Antenna module and communication device equipped with it

Abstract

To improve the radiation efficiency of the antenna module. [Solution] The antenna module 100 comprises a dielectric substrate 125, a radiating element 121, a ground electrode 140, a strip-shaped coupling wire 130H, and a strip-shaped ground wire 132H. The dielectric substrate has an upper surface 126 and a lower surface 127, and a plurality of dielectric layers are stacked on it. The radiating element is placed on the dielectric substrate. The ground electrode is placed between the radiating element and the lower surface, facing the radiating element. The coupling wire is placed between the radiating element and the ground electrode and extends in the positive direction of the X axis. The ground wire is placed between the coupling wire and the ground electrode and extends in the positive direction of the X axis. The coupling wire transmits a high-frequency signal to the feed point 121HP of the radiating element by capacitive coupling. When the dielectric substrate is viewed in plan from the stacking direction, the radiating element overlaps with a part of the coupling wire, and the coupling wire overlaps with the ground wire.

Description

[Technical Field]

[0001] The present disclosure relates to an antenna module and a communication device equipped with the same, and more specifically relates to a technique for improving the radiation efficiency of an antenna module. [Background Art]

[0002] In a general antenna module, as a method for feeding power to a radiating element, a method called via feeding is known, in which a feeding wiring and the radiating element are directly connected by a via to supply power. However, along with the trend toward higher frequencies in communication, the influence of a decrease in radiation efficiency of an antenna module caused by conductor loss from vias, reflection loss from via pads, conduction defects due to formation failures, and the like is becoming more prominent. To address such problems, in an antenna module, a method called proximity coupled feeding is sometimes used as a method for feeding power to a radiating element, in which the feeding wiring and the radiating element are indirectly coupled by capacitive coupling instead of vias for feeding.

[0003] For example, the paper "Terahertz Antenna-in-Package Design and Measurement for 6G Communications Systems" (Non-Patent Document 1) discloses an antenna module that transmits a high-frequency signal to a radiating element using proximity coupled feeding. [Prior Art Documents] [Non-Patent Documents]

[0004] [Non-Patent Document 1] Jung Dongjin et al.,“Terahertz Antenna-in-Package Design and Measurement for 6G Communications Systems”,IEEE Transactions on Antennas and Propagation,vol. 72,issue 2,pp. 1085-1096,February 2024 [Summary of the Invention] [Problems that the invention aims to solve]

[0005] When using close-range coupled feeding, it is desirable to use a narrow feed line to minimize the influence of the feed line on the electromagnetic field coupling between the radiating element and the ground electrode. To match the impedance between the radiating element and the feed line, it is necessary to reduce the distance between the radiating element and the feed line as the feed line becomes narrower, thereby ensuring sufficient capacitance between them. Here, since the feed line and the ground electrode form a microstrip line, the ground electrode also needs to be brought closer to the feed line in order to maintain the characteristic impedance of the feed line. However, in this case, the distance between the radiating element and the ground electrode becomes shorter, which can strengthen the coupling between the radiating element and the ground electrode, potentially reducing the radiation efficiency of the antenna module.

[0006] This disclosure was made to solve these problems, and its purpose is to improve the radiation efficiency of antenna modules. [Means for solving the problem]

[0007] An antenna module according to a certain aspect of this disclosure comprises a dielectric substrate, a radiating element, a ground electrode, a strip-shaped first coupling wiring, and a strip-shaped first ground wiring. The dielectric substrate has a first main surface and a second main surface, and a plurality of dielectric layers are laminated therein. The radiating element is disposed on the dielectric substrate. The ground electrode is disposed between the radiating element and the second main surface, facing the radiating element. The first coupling wiring is disposed between the radiating element and the ground electrode and extends in a first direction. The first ground wiring is disposed between the first coupling wiring and the ground electrode and extends in a first direction. The first coupling wiring transmits a high-frequency signal to a first feed point of the radiating element by capacitive coupling. When the dielectric substrate is viewed in plan from the lamination direction, the radiating element overlaps with a portion of the first coupling wiring, and the first coupling wiring overlaps with the first ground wiring. [Effects of the Invention]

[0008] In the antenna module of this disclosure, a strip-shaped grounding wire is placed between the coupling wire for close-range coupled feeding and the grounding electrode for the radiating element to form a microstrip line. By doing so, the coupling between the radiating element and the grounding wire can be weakened while maintaining the distance between the radiating element and the grounding electrode, thereby improving the radiation efficiency of the antenna module. [Brief explanation of the drawing]

[0009] [Figure 1] This is a block diagram of a communication device to which the antenna module according to Embodiment 1 is applied. [Figure 2] These are a plan view and a side perspective view of the antenna module according to Embodiment 1. [Figure 3] These are a plan view and a side perspective view of an antenna module related to a comparative example. [Figure 4] These are a plan view and a partial side perspective view of an antenna module designed for maximum radiation efficiency. [Figure 5] This diagram illustrates the arrangement of coupling wires when they are placed as close together as possible. [Figure 6] This graph shows the relationship between the area ratio S1 / S2 and the radiative efficiency. [Figure 7] These are a plan view and a side perspective view of the antenna module according to Embodiment 2. [Figure 8] These are a plan view and a side perspective view of the antenna module according to Embodiment 3. [Modes for carrying out the invention]

[0010] The embodiments of this disclosure will be described in detail below with reference to the drawings. Note that the same or equivalent lines in the drawings are denoted by the same reference numerals, and their descriptions will not be repeated.

