Patent Application
20230352824
The present disclosure relates to an antenna module and a communication device including the antenna module, and a technique for preventing deformation of an antenna module and improving characteristics of the antenna module.
International Publication No. 2019/026595 (Patent Document 1) describes an antenna module in which a plate-shaped radiation electrode is disposed on the front surface side of a dielectric substrate and in which an RFIC is disposed on the back surface side.
In the antenna module described above, a plate-shaped grounding electrode may be disposed across the entire area on the back surface side of the dielectric substrate. Typically, a dielectric substrate is shaped like a plate. If the width dimension of a cross section of the dielectric substrate is large relative to the thickness of the dielectric substrate, the difference in thermal contraction between the front surface and the back surface of the substrate in heating and cooling processes in forming the substrate increases the difference in thermal stress, which may cause the dielectric substrate to be warped.
In contrast, when the width dimension of the dielectric substrate is made small, although occurrence of warping of the dielectric substrate is suppressed, the area of the grounding electrode is made small relative to the radiation electrode, and a small amount of electric flux occurs between the radiation electrode and the grounding electrode. This may lead to a reduction of the gain of the antenna module.
An aspect of the present disclosure is to solve such an issue. Thus, aspects of the present disclosure prevent occurrence of warping of a dielectric substrate in an antenna module while a reduction of the antenna gain is suppressed.
An exemplary antenna module includes a first dielectric substrate, a first radiating element, a first grounding electrode, and a second grounding electrode. The first dielectric substrate has a first surface facing a second surface. The first dielectric substrate includes a first portion and a second portion. The first portion and the second portion are both plate-shaped. The second portion has a thickness less than that of the first portion. The first radiating element is included in the first portion. The first grounding electrode is disposed in the first portion at a position, which is located apart from the first radiating element in the direction from the first radiating element to the second surface, so as to face the first radiating element. The second grounding electrode is disposed between the first surface and the second surface in the second portion and is electrically connected to the first grounding electrode. The second surface in an area of the second portion includes a recess disposed at an end of the first dielectric substrate.
In the antenna module provided by the present disclosure, the dielectric substrate has the first portion and the second portion which have different thicknesses. The radiating element is disposed in the first portion which is relatively thick. The grounding electrode (second grounding electrode) in the second portion which is relatively thin is disposed in an inner layer between the front surface (first surface) and the back surface (second surface) of the second portion. Such a configuration enables the area of the grounding electrodes to be made large relative to that of the radiating element, achieving suppression of a reduction of the antenna gain. Further, the dielectric substrate in the second portion, in which the radiating element is not disposed, is thin, achieving prevention of occurrence of warping of the dielectric substrate.
Exemplary embodiments of the present disclosure will be described below in detail by referring to the drawings. Identical parts or corresponding parts in the figures are designated with identical reference numerals, and repeated description will be avoided.
(The Basic Configuration of a Communication Device)
Referring to
For ease of description,
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/splitter 116, a mixer 118, and an amplifier circuit 119.
In transmission of radio-frequency signals, the switches 111A to 111D and 113A to 113D are switched to the power amplifiers 112AT to 112DT side; the switch 117 is connected to the transmit-side amplifier of the amplifier circuit 119. In reception of radio-frequency signals, the switches 111A to 111D and 113A to 113D are switched to the low-noise amplifiers 112AR to 112DR side; the switch 117 is connected to the receive-side amplifier of the amplifier circuit 119.
Signals transported from the BBIC 200 are amplified by the amplifier circuit 119, and are upconverted by the mixer 118. The transmit signals, which are radio-frequency signals obtained through the upconverting, are split by the signal combiner/splitter 116 into four. The four signals pass through four signal paths and are fed to corresponding radiating elements 121 different from each other. At that time, the degrees of phase shifts of the phase shifters 115A to 115D disposed on the respective signal paths are individually adjusted, enabling the directivity of the antenna device 120 to be adjusted. In addition, the attenuators 114A to 114D adjust the strengths of the transmit signals.
Receive signals, which are radio-frequency signals received by corresponding radiating elements 121, pass through four corresponding signal paths different from each other, and are combined by the signal combiner/splitter 116 into a single signal. The combined receive signal is down-converted by the mixer 118 and is amplified by the amplifier circuit 119. The amplified signal is transported to the BBIC 200.
