Patent Application
20240072441
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2022-138652, filed on Aug. 31, 2022, the entire contents of which are incorporated herein by reference.
Embodiments relate to antenna device and radar device.
For an antenna with directivity in a direction parallel to the substrate, a technique of using strip conductors as a feed element and directors of a planar Yagi-Uda antenna is known. Another example is post-wall waveguides or substrate integrated waveguides (SIWs), which are techniques of forming an antenna with a directivity in a direction parallel to the substrate, using a waveguide structure in which two rows of conductor vias are continuously arranged on parallel plates or dielectric substrate with metal top and bottom surfaces, and using a director formed from a strip conductor and conductor via.
However, the aforementioned techniques all have a problem in that the antenna device cannot be designed to have the desired directivity due to the influence of the substrate unless the substrate thickness is sufficiently small relative to the operating wavelength of the antenna device (i.e., the wavelength of the radio wave to be transmitted or received by the antenna device).
An antenna device typically includes an antenna, a power supply component that supplies power, a radio frequency integrated circuit (RFIC), and a controller component for the antenna device. These components can be placed on a substrate by surface mount technology (SMT) and connected together via a conductive pattern formed on the substrate. Furthermore, if the substrate is multilayered and conductive patterns are formed on a plurality of layers, complex wiring can be accommodated in a single substrate.
On the other hand, to multilayer a substrate, it is necessary to increase the layer thickness of the substrate according to the number of layers. Although flame retardant type 4 (FR-4) substrates are widely used for power lines and wiring between components, these substrates are not suitable for use in high-frequency bands such as the millimeter wave band due to their high transmission loss. High-frequency substrates made of low-dielectric-loss materials are suitable as substrates for transmitting signals in high-frequency bands.
In antenna devices for high-frequency bands such as the millimeter wave band, laminated substrates are often used, in which feeding lines and feed elements are formed on or inside of high-frequency substrates, wiring for various components such as controller components of antenna devices is formed on or inside of generic substrates such as FR-4 substrates, which are less expensive than high-frequency substrates, and these substrates are bonded together with prepregs or other materials. In this configuration, the substrate thickness becomes thicker, and in high-frequency bands such as the millimeter wave band, the substrate thickness may be non-negligible in relation to the operating wavelength of the antenna device. In such cases antenna devices that use the direction parallel to the substrate's surface or inclined from the substrate's surface as the target direction of radiation have a problem in that the directivity of the antenna device does not match the desired target direction of radiation due to the influence of the substrate thickness.
According to one embodiment, an antenna device includes a substrate; a feed element provided on or inside the substrate; a feeder line provided on or inside the substrate and configured to feed power to the feed element; and at least one of a director provided on or inside the substrate and away from the feed element, and a reflector provided on or inside the substrate and away from the feed element, wherein the substrate includes a first portion having a first thickness and a second portion having a second thickness greater than the first thickness, at least one of at least a part of the feed element and at least a part of the director is provided on or inside the first portion, and at least a part of the feeder line is provided on or inside the second portion.
This embodiment will now be described in detail with reference to the accompanying drawings. In the following description, the X-, Y-, and Z-axes represent mutually orthogonal axes, and the +X-, +Y-, and +Z-axis directions represent positive directions parallel to the X-, Y-, and Z-axes, respectively. The −X-, −Y-, and −Z-axis directions represent negative directions parallel to the X-, Y-, and Z-axes, respectively. When simply referred to as the X-, Y-, and Z-axes, each includes both + and − directions along the X-, Y-, and Z-axes, respectively.
The antenna device according to the first embodiment will now be described with reference to
The antenna device 100 according to the first embodiment shown in
The antenna device 100 includes a substrate 101, a grounding conductor 104, a first feeder line 105, a balun 106, a second feeder line 107, a feed element 108, a director 109, a via 110a, a via 110b, a via 110c, and a via 110d.
The substrate 101 includes a high-frequency substrate 102 (first substrate) and a generic substrate 103 (second substrate). The high-frequency substrate 102 includes a high-frequency substrate 102a, a high-frequency substrate 102b, and a high-frequency substrate 102c. The high-frequency substrates 102a to 102c are also referred to as substrates 102a to 102c.
The generic substrate 103 includes a generic substrate 103a and a generic substrate 103b. The generic substrates 103a and 103b are also referred to as substrates 103a and 103b.
The substrate 101 includes a substrate's surface 203, a substrate's surface 204, and a substrate's surface 205.
The high-frequency substrate 102 (first substrate) and the generic substrate 103 (second substrate) are stacked in the first direction (Z-axis direction) perpendicular to the substrate's surface 203 of the substrate 101, thereby forming the substrate 101.