[0011] [Embodiment 1] (Basic configuration of communication equipment) Figure 1 is a block diagram of a communication device 10 to which the antenna module 100 according to Embodiment 1 is applied. The communication device 10 is, for example, a mobile terminal such as a mobile phone, smartphone or tablet, or a personal computer equipped with communication functions. An example of the frequency band of radio waves used in the antenna module 100 according to Embodiment 1 is, for example, millimeter-wave radio waves with center frequencies of 28 GHz, 39 GHz and 60 GHz, but it is also applicable to radio waves in frequency bands other than those mentioned above.

[0012] Referring to Figure 1, the communication device 10 comprises an antenna module 100 and a BBIC 200 that constitutes a baseband signal processing circuit. The antenna module 100 comprises an RFIC 110 that supplies high-frequency signals, an antenna device 120, and power supply lines 131, 132, 133, and 134. The communication device 10 upconverts the signal transmitted from the BBIC 200 to the antenna module 100 into a high-frequency signal and radiates it from the antenna device 120 via the power supply lines 131-134 and the RFIC 110. The communication device 10 also downconverts the high-frequency signal received by the antenna device 120 and processes the signal in the BBIC 200 via the power supply lines 131-134.

[0013] The antenna device 120 includes a dielectric substrate 125 on which multiple radiating elements are arranged. In Figure 1, a configuration in which radiating elements 121, 122, 123, and 124 are arranged on the dielectric substrate 125 is shown as an example, but the number of radiating elements arranged on the dielectric substrate 125 is not limited to this; at least one radiating element is sufficient. Also, in Figure 1, an example is shown in which the radiating elements 121 to 124 are arranged in a one-dimensional array in a single line on the dielectric substrate 125, but the radiating elements 121 to 124 may also be arranged in a two-dimensional array. In Embodiment 1, the radiating elements 121 to 124 are described as patch antennas having a substantially square flat plate shape, but the shape of the radiating elements 121 to 124 may be circular, elliptical, or other polygons such as hexagons.

[0014] RFIC 110 comprises switches 111A-111D, 113A-113D, 117, power amplifiers 112AT-112DT, low-noise amplifiers 112AR-112DR, attenuators 114A-114D, phase shifters 115A-115D, a signal combiner / divider 116, a mixer 118, and an amplifier circuit 119.

[0015] When transmitting a high-frequency signal, the switches 111A-111D and 113A-113D are switched to the power amplifier 112AT-112DT side, and the switch 117 is connected to the transmission-side amplifier of the amplifier circuit 119. When receiving a high-frequency signal, the switches 111A-111D and 113A-113D are switched to the low-noise amplifier 112AR-112DR side, and the switch 117 is connected to the reception-side amplifier of the amplifier circuit 119.

[0016] A signal transmitted from BBIC 200 is amplified by the amplifier circuit 119 and up-converted by the mixer 118. The up-converted high-frequency transmission signal is split into four by the signal combiner / divider 116, passes through corresponding signal paths, and is fed to radiating elements 121-124 via feeding wirings 131-134, respectively.

[0017] By individually adjusting the phase shift degrees of the phase shifters 115A-115D arranged in each signal path, the directivity of high-frequency radio waves radiated from the radiating elements 121-124 on the dielectric substrate 125 can be adjusted. Furthermore, the attenuators 114A-114D adjust the intensity of the transmission signal.

[0018] Reception signals, which are high-frequency signals received by the radiating elements 121-124, are transmitted to the RFIC 110 via the feeding wirings 131-134, pass through corresponding signal paths, and are combined in the signal combiner / divider 116. The combined reception signal is down-converted by the mixer 118, further amplified by the amplifier circuit 119, and transmitted to the BBIC 200.

[0019] BFIC 110 is formed, for example, as a one-chip integrated circuit component including the above circuit configuration. Alternatively, devices (switches, power amplifiers, low-noise amplifiers, attenuators, phase shifters) corresponding to each radiation element in BFIC 110 may be formed as a one-chip integrated circuit component for each corresponding radiation element.

[0020] (Structure of Antenna Module) Next, the configuration of the antenna module 100 according to Embodiment 1 will be described in detail with reference to FIG. 2. FIG. 2 is a plan view (upper diagram (a)) and a side perspective view (lower diagram (b)) of the antenna module 100 according to Embodiment 1.

[0021] The antenna module 100 is a so-called dual-polarization type antenna module capable of radiating radio waves in two different polarization directions. Referring to FIG. 2, the antenna module 100 includes the antenna device 120 shown in FIG. 1 and a feeding circuit 180.

[0022] The antenna device 120 includes a dielectric substrate 125, a radiation element 121, feeding wirings 131H and 131V, ground wirings 132H and 132V, a ground electrode 140, and solder bumps 144.

