Patent Grant
12148987
The present disclosure relates to an antenna module, a communication device, and an array antenna and more specifically to a technique for broadening the antenna module.
International Publication No. 2016/063759 (Patent Document 1) discloses a patch antenna in which a plurality of radiation electrodes (feed elements, parasitic elements) having a planar shape are stacked.
For the above antenna, permittivity of a dielectric substrate on which antenna elements (radiation electrodes) are implemented has an effect on its antenna characteristics, such as a frequency band width, a peak gain, and a loss of a transmittable radio-frequency signal. Among them, the frequency band width typically increases with the increase in the thickness of the dielectric substrate (that is, the distance between a radiation electrode and a ground electrode and the distance between radiation electrodes).
In particular, mobile terminals, such as smartphones, have been increasingly required to be thinner in recent years, and thus an antenna module itself has been needed to be more compact and thinner. If a dielectric substrate becomes thinner, however, an issue arises in that the frequency band width of the antenna becomes narrower.
The present disclosure is made to solve that problem, and an object thereof is to achieve a broad band without increasing the size of an antenna module.
An antenna module includes a dielectric substrate having a multilayer structure, a first radiation electrode, a second radiation electrode, and a ground electrode. The second radiation electrode is arranged between the first radiation electrode and the ground electrode in a lamination direction of the dielectric substrate. In the dielectric substrate, a hollow portion is disposed in at least a portion between the first radiation electrode and the second radiation electrode.
In the antenna module according to the present disclosure, the hollow portion is disposed in at least the portion between the stacked two radiation electrodes. In that configuration, in comparison with an antenna module in which the dielectric substrate has no hollow portion, the effective permittivity between the two radiation electrodes is reduced. Accordingly, the broad band can be achieved without increasing the size of the antenna module.
Embodiments of the present disclosure are described in detail below with reference to the drawings. The same reference numerals are used in the same or corresponding sections in the drawings, and the description about them is not repeated.
(Basic Configuration of Communication Device)
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/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 side corresponding to the power amplifiers 112AT to 112DT, and the switch 117 becomes connected to a transmission-side amplifier in the amplifier circuit 119. In reception of radio-frequency signals, the switches 111A to 111D and 113A to 113D are switched to the side corresponding to the low-noise amplifiers 112AR to 112DR, and the switch 117 becomes connected to a reception-side amplifier in the amplifier circuit 119.
A signal conveyed from the BBIC 200 is amplified in the amplifier circuit 119 and is upconverted in the mixer 118. The transmission signal being the upconverted radio-frequency signal is split into four signals in the signal combiner/splitter 116, and they pass through four signal paths and are fed to mutually different radiation electrodes 121. At that time, the directivity of the antenna array 120 can be adjusted by individually adjusting the phase-shift degrees of the phase shifters 115A to 115D arranged in the signal paths.
Reception signals being radio-frequency signals received at the radiation electrodes 121 pass through mutually different signal paths and are combined in the signal combiner/splitter 116. The combined reception signal is downconverted in the mixer 118, is amplified in the amplifier circuit 119, and is conveyed to the BBIC 200.
One example of the RFIC 110 may be formed as a one-chip integrated circuit component having the above-described circuitry. Alternatively, equipment (switches, power amplifiers, low-noise amplifier, attenuator, phase shifter) corresponding to each of the radiation electrodes 121 in the RFIC 110 may be formed as a one-chip integrated circuit component for each corresponding radiation electrode 121.
(Structure of Antenna Module)
In the following description, an example in which the radiation electrode 121 is a feed element and the radiation electrode 122 is a parasitic element is described. Both the radiation electrode 121 and the radiation electrode 122 may be feed elements. Conversely, the radiation electrode 121 may be a parasitic element, and the radiation electrode 122 may be a feed element.