The substrate 101 includes a first portion 201 having a first thickness and a second portion 202 having a second thickness with respect to the second direction (Y-axis direction) parallel to the substrate's surface 203. The first thickness is approximately equal to the thickness of the high-frequency substrate 102. The second thickness is approximately equal to the combined thickness of the high-frequency substrate 102 and the generic substrate 103. Thus, the first thickness is thinner than the second thickness. The generic substrate 103 has a shorter length than the high-frequency substrate 102 with respect to the Y-axis direction.
The grounding conductor 104 includes a first grounding conductor 104a, a second grounding conductor 104b, a third grounding conductor 104c, a fourth grounding conductor 104d, and a fifth grounding conductor 104e, each of which has a planar shape. The first grounding conductor 104a, the second grounding conductor 104b, the third grounding conductor 104c, the fourth grounding conductor 104d and the fifth grounding conductor 104e are also referred to as the grounding conductor 104a, the grounding conductor 104b, the grounding conductor 104c, the grounding conductor 104d, and grounding conductor 104e, respectively.
The first feeder line 105, the balun 106, the second feeder line 107, the feed element 108 (radiator element), and the director 109 are formed as a metal pattern between the substrate 102a and substrate 102b in the high-frequency substrate 102. To be specific, this metal pattern is provided on or inside the substrate 102b: more specifically, with its surface exposed, the metal pattern is embedded in a part of the surface area of the substrate 102b. The first grounding conductor 104a is formed on the substrate's surface 203. The second grounding conductor 104b is formed inside the high-frequency substrate 102. To be specific, with its surface exposed, the second grounding conductor 104b is embedded in a part of the surface area of the high-frequency substrate 102c. The third grounding conductor 104c is formed at the boundary between the high-frequency substrate 102 and the generic substrate 103. The fourth grounding conductor 104d is formed inside the generic substrate 103. The fifth grounding conductor 104e is formed on the substrate's surface 204.
The second feeder line 107 includes a feeder line 107a and a feeder line 107b. The feed element 108 includes a feed element portion 108a and a feed element portion 108b. At least a part of the second feeder line 107 is provided inside or on the second portion 202 of the substrate 101. In the example shown in
The substrate 101 is composed mainly of dielectric material. Examples include resin substrates of flame retardant type 4 (FR-4), polytetrafluoroethylene (PTFE), modified polyphenylene ether (PPE) and the like; film substrates made mainly of resin foam, liquid crystal polymer, polyimide and the like; ceramic substrates; and glass substrates. The substrate 101 may also be a flexible substrate with flexibility.
The substrate 101 in the antenna device 100 includes a substrate's surface 203, a substrate's surface 204, and a substrate's surface 205. For example, the substrate's surface 203 may have surface mount technology (SMT) components and electronic circuits mounted on it, and the substrate's surface 204 may have the fifth grounding conductor 104e formed on it. The antenna device 100 may include a plurality of grounding conductors, and the grounding conductors may be formed not only on but inside the substrate. The grounding conductors should not necessarily be formed on or inside the substrate. For instance, a conductor via may be formed in the substrate and brought into conduction for grounding by making it into contact with or soldering it to a grounding conductor located outside the substrate.
The substrate 101 should not necessarily be composed of a single dielectric material, but may be composed of a combination of a plurality of materials. For instance, a substrate may be composed of a plurality of identical dielectric materials bonded together with a prepreg or bonding film. Alternatively, the substrate may be composed of a plurality of dielectric materials having different electrical characteristics, such as a high-frequency substrate made of low dielectric loss material and a generic substrate such as an FR-4 substrate bonded and laminated together with prepregs, bonding films, or the like.
In the antenna device 100 according to the first embodiment, the substrate 101 is composed of a laminated substrate of the high-frequency substrate 102 and generic substrate 103. The high-frequency substrate 102 is composed of a laminated substrate of the substrates 102a, 102b, and 102c. The generic substrate 103 is composed of a laminated substrate of the substrates 103a and 103b.
When a substrate formed from a high-frequency substrate and a generic substrate bonded together is used to compose an antenna device, it is possible to form feeder lines, feed elements, directors, and the like for high frequencies on the high-frequency substrate and electronic circuits on or inside the generic substrate, for example. A high-frequency substrate is a substrate suitable for transmission of high-frequency (e.g., frequencies of 1 GHz or higher) signals and is composed of a material that has a low dielectric loss tangent and low transmission loss to high frequencies. Forming feeder lines, feed elements, directors, and the like on a high-frequency substrate reduces dielectric loss and enhances the characteristics of the antenna device. Although the antenna device may be composed of only a high-frequency substrate, high-frequency substrates, which use materials with the aforementioned characteristics, are generally more expensive than generic substrates. Generic substrates are less affected by transmission loss and the like to low frequencies (e.g., frequencies below 1 GHz), and are less expensive because they are composed of low-cost materials such as FR-4 but are not suitable for high frequencies due to their high transmission loss. For this reason, forming an electronic circuit on or inside the generic substrate while forming a feed element and director on the high-frequency substrate makes it possible to reduce the manufacturing cost of the antenna device while enhancing the characteristics of the antenna device.