[0023] The dielectric substrate 125 is, for example, a multilayer resin substrate formed by laminating a plurality of resin layers made of resin such as epoxy or polyimide, or a low temperature co-fired ceramics (LTCC) multilayer substrate. Alternatively, the dielectric substrate 125 is, for example, a multilayer resin substrate formed by laminating a plurality of resin layers made of liquid crystal polymer (LCP) having a lower dielectric constant. Further, the dielectric substrate 125 may be, for example, a multilayer resin substrate formed by laminating a plurality of resin layers made of fluorine-based resin.

[0024] Furthermore, the dielectric substrate 125 is, for example, a multilayer resin substrate formed by laminating multiple resin layers made of PET (Polyethylene Terephthalate) material, or a ceramic multilayer substrate other than LTCC. Note that the dielectric substrate 125 does not necessarily have a multilayer structure; it may be a single-layer substrate.

[0025] The dielectric substrate 125 has a flat plate shape with two main surfaces. When viewed from above from the direction normal to the main surfaces, the dielectric substrate 125 has a roughly rectangular shape. In the following description, the direction normal to the main surfaces will be referred to as the Z-axis direction, the direction along the long side of the main surfaces as the X-axis direction, and the direction along the short side of the main surfaces as the Y-axis direction. Furthermore, the positive Z-axis direction may be referred to as upward, and the negative Z-axis direction as downward.

[0026] The dielectric substrate 125 has an upper surface 126, which is the main surface in the positive Z-axis direction, and a lower surface 127, which is the main surface in the negative Z-axis direction, and has a structure in which multiple dielectric layers are stacked. On the upper surface 126, the radiating element 121 is arranged so as to be exposed on the upper surface 126 of the dielectric substrate 125. Note that each radiating element may be arranged in a layer close to the upper surface 126 inside the dielectric substrate 125. In the following description, the case in which one radiating element is arranged on the dielectric substrate 125 as an antenna device 120 will be described, but two or more radiating elements may be arranged on the dielectric substrate 125. In this case, an additional radiating element is arranged in the positive X-axis direction from the radiating element 121.

[0027] The ground electrode 140 is positioned in the dielectric layer between the radiating element 121 and the lower surface 127, facing the radiating element 121. When the dielectric substrate 125 is viewed in plan from the Z-axis direction, the ground electrode 140 is almost the same size as the dielectric substrate 125.

[0028] A power supply circuit 180 is located on the lower surface 127 of the dielectric substrate 125 via solder bumps 144. The power supply circuit 180 is, for example, a System in Package (SiP) and includes the RFIC 110 described in Figure 1. Although not shown in the figure, the power supply circuit 180 may also include a Power Management Integrated Circuit (PMIC) and power inductors to control the power supply to the RFIC 110.

[0029] High-frequency signals are supplied to the radiating element 121 from the RFIC 110 included in the power supply circuit 180 via power supply wiring 131H located on the dielectric substrate 125. Power supply wiring 131H includes coupling wiring 130H, vias 133H and 135H, and wiring pattern 134H. Coupling wiring 130H and wiring pattern 134H are portions of power supply wiring 131H that extend in the XY direction and are located on the main surface of the dielectric layer. Vias 133H and 135H are portions of power supply wiring 131H that penetrate the dielectric layer and extend in the Z-axis direction. More specifically, a through-hole (not shown) is formed in the ground wiring 132H through which via 133H passes, and the ground wiring 132H and via 133H do not come into contact. Also, a through-hole (not shown) is formed in the ground electrode 140 through which via 135H passes, and the ground electrode 140 and via 135H do not come into contact.

[0030] Via 135H is connected to wiring pattern 134H from solder bump 144, through ground electrode 140. The ground electrode 140 may also be located on the bottom surface 127. In the layer between the ground electrode 140 and coupling wiring 130H, wiring pattern 134H extends in the XY plane to below coupling wiring 130H and is connected to coupling wiring 130H via via 133H. Together with the ground electrode 140, wiring pattern 134H constitutes a microstrip line.

[0031] A grounding wire 132H is positioned in the dielectric layer between the coupling wire 130H and the wiring pattern 134H. The grounding wire 132H is positioned between the coupling wire 130H and the grounding electrode 140, and is a strip-shaped electrode slightly larger than the coupling wire 130H. Although not shown in the figure, it is connected to the grounding electrode 140. When viewed from a plan view from the Z-axis direction, the coupling wire 130H overlaps with the grounding wire 132H. Together with the grounding wire 132H, the coupling wire 130H constitutes a microstrip line.

[0032] The coupling wiring 130H is positioned between the radiating element 121 and the ground electrode 140, and is a strip-shaped electrode extending in the X-axis direction, with its positive X-axis end extending below the feed point 121HP on the radiating element 121. In other words, when viewed from a plan view from the Z-axis direction, a portion of the coupling wiring 130H overlaps with the radiating element 121. The feed point 121HP is positioned offset from the center of the radiating element 121 in the negative X-axis direction. The coupling wiring 130H transmits a high-frequency signal to the feed point 121HP of the radiating element 121 by capacitive coupling. When a high-frequency signal with a frequency corresponding to the resonant frequency of the radiating element 121 is supplied from the RFIC 110 to the radiating element 121 via the feed wiring 131H, radio waves with polarization in the X-axis direction are radiated from the radiating element 121 in the positive Z-axis direction.