The dielectric substrate 160 has a substantially rectangular shape when the antenna module 100 is seen in plan view from the direction of the normal to the dielectric substrate 160 (Z-axis direction in the drawing) and has a first side 161 to a fourth side 164. In the example of the dielectric substrate 160 in
The dielectric substrate 160 has a multilayer structure in which a plurality of dielectric layers are laminated. The dielectric layers in the dielectric substrate 160 may be made of a resin, such as epoxy or polyimide. The dielectric layers may also be made by using a liquid crystal polymer (LCP) having lower permittivity, a fluorine-based resin, low temperature co-fired ceramics (LTCC), or the like. The RFIC 110 is implemented on one principal surface (lower surface) of the dielectric substrate 160 with solder bumps 130 disposed therebetween.
A plurality of columnar conductors 145 are arranged at predetermined intervals along the sides of the dielectric substrate 160 in its outer region. The plurality of columnar conductors 145 are connected to the ground electrode GND inside the dielectric substrate 160. The plurality of columnar conductors 145 function as a shield on the side-surface side of the dielectric substrate 160. In antenna modules described below with reference to
The ground electrode GND is arranged on a layer near the lower surface of the dielectric substrate 160. The rectangular radiation electrode 122 (first radiation electrode) is arranged on a layer near the other principal surface (upper surface) of the dielectric substrate 160. The rectangular radiation electrode 121 (second radiation electrode) is arranged on a layer between the radiation electrode 122 and the ground electrode GND. The radiation electrode 121 and the radiation electrode 122 overlap each other such that the points of intersection of their respective diagonal lines (that is, centers) coincide when the antenna module 100 is seen in plan view. In the example illustrated in
The radiation electrode 121 is electrically connected to the RFIC 110 with a feed line 140 disposed therebetween. The feed line 140 extends through the ground electrode GND and is connected to the feed point SP1 for the radiation electrode 121. The feed point SP1 is arranged in a position displaced from the center of the radiation electrode 121 toward the second side 162, which extends along the X axis, on the radiation electrode 121. Thus, the radiation electrode 121 radiates a radio wave whose polarization direction is the Y-axis direction.
When the radiation electrode 122 is the feed element, one example of the feed line 140 may extend through the radiation electrode 121 and be connected to a feed point for the radiation electrode 122 by a via extending through a hollow portion 150. Alternatively, the feed line 140 may be diverted around the hollow portion 150, extend inside the dielectric substrate 160, and be connected to the radiation electrode 122.
In the dielectric substrate 160, the hollow portion 150 is disposed in a layer between the radiation electrodes 121 and 122. The dielectric substrate 160 includes a layer 165 supported by the first side 161 (hereinafter also referred to as “beam portion”) on the upper-surface side of the hollow portion 150, and the radiation electrode 122 is arranged in the beam portion 165. A cavity portion 152 is disposed along the second side 162 to the fourth side 164 around the beam portion 165, and the cavity portion 152 extends through the dielectric substrate 160 to the hollow portion 150.
It is known that in the above-described stack-type antenna module including the plurality of radiation electrodes stacked, the frequency band width of radio waves that can be radiated by the radiation electrodes is determined by the strength of electromagnetic-field coupling between the radiation electrode and the ground electrode and the strength of electromagnetic-field coupling between the radiation electrodes. As the strength of electromagnetic-field coupling increases, the frequency band width decreases, and as the strength of electromagnetic-field coupling decreases, the frequency band width increases.
Typically, an increase in the thickness of the dielectric substrate is needed for expanding the frequency band width of a radio wave radiated by a radiation electrode. The increased thickness of the dielectric substrate, however, may be a hindrance to a reduction in size and thickness of a communication device, such as a smartphone, that uses an antenna module and that is required to be smaller and thinner.
Here, the effective permittivity between the two electrodes also has an effect on the strength of electromagnetic-field coupling. More specifically, as the effective permittivity increases, the electromagnetic-field coupling becomes stronger, and as the effective permittivity decreases, the electromagnetic-field coupling becomes weaker. That is, the frequency band width can be expanded by a reduction in the effective permittivity between the two electrodes.
In the antenna module 100 according to the first embodiment, as described above, the hollow portion 150 is disposed between the radiation electrodes 121 and 122. Typically, the permittivity of air is lower than that of the dielectric forming the dielectric substrate 160. Thus, the effective permittivity between the radiation electrodes 121 and 122 can be reduced by the presence of the hollow portion 150. That can result in weakened electromagnetic-field coupling between the radiation electrodes 121 and 122. Accordingly, in the antenna module 100 according to the first embodiment, the frequency band width can be expanded without increasing the overall size of the module.