The RFIC 110 is formed, for example, as a single-chip integrated-circuit component including the circuit configuration described above. Alternatively, the devices (the switches, the power amplifier, the low-noise amplifier, the attenuator, and the phase shifter), corresponding to each radiating element 121, in the RFIC 110 may be formed as a single-chip integrated-circuit component corresponding to the radiating element 121.
(The Configuration of the Antenna Module)
The dielectric substrate 130 is, for example, an LTCC (Low Temperature Co-fired Ceramics) multilayer substrate, a multilayer resin substrate which is formed by laminating multiple resin layers formed of resin, such as epoxy or polyimide, a multilayer resin substrate which is formed by laminating multiple resin layers formed of LCP (Liquid Crystal Polymer) having a lower dielectric constant, a multilayer resin substrate formed by laminating multiple resin layers formed of fluorocarbon resin, a multilayer resin substrate formed by laminating multiple resin layers formed of a PET (Polyethylene Terephthalate) member, or a multilayer ceramic substrate other than an LTCC. The dielectric substrate 130 does not necessarily have a multilayer structure, and may have a single-layer substrate.
As illustrated in
The dielectric substrate 130 is substantially rectangular in plan view in the normal direction (the Z-axis direction). The radiating element 121 is disposed on the top surface 131 side (the side in the positive direction of the Z axis) of the first portion P1. The grounding electrode GND1 is disposed on the bottom surface 132 side of the first portion P1 so as to face the radiating element 121. Alternatively, the radiating element 121 may be exposed on the top surface 131 of the dielectric substrate 130, or may be disposed near the top surface 131 in an inner layer of the dielectric substrate 130 as in the example in
The grounding electrode GND2 is disposed between the top surface 131 and the bottom surface 132 of the second portion P2 of the dielectric substrate 130. The grounding electrode GND2 is electrically connected to the grounding electrode GND1 through a via V1 formed of a conductive member, such as copper or aluminum. When the dielectric substrate 130 is viewed in plan in the normal direction, the grounding electrode GND2 is disposed so as not to overlap the radiating element 121.
The feed wire 140, which extends through the grounding electrode GND1 from the RFIC 110, is connected to a feed point SP1 of the radiating element 121. Radio-frequency signals are transported from the RFIC 110 through the feed wire 140 to the radiating element 121. When the radiating element 121 is viewed in plan in the normal direction (the Z-axis direction), the feed point SP1 is disposed at a position offset from the center of the radiating element 121 in the positive direction of the X axis. Supply of radio-frequency signals to the feed point SP1 causes radio waves, whose polarization direction is the X-axis direction, to be radiated from the radiating element 121.
A feature of the antenna module 100 according to the first exemplary embodiment will be described by using comparison examples in
The first comparison example is an example in which the dimension, in the X-axis direction, of the dielectric substrate 130X is set to the dimension W1 which is the same as that of the first portion P1 of the antenna module 100. The second comparison example is an example in which the dimension, in the X-axis direction, of the dielectric substrate 130Y is set to a dimension W3(=W1+W2) which is the same as that, in the X-axis direction, of the antenna module 100. The grounding electrode GND1Y in the second comparison example is disposed at the same position in the thickness direction across the entirety of the dielectric substrate 130Y.
As in the antenna module 100Y in the second comparison example, a grounding electrode GND1Y is disposed uniformly in the dielectric substrate 130Y having a larger size than the radiating element 121. In such a case, the difference between the thermal expansion coefficient of the dielectric and that of the grounding electrode GND1Y may cause a difference in thermal stress in heating and cooling processes in forming the dielectric substrate 130Y, resulting in occurrence of warping of the dielectric substrate 130Y. The warping may cause difficulty in mounting the RFIC 110, or may affect the characteristics, such as the frequency band and the directivity of radio waves which are to be radiated.
As in the antenna module 100X in the first comparison example in
In the antenna module 100 according to the first exemplary embodiment, the radiating element 121 and the grounding electrode GND1 are disposed in the first portion P1, which is relatively thick, of the dielectric substrate 130. The grounding electrode GND2, which is connected electrically to the grounding electrode GND1, is disposed in the inner layer in the second portion P2, which is relatively thin, of the dielectric substrate 130. Thus, the second portion P2, in which the radiating element 121 is not disposed, of the dielectric substrate is formed so as to be thin, preventing occurrence of warping of the dielectric substrate 130. Further, the area of the entire grounding electrodes may be made large relative to that of the radiating element 121, achieving suppression of a reduction of the antenna gain.