The electronic circuit mounted on the substrate 101 is a circuit having, for example, at least one of the following functions: a transmission function for transmitting signals via the feed element 108 and the director 109, and a reception function for receiving signals via the feed element 108 and the director 109. An electronic circuit includes, for example, an integrated circuit (IC) chip. The electronic circuit includes, for example, a radio frequency integrated circuit (RFIC) chip that processes the high-frequency signals transmitted or received by the antenna device 100.
The antenna device 100 has a first feeder line 105 and a second feeder line 107. Examples of feeder lines include microstrip lines, strip lines, coplanar lines, coplanar lines with ground (coplanar lines with a grounding conductor facing signal lines), and slot lines. Other examples of feeder lines include feeder lines formed from two rows of conductor vias continuously aligned on parallel plates or dielectric substrate with metal top and bottom surfaces, which are called post-wall waveguides or substrate integrated waveguides (SIWs). The antenna device 100 may, for example, have a plurality of feeder lines having the same or different shapes. The feeder lines may be formed inside the substrate 101 or on the substrate 101. In the examples shown in
The first feeder line 105 and the second feeder line 107 are connected together, for example, through the balun 106. Herein, a balun is defined as any device that brings mutual conversion between balanced and unbalanced lines. In the antenna device 100 according to the first embodiment, the first feeder line 105 is an unbalanced line and the second feeder line 107 is a balanced line.
In the antenna device 100 according to the first embodiment, the balun 106 shown in
The antenna device 100 according to the first embodiment includes a feed element 108. The feed element 108 includes, for example, a feed element portion 108a and a feed element portion 108b. The feed element 108 is connected to the end of the second feeder line 107. The feed elements may be formed inside the substrate 101 or on the substrate 101. For instance, the feed element 108 is a conductive pattern formed inside the high-frequency substrate 102 in the first portion 201. The feed element in the antenna device 100 according to the first embodiment may feed power in a noncontact manner, for example, by electromagnetic field coupling with a feeder line. The feed element may be formed across the first portion 201 and the second portion 202.
The feed element 108 has a conductive portion having a longitudinal direction along, for example, the X-axis shown in
The antenna device 100 according to the first embodiment includes at least one director 109 distanced from the feed element 108 in a particular direction (in
The length of the director 109 is preferably shorter than that of the feed element 108.
The feed element 108 and the director 109 are preferably arranged in such a manner that their longitudinal directions are parallel or approximately parallel. The distance between the feed element 108 and the director 109 (the minimum distance between the feed element 108 and the director 109) d1 is preferably 0.2 to 0.3 times the operating wavelength λ of the feed element 108.
The director 109 and the feed element 108 may be either in the same plane or different planes. Similarly, if the antenna device includes a plurality of directors (see
As shown in
The grounding conductors 104a to 104e, particularly the outer edges Ta to Te of these grounding conductors act as reflectors, for example, to reflect electromagnetic waves radiated from the feed element 108 and electromagnetic waves arriving at the antenna device 100. The longitudinal direction of the feed element 108 and the outer edges Ta to Te of the grounding conductors used as reflectors are preferably parallel or approximately parallel. The distance between the feed element 108 and the reflectors (outer edges Ta to Te), i.e., the minimum distance between the feed element 108 and the reflectors (d2 in
Although the antenna device 100 includes a single antenna formed from a feed element 108 and a director 109 in the example shown in
For instance, when the antenna device has two antennas, one of the antennas may be an antenna as that in the antenna device 100 formed from a feed element 108 and a director 109 which are composed of a conductive pattern. The other antenna may be composed, for example, of a feeder line, a feed element, and a director in such a manner that a SIW is provided as the feeder line and the feed element formed from a conductive pattern and vias is provided in an open-end of the SIW provided on the side surface of the substrate having the SIW, and the director formed from a conductive pattern and vias away from the feed element is provided.
Even in an antenna device with an antenna composed of a SIW, a feed element, and a director, the substrate of the antenna device has a first portion having a first thickness and a second portion having a second thickness. In addition, at least one of at least a part of the feed element and at least a part of the director is formed in the first portion having the first thickness, thereby achieving the same effect as the antenna device 100.
