitting antenna Tx and the first conductor layer 21 of the receiving antennas Rx1, Rx2, and Rx3. This shielding layer 41 is capable of blocking unwanted electric fields (radio waves) that directly enter the receiving antennas Rx1, Rx2, and Rx3 from the transmitting antenna Tx.

[0110] The shielding layer 41 is formed in a ring shape (and strip shape) on the surface 10a of the dielectric layer 10 so as to surround the first conductor layer 21 of the transmitting antenna Tx. In this example, the shielding layer 41 is formed in a rectangular ring shape, but it may have another shape, such as an elliptical ring shape.

[0111] The shielding layer 41 is typically a metal layer formed on the surface 10a of the dielectric layer 10. Examples of metal materials used for the shielding layer 41 include copper and aluminum, but the material is not particularly limited. The material may be the same as or different from the first conductor layer 21 and the second conductor layer 22. The thickness of the shielding layer 41 is also not particularly limited, and may be the same as or different from the thickness of the first conductor layer 21 and the second conductor layer 22.

[0112] In this example, the outer periphery of the shielding layer 41 is 3.5 mm x 3.5 mm (X-axis x Y-axis), and the width (band width) of the shielding layer 41 is 0.25 mm. In the Y-axis direction, the distance between the inner periphery of the shielding layer 41 and the long side of the first conductor layer 21 of the transmitting antenna Tx is 1 mm. In the X-axis direction, the distance between the inner periphery of the shielding layer 41 and the short side of the first conductor layer 21 of the transmitting antenna Tx is 0.6 mm.

[0113] The antenna module 400 (antenna array) also has a plurality of third interlayer connections 42. The third interlayer connections 42 penetrate the dielectric layer 10 in its thickness direction (Z-axis direction) and electrically connect between the shielding layer 41 and the second conductor layer 22. The third interlayer connections 42 are cylindrical conductors, similar to the first interlayer connections 31 and the second interlayer connections 32, and are formed by through-hole plating provided in the dielectric layer 10 or buried vias filled with a conductive material.

[0114] Because the third interlayer connection portion 42 is connected perpendicularly to the shielding layer 41 and the second conductor layer 22, the length (height) of the third interlayer connection portion 42 corresponds to the thickness (0.65 mm) of the dielectric layer 10. The diameter of the third interlayer connection portion 42 is, for example, the same as the width (band width) of the shielding layer 41. The diameter of the third interlayer connection portion 42 may be the same as or different from those of the first interlayer connection portion 31 and the second interlayer connection portion 32.

[0115] The multiple third interlayer connections 42 are arranged at predetermined intervals (0.8 mm) along the circumferential direction of the shielding layer 41. In this example, the multiple third interlayer connections 42 are not provided around the entire circumference of the shielding layer 41, but are provided along a portion of the entire circumference of the shielding layer 41. Specifically, the multiple third interlayer connections 42 are provided at a location corresponding to one side along the Y-axis direction (the side between the transmitting antenna Tx and the receiving antenna Rx) and two sides along the X-axis direction, among the four sides of the rectangle of the shielding layer 41. The multiple third interlayer connections 42 may also be provided around the entire circumference of the shielding layer 41.

[0116] Here, the shielding layer 41 is connected to the second conductor layer 22 via a plurality of third interlayer connectors 42. Since the second conductor layer 22 is grounded, the shielding layer 41 is also set to ground potential. By setting the shielding layer 41 to ground potential in this way, it is possible to appropriately shield the electric field (radio waves) from the transmitting antenna Tx to the receiving antennas Rx1, Rx2, and Rx3.

[0117] Fig. 44 is a diagram showing the isolation characteristics of the antenna module 400. In Fig. 44, the horizontal axis represents the frequency [GHz] of the radio waves used in the antenna element 100, and the vertical axis represents the isolation characteristics [dB]. Note that a lower value [dB] on the vertical axis means higher isolation characteristics.