[0033] Similarly, the radiating element 121 is supplied with a high-frequency signal from the RFIC 110 via a power supply wiring 131V located on the dielectric substrate 125. The power supply wiring 131V includes a coupling wiring 130V, vias 133V and 135V, and a wiring pattern 134V. The coupling wiring 130V and the wiring pattern 134V are portions of the power supply wiring 131V that extend in the XY direction. The vias 133V and 135V are portions of the power supply wiring 131V that penetrate the dielectric layer and extend in the Z-axis direction. More specifically, a through-hole (not shown) is formed in the ground wiring 132V through which via 133V passes, and the ground wiring 132V and via 133V do not come into contact. Also, a through-hole (not shown) is formed in the ground electrode 140 through which via 135V passes, and the ground electrode 140 and via 135V do not come into contact.

[0034] Via 135V connects to wiring pattern 134V, passing through solder bump 144 and ground electrode 140. Wiring pattern 134V extends in the XY plane to below coupling wire 130V in the layer between ground electrode 140 and coupling wire 130V, and connects to coupling wire 130V via via 133V. Wiring pattern 134V, together with ground electrode 140, forms a microstrip line.

[0035] A ground wire 132V is located in the dielectric layer between the coupling wire 130V and the wiring pattern 134V. The ground wire 132V is located between the coupling wire 130V and the ground electrode 140, and is a strip-shaped electrode slightly larger than the coupling wire 130V. Although not shown in the figure, it is connected to the ground electrode 140. The coupling wire 130V and the coupling wire 130H are located in the same dielectric layer, spaced apart from each other, and extend in a direction intersecting the X-axis direction. In Figure 2, the coupling wire 130V extends in the Y-axis direction. When viewed from the Z-axis direction in a plan view, the coupling wire 130V overlaps with the ground wire 132V. The coupling wire 130V, together with the ground wire 132V, constitutes a microstrip line.

[0036] The coupling wire 130V is positioned between the radiating element 121 and the ground electrode 140, and is a strip-shaped electrode extending in the Y-axis direction, with its positive Y-axis end extending below the feed point 121VP on the radiating element 121. In other words, when viewed from a plan view from the Z-axis direction, a portion of the coupling wire 130V overlaps with the radiating element 121. The feed point 121VP is positioned offset from the center of the radiating element 121 in the negative Y-axis direction. The coupling wire 130V transmits a high-frequency signal to the feed point 121VP of the radiating element 121 by capacitive coupling. When a high-frequency signal with a frequency corresponding to the resonant frequency of the radiating element 121 is supplied from the RFIC 110 to the radiating element 121 via the coupling wire 130V, radio waves with polarization in the Y-axis direction are radiated from the radiating element 121 in the positive Z-axis direction.

[0037] The wiring pattern 134H may also be placed on the dielectric substrate 125 between the ground electrode 140 and the bottom surface 127. In this case as well, the wiring pattern 134H, together with the ground electrode 140, constitutes a microstrip line. Similarly, the wiring pattern 134V may also be placed on the dielectric substrate 125 between the ground electrode 140 and the bottom surface 127. In this case as well, the wiring pattern 134V, together with the ground electrode 140, constitutes a microstrip line.

[0038] In typical antenna modules, a method called close-range coupling is sometimes used to feed power to the radiating element. This method involves indirectly connecting the feed wiring and the radiating element via capacitive coupling rather than vias. Compared to via feeding, close-range coupling prevents a decrease in the radiation efficiency of the antenna module caused by conductor loss due to vias, reflection loss due to via pads, and conduction problems due to poor formation.

[0039] When using close-range coupled power supply, it is desirable to use a narrower wire width for the power supply wiring to minimize the influence of the power supply wiring on the electromagnetic field coupling between the radiating element and the ground electrode. In order to match the impedance between the radiating element and the power supply wiring, it is necessary to reduce the distance between the radiating element and the power supply wiring as the power supply wiring becomes narrower, thereby ensuring sufficient capacitance between the radiating element and the power supply wiring.

[0040] Here, the feed line, together with the ground electrode, forms a microstrip line. Therefore, in order to maintain the feed line at its characteristic impedance, the ground electrode also needs to be brought close to the feed line. However, in this case, the distance between the radiating element and the ground electrode becomes shorter, which can increase the coupling between the radiating element and the ground electrode, potentially reducing the radiation efficiency of the antenna module.

[0041] Therefore, in the antenna module according to this disclosure, instead of bringing the ground electrode close to the coupling wiring for close-range coupled feeding, a strip-shaped ground wiring is placed between the coupling wiring and the ground electrode to make the coupling wiring a microstrip line. By doing so, the coupling between the radiating element and the ground wiring can be weakened while maintaining the distance between the radiating element and the ground electrode, thereby improving the radiation efficiency of the antenna module.