As mentioned above, in
As mentioned above, a reflector is formed on or inside the substrate 101 so that it is located on the opposite side of the radiation direction as seen from the feed element 108. As mentioned above, in the antenna device 100 according to the first embodiment shown in
The antenna device 100 only needs to include at least one of a director and a reflector. For example, even when the antenna device 100 shown in
In
The antenna device 100 according to the first embodiment will be described below in comparison with the antenna device according to a comparative example.
When an antenna device is formed by laminating a high-frequency substrate and a generic substrate together, as in the antenna device 100a according to the comparative example shown in
However, in the configuration of the antenna device 100 according to the comparative example, the thickness of, of the substrate 1001, a part of the substrate where the feed element 108 and the director 109 are formed is thicker than the that of a part of the substrate where the feed element 108 and the director 109 are formed in the antenna device 100 according to the first embodiment (the first portion 201). In the antenna device 100a according to the first embodiment, the thickness of the first portion 201 where the feed element 108 and the director 109 are formed approximately equal to that of the high-frequency substrate 102. Meanwhile, in the antenna device 100a according to the comparative example, the thickness of the substrate 1001 is not dependent on the position and is approximately equal to the combined thickness of the high-frequency substrate 102 and the generic substrate 1003. Hence, in the antenna device 100a according to the comparative example, the thickness of a part of the substrate where the feed element 108 and the director 109 are formed is approximately equal to the combined thickness of the high-frequency substrate 102 and the generic substrate 1003.
The thickness of an area of the substrate where at least part of the feed element or director is formed affects the operating characteristics of the feed element and director. If the thickness of the substrate is sufficiently small in relation to the operating wavelength λ of the feed element, the electrical properties of the substrate (e.g., relative permittivity) have little impact on the operation of the feed element and director.
However, in high-frequency bands such as the millimeter wave band, the thickness of the substrate and the operating wavelength λ of the feed element are about the same degree. The higher the relative permittivity of the area where at least part of the feed element or director is formed, the more difficult it becomes to achieve impedance matching between the feed element and director and the free space, making it difficult to design an antenna device that achieves the desired target direction of radiation. In addition, the longer the electrical length from the surface of the substrate to the feed element or director, the more difficult it becomes to achieve impedance matching between the feed element and director and the free space, making it difficult to design an antenna device that achieves the desired target direction of radiation. In other words, in the area of the substrate where at least a part of the feed element or director is formed, the substrate thickness is preferably thin and the relative permittivity of the substrate is preferably low.
In the antenna device 100 according to the first embodiment shown in
Meanwhile, in the antenna device 100a according to the comparative example, the distance from the feed element 108 and director 109 to the substrate's surface of the substrate 1001 located in the +Z-axis direction, i.e., the distance from the feed element 108 and director 109 to the substrate's surface 203 is approximately equal to the thickness of the substrate 102a. The distance from the feed element 108 and director 109 to the substrate's surface of the substrate 1001 located in the −Z-axis direction, i.e., the distance from the feed element 108 and director 109 to the substrate's surface 204 is approximately equal to the combined thickness of the substrates 102b and 102c and generic substrate 1003.
In the antenna device 100a according to the comparative example shown in
However, in the antenna device 100a according to the comparative example shown in
According to the antenna device 100 according to the first embodiment, the thickness (first thickness) of the first portion 201 of the substrate 101 where at least part of the feed element 108 or director 109 is made thinner than the thickness (second thickness) of the second portion 202. This allows the gap between the electrical length from the feed element 108 and director 109 to the substrate's surface located in the +Z-axis direction and the electrical length to the substrate's surface located in the −Z-axis direction to be small compared with the antenna device 100a according to the comparative example. Thus, it is possible to solve the problem that the asymmetric shape between the patterns of radiation in the +Z- and −Z-axis directions with respect to the XY plane of the antenna device 100a according to the comparative example becomes larger.
In the antenna device 100 according to the first embodiment, the thickness of the first portion 201 does not depend on the thickness of the second portion 202. Therefore, using a substrate sufficiently thin compared to the operating wavelength λ of the feed element 108 for the first portion 201 makes it easy to design the antenna device that achieves the target direction of radiation compared with the antenna device 100a according to the comparative example.
The antenna device 100 according to the first embodiment and the antenna device 100a according to the comparative example transmit or receive horizontally polarized waves, i.e., polarized waves parallel to the XY plane shown in
In
In
In
Referring to
As explained above, in the antenna device 100 according to the first embodiment, the substrate 101 has a first portion having a first thickness along a direction parallel to the surface of the substrate 101 and a second portion having a second thickness, and the first thickness is smaller than the second thickness. At least a part of the feed element 108 or at least a part of the director 109 is formed in the first portion 201. This can reduce radiation pattern distortion caused by the thickness of the first portion where at least a part of the feed element 108 or at least a part of the director 109 is formed. It can also reduce the difference between the target direction of radiation of the antenna device 100 and the direction of radiation of the antenna device 100, which enables high-gain antenna operation.