Because the loss of electric energy inside the dielectric can be reduced by the presence of the hollow portion 150, the efficiency of the antenna module can be improved.
(Simulation Results)
In the simulation described below, an example in which the used frequency range is a millimeter-wave frequency range (gigahertz range) is described. The configuration of the present disclosure is also applicable to frequency ranges other than the millimeter wave.
Referring to
In the graph of the gain in the middle row, the lines LN2 and LN2A indicate the gain directivity, and the lines LN3 and LN3A indicate the performance gain. The difference between the gain directivity and the performance gain is the loss in the antenna module. In the graph of the gain, the range where the gain directivity and the performance gain are close is also the above-described range RNG1A in the comparative example and the range RNG1 in the first embodiment, and it is revealed that the range where the loss is low in the antenna module 100 according to the first embodiment is wider. The efficiency at 60.48 GHz (ratio of the radiated power to the input power), which is 91.4% in the comparative example, is improved to 94.0% in the first embodiment.
Hence, in the stack-type antenna module, the frequency band width can be expanded and the efficiency can be improved by disposing the hollow portion between the two radiation electrodes.
(Variations)
Next, antenna modules 100A to 100G according to variations are described with reference to
Variations 2 to 5 in
In the antenna module 100C according to Variation 3 in
The antenna module 100F according to Variation 6 in
In the antenna module 100F in
Here, the relation between the position of the hollow portion 150 and the frequency band width in the cases where the hollow portion 150 partially overlaps a portion of the radiation electrodes, as in the antenna module 100G in
First, the relation between the position of the hollow portion in the Y-axis direction and the frequency band width is described with reference to
In
The line LN11 in
In the case where a radio wave whose polarization direction is the Y-axis direction is radiated, as in
Next, the relation between the position of the hollow portion in the X-axis direction and the frequency band width is described with reference to
In
The line LN16 in
The above-described simulation results reveal that, as in the antenna module 100G in
As described above, in the stack-type antenna modules including the two radiation electrodes, the expanded frequency band width of a radiated radio wave can be achieved by disposing the hollow portion in at least a portion between the two radiation electrodes.
The size and position of the hollow portion 150 and the arrangement of the cavity portion 152 can be determined in accordance with a desired frequency band width and stiffness (durability) of the antenna module.
The hollow portion 150 disposed inside the dielectric substrate 160 may consist of a plurality of sections separated by a dielectric wall portion 167, as in an antenna module 100X according to Variation 8 in
In the first embodiment, the hollow portion 150 disposed inside the dielectric substrate 160 is basically an air layer.
In a second embodiment, an example in which the hollow portion 150 disposed between the two the radiation electrodes 121 and 122 is at least partially filled with another dielectric having permittivity lower than that of the dielectric substrate 160 is described.
Because the hollow portion 150 is filled with the different dielectric material having the lower permittivity, the effective permittivity can be more reduced than that in the case where the substrate is entirely made of the same dielectric material, and the frequency band width can be expanded. In that configuration, although the amount of expansion of the frequency band width is smaller than that in the case where the hollow portion 150 is the air layer, the stiffness of the antenna module can be enhanced. In the antenna module 100H, the hollow portion 150 is entirely filled with another dielectric material. The hollow portion 150 may be only partially filled with another dielectric material.
As in an antenna module 100I according to Variation 11 in
Similarly, the hollow portion 150 in each of the variations of the first embodiment may be filled with a dielectric material having low permittivity. For example, an antenna module 100J according to Variation 12 in
The antenna module in the first embodiment has the configuration in which the two radiation electrodes are stacked. The number of radiation electrodes stacked may be three or more.
In a third embodiment and its variations, examples in which the same configuration as that of the first embodiment is applied to an antenna module including three stacked radiation electrodes are described.
The radiation electrode 123 is disposed on a layer between the radiation electrodes 121 and 122. In the example of the antenna module 100L, the radiation electrodes 122 and 123 have the same dimensions and the same shape, and when the antenna module 100L is seen in plan view, the radiation electrodes 122 and 123 overlap each other.