[0042] Figure 3 shows a plan view (upper figure (a)) and a side perspective view (lower figure (b)) of the antenna module 100X according to a comparative example. Referring to Figure 3, when close-range coupled feeding is performed in the antenna module 100X, it is desirable for the coupling wires 130H and 130V to be thin in order to reduce the effect of the coupling wires 130H and 130V on the capacitive coupling between the radiating element 121 and the ground electrode 132X. In order to make the coupling wires 130H and 130V thin while maintaining a constant impedance, it is necessary to reduce the distance between the radiating element 121 and the coupling wires 130H and 130V. In this case, in order for the coupling wires 130H and 130V to function as microstrip lines, the ground electrode 132X also needs to be brought close to the radiating element 121, similar to the coupling wires 130H and 130V. However, in this case, the distance between the radiating element 121 and the ground electrode 132X becomes closer, which may lead to increased capacitive coupling between the radiating element 121 and the ground electrode 132X, potentially reducing the radiation efficiency.

[0043] In the antenna module 100 according to Embodiment 1, which performs close-range coupled feeding as described in Figure 2, strip-shaped grounding wires 132H and 132V are placed between the coupling wires 130H and 130V for close-range coupled feeding and the grounding electrode 140 for the radiating element 121, instead of the flat grounding electrode 132X in the comparative example antenna module 100X that performs close-range coupled feeding as described in Figure 3. By adopting this configuration, the coupling between the radiating element 121 and the grounding wires 132H and 132V can be weakened while ensuring the distance between the radiating element 121 and the grounding electrode 140. Therefore, the radiation efficiency of the antenna module 100 can be improved.

[0044] Furthermore, if BA is the distance between the radiating element 121 and the coupling wiring 130H or coupling wiring 130V, and λ is the wavelength of the radio waves transmitted by the radiating element 121 in air, then it is preferable that the distance BA is 0.0065λ or more and 0.0474λ or less (0.0065λ ≤ BA ≤ 0.0474λ).

[0045] Furthermore, if BB is the distance between the radiating element 121 and the grounding wire 132H or grounding wire 132V, then the longer the distance BB, the fewer electric field lines are coupled between the radiating element 121 and the grounding wire 132H or grounding wire 132V, and the relatively larger the electric field lines radiated from the radiating element 121, thus improving the radiation efficiency.

[0046] Furthermore, if the distance between the radiating element 121 and the ground electrode 140 is denoted as BC, the longer the distance BC, the fewer electric field lines are coupled between the radiating element 121 and the ground electrode 140, and the relatively greater the electric field lines emitted from the radiating element 121, thus improving the radiation efficiency. It is also preferable that the distance BC is 0.0439λ or more and 0.0949λ or less (0.0439λ ≤ BC ≤ 0.0949λ).

[0047] Furthermore, the distance between the coupling wire 130H and the grounding wire 132H, or between the coupling wire 130V and the grounding wire 132V, is defined as BD. In this case, the shorter the distance BD is relative to the distance BA, the more electric field lines are coupled between the coupling wire 130H and the grounding wire 132H, or between the coupling wire 130V and the grounding wire 132V, compared to the electric field lines coupled between the radiating element 121 and the coupling wire 130H or coupling wire 130V, and the more electric field lines are coupled between the coupling wire 130H and the grounding wire 132V, the less power is supplied to the radiating element 121. For this reason, it is preferable that the distance BA / BD is 1 or less. That is, since the distance BD is the distance BB-BA, it is preferable that the distance BB is 2BA or more, and the greater the distance BB is, the greater the radiation efficiency. It is preferable that the distance BB is 2BA or more and 6.7143BA or less (2BA ≤ BB ≤ 6.7143BA).

[0048] Next, we will explain in more detail the position of the coupling wiring to the radiating elements in the antenna module. Figure 4 shows a plan view (upper figure (a)) and a partial side perspective view (lower figure (b)) of antenna module 100A, which maximizes radiation efficiency. Note that in lower figure (b), the configuration in which coupling wiring 130HA and 130VA are positioned in the negative Z-axis direction is omitted.

[0049] In an antenna module using close-range coupled feeding, the condition for maximizing radiation efficiency is that, for radio waves with polarization in the X-axis direction, when viewed from a planar perspective from the Z-axis direction, the optimal feeding point 121HP of the radiating element 121 and the optimal transmission point 130HPA of the coupling wiring 130HA coincide.

[0050] The optimal feed point 121HP for the radiating element 121 is the point where the impedance of the radiating element 121 and the coupling wiring 130HA match. More specifically, the optimal feed point 121HP for the radiating element 121 is a point located Δk away from the input point 1P of the radiating element 121 in the positive X-axis direction. Δk varies depending on the length in the Z direction and the relative permittivity of the dielectric substrate 125. If the wavelength of the high-frequency signal of the radio waves transmitted by the radiating element 121 is λ, then Δk is generally between λ / 32 and λ / 8.

