The present disclosure relates to an antenna module, a communication device in which the antenna module is installed, and a method of manufacturing the antenna module, and more specifically, to the structure of an antenna module that improves radiation efficiency.
International Publication No. 2016/067969 (Patent Document 1) discloses an antenna module that includes a radiating element having a flat plate shape and a ground electrode that face each other.
Patent Document 1: International Publication No. 2016/067969
In some cases, the antenna module disclosed in International Publication No. 2016/067969 (Patent Document 1) is installed in a mobile communication device, such as a cellular phone or smartphone. There is a need for a communication device that has improved communication quality. For this purpose, it is necessary to improve the radiation efficiency of an antenna.
The present disclosure improves the radiation efficiency of an antenna module that includes a patch antenna that has a flat plate shape.
An antenna module according to an aspect of the present disclosure is to be installed in a communication device. The antenna module includes a dielectric substrate, a ground electrode that is disposed in the dielectric substrate, and a first radiating element that has a flat plate shape. The first radiating element has a first surface and a second surface that has a higher degree of surface roughness than that of the first surface. The first surface of the first radiating element faces the ground electrode.
A method of manufacturing an antenna module according to an aspect of the present disclosure is a method of manufacturing an antenna module that includes a first layer that contains a first radiating element and a second layer that contains a ground electrode. The first radiating element and the ground electrode have respective smooth surfaces that have a relatively low degree of surface roughness and respective rough surfaces that have a relatively high degree of surface roughness. The method includes (i) a step of joining the rough surface of the first radiating element and a dielectric layer to each other to form the first layer, (ii) a step of joining the rough surface of the ground electrode and a dielectric layer to each other to form the second layer, and (iii) a step of stacking the first layer on the second layer such that the smooth surface of the first radiating element and the smooth surface of the ground electrode face in the same direction, and the smooth surface of the first radiating element faces the ground electrode.
In an antenna module according to the present disclosure, a smooth surface of at least one radiating element that is included in the antenna module faces a ground electrode. Consequently, a loss due to an electric current that flows through the radiating element is reduced, and the radiation efficiency of the antenna module can be improved.
Embodiments of the present disclosure will hereinafter be described in detail with reference to the drawings. In the drawings, portions like or corresponding to each other are designated by like reference signs, and a description thereof is not repeated.
Referring to
In
The RFIC 110 includes switches 111A to 111D, 113A to 113D, and 117, power amplifiers 112AT to 112DT, low-noise amplifiers 112AR to 112DR, attenuators 114A to 114D, phase shifters 115A to 115D, a signal combiner/demultiplexer 116, a mixer 118, and an amplifier circuit 119.
In the case where the radio frequency signal is transmitted, the switches 111A to 111D, and 113A to 113D are switched to the power amplifiers 112AT to 112DT, and the switch 117 is connected to a transmission amplifier of the amplifier circuit 119. In the case where the radio frequency signal is received, the switches 111A to 111D, and 113A to 113D are switched to the low-noise amplifier 112AR to 112DR, and the switch 117 is connected to a reception amplifier of the amplifier circuit 119.
The signal that is transmitted from the BBIC 105 is amplified by the amplifier circuit 119 and is up-converted by the mixer 118. A transmission signal that is the up-converted radio frequency signal is demultiplexed by the signal combiner/demultiplexer 116 into four signals, which pass through four signal paths and are fed to the different driven elements 121. At this time, the directivity of the antenna device 120 can be adjusted by separately adjusting phase shifts of the phase shifters 115A to 115D that are arranged on the signal paths.
Reception signals that are the radio frequency signals that are received by the driven elements 121 pass through four different reception paths and are multiplexed by the signal combiner/demultiplexer 116. The multiplexed reception signal is down-converted by the mixer 118, amplified by the amplifier circuit 119, and transmitted to the BBIC 105.
An example of the RFIC 110 is an integrated circuit component of a chip that includes the circuit structure described above. Devices (the switches, the power amplifiers, the low-noise amplifiers, the attenuators, and the phase shifters) associated with each driven element 121 of the RFIC 110 may be an integrated circuit component of a chip for the driven element 121 associated therewith.
Examples of the dielectric substrate 130 include a low temperature co-fired ceramic (LTCC) multilayer substrate, a multilayer resin substrate that has a stack of resin layers composed of, for example, an epoxy resin or a polyimide resin, a multilayer resin substrate that has a stack of resin layers composed of liquid crystal polymer (LCP) that has a decreased dielectric constant, a multilayer resin substrate that has a stack of resin layers composed of a fluorine resin, and a ceramic multilayer substrate other than the LTCC.