The hollow portion 150 is disposed between the radiation electrodes 121 and 123, and the cavity portion 152 extends from the upper surface of the dielectric substrate 160 through the dielectric substrate 160 to the hollow portion 150. The cavity portion 152 in the antenna module 100L is disposed along the second side 162, the third side 163, and the fourth side 164 of the antenna module 100L having a rectangular shape as seen in plan view, as in the case of the antenna module 100 according to the first embodiment. The radiation electrodes 122 and 123, which are parasitic elements, are arranged in the beam portion 165 supported by the first side 161.
The layer where the hollow portion 150 is disposed is not limited to the layer between the radiation electrodes 121 and 123. The hollow portion 150 may be disposed between the radiation electrodes 122 and 123, as in an antenna module 100M according to Variation 14 in
As in an antenna module 100N according to Variation 15 in
Although not illustrated, the hollow portion 150 in the third embodiment may be at least partially filled with the dielectric material having lower permittivity than that of the dielectric material forming the dielectric substrate 160, as in the case of the second embodiment.
In the above-described antenna modules including the three or more stacked radiation electrodes, the expanded frequency band width of a radiated radio wave can be achieved by disposing the hollow portion between any radiation electrodes.
In each of the antenna modules described in the first to third embodiments, the beam portion 165 where the radiation electrode 122, which is a parasitic element, is arranged includes the upper surface of the dielectric substrate 160.
However, in the configuration in which the hollow portion is an air layer and the cavity portion is open in the upper surface of the dielectric substrate, because the portion supporting the beam portion is limited, the portion supporting the beam portion may be broken, depending on the force acting thereon during handling of the antenna module.
In a fourth embodiment, the beam portion where the radiation electrode is arranged is disposed so as to be supported in a position displaced from the uppermost surface of the dielectric substrate in the lamination direction. In that configuration, the occurrence of incidents in which an external force directly acts on the beam portion during handling is reduced, and the possibility of breakage of the beam portion is decreased.
In the example of the antenna module 100P in
In the first to fourth embodiments, the antenna modules including the single unit of the antenna element and the RFIC are described. In a fifth embodiment, an array antenna, in which antenna elements are arranged in an array, is described.
In that array antenna 300, the expanded frequency band width of a radiated radio wave can be achieved by disposing the hollow portion between the radiation electrodes in each of the antenna modules. Although not illustrated, in the case of the array antenna, the plurality of antenna modules may include their respective RFICs or may share a single RFIC.
In the case of the array antenna, the dielectric wall between the neighboring antenna modules may be omitted such that the hollow portions communicate with each other.
As described above, because the hollow portions in the neighboring antenna modules in the array antenna communicate with each other, the dielectric section is decreased, and the effective permittivity can be further reduced, and the frequency band width can be still further expanded.
In a sixth embodiment, a configuration where in a so-called dual-band type antenna module, which can radiate radio waves in two frequency ranges, the expanded frequency band widths of radiated radio waves can be achieved by disposing a hollow in a dielectric substrate is described.
Two feed points SP1 and SP2 are arranged on the radiation electrode 121. The feed point SP1 is arranged in a position displaced from the center of the radiation electrode 121 toward the negative direction of the Y axis when the antenna module 100Q is seen in plan view. A radio-frequency signal is conveyed from the RFIC 110 to the feed point SP1 through a feed line 141. When the radio-frequency signal is supplied to the feed point SP1, a radio wave whose polarization direction is the Y-axis direction is radiated.
The feed point SP2 is arranged in a position displaced from the center of the radiation electrode 121 toward the positive direction of the X axis when the antenna module 100Q is seen in plan view. A radio-frequency signal is conveyed from the RFIC 110 to the feed point SP2 through a feed line 142. When the radio-frequency signal is supplied to the feed point SP2, a radio wave whose polarization direction is the X-axis direction is radiated. That is, the antenna module 100Q is also a dual-polarization type antenna module capable of radiating radio waves in two different polarization directions.
The feed lines 141 and 142 extend from the RFIC 110 through the radiation electrode 124 to the radiation electrode 121. Thus, when radio-frequency signals corresponding to the resonant frequency of the radiation electrode 124 being the parasitic element are supplied to the feed lines 141 and 142, the radiation electrode 124 radiates radio waves.