[0051] The optimal transmission point 130HPA of the coupling wiring 130HA is the point where the amplitude of the standing wave, created by the interference of the traveling wave and reflected wave on the coupling wiring 130HA, is maximum. Since the positive X-axis end 2P of the coupling wiring 130HA is an open end, the optimal transmission point 130HPA of the coupling wiring 130HA, where the amplitude of the standing wave is maximum, is a point λ / 4 away from end 2P in the negative X-axis direction. In other words, when viewed from a plane from the Z-axis direction, the transmission point 130HPA is a point on the coupling wiring 130HA at a distance of λ / 4 in the X-axis direction from the end of the coupling wiring 130HA that is closer to the center of the radiating element 121.

[0052] Similarly, for radio waves with polarization in the Y-axis direction, the optimal feed point 121VP of the radiating element 121 is a point located Δk away from the input side of the radiating element 121 in the positive Y-axis direction. Also, the optimal transmission point 130VPA of the coupling wiring 130VA is a point located λ / 4 away from the positive Y-axis end of the coupling wiring 130VA in the negative Y-axis direction.

[0053] It is possible to transmit high-frequency signals even if the feed point 121HP and the transmission point 130HPA do not overlap. Furthermore, the closer the feed point 121HP and the transmission point 130HPA are, the greater the radiation efficiency. The same applies to the coupling wiring 130VA.

[0054] Thus, in order to overlap the feed point 121HP and the transmission point 130HPA, the end 2P of coupling wiring 130H must be positioned beyond the center of the radiating element 121 in the positive X-axis direction. However, in the case of dual polarization, there are two coupling wirings extending in different directions. Therefore, as shown in Figure 4, the end of coupling wiring 130VA in the positive Y-axis direction must be positioned beyond the center of the radiating element 121 in the positive Y-axis direction. In that case, coupling wiring 130HA and coupling wiring 130VA will come into contact in the same dielectric layer.

[0055] In reality, when coupling wires 130HA and 130VA come into contact, antenna module 100A loses its isolation and therefore cannot function as a dual-polarization antenna module. Thus, it is practically impossible for antenna module 100A in Figure 4 to radiate radio waves in both polarization directions in the ideal state where radiation efficiency is maximized.

[0056] In a dual-polarization antenna module using close-range coupling, improving radiation efficiency requires bringing the feed point of the radiating element and the transmission point of the coupling wiring as close together as possible while avoiding contact between the two coupling wires. In other words, in a dual-polarization antenna module using close-range coupling, improving radiation efficiency requires bringing the two coupling wires as close as possible to the center of the radiating element 121.

[0057] The coupling wiring 130HA can only approach the center of the radiating element 121 to a position half the length of the coupling wiring 130VA in the X-axis direction (the width of the coupling wiring 130VA). Similarly, the coupling wiring 130VA can only approach the center of the radiating element 121 to a position half the length of the coupling wiring 130HA in the Y-axis direction (the width of the coupling wiring 130HA).

[0058] In other words, in order to bring both coupling wires 130HA and 130VA as close as possible to the center of the radiating element 121 and to bring the optimal feed point and transmission point closer together, it is necessary to narrow the width of coupling wires 130HA and 130VA. Therefore, by narrowing the coupling wires and bringing the two feed wires as close as possible without connecting them to each other, the radiation efficiency of the antenna module can be improved.

[0059] Figure 5 illustrates the arrangement of coupling wires when they are placed as close together as possible. Note that in Figure 5, components other than the radiating elements and coupling wires in the antenna module are omitted.

[0060] Even if coupling wires 130HB and 130VB are brought closer together to bring the optimal power supply point and transmission point closer, they will interfere with each other, so they can only be brought closer to a position half the width of coupling wires 130HA and 130VA.

[0061] On the other hand, coupling wires 130HC and 130VC are thinner (smaller in width) than coupling wires 130HB and 130VB. Furthermore, the end of coupling wire 130HC is positioned as close as possible to the center point of the radiating element 121 on a straight line in the X-axis direction passing through the center point of the radiating element 121.

[0062] As a result, the distance 100DC between the feed point 121HP of the radiating element 121 and the transmission point 130HPC of the coupling wiring 130HC can be made smaller than the distance 100DB between the feed point 121HP of the radiating element 121 and the transmission point 130HPB of the coupling wiring 130HB.

[0063] Thus, the thinner the coupling wire, the closer the two feed wires can be brought, and as a result, the distance between the feed point and the transmission point can be shortened. Therefore, by making the coupling wire thinner, the radiation efficiency of the antenna module can be improved. Note that the ground wires may be connected to each other.

[0064] Furthermore, considering only the coupling wiring, a larger coupling wiring line width results in higher radiation efficiency. For example, if the thickness of one dielectric layer of the dielectric substrate 125 is 0.04 mm and the impedance is 50 Ω, then a coupling wiring line width of 0.09 mm or more is preferable. Therefore, considering only the coupling wiring line width, an antenna module using coupling wiring 130HB is considered to have higher radiation efficiency than coupling wiring 130HC.