A planar shape of the dielectric substrate 130 is rectangular. The driven element 121 that has a substantially square shape is disposed in a layer in the dielectric substrate 130 or on a front surface 131 facing in the upward direction. In the dielectric substrate 130, the ground electrode GND that has a flat plate shape is disposed in a layer away from the driven element 121 in the downward direction. The RFIC 110 is disposed below a back surface 132 of the dielectric substrate 130 facing in the downward direction with a solder bump 150 interposed therebetween.
The parasitic element 125 is disposed in a layer between the driven element 121 and the ground electrode GND and faces the driven element 121. That is, the antenna module 100 is a stack antenna module in which the driven element 121 faces the parasitic element 125. The radio frequency signal is transmitted from the RFIC 110 to the driven element 121. However, no radio frequency signal is transmitted to the parasitic element 125. The driven element 121 and the parasitic element 125 are electrodes that have a substantially square flat plate shape. The size of the parasitic element 125 is larger than that of the driven element 121. In the description below, the driven element and the parasitic element are collectively referred to as “radiating elements” in some cases.
The power-supply wiring line 140 extends through the ground electrode GND and the parasitic element 125 and is connected to a feed point SP1 of the driven element 121. Through the power-supply wiring line 140, the radio frequency signal is transmitted from the RFIC 110 to the driven element 121. The power-supply wiring line 140 is not connected to the parasitic element 125. However, the power-supply wiring line 140 extends through the parasitic element 125. Accordingly, coupling occurs between the power-supply wiring line 140 and the parasitic element 125, and a radio wave is radiated also from the parasitic element 125. As the size of each radiating element increases, the resonant frequency of the radiating element typically decreases, and the frequency of a radio wave that is radiated from the radiating element decreases. For this reason, the frequency of the radio wave that is radiated from the parasitic element 125 is lower than that from the driven element 121. That is, the antenna module 100 is a co-called dual-band antenna module that can radiate radio waves in two frequency bands.
In
In
The antenna module described above functions as an antenna as a result that electromagnetic field coupling occurs between the driven element 121 and the ground electrode GND and between the parasitic element 125 and the ground electrode GND. It is kwon that at this time, an electric current that flows through each radiating element concentrates on the surface facing the ground electrode GND.
As for the electrode that has a flat plate shape and that forms each radiating element, the surface roughness of a first surface relatively decreases, (also referred to below as a “smooth surface”), and the surface roughness of a second surface relatively increases unlike the smooth surface (also referred to below as a “rough surface”) during manufacturing processing in some cases. For example, in the case where “electrolytic copper foil” produced by electroplating is used as the electrode for forming the radiating element, a surface that comes into contact with a copper foil cathode drum has a low degree of surface roughness, and a surface on which plating is deposited opposite the copper foil cathode drum has fine irregularities of about several μm.
In each radiating element, the electric current concentrates on the surface (the facing surface) facing the ground electrode as described above. When the facing surface has an increased degree of surface roughness, however, electric resistance increases. Consequently, there is a possibility that the radiation efficiency decreases.
In view of this, as for the radiating elements that are included in the antenna module according to the present embodiment, the smooth surfaces face the ground electrode. This reduces heat generated by the electric current that flows through each radiating element and improves the radiation efficiency.
The surface roughness can be measured, for example, as a root mean square Rq, maximum height roughness Rz, arithmetic mean roughness Ra, or ten-point average roughness Rzjis defined as JISB0601. As for the radiating elements, a surface that has a relatively low degree of surface roughness is referred to as the “smooth surface”, and a surface that has a relatively high degree of surface roughness is referred to as the “rough surface” regardless of a measurement method.
The simulations are performed in conditions in which the root mean square Rq is used for the surface roughness of the radiating elements, the surface roughness of each rough surface is 1 μm, and the surface roughness of each smooth surface is 0 μm. In the first to third examples and the comparative example, the surface of the ground electrode GND that faces the radiating elements is the rough surface.
Referring to
In the third example in which the smooth surface of the driven element 121 faces the ground electrode GND, however, the radiation efficiency at 38.5 GHz is −0.711 dB and is improved. In the second example in which the smooth surface of the parasitic element 125 faces the ground electrode GND, the radiation efficiency at 28 GHz is −0.717 dB and is improved. In the first example in which the smooth surface of the driven element 121 and the smooth surface of the parasitic element 125 face the ground electrode GND, the radiation efficiency at 38.5 GHz is −0.630 dB and is improved, and the radiation efficiency at 28 GHz is −0.689 dB and is improved.