In an actual antenna module, a current distribution occurs also in a grounding electrode, and not a small amount of current flows even in the grounding electrode. Thus, some radio waves may be radiated, not only from a radiating element, but also from the grounding electrode. Therefore, the area of the grounding electrode, which is made large relative to that of the radiating element 121, also achieves a wider frequency bandwidth of radio waves that are to be radiated.
“Top surface 131” and “bottom surface 132” in the first exemplary embodiment correspond to “first surface” and “second surface”, respectively, in the present disclosure. “Radiating element 121” in the first exemplary embodiment corresponds to “first radiating element” in the present disclosure. “Grounding electrode GND1” and “grounding electrode GND2” in the first exemplary embodiment correspond to “first grounding electrode” and “second grounding electrode”, respectively, in the present disclosure.
In the antenna module 100 according to the first exemplary embodiment, the configuration in which the grounding electrode GND1 in the first portion P1 and the grounding electrode GND2 in the second portion P2 are disposed in the dielectric substrate 130 at different positions in the thickness direction is described.
In an antenna module 100A according to a first modified example illustrated in
In the antenna module 100 according to the first exemplary embodiment, when the dielectric substrate 130 is viewed in plan in the normal direction, the grounding electrode GND2 in the second portion P2 is disposed so as not to overlap the radiating element 121. However, the grounding electrode in the second portion P2 may overlap the radiating element 121 partially.
In the antenna module 100B, the area of the overlapping portion between the radiating element 121 and the grounding electrode GND1 in viewing the dielectric substrate 130 in plan in the normal direction is smaller than that of the antenna module 100 according to the first exemplary embodiment. Therefore, compared with the antenna module 100, the antenna characteristics such as antenna gain slightly degrade. However, like the antenna module 100, the recess 160 is formed on the bottom-surface side of the second portion P2 of the dielectric substrate 130. In addition, the area of the entire grounding electrodes may be ensured relative to that of the radiating element 121. Thus, compared with the compared examples, occurrence of warping of the dielectric substrate 130 is prevented, while suppression of a reduction of the antenna gain is achieved.
(Comparison of Gain Characteristics)
In
As illustrated in
Therefore, as in the antenna module 100C according to the third modified example, when the dimension of the second portion P2A of the dielectric substrate 130C is large, in some exemplary embodiments, the thickness of the second portion P2A may be made smaller (H3<H2). The smaller thickness of the second portion P2A causes a reduction of the difference in density of conductors (the radiating element and the grounding electrodes) in the thickness direction of the dielectric substrate 130C, achieving reduction of warping of the dielectric substrate 130C.
The grounding electrode GND2 may be disposed closer to the top surface 131 than the case of the antenna module 100, while the thickness of the second portion P2A is at the comparable level of that of the antenna module 100.
In addition, a connector 180 for connection to a mount board may be disposed in a portion, in the recess 160C, on the bottom surface 132 of the dielectric substrate 130C. Placement of the connector 180 in a portion in the recess 160C causes a reduction of the dimension, which includes the mount board, in the Z-axis direction. Alternatively, instead of or in addition to the connector 180, another component may be disposed in a portion on the bottom surface 132 in the recess 160C.
In the case of the antenna module 100E, the electric flux from the radiating element through the recess 170 to the grounding electrode GND2 passes through the dielectric layer, the air layer, and the dielectric layer in this sequence. Thus, unnecessary reflection may occur at the boundaries between the dielectric layers and the air layer. Therefore, it is desirable that employment of forming the recess 170 be determined in view of influence of the reflection.
Typically, the dielectric constant of an air layer is lower than that of a dielectric substrate. Thus, as in the antenna module 100E, the air layer, which is provided on the path through which the electric flux passes, achieves a reduction of the effective dielectric constant of the antenna module 100E. Therefore, the antenna module 100E achieves a frequency bandwidth wider than that of the antenna module 100 according to the first embodiment.
In the first exemplary embodiment, the example in which a single radiating element is disposed in the dielectric substrate is described. In a second exemplary embodiment, a configuration in which substantially the same feature as that of the first exemplary embodiment is applied to an array antenna having two different radiating surfaces will be described.