[0065] However, in the case of dual-polarization antenna modules, as explained with reference to Figure 5, increasing the width of the coupling wiring increases the distance between the feed point of the radiating element and the transmission point of the coupling wiring, which can actually lead to a decrease in radiation efficiency. Furthermore, increasing the width of the coupling wiring may necessitate increasing the width of the grounding wiring to achieve the desired impedance. In such cases, as will be discussed later, the radiation efficiency may decrease as the degree of overlap between the radiating element and the grounding wiring increases. In other words, increasing the width of the coupling wiring has a trade-off relationship with radiation efficiency. Therefore, the width of the coupling wiring must be determined appropriately, taking the above points into consideration.

[0066] As described above, the radiation efficiency of an antenna module can vary depending on the distance between the radiating element and the ground electrode, the size of the grounding wire, and the position of the feed wire relative to the radiating element. Furthermore, if the degree of overlap between the radiating element and the grounding wire changes, the electric field lines that couple with the grounding wire among the electric field lines generated by the radiating element will change, so the radiation efficiency of the antenna module can also change depending on the degree of overlap between the radiating element and the grounding wire.

[0067] Next, referring to Figure 6, we will explain how the radiation efficiency of the antenna module changes depending on the degree of overlap between the radiating element and the grounding wiring when viewed from above. In the following explanation, the area where the radiating element and the grounding wiring overlap will be denoted as S1, and the total area of ​​the radiating element will be denoted as S2. Note that the area where the radiating element or grounding wiring overlaps with the coupling wiring when the dielectric substrate is viewed from above in the stacking direction will not be deducted from S1. Also, the area of ​​the through-hole formed in the grounding wiring so that the feed wiring vias penetrate the grounding wiring will not be deducted from S1.

[0068] Figure 6 is a graph showing the relationship between the area ratio S1 / S2 and the radiation efficiency. The horizontal axis represents the area ratio S1 / S2, and the vertical axis represents the radiation efficiency of the antenna module. As explained above, the radiation efficiency of the antenna module changes depending on the distance between the feed point of the radiating element and the transmission point of the coupling wiring; therefore, the position of the coupling wiring was fixed when the data in Figure 6 was measured.

[0069] As the overlapping area S1 between the radiating element and the grounding wire increases, the number of electric field lines generated by the radiating element that couple with the grounding wire increases. In Figure 6, as S1 / S2 decreases and the overlapping area with the grounding wire decreases, the radiation efficiency of the antenna module increases.

[0070] Here, for example, if the target radiation efficiency is 70% or more, it can be seen that the area where the radiating element and the grounding wiring overlap should be designed to be 32% or less (S1 / S2 ≤ 32%) of the total area of ​​the radiating element. In the case of a dual-polarization type antenna module, such as the antenna module 100 of Embodiment 1, since it has two coupling wires, when viewed from the Z-axis direction in a plan view, the sum of the area of ​​the coupling wire 130HA overlapping the radiating element 121 and the area of ​​the coupling wire 130VA overlapping the radiating element 121 should be 32% or less of the total area of ​​the radiating element 121. Furthermore, in order to maintain the impedance of the grounding wiring, the area where the radiating element and the grounding wiring overlap is designed to be, for example, 19.8% or more and 32% or less (19.8% ≤ S1 / S2 ≤ 32%) of the total area of ​​the radiating element.Therefore, within the range in which the grounding wiring can maintain impedance, the radiation efficiency of the antenna module can be made to the desired value by minimizing the overlapping area between the radiating element and the grounding wiring as much as possible.

[0071] In Embodiment 1, "coupling wiring 130H" and "coupling wiring 130V" correspond to "first coupling wiring" and "second coupling wiring" in this disclosure, respectively. In Embodiment 1, "grounding wiring 132H" and "grounding wiring 132V" correspond to "first grounding wiring" and "second grounding wiring" in this disclosure, respectively. In Embodiment 1, "power supply point 121HP" and "power supply point 121VP" correspond to "first power supply point" and "second power supply point" in this disclosure, respectively. In Embodiment 1, "transmission point 130HPA" and "transmission point 130VPA" correspond to "first transmission point" and "second transmission point" in this disclosure, respectively.

[0072] [Embodiment 2] In Embodiment 2, a configuration is described in which the radiation efficiency of the antenna module is improved by further reducing the area of ​​the grounding wiring.

[0073] Figure 7 shows a plan view (upper figure (a)) and a side perspective view (lower figure (b)) of the antenna module 100D according to Embodiment 2. Referring to Figure 7, the antenna device 120D of the antenna module 100D according to Embodiment 2 includes divided grounding wires 132HD and 132VD. More specifically, the grounding wires 132HD and 132VD of the antenna module 100D are divided into multiple parts in a direction intersecting the X-axis direction. In Figure 7, the grounding wire 132HD of the antenna module 100D is divided into multiple parts in the Y-axis direction. Also, the grounding wire 132VD of the antenna module 100D is divided into multiple parts in the X-axis direction.

[0074] By adopting this configuration, the area of ​​the grounding wire 132HD becomes smaller than the area of ​​the grounding wire 132H in Embodiment 1. Similarly, the area of ​​the grounding wire 132VD becomes smaller than the area of ​​the grounding wire 132V in Embodiment 1.