In addition, the antenna device 100 according to the first embodiment provides the aforementioned advantageous effects independently of the thickness of the second portion 202 having the second thickness. Therefore, there is no need to reduce the thickness of the second portion 202. This makes it possible to reduce restrictions on the number of substrate layers and substrate thickness of the second portion 202 when wiring power lines, those for control signals, and the like, forming electronic circuits, and mounting surface mount technology components, such as IC chips, in the second portion 202 having the second thickness. As a result, greater design freedom of the antenna device can be achieved.
Although the antenna device 100 according to the aforementioned first embodiment includes director, the antenna device 100 may include a plurality of directors.
The feed element 108, director 109a, and director 109b are preferably arranged so that they are parallel or approximately parallel. The distance between the feed element 108 and the director 109a and the distance between the director 109a and the director 109b are both preferably 0.2 to 0.3 times the operating wavelength A of the feed element 108, as the distance d1 between the feed element 108 and the director 109 according to the first embodiment (the shortest distance between the feed element 108 and the director 109). Although Modification 1 in
Although the antenna device 100 according to the aforementioned first embodiment uses the outer edge of the grounded conductor as a reflector, alternatively, for example, a reflector may be formed using a conductive pattern having a longitudinal direction along a direction orthogonal to the radiation direction (direction along the X-axis in
The antenna device 125 includes a reflector formed using a conductive pattern 112 having a longitudinal direction along a direction orthogonal to the radiation direction (direction along the X-axis in
The conductive patterns 112a and 112b, particularly side surfaces (outer edges) Tf and Tg adjacent to the feed element 108 with respect to the X-axis direction function as reflectors. The length of the conductive patterns 112a and 112b is preferably larger than the length of the feed element 108. The feed element 108 and the conductive patterns 112a and 112b are preferably arranged parallel or approximately parallel with each other, and the distance between the feed element 108 and the conductive patterns 112a and 112b (the shortest distance between the feed element 108 and the reflector: the distance d22 in
The reflectors formed using the conductive patterns 112a and 112b may be on the same or different planes as the feed element 108. The antenna device 100 may include a plurality of reflectors formed using a conductive pattern. When the reflectors are formed using a conductive pattern having a longitudinal direction along a direction orthogonal to the radiation direction (along the X-axis in
An antenna device according to the second embodiment will be described with reference to
Descriptions of, among the configurations in the second embodiment, configurations similar to those in the first embodiment will be omitted or simplified by referring to the description of the first embodiment above.
The antenna device 130 has a first portion 201 having a first thickness and a second portions 202a, 202b, and 202c having a second thickness. The antenna device 130 has a plurality of second portions. The antenna device 130 differs from the antenna device 100 according to the first embodiment in that it has a plurality of portions having the second thickness.
The thickness (first thickness) of the first portion 201 where at least a part of the feed element 108 or at least a part of the director 109 is formed is smaller than the second thickness of the second portions 202a, 202b, and 202c of the substrate.
The portion of the substrate having the first thickness is thinner than the portion of the substrate having the second thickness and may be deformed or broken, for example, when external force is applied to the substrate. For this reason, a plurality of portions having the second thickness are formed as in the antenna device 130 shown in
In
The second portion 202a having the second thickness includes a part of the high-frequency substrate 102 and the substrates 103a and 103b. The second portion 202b having the second thickness (see
At least a part of the feed element 108 or at least a part of the director 109 is formed in the first portion 201 having the first thickness.
The results of the radiation pattern analysis shown in
An antenna formed from a feed element portion 108a, a feed element portion 108b, and a director 109a is fed from the end on the +Y-axis side of the parallel two lines formed from feeder lines 107a and 107b. The antenna formed from the feed element portions 108c and 108d and the director 109b is fed from the end on the +Y-axis side of the parallel two-wire line formed from the feeder lines 107c and 107d.
The antenna device 140 includes first portions 201a and 201b having a first thickness, and a second portion 202 having a second thickness. This configuration also provides the effect of reinforcing the portions having the first thickness as in the antenna device 130. The first portions 201a and 201b are distanced in a direction parallel to the X-axis (third direction), but may also be distanced in a direction parallel to the Y-axis (second direction).