Also, as for the driven element 121 in the second example and the parasitic element 125 in the third example in which the rough surface faces the ground electrode GND, the radiation efficiency is slightly improved unlike the comparative example. This is presumably achieved due to an improvement in the radiation efficiency of the other radiating element.
As illustrated in
An example of processing of manufacturing the antenna module will now be described with reference to
Referring to
Subsequently, at a second step, the metal layer 220 of one of the dielectric sheets 200 is etched to pattern an electrode that has a desired shape as illustrated in
At a third step illustrated in
Subsequently at a fourth step illustrated in
At a fifth step illustrated in
In the antenna module illustrated in
The use of the manufacturing processing illustrated in
The manufacturing processing is used when the direction in which the smooth surface of one of the radiating elements faces differs from that of another electrode pattern (the other radiating element and the ground electrode), such as those in the second example and the third example in
Referring
Subsequently, the formed dielectric sheets 200 are stacked at the step illustrated in
The hot press process on the dielectric sheets that are thus stacked is performed to form the antenna module with the direction in which the smooth surface of one of the radiating elements faces is inverted. In an example in
The manufacturing processing illustrated in
Referring to
The core substrate 310 can be composed of, for example, a LCP, a glass epoxy material (for example, FR4: Flame Retardant Type 4), or polyimide. Electrode patterns that are formed into a desired shape by, for example, punching in advance may be joined as the metal layers, or after the metal layers are entirely joined to the surfaces of the core substrate 310, electrode patterns that have a desired shape may be formed by, for example, etching as illustrated in
At the first step, the metal layers 312 and 313 are joined such that the rough surfaces face the core substrate 310. This enables bonding strength between the core substrate 310 and the metal layers 312 and 313 to be ensured.
In a second step illustrated in
Subsequently, at a third step illustrated in
Subsequently, at the step illustrated in
At a first step illustrated in
Subsequently, at a second step illustrated in
In a fourth step illustrated in
According to the first embodiment, the stack antenna module that supports a dual-band is described. However, the features of the arrangement of the radiating elements according to the present disclosure can be used for antenna modules that have other structures as in a first modification to a third modification described below.
In the antenna module 100 according to the first embodiment described above, the driven element 121 is disposed near the surface of the dielectric substrate 130 facing in the upward direction, and the parasitic element 125 is disposed in the layer between the driven element 121 and the ground electrode GND.
A structure described according to the first modification includes the same stack structure. In the first modification, the parasitic element is disposed away from the driven element in the upward direction, and the driven element is disposed in a layer between the parasitic element and the ground electrode.
As for the antenna module 100A, electrodes that have substantially the same size are used as the driven element 121 and the parasitic element 125A. With this structure, radiation can be emitted only in a single frequency band. However, the parasitic element 125A can increase a frequency band width and enables multiple frequency bands to be supported. The sizes of the electrodes of the driven element 121 and the parasitic element 125A may differ from each other.
Also, with this structure, the electromagnetic field coupling occurs between the radiating elements and the ground electrode GND and between the radiating elements, and the electric current that flows through each radiating element concentrates on the surface of the electrode. Accordingly, the radiation efficiency can be improved by the arrangement in which the smooth surface of the driven element 121 and/or the parasitic element 125A faces the ground electrode GND as in the first embodiment.
According to the first modification, the driven element 121 and the parasitic element 125A are disposed in the same dielectric substrate 130. The parasitic element, however, is not necessarily integrated in the dielectric substrate 130.
Also, with this structure, the radiation efficiency can be improved by the arrangement in which the smooth surface of the driven element 121 and/or the parasitic element 125B faces the ground electrode GND.
According to the first embodiment and the second modification, the stack antenna module that includes the two radiating elements of the driven element and the parasitic element is described. The features of the present disclosure can be used for an antenna module that has a single radiating element.
Also, in this case, the radiation efficiency can be improved by the arrangement in which the smooth surface of the driven element 121 faces the ground electrode GND.
The arrangement of the smooth surfaces of the radiating elements described according to the first embodiment is used for the antenna module that radiates the radio wave in one direction. In an example described according to a second embodiment, the radiating elements according to the present disclosure are disposed in an antenna module that can radiate the radio waves in multiple directions.