The size of the radiation electrode 124 is larger than that of the radiation electrode 121. The resonant frequency of the radiation electrode 124 is lower than that of the radiation electrode 121. Thus, the radiation electrode 124 radiates a radio wave in a frequency range lower than that for the radiation electrode 121.
In the antenna module 100Q, a hollow portion 155 is disposed in a layer between the radiation electrodes 121 and 124. When the antenna module 100Q is seen in plan view, the hollow portion 155 has substantially the same shape as that of the radiation electrode 121 and is disposed in a position overlapping the radiation electrode 121.
The radiation electrode 121 functions as an antenna when an electric line of force occurs between the radiation electrodes 121 and 124. Thus, the effective permittivity between the radiation electrodes 121 and 124 has an effect on the antenna characteristics. In the antenna module 100Q, because the hollow portion 155 is disposed in the layer between the radiation electrodes 121 and 124, as described above, the effective permittivity is lower than that when the hollow portion 155 is filled with the dielectric. Therefore, the electromagnetic-field coupling between the radiation electrodes 121 and 124 can be weakened, and the expanded frequency band width of a radio wave radiated by the radiation electrode 121 can be achieved.
The effective permittivity between the radiation electrode 124 and the ground electrode GND has an effect on the frequency band width of the radio wave radiated by the radiation electrode 124. Thus, when the hollow portion 155 is disposed between the radiation electrodes 121 and 124, the frequency band width of the radio wave radiated by the radiation electrode 124 basically remains unchanged. That is, when the hollow portion 155 is disposed between the radiation electrodes 121 and 124, the expanded frequency band width of the radio wave radiated by the radiation electrode 121 can be achieved while at the same time the frequency band width of the radio wave radiated by the radiation electrode 124 is maintained.
The expanded frequency band width of the radio wave radiated by the radiation electrode 124 can be achieved by disposing a hollow portion 156 in a layer between the radiation electrode 124 and the ground electrode GND, as in an antenna module 100R in a reference example illustrated in
Furthermore, although not illustrated, the expanded frequency band widths of both the radio wave radiated by the radiation electrode 121 and that by the radiation electrode 124 can be achieved by disposing the hollow portion in each of a layer between the radiation electrodes 121 and 124 and a layer between the radiation electrode 124 and the ground electrode GND.
In the antenna modules illustrated in
In the antenna module 100Q in
As described above, in dual-band type antenna modules including the two stacked radiation electrodes and capable of radiating radio waves in different frequency ranges, the frequency band width of each of the radio waves can be individually adjusted by disposing the hollow portion in the layer between the two radiation electrodes and/or the layer between the radiation electrode on the low-frequency side and the ground electrode.
It is to be understood that the embodiments disclosed here are illustrative and not restrictive in all respects. The scope of the present disclosure is indicated by not the above description of the embodiments but the claims, and it is intended to include all changes in the meaning and scope equivalent to the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-182098 | Sep 2018 | JP | national |
This is a continuation of International Application No. PCT/JP2019/035606 filed on Sep. 11, 2019 which claims priority from Japanese Patent Application No. 2018-182098 filed on Sep. 27, 2018. The contents of these applications are incorporated herein by reference in their entireties.
| Number | Name | Date | Kind |
|---|---|---|---|
| 20170222316 | Mizunuma et al. | Aug 2017 | A1 |
| Number | Date | Country |
|---|---|---|
| H02-256305 | Oct 1990 | JP |
| H11-150373 | Jun 1999 | JP |
| 2000-138525 | May 2000 | JP |
| 2006229871 | Aug 2006 | JP |
| WO-2016063759 | Apr 2016 | WO |
| Entry |
|---|
| International Search Report for PCT/JP2019/035606 dated Oct. 8, 2019. |
| Written Opinion for PCT/JP2019/035606 dated Oct. 8, 2019. |
| Number | Date | Country | |
|---|---|---|---|
| 20210184344 A1 | Jun 2021 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2019/035606 | Sep 2019 | WO |
| Child | 17189442 | US |