As in the third embodiment, the configuration with a plurality of portions having the first thickness can achieve high-gain antenna operation by reducing the difference between the target direction of radiation (i.e., the +Y-axis direction, 0° in
Still another modification of the second embodiment can be a configuration including a plurality of portions having a first thickness and a plurality of portions having a second thickness. In this case also, high-gain antenna operation can be achieved by reducing the difference between the target direction of radiation (i.e., the +Y-axis direction, 0° in
The antenna device according to the third embodiment will now be described with reference to
In the antenna device 150, the thickness of the first portion 201 where at least a part of the feed element 108 or at least a part of the director 109 is formed (first thickness), i.e., the first thickness is smaller than the thickness of the second portion 202 (second thickness).
The first portion 201 having the first thickness has a smaller substrate thickness than the portion 202 having the second thickness and may thus be deformed or broken when external force is applied to the substrate. To avoid this, as in the antenna device 150, for example, the first portion 201 having the first thickness is reinforced with a low dielectric constant material 151 (dielectric layer). The low dielectric constant material 151 is in contact with the first portion 201 from the opposite side of the surface 203 of the substrate in a direction perpendicular to the surface of the substrate (first direction).
The antenna device 150 includes a low dielectric constant material 151. The relative permittivity of the low dielectric constant material 151 is lower than those of all substrates included in the substrate 101 (e.g., the substrates 102a, 102b, and 102c constituting the high-frequency substrate 102, and the substrates 103a and 103b constituting the generic substrate 103 in the antenna device 150). Examples of the low dielectric constant material include synthetic resins, such as polyurethane, polypropylene, polyimide, polystyrene, melamine resin, and silicone, and porous or foamed materials formed by foaming polymer compounds.
The thickness of the low dielectric constant material 151 is approximately equal to the thickness of the generic substrate 103. The length of the low dielectric constant material 151 in the X-axis direction is approximately equal to L3 shown in
The outer shape of the low dielectric constant material 151 viewed from the +Z-axis direction is not necessarily rectangular or square and may have, for example, convex or concave portions, and the outer edge of the low dielectric constant material 151 may have a curve. The low dielectric constant material 151 may have, for example, a cylindrical or rectangular cavity.
The antenna device 150 may have a plurality of portions having the first thickness like the antenna device 140 (see
The low dielectric constant material 151 is placed in contact with the substrate's surface 205 of the substrate 101, for example. The low dielectric constant material 151 may be simply placed in contact with the substrate's surface 205 or, for example, fixed in place by bonding it with a material such as an adhesive or prepreg, or bonded adhesively with a material, such as an adhesive or double-sided tape. Alternatively, the low dielectric constant material placed in contact with the substrate's surface 205 of the substrate 101 may be placed by, for example, fixing it using a jig.
The thickness of, of the substrate in the antenna device 150, the substrate in the first portion 201 where at least a part of the feed element 108 or at least a part of the director 109 is formed, i.e., the first thickness is smaller than that of the second portion 202. This reduces the difference between the target direction of radiation of the antenna device 150 and the direction of radiation of the antenna device. In this case, the relative permittivity of the low dielectric constant material 151 is sufficiently low, so that even when the antenna device 150 includes a low dielectric constant material, the low dielectric constant material has a low impact on the impedance matching between the antenna and the free space. Therefore, even when the antenna device 150 includes the low dielectric constant material 151, as in the antenna device 100 according to the first embodiment, the difference between the target direction of radiation of the antenna device and the direction of radiation of the antenna device can be made smaller than in the antenna device according to the comparative example.
The length of the low dielectric constant material 151 in the antenna device 150 in the X-axis direction is approximately equal to L3 shown in
The results in
The antenna device 155 includes a plurality of low dielectric constant materials 151a and 151b. These low dielectric constant materials may be made of the same material or different materials. These low dielectric constant materials may have the same shape or different shapes. The low dielectric constant material 151a is placed so that its surface to the +Z-axis direction is in contact with the substrate's surface 205, for example. The low dielectric constant material 151b is placed so that its surface to the +Z-axis direction is in contact with the surface of the low dielectric constant material 151a to the −Z-axis direction. The combined thickness of the low dielectric constant material 151a and the low dielectric constant material 151b is approximately equal to the thickness of, for example, the generic substrate 103.
The antenna device 155 may include a plurality of portions having the first thickness like the antenna device 140 (see
When the antenna device includes a plurality of low dielectric constant materials, as in the case where only a single dielectric is used, they may be placed so that the substrate and low dielectric constant material can be in contact with each other or the low dielectric constant materials can be in contact with each other or, for example, fixed in place by bonding it with a material such as an adhesive or prepreg, or bonded adhesively with a material, such as an adhesive or double-sided tape. Alternatively, the low dielectric constant materials may be placed by, for example, fixing them using a jig.