Referring to
In the antenna module 100F, four radiating elements are disposed in a line in the Y-axis direction on each of the two dielectric substrates 130F1 and 130F2. Each radiating element includes a feed element (first element) and a parasitic element (second element). In the description below, for ease of understanding, an arrangement example in which the feed elements are exposed on the surfaces of the dielectric substrates 130F1 and 130F2 will be described. The feed elements may be disposed inside the dielectric substrates 130F1 and 130F2 as one of ordinary skill will recognize.
The dielectric substrate 130F1 is substantially rectangular. The feed elements 125 of four radiating elements 121F are disposed in a line in the Y-axis direction on the surface of the dielectric substrate 130F1. The grounding electrode GND1 is disposed on the dielectric substrate 130F1 so as to face the feed elements 125. Parasitic elements 126 are disposed between the feed elements 125 and the grounding electrode GND1 so as to face the feed elements 125. Each of the feed elements 125 and the parasitic elements 126 is a rectangular patch antenna. Each side of the feed elements 125 and the parasitic elements 126 is disposed so as to be parallel to the corresponding side of the dielectric substrate 130F1.
The size of each parasitic element 126 is larger than that of the corresponding feed element 125. Therefore, the resonant frequency of each parasitic element 126 is lower than that of the corresponding feed element 125. The frequency band of radio waves radiated from each parasitic element 126 is lower than that from the corresponding feed element 125.
The RFIC 110 is connected on the bottom-surface side (the surface in the negative direction of the Z axis) of the dielectric substrate 130F1. The RFIC 110 is mounted on a mount board 105 with solder bumps 106 interposed in between. Instead of connection using solder, the RFIC 110 may be mounted on the mount board 105 by using a multipolar connector.
Like the first exemplary embodiment, the dielectric substrate 130F1 has the recess 160 formed in a portion (second portion) in which the radiating elements 121F and the RFIC 110 are not disposed. The grounding electrode GND2 is disposed in the second portion, and is electrically connected to the grounding electrode GND1.
The feed elements 125 are supplied with radio-frequency signals from the RFIC 110 through feed wires 141 and 142. The feed wires 141 and 142, which extend from the RFIC 110 through the grounding electrode GND1 and the parasitic elements 126, are connected to feed points SP1 and SP2, respectively, of the feed elements 125.
The feed points SP1 are disposed at positions offset from the centers of the respective feed elements 125 in the positive direction of the X axis. Therefore, supply of the feed points SP1 with radio-frequency signals having a frequency corresponding to the feed elements 125 causes radio waves, whose polarization direction is the X-axis direction, to be radiated from the feed elements 125. The feed points SP2 are disposed at positions offset from the centers of the respective feed elements 125 in the positive direction of the Y axis. Therefore, supply of the feed points SP2 supplied with radio-frequency signals having a frequency corresponding to the feed elements 125 causes radio waves, whose polarization direction is the Y-axis direction, to be radiated from the feed elements 125.
Supply of the feed points SP1 with radio-frequency signals having a frequency corresponding to the parasitic elements 126 causes radio waves, whose polarization direction is the X-axis direction, to be radiated from the parasitic elements 126. Supply of the feed points SP2 with radio-frequency signals having a frequency corresponding to the parasitic elements 126 causes radio waves, whose polarization direction is the Y-axis direction, to be radiated from the parasitic elements 126.
That is, the antenna module 100F is a so-called dual-polarization, dual-band antenna module.
The dielectric substrate 130F2 is shaped like a plate. The feed elements 125A of four radiating elements 121FA are disposed in a line in the Y-axis direction on the surface of the dielectric substrate 130F2. As described above, the dielectric substrate 130F2 is connected to the dielectric substrate 130F1 through the bends 135. In the dielectric substrate 130F2, notches 136 are formed in portions to which the bends 135 are connected. In the dielectric substrate 130F2, protrusions 137 are formed in portions in which the notches 136 are not formed. The protrusions 137 protrude from boundary portions, in which the bends 135 are connected to the dielectric substrate 130F2, in the direction, which extends along the dielectric substrate 130F2 toward the dielectric substrate 130F1 (that is, the positive direction of the Z axis).