[0118] Also, in Figure 44, three graphs respectively show the isolation characteristics of receiving antenna Rx1 relative to transmitting antenna Tx (Tx → Rx1), the isolation characteristics of receiving antenna Rx2 relative to transmitting antenna Tx (Tx → Rx2), and the isolation characteristics of receiving antenna Rx3 relative to transmitting antenna Tx (Tx → Rx3).

[0119] Also, in the upper right corner of FIG. 44, a map (in thermography format) is shown for visualizing the influence of the transmitting antenna Tx on the receiving antennas Rx1, Rx2, and Rx3.

[0120] 41 (second embodiment), the graphs of Tx→Rx1, Tx→Rx2, and Tx→Rx3 all tend to slope downward overall. This means that the fourth embodiment, which is a combination of the above-mentioned (A) "cutout portion 210," (B) "distance D," and (C) "shielding layer 42," has further improved isolation characteristics compared to the second embodiment, which uses only the above-mentioned (A) "cutout portion."

[0121] Furthermore, in the three graphs in Fig. 44, the value indicating the isolation characteristic is set to approximately 30 [dB] or less. In this way, by setting the value indicating the isolation characteristic to 30 [dB] or less, sufficient isolation characteristics can be obtained.

[0122] As described above, in the fourth embodiment, the shielding layer 41 (metal layer) that shields the electric field from the transmitting antenna Tx to the receiving antennas Rx1, Rx2, and Rx3 is provided between the first conductor layer 21 of the transmitting antenna Tx and the first conductor layer 21 of the receiving antennas Rx1, Rx2, and Rx3 on the surface 10a of the dielectric layer 10. This makes it possible to further improve the isolation characteristics of the receiving antennas Rx1, Rx2, and Rx3 from the transmitting antenna Tx.

[0123] In the fourth embodiment, the shielding layer 41 is formed in a ring shape on the surface 10a of the dielectric layer 10 so as to surround the first conductor layer 21 of the transmitting antenna Tx. This makes it possible to further improve the isolation characteristics of the receiving antennas Rx1, Rx2, and Rx3 from the transmitting antenna Tx.

[0124] Furthermore, in the fourth embodiment, a third interlayer connector 42 is provided that penetrates the dielectric layer 10 and connects between the shielding layer 41 and the second conductor layer 22. This allows the shielding layer 41 to be at ground potential, and allows appropriate shielding of the electric field (radio waves) from the transmitting antenna Tx to the receiving antennas Rx1, Rx2, and Rx3.

[0125] In the fourth embodiment, the third interlayer connection portion 42 is a through-hole plating or a buried via provided in the dielectric layer 10. This allows for an appropriate connection between the shielding layer 41 and the second conductor layer 22.

[0126] Furthermore, in the fourth embodiment, when the wavelength of the radio waves used is λ and the distance in the planar direction between the center position of the transmitting antenna Tx and the center positions of the receiving antennas Rx1, Rx2, and Rx3 is D, the relationship 0.5λ≦D≦1.5λ is satisfied. By setting the distance D to a length equal to or greater than half the wavelength (½λ), the isolation characteristics of the receiving antennas Rx1, Rx2, and Rx3 relative to the transmitting antenna Tx can be further improved. Furthermore, by setting the distance D to 1.5 times (1.5λ) or less the wavelength of the radio waves used, the isolation characteristics can be appropriately improved without increasing the size of the antenna module 400.

[0127] <Various Modifications of the Fourth Embodiment> Next, various modifications of the fourth embodiment will be described.