[0075] As a result, the coupling between the radiating element 121 and the grounding wires 132HD and 132VD can be made weaker than the coupling between the radiating element 121 and the grounding wires 132H and 132V of the antenna module 100 of Embodiment 1. Therefore, the radiation efficiency of the antenna module can be further improved.

[0076] [Embodiment 3] Embodiments 1 and 2 described a dual-polarization type antenna module capable of radiating radio waves in two different polarization directions from a radiating element. Embodiment 3 describes a configuration in which the features of the present invention are applied to a so-called single-polarization type antenna module that radiates radio waves in a single polarization direction from a radiating element.

[0077] Figure 8 shows a plan view (upper figure (a)) and a side perspective view (lower figure (b)) of the antenna module 100E according to Embodiment 3. Referring to Figure 8, the antenna device 120E of the antenna module 100E according to Embodiment 3 is equipped with only one coupling wire and one grounding wire. Therefore, the two coupling wires for different polarizations do not come into contact with each other, and the coupling wire 130HE and the grounding wire 132HE can be placed in the ideal positions as described in Figure 4.

[0078] In the antenna module 100E, similar to embodiments 1 and 2, a strip-shaped grounding wire 132HE is arranged between the coupling wire 130HE for close-range coupled feeding and the grounding electrode 140 for the radiating element 121 to form a microstrip line. By adopting this configuration, the coupling between the radiating element 121 and the grounding electrode 140 can be weakened while maintaining the distance between the radiating element 121 and the grounding electrode 140, thereby improving the radiation efficiency of the antenna module 100E.

[0079] Furthermore, since the antenna module 100E is equipped with only one coupling wire and one ground wire, the feed point 121HP of the radiating element 121 and the transmission point 130HPE of the coupling wire 130HE can be aligned. Therefore, the radiation efficiency of the antenna module can be further improved.

[0080] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the description of the embodiments above, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of symbols]

[0081] 10 Communication equipment, 100, 100A, 100B, 100C, 100E, 100X Antenna modules, 111A~111D, 113A~113D, 117 Switches, 112AR, 112DR Low-noise amplifiers, 112AT, 112DT Power amplifiers, 114A~114D Attenuators, 115A~115D Phase shifters, 116 Distributors, 118 Mixers, 119 Amplifier circuits, 120, 120A, 120D, 120E, 120X Antenna devices, 121~124 Radiating elements, 125 Dielectric substrates, 130V, 130VA~130VC, 130H, 130HA~130HC, 130HE Coupling wiring, 131V, 131H, 131~134 Power supply wiring: 133V, 133H, 135V, 135H vias: 132V, 132VA~130VD, 132H, 132HA~132HE grounding wiring: 132X, 140 grounding electrodes: 134V, 134H wiring pattern: 144 solder bump: 150 power supply wiring: 180 power supply circuit.

Claims

1. A dielectric substrate having a first main surface and a second main surface, and having multiple dielectric layers stacked on top of each other, A radiating element arranged on the dielectric substrate, Between the radiating element and the second main surface, a ground electrode is positioned opposite the radiating element, A strip-shaped first coupling wire is disposed between the radiating element and the ground electrode and extends in a first direction, The first grounding wiring comprises a strip-shaped first grounding wiring positioned between the first coupling wiring and the grounding electrode, extending in the first direction, The first coupling wiring transmits a high-frequency signal by capacitive coupling to a first feeding point offset in the first direction from the center of the radiating element. When the dielectric substrate is viewed in plan from the stacking direction, The radiating element overlaps with a portion of the first coupling wiring, The first coupling wire overlaps with the first ground wire in the antenna module.

2. The antenna module according to claim 1, wherein the first grounding wire is divided into a plurality of parts in a direction intersecting the first direction.

3. The antenna module according to claim 1 or claim 2, wherein the distance between the radiating element and the ground electrode is at least twice the distance between the radiating element and the first coupling wiring.

4. A strip-shaped second coupling wire is disposed between the radiating element and the ground electrode, and extends in a second direction intersecting the first direction, The system further comprises a strip-shaped second grounding wire positioned between the second coupling wire and the grounding electrode, extending in the second direction, The second coupling wiring transmits a high-frequency signal by capacitive coupling to a second feeding point offset in the second direction from the center of the radiating element. When viewed from the stacking direction, The radiating element overlaps with a portion of the second coupling wiring, The antenna module according to any one of claims 1 to 3, wherein the second coupling wiring overlaps with the second grounding wiring.

5. The antenna module according to claim 4, wherein the first coupling wiring and the second coupling wiring are arranged within the same dielectric layer, spaced apart from each other.

6. The antenna module according to claim 4 or claim 5, wherein the second grounding wire is divided into multiple parts in a direction intersecting the second direction.

7. The antenna module according to any one of claims 4 to 6, wherein the distance between the radiating element and the ground electrode is at least twice the distance between the radiating element and the second coupling wiring.

8. The antenna module according to any one of claims 4 to 7, wherein, when viewed in plan from the stacking direction, the sum of the area of ​​the first grounding wire overlapping the radiating element and the area of ​​the second grounding wire overlapping the radiating element is 32% or less of the area of ​​the radiating element.

9. A communication device comprising an antenna module according to any one of claims 1 to 8.

Images