The grounding electrode GND1 is disposed in a layer on the back surface side of the dielectric substrate 130F2 (the side in the positive direction of the X axis in
Each of the feed elements 125A and the parasitic elements 126A is a rectangular patch antenna. Each side of the feed elements 125A and the parasitic elements 126A is disposed so as to be inclined with respect to the corresponding side of the dielectric substrate 130F2.
The feed elements 125A are supplied with radio-frequency signals from the RFIC 110 through feed wires 141A and 142A. The feed wires 141A and 142A, which extend from the RFIC 110 through the grounding electrode GND1 via the bends 135 and further extend through the parasitic elements 126A, are connected to the feed points SP1A and SP2A, respectively, of the feed elements 125A. The feed points SP1A are disposed at positions offset from the centers of the feed elements 125A in a first direction having an angle φ (0°<φ<90°) with respect to the Z axis. The feed points SP2A are disposed at positions offset from the centers of the feed elements 125A in a second direction orthogonal to the first direction.
Therefore, supply of the feed points SP1A with radio-frequency signals having a frequency corresponding to the feed elements 125A causes radio waves, whose polarization direction is the first direction, to be radiated from the feed elements 125A. Supply of the feed points SP2A with radio-frequency signals having a frequency corresponding to the feed elements 125A causes radio waves, whose polarization direction is the second direction, to be radiated from the feed elements 125A. Supply of the feed points SP1A with radio-frequency signals having a frequency corresponding to the parasitic elements 126A causes radio waves, whose polarization direction is the first direction, to be radiated from the parasitic elements 126A. Supply of the feed points SP2A with radio-frequency signals having a frequency corresponding to the parasitic elements 126A causes radio waves, whose polarization direction is the second direction, to be radiated from the parasitic elements 126A.
Similarly, in the antenna module 100F having the configuration described above, the dielectric substrate 130F1 has a configuration in which the second portion, in which the radiating elements 121F are not disposed, has a thickness less than that of the first portion in which the radiating elements 121F are disposed; the grounding electrode GND2 is disposed in an inner layer of the second portion. Therefore, while occurrence of warping of the dielectric substrate 130F1 is prevented, suppression of a reduction of the antenna gain is achieved.
Each of the “feed elements 125 and 125A” in the second exemplary embodiment corresponds to “first element” in the present disclosure. Each of the “parasitic elements 126 and 126A” in the second exemplary embodiment corresponds to “second element” in the present disclosure. “Dielectric substrate 130F1” and “dielectric substrate 130F2” in the second exemplary embodiment correspond to “first dielectric substrate” and “second dielectric substrate”, respectively, in the present disclosure. Any one of the radiating elements 121F in the second exemplary embodiment corresponds to “first radiating element” in the present disclosure; another radiating element 121F disposed adjacent to the radiating element 121F corresponds to “second radiating element” in the present disclosure.
Referring to
In the dielectric substrate 130F1, the second portion, in which the radiating elements 121F are not disposed, has a thickness less than that of the first portion in which the radiating elements 121F are disposed; the grounding electrode GND2 is disposed in an inner layer of the second portion. Therefore, while occurrence of warping of the dielectric substrate 130F1 is prevented, suppression of a reduction of the antenna gain is achieved.
In the antenna module 100G, the recess 160 is formed along the end portion on the long side, along the Y axis, of the dielectric substrate 130F1. In the antenna module 100H, a recess 160H is formed in a portion, in which the radiating elements 121 are not disposed, along the end portion on the short side, along the X axis, of the dielectric substrate 130H1. In the dielectric substrate 130H1, the grounding electrode GND2 is disposed in an inner layer of the second portion which is thin and in which the recess 160H is formed (not illustrated in
In addition to the end portion on the short side of the dielectric substrate 130H1, a recess may be formed along the end portion on the long side of the dielectric substrate 130H1 as in the sixth modified example.
The exemplary embodiments disclosed in the specification are to be considered to be illustrative and not restrictive in all respects. It is intended that the scope of the present disclosure is set forth in the claims, not in the description of the exemplary embodiments described above, and that all variations within the meaning and scope of the claims and their equivalents are encompassed.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-213397 | Dec 2020 | JP | national |
This application is a continuation of, and claims priority to, international application no. PCT/JP2021/044261, filed Dec. 2, 2021, which claims priority to Japanese patent application no. 2020-213397, filed Dec. 23, 2020. The contents of all prior applications are hereby incorporated by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2021/044261 | Dec 2021 | US |
| Child | 18337432 | US |