[0128] In the above-described fourth embodiment, a case has been described in which three combinations of (A) "cutout portion 210", (B) "distance D", and (C) "shielding layer 42" are used. On the other hand, the combination of (A) "cutout portion 210", (B) "distance D", and (C) "shielding layer 42" may be any of the following combinations: 1. Configuration of (A) "cutout portion 210" only (second embodiment) 2. Configuration of (B) "distance D" only 3. Configuration of (C) "shielding layer 42" only 4. Configuration of combination of (A) "cutout portion 210" and (B) "distance D" 5. Configuration of combination of (A) "cutout portion 210" and (C) "shielding layer 42" 6. Configuration of combination of (B) "distance D" and (C) "shielding layer 42" 7. (A) Combination of "Notch 210", (B) "Distance D", and (C) "Shielding layer 42" (Fourth embodiment)

[0129] Here, in the case of a configuration including the "shielding layer 42" in (C) above, that is, in the four configurations of 3, 5, 6, and 7 above, (c) the "third interlayer connection 42" may be provided, or (c) the "third interlayer connection 42" may be omitted. Therefore, the four configurations of 3, 5, 6, and 7 above are branched into two depending on whether or not the (c) "third interlayer connection 42" is provided, and either of these configurations may be used. Note that the above-mentioned fourth embodiment has representatively described a configuration that is a combination of the three configurations of 7. (A) "notch 210", (B), and (C) and includes (c).

[0130] Here, a typical example of the combination of (A) "notch 210" and (B) "distance D" in the above 4. will be described.

[0131] Fig. 45 is a see-through perspective view of an antenna module 500 according to a modification of the fourth embodiment. In the antenna module 500 shown in Fig. 45, the shielding portion 41 and the third interlayer connection portion 42 are omitted compared to the antenna module 400 shown in Fig. 42. The rest is the same as Fig. 42.

[0132] In the antenna module 500, the first conductor layers 21 of the transmitting antenna Tx and the receiving antennas Rx1, Rx2, and Rx are each provided with a notch 210 on the short sides that face each other in the X-axis direction. In addition, the distance D between the center position of the transmitting antenna Tx and the centers of the three receiving antennas Rx1, Rx3, and Rx3 in the XY directions (planar directions) is 5 mm. In other words, the distance D satisfies the condition 0.5λ≦D≦1.5λ.

[0133] Fig. 46 is a diagram showing the isolation characteristics of the antenna module 500. In Fig. 46, the horizontal axis represents the frequency [GHz] of the radio waves used in the antenna element 100, and the vertical axis represents the isolation characteristics [dB]. Note that a lower value [dB] on the vertical axis indicates higher isolation characteristics.

[0134] Also, in Figure 46, three graphs respectively show the isolation characteristics of receiving antenna Rx1 relative to transmitting antenna Tx (Tx → Rx1), the isolation characteristics of receiving antenna Rx2 relative to transmitting antenna Tx (Tx → Rx2), and the isolation characteristics of receiving antenna Rx3 relative to transmitting antenna Tx (Tx → Rx3).

[0135] Also, in the upper right corner of FIG. 46, a map (in thermography format) is shown for visualizing the influence of the transmitting antenna Tx on the receiving antennas Rx1, Rx2, and Rx3.

[0136] 46 (variant of the fourth embodiment) with FIG. 41 (second embodiment), the graphs of Tx→Rx1, Tx→Rx2, and Tx→Rx3 all tend to slope downward overall. This means that the variant of the fourth embodiment, which is a combination of (A) "cutout portion 210" and (B) "distance D," has further improved isolation characteristics compared to the second embodiment, which uses only (A) "cutout portion."

[0137] In the above description, the shielding layer 41 entirely surrounds the first conductor layer 21 of the transmitting antenna Tx. However, the shielding layer 41 may be formed so as to partially surround the first conductor layer 21 of the transmitting antenna Tx. Typically, the shielding layer 41 may be formed so as to be interposed between the first conductor layer 21 of the transmitting antenna Tx and the first conductor layer 21 of the receiving antennas Rx1, Rx2, and Rx3.

[0138] In the above description, the shielding layer 41 surrounds the transmitting antenna Tx, but the shielding layer 42 may be formed to surround (partially or entirely) the receiving antennas Rx1, Rx2, and Rx3. In this case, the shielding layer 41 may be formed to surround entirely all three receiving antennas Rx1, Rx2, and Rx3, or may be formed to surround each of the three receiving antennas Rx1, Rx2, and Rx3 individually.