An antenna device according to the fourth embodiment will now be described with reference to
The antenna device 160 according to the fourth embodiment includes a cylindrical support 161a and a cylindrical support 161b. The supports 161a and 161b have circular or generally circular end surfaces parallel to, for example, the XY plane and have a longitudinal direction parallel or generally parallel to the Z-axis. The length of the support 161 in the Z-axis direction is approximately equal to the thickness of the generic substrate 103. The supports 161a and 161b are placed so that their circular or generally circular end surfaces are in contact with the substrate's surface 205. The supports 161a and 161b are used to reinforce the first portion 201 to prevent the antenna device 160 from being deformed or broken when, for example, external force is applied to the antenna device 160. The shape of the supports 161a and 161b may be, for example, a rectangular, hexagonal, or octagonal.
The supports 161a and 161b may be simply placed in contact with the substrate's surface 205 or, for example, fixed in place by bonding it with an adhesive, or fixed adhesively with an adhesive or double-sided tape. Alternatively, for example, screw holes may be provided in the supports 161a and 161b and through holes in the first portion 201, and screws are passed through the through holes from the +Z-axis direction so that the supports 161a and 161b placed in contact with the substrate's surface 205 may be fastened with the screws. This fixes the supports 161a and 161b.
Examples of the material for the supports 161a and 161b include insulators, such as resin, rubber, and glass, and metals, such as aluminum, iron, and stainless steel. The shapes and materials of the supports may all be the same or may differ from each other. Although the example shown in
If a support is formed in a portion of the substrate 101 including the feed element 108 and the director 109, as in the antenna device 100a according to the comparative example, the difference between the target direction of radiation of the antenna device and the direction of radiation of the antenna device becomes large. Alternatively, the support may cause the electromagnetic waves transmitted or received by the antenna device to diffract and distort the radiation pattern.
For this reason, the supports 161a and 161b are provided in positions distanced from the feed element 108 and the director 109 when viewed from a direction perpendicular to the surface of the substrate 101. To be specific, the supports 161a and 161b in the XY plane are provided in positions distanced above and below the feed element 108 and the director 109 (in +X-axis and −X-axis directions). This reduces the risk of a large difference between the target direction of radiation and the radiation direction due to the influence of the supports, or reduces the risk of distortion of the radiation pattern. The supports may be provided in positions distanced in the Y-axis direction. The supports may be provided in positions distanced in at least one of the X-axis and Y-axis directions.
A material with a relative permittivity lower than that of the substrate may be used as the material for the supports. This makes the characteristics of the antenna device 160 less susceptible to the influence of the presence of the supports for the same reason as in the third embodiment. Consequently, even if the supports are provided in positions close to the feed element 108 and the director 109 in the XY plane, the same characteristics of the antenna device as in the third embodiment can be obtained.
In the case of electromagnetic field analysis of directivity in
The results in
The antenna device according to the fifth embodiment will now be described with reference to
Descriptions of, among the configurations in the fifth embodiment, configurations similar to those in the first embodiment will be omitted or simplified by referring to the description of the first embodiment above.
In the antenna device 100 according to the first embodiment, the side surfaces of the generic substrate 103 are always parallel or generally parallel to the Z-axis. Therefore, the first portion 201 having the first thickness and the second portion 202 having the second thickness have boundary surfaces that are generally parallel to the Z-axis.
In other words, since the substrate has a generally sheet-like shape, the side surfaces of the substrate are plane surfaces perpendicular or generally perpendicular to the top surface. For this reason, in the case where the antenna device is formed by laminating substrates, the boundary surface between the first portion 201 having the first thickness and the second portion 202 having the second thickness is parallel or generally parallel to the Z-axis.
Here, a generic substrate and a high-frequency substrate that have the same shape may be laminated and the substrates may be processed with a cutting machine, substrate processing machine, router processing machine, or numerical control (NC) machine, thereby forming a portion having the first thickness and a portion having the second thickness in the substrates included in the antenna device.
In this case, for example, the corners of the processed part are usually rounded (so-called corner R) because processing so-called sharp angles (i.e., angular shapes) with a cutting machine takes time. For this reason, as shown in
In addition, as in the antenna device 170b shown in
Thus, in the antenna devices 170a, 170b, and 170c shown in
Similarly, when the antenna device has at least one of a plurality of first portions or a plurality of second portions, the thicknesses of the substrates in the antenna device may vary continuously or discretely from the first portion having the first thickness toward the second portion having the second thickness. In this case also, if at least a part of the director or at least a part of the power feed element in the antenna device is formed in the first portion having the first thickness, the same advantageous effects as in the antenna device 100 are obtained.