The structure of an antenna module 100D according to the second embodiment will be described with reference to
Referring to
The flexible substrate 160 includes a flat first portion 161 along the main surface 21 of the mounting substrate 20, a bent portion 162 that is bent from the first portion, and a flat second portion 163 that extends from the bent portion 162 and that faces a side surface 22 of the mounting substrate 20. The flexible substrate 160 is composed of, for example, epoxy resin or polyimide resin. The flexible substrate 160 may be composed of fluorine resin or LCP that has a decreased dielectric constant.
The dielectric substrate 130 is disposed on the first portion 161 of the flexible substrate 160, and the radiating elements (the driven elements 121 and the parasitic elements 125) are disposed such that the radio wave is radiated in the normal direction (the positive Z-axis direction) of the main surface 21. The radio frequency signal from the RFIC 110 is transmitted to each driven element 121 in the dielectric substrate 130 via the power-supply wiring line 140.
The dielectric substrate 135 is disposed on the second portion 163 of the flexible substrate 160, and the radiating elements (the driven elements 121 and the parasitic elements 125) are disposed such that the radio wave is radiated in the normal direction (the positive X-axis direction) of the side surface 22. The radio frequency signal from the RFIC 110 is transmitted to each driven element 121 in the dielectric substrate 135 via a power-supply wiring line 141 that extends in the flexible substrate 160.
Also, as for the antenna module 100D that has this structure, the smooth surface of each driven element 121, the smooth surface of each parasitic element 125, or both smooth surfaces face the ground electrode GND in an antenna portion that is disposed on the first portion 161 of the flexible substrate 160 and an antenna portion that is disposed on the second portion 163 of the flexible substrate 160 as illustrated in the first example to the third example in
In an example described above, the arrangement of the smooth surfaces of the radiating elements according to the present disclosure is used for the antenna module 100D according to the above-described second embodiment that radiates the radio waves in two directions. However, the arrangement can be used for an antenna module that radiates the radio waves in three or more directions. For example, the flexible substrate 160 in
In the structure of the antenna module described above with reference to
In a structure described according to a fourth modification, the radiating elements are disposed near two surfaces (the front surface and the back surface) of the dielectric substrate that faces away from each other such that the radio waves are radiated in two directions.
The driven elements 121, the parasitic elements 125, or both are disposed such that the smooth surface of each electrode faces the ground electrode GND. Consequently, a loss due to the electric current that flows through each radiating element is reduced, and the radiation efficiency of the antenna module can be improved.
Also, according to the fourth modification, an element an end surface of which is connected to the ground electrode may be used as each radiating element.
In the structures according to the embodiments and the modifications described above, the radiating elements and the ground electrode are disposed in the same dielectric substrate except for the parasitic element (the parasitic element 125B in
It should be considered that the embodiments disclosed herein are examples in all aspects and are not restrictive. The scope of the present disclosure is not shown by the embodiments described above but by claims and includes all modifications having equivalent meaning and scope to those of the claims.
10 communication device, 20 mounting substrate, 21 main surface, 22 side surface, 50 housing, 100, 100A to 100E antenna module, 105 BBIC, 110 RFIC, 111A to 111D, 113A to 113D, 117 switch, 112AR to 112DR low-noise amplifier, 112AT to 112DT power amplifier, 114A to 114D attenuator, 115A to 115D phase shifter, 116 signal combiner/demultiplexer, 118 mixer, 119 amplifier circuit, 120 antenna device, 121 driven element, 125, 125A, 125B parasitic element, 130, 135 dielectric substrate, 131 front surface, 132 back surface, 140 to 142 power-supply wiring line, 150 solder bump, 160 flexible substrate, 161 first portion, 162 bent portion, 163 second portion, 200, 200A to 200D dielectric sheet, 210, 300, 400, 440 dielectric layer, 220, 312, 313, 340, 412, 413, 442 metal layer, 230 conductive paste, 310, 410, 441 core substrate, 320, 420 adhesive layer, 330, 430 via, AGP air gap, GND ground electrode, SP1 feed point.
Number | Date | Country | Kind |
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2019-006182 | Jan 2019 | JP | national |
This is a continuation of International Application No. PCT/JP2019/051185 filed on Dec. 26, 2019 which claims priority from Japanese Patent Application No. 2019-006182 filed on Jan. 17, 2019. The contents of these applications are incorporated herein by reference in their entireties.
Number | Date | Country | |
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Parent | PCT/JP2019/051185 | Dec 2019 | US |
Child | 17366619 | US |