[0139] When the shielding layer 41 is provided on the receiving antennas Rx1, Rx2, and Rx3 side, typically, a third interlayer connector 42 is provided on the shielding layer 41, and the shielding layer 41 is set to the ground potential.

[0140] Here, when the shielding layer 41 is provided on the receiving antennas Rx1, Rx2, and Rx3 side, if the shielding layer 41 is not set to ground potential, it has been found from experimental results that the shielding layer 41 adversely affects the isolation characteristics. This is because if the shielding layer 41 that is not grounded is provided near the receiving antennas Rx1, Rx2, and Rx3, the shielding layer 41 acts as a bridge for the electric field (radio wave) from the transmitting antenna Tx to the receiving antennas Rx1, Rx2, and Rx3. Therefore, when the shielding layer 41 is provided on the receiving antennas Rx1, Rx2, and Rx3 side, a third interlayer connector 42 is typically provided in the shielding layer 41, and the shielding layer 41 is set to ground potential.

[0141] The present technology may also be configured as follows. (1) An antenna element including: a first conductor layer having a planar element shape; a second conductor layer connected to a ground potential; a dielectric layer provided between the first conductor layer and the second conductor layer; a first inter-layer connection portion that penetrates the dielectric layer and connects the first conductor layer to a power feed portion; and a second inter-layer connection portion that penetrates the dielectric layer and connects the first conductor layer and the second conductor layer. (2) The antenna element described in (1) above, wherein the first conductor layer is formed with an area smaller than that of the second conductor layer. (3) The antenna element described in (2) above, wherein a loop length formed by the first inter-layer connection portion, the first conductor layer, and the second inter-layer connection portion is equal to or shorter than one wavelength of a used radio wave. (4) The antenna element described in (3) above, wherein the loop length is a length equivalent to half the wavelength of a used radio wave. (5) The antenna element according to any one of (2) to (4) above, wherein the planar shape of the first conductor layer is a rectangle having long sides and short sides. (6) The antenna element according to (5) above, wherein the first conductor layer has a first region to which the first inter-layer connection portion is connected and a second region to which the second inter-layer connection portion is connected, and the first region and the second region are arranged at a distance from the peripheral edge of the first conductor layer. (7) The antenna element according to (6) above, wherein the first region and the second region are arranged in a direction parallel to the long sides. (8) The antenna element according to (6) or (7) above, wherein the first region and the second region are arranged in a direction intersecting the direction parallel to the long sides. (9) An antenna element according to any one of (1) to (8) above, wherein the dielectric layer is a dielectric substrate made of a dielectric material, the first conductor layer is a metal layer formed on a first main surface of the dielectric substrate, and the second conductor layer is a metal layer formed on a second main surface of the dielectric substrate opposite to the first main surface.(10) The antenna element according to any one of (1) to (9), wherein the second conductor layer has an opening formed with a diameter larger than an outer diameter of the first inter-layer connection portion. (11) The antenna element according to any one of (1) to (10), wherein the first inter-layer connection portion and the second inter-layer connection portion are through-hole plating or buried vias provided in the dielectric layer. (12) An antenna array comprising a plurality of antenna elements each having a first conductor layer having a planar element shape, a second conductor layer connected to a ground potential, a dielectric layer provided between the first conductor layer and the second conductor layer, a first inter-layer connection portion that penetrates the dielectric layer and connects the first conductor layer to a power feed portion, and a second inter-layer connection portion that penetrates the dielectric layer and connects the first conductor layer and the second conductor layer, wherein the first conductor layer of each of the plurality of antenna elements is arranged on one surface of the dielectric layer. (13) The antenna array according to (12) above, wherein at least one of the plurality of antenna elements is a transmitting antenna element and at least one of the other is a receiving antenna element. (14) The antenna array according to (13) above, wherein the plurality of antenna elements are arranged in a matrix on the surface along a first axis direction and a second axis direction that are orthogonal to each other. (15) The antenna array according to (14) above, wherein the first conductor layer has a rectangular planar shape having long sides parallel to the first axis direction and short sides parallel to the second axis direction, and the opposing short sides of two of the first conductor layers arranged in the first axis direction have cutouts that partially expand the gap between the two first conductor layers. (16) The antenna array according to any one of (12) to (15) above, wherein the second conductor layer of each of the plurality of antenna elements is formed from a common conductor layer.(17) The antenna array according to any one of (13) to (16) above, further comprising: a shielding layer provided on the surface of the dielectric layer between the first conductor layer of the transmitting antenna element and the first conductor layer of the receiving antenna element, shielding an electric field from the transmitting antenna element to the receiving antenna. (18) The antenna array according to (17) above, wherein the shielding layer is formed in a ring shape on the surface of the dielectric layer so as to surround the first conductor layer of the transmitting antenna element. (19) The antenna array according to (17) or (18) above, further comprising: a third interlayer connection portion that penetrates the dielectric layer and connects the shielding layer and the second conductor layer. (20) The antenna array according to (19) above, wherein the third interlayer connection portion is a through-hole plating or a buried via provided in the dielectric layer. (21) The antenna array according to any one of (17) to (20) above, wherein the shielding layer is a metal layer formed on the surface of the dielectric layer. (22) The antenna array according to any one of (13) to (21) above, wherein the plurality of antenna elements include one transmitting antenna element and multiple receiving antenna elements, and wherein, when the wavelength of the radio wave used is λ and the distance in a planar direction between the center position of the one transmitting antenna element and the center positions of the multiple receiving antenna elements is D, 0.5λ≦D is satisfied. (23) The antenna array according to (22) above, wherein D≦1.5λ is satisfied. (24) An antenna module comprising: a plurality of antenna elements each having a first conductor layer having a planar element shape; a second conductor layer connected to a ground potential; a dielectric layer provided between the first conductor layer and the second conductor layer; a first interlayer connection portion penetrating the dielectric layer and connecting the first conductor layer to a power supply portion; and a second interlayer connection portion penetrating the dielectric layer and connecting between the first conductor layer and the second conductor layer; and a signal processing circuit connected to the plurality of antenna elements.