The antenna device according to the sixth embodiment will now be described with reference to
The antenna device 180 has a conductor 182 on, of the boundary surface between the first portion 201 having the first thickness and the second portion 202 having the second thickness, the boundary surface 181 located at the side surface of the generic substrate 103 on the +Y-axis side.
The conductor 182 is a conductor with a surface parallel or generally parallel to the XZ plane, and placed in contact with the boundary surface 181 (the side surface of the generic substrate 103 on the +Y-axis side). The conductor 182 is provided on the side surface (boundary surface 181) of the second portion 202 adjacent to the first portion 201. The length of the conductor 182 in the Z-axis direction is approximately equal to the thickness of the generic substrate 103, and it is placed in contact with the fifth grounding conductor 104e. The conductor 182 should not necessarily be in contact with the grounding conductor included in the antenna device 180.
The conductor 182 may be formed, for example, by plating the side surfaces of the substrate 101 included in the antenna device 180 and placing it on the boundary surface 181. Alternatively, the conductor 182 may be formed by, for example, attaching a conductive tape using a conductor, such as an aluminum foil or copper foil, as a base to the boundary surface 181. Alternatively, a thin plate made of a conductor, for example, may be placed in contact with the boundary surface 181.
It is possible that the radio waves transmitted from the antenna device 180 do not only travel in the target direction of radiation of the antenna device 180, but also in a direction from the feed element 108 toward the interior of the antenna device 180 through the boundary surface 181. Alternatively, the radio waves received by the antenna device 180 may travel directly from the direction of arrival of the radio waves or by reflection or diffraction at the antenna device or outside the device, toward the interior of the antenna device 180 through the boundary surface 181.
If radio waves transmitted or received by the antenna device 180 enter the interior of the antenna device 180 from the boundary surface 181, these radio waves may affect the operation of the device. For example, if radio waves transmitted by the antenna device 180 may pass through the boundary surface 181 and excite electronic circuits such as RFICs in the antenna device 180 and cause, for example, interference with signals received by the RFICs, which may interfere with the operation of the antenna device 180.
When the boundary surface 181 is covered by the conductor 182, radio waves transmitted or received by the antenna device 180 and entering the antenna device 180 through the boundary surface 181 are suppressed by the conductor 182. This prevents, for example, radio waves from entering the antenna device 180 through the boundary surface 181 and reduces interference with the electronic circuits and the like in the antenna device 180, thereby improving the operating characteristics of the antenna device.
The conductor 182, which controls radio waves from traveling toward the interior of the antenna device 180, can also function, for example, as a reflector that reflects the radio waves transmitted or received by the antenna device 180.
A radar device according to the seventh embodiment will now be described with reference to
Descriptions of, among the configurations in the seventh embodiment, configurations similar to those in the first embodiment will be omitted or simplified by referring to the description of the first embodiment above.
The radar device in
The signal processor 310 in the processor circuit 301 generates control voltage for forming transmission signals by the frequency modulated continuous wave (FMCW) scheme. The D/A converter 311 converts digital voltages generated by the signal processor 310 into analog voltages and give them to the voltage-controlled oscillator (VCO) 312. The VCO 312 generates transmission signals with a continuously varying wavelength. The directional coupler 313 outputs a part of the signal output from the VCO 312, to the circulator 315 and another part of the signal as a local signal to the mixer 317. The circulator 315 outputs the signal input from the directional coupler 313 to the antenna device 314. In the antenna device 314, the input signal is fed to the feed element 108 through, for example, the feeder line 105, and radio waves are radiated from the feed element 108 into space. The reflected waves from the target are received at the feed element 108. A signal based on the received reflected wave is output from the antenna device 314 through, for example, the feeder line 105 and is input to the circulator 315. The circulator 315 outputs the signal input from the antenna device 314 to the low noise amplifier (LNA) 316. The mixer 317 combines the received signal that has been amplified by the LNA 316 and the local signal that has been input to the mixer 317 through the directional coupler 313 to generate a beat signal. The generated beat signal is converted from an analog signal to a digital signal by the A/D converter 318 and is input to the signal processor 310. The signal processor 310 performs signal processing on the input beat signal based on the FMCW algorithm to calculate the relative speed of the target, relative distance, intensity of reflected waves from the target, and the like. The antenna device 314 may be an array antenna including a plurality of antennas (a plurality of feed elements).
In the radar device shown in
The antenna devices 314a and 314b in the radar device in
Although this embodiment has described the radar device based on the FMCW scheme, radar devices based on other schemes may also be used as long as they include the antenna device with the configuration described herein.
While certain embodiment have been described, these embodiment have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
The embodiments as described before may be configured as below.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-138652 | Aug 2022 | JP | national |