[0142] REFERENCE SIGNS LIST 10...Dielectric layer 10a...First main surface 10b...Second main surface 21...First conductor layer 22...Second conductor layer 22a...Opening 31...First interlayer connection portion 32...Second interlayer connection portion 41...Shielding layer 42...Third interlayer connection portion 100, 151 to 156...Antenna element 200...Antenna array 210...Notch portion 300, 400, 500...Antenna module 301...Signal processing circuit

Claims

1. An antenna element comprising: a first conductor layer having a planar element shape; a second conductor layer connected to a ground potential; a dielectric layer provided between the first conductor layer and the second conductor layer; a first interlayer connection portion that penetrates the dielectric layer and connects the first conductor layer to a power supply portion; and a second interlayer connection portion that penetrates the dielectric layer and connects between the first conductor layer and the second conductor layer.

2. An antenna element according to claim 1, wherein the first conductor layer is formed with an area smaller than that of the second conductor layer.

3. An antenna element as claimed in claim 2, wherein the length of the loop formed by the first interlayer connection part, the first conductor layer and the second interlayer connection part is equal to or less than one wavelength of the radio wave used.

4. An antenna element according to claim 3, wherein the loop length is equivalent to a half wavelength of the radio wave used.

5. An antenna element according to claim 2, wherein the planar shape of the first conductor layer is a rectangle having long and short sides.

6. An antenna element as claimed in claim 5, wherein the first conductor layer has a first region to which the first interlayer connection part is connected and a second region to which the second interlayer connection part is connected, and the first region and the second region are arranged at a distance from the peripheral edge of the first conductor layer.

7. An antenna element according to claim 6, wherein the first region and the second region are arranged in a direction parallel to the long side.

8. An antenna element according to claim 6, wherein the first region and the second region are arranged in a direction intersecting a direction parallel to the long side.

9. An antenna element as claimed in claim 1, wherein the dielectric layer is a dielectric substrate made of a dielectric material, the first conductor layer is a metal layer formed on a first main surface of the dielectric substrate, and the second conductor layer is a metal layer formed on a second main surface of the dielectric substrate opposite to the first main surface.

10. An antenna element as claimed in claim 1, wherein said second conductor layer has an opening formed with a diameter larger than the outer diameter of said first interlayer connection portion.

11. An antenna element according to claim 1, wherein the first interlayer connection portion and the second interlayer connection portion are through-hole plating or buried vias provided in the dielectric layer.

12. An antenna array comprising a plurality of antenna elements each having a first conductor layer of a planar element shape, a second conductor layer connected to ground potential, a dielectric layer provided between the first conductor layer and the second conductor layer, a first interlayer connection portion penetrating the dielectric layer and connecting the first conductor layer to a power supply portion, and a second interlayer connection portion penetrating the dielectric layer and connecting between the first conductor layer and the second conductor layer, wherein the first conductor layer of each of the plurality of antenna elements is arranged on one surface of the dielectric layer.

13. An antenna array according to claim 12, wherein at least one of said plurality of antenna elements is a transmitting antenna element and at least one of said plurality of antenna elements is a receiving antenna element.

14. An antenna array according to claim 13, wherein the plurality of antenna elements are arranged in a matrix on the surface along a first axis direction and a second axis direction which are mutually orthogonal.

15. An antenna array as described in claim 14, wherein the first conductor layer has a rectangular planar shape having long sides parallel to the first axial direction and short sides parallel to the second axial direction, and the opposing short sides of the two first conductor layers arranged in the first axial direction have cutout portions that partially expand the gap between the two first conductor layers.

16. An antenna array as claimed in claim 12, wherein the second conductor layer of each of the plurality of antenna elements is formed from a common conductor layer.

17. An antenna array as claimed in claim 13, further comprising a shielding layer provided on the surface of the dielectric layer between the first conductor layer of the transmitting antenna element and the first conductor layer of the receiving antenna element, for shielding an electric field from the transmitting antenna element to the receiving antenna.

18. An antenna array according to claim 17, wherein the shielding layer is formed in an annular shape on the surface of the dielectric layer so as to surround the first conductor layer of the transmitting antenna element.

19. An antenna array as claimed in claim 17, further comprising a third interlayer connection portion penetrating said dielectric layer and connecting between said shielding layer and said second conductor layer.

20. An antenna array according to claim 19, wherein the third interlayer connection is a through-hole plating or a buried via provided in the dielectric layer.

21. An antenna array according to claim 17, wherein the shielding layer is a metal layer formed on the surface of the dielectric layer.

22. An antenna array as claimed in claim 13, wherein the plurality of antenna elements include one transmitting antenna element and a plurality of receiving antenna elements, and wherein, when the wavelength of the radio wave used is λ and the distance in a planar direction between the central position of the one transmitting antenna element and the central positions of the plurality of receiving antenna elements is D, 0.5λ≦D is satisfied.

23. The antenna array of claim 22, wherein D≦1.5λ.

24. An antenna module comprising: a plurality of antenna elements each having a first conductor layer having a planar element shape; a second conductor layer connected to a ground potential; a dielectric layer provided between the first conductor layer and the second conductor layer; a first interlayer connection portion penetrating the dielectric layer and connecting the first conductor layer to a power supply portion; and a second interlayer connection portion penetrating the dielectric layer and connecting between the first conductor layer and the second conductor layer; and a signal processing circuit connected to the plurality of antenna elements.

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