Antenna module and communication device

Abstract

This antenna module comprises: a dielectric substrate (130) having a first main surface (11) and a second main surface that face each other; an RF pad (20) disposed on the first main surface (11); a first ground pad (40) disposed on the first main surface (11); and a radiation electrode disposed on the dielectric substrate (130) at a position different from the first main surface (11). The dielectric substrate (130) has a resist layer (140) formed on the first main surface (11). In a plan view of the dielectric substrate (130) from the normal direction, the resist layer (140) is not formed on a straight line connecting one point on the RF pad (20) and one point on the first ground pad (40).

Description

Antenna module and communication device

[0001] The present disclosure relates to an antenna module and a communication device.

[0002] A resist layer is formed on the surface of a substrate used in an antenna module. Japanese Patent No. 7294525 (Patent Document 1) describes that the structure of the resist layer formed on the dielectric substrate may be either an over resist, in which the resist covers part of the electrode pad, or a clearance resist, in which a gap exists between the electrode pad and the resist.

[0003] Patent No. 7294525

[0004] However, Patent Document 1 does not describe the relationship between the antenna gain and the resist layer.

[0005] The present disclosure aims to improve the antenna gain of an antenna module.

[0006] An antenna module according to one aspect of the present disclosure comprises a dielectric substrate having opposing first and second main surfaces, an RF pad arranged on the first main surface, a first ground pad arranged on the first main surface, and a radiating electrode arranged on the dielectric substrate at a position different from the first main surface, wherein the dielectric substrate has a resist layer formed on the first main surface, and when the dielectric substrate is viewed in a plan view from the normal direction, the resist layer is not formed on a straight line connecting a point on the RF pad and a point on the first ground pad.

[0007] an antenna module according to another aspect of the present disclosure, the antenna module including: a dielectric substrate having first and second principal surfaces facing each other; a radiation electrode arranged on the dielectric substrate in a direction perpendicular to the dielectric substrate; a first ground electrode arranged on the dielectric substrate closer to the first principal surface than the radiation electrode so as to face the radiation electrode; a second ground electrode arranged on the dielectric substrate on the first principal surface so as to face the first ground electrode; a feed circuit; and a feed line connecting the feed circuit and the radiation electrode, the feed circuit including a third ground electrode and the feed line including a conductor electrode arranged so as to face the first ground electrode;

[0008] According to the antenna module according to the present disclosure, the antenna gain of the antenna module can be improved.

[0009] 8A and 8B are graphs showing the antenna gain of the antenna module shown by the equivalent circuits shown in FIGS. 8A and 8B ; and FIG. 8B is a graph showing the reflection loss of the antenna module shown by the equivalent circuits shown in FIGS. 8A and 8B ; and FIG. 8C is a graph showing the heat loss of the stripline of the antenna module according to the present embodiment and the heat loss of the stripline of the antenna module according to the comparative example. 2 is a graph showing the antenna gain of the antenna module according to the present embodiment and the antenna gain of the antenna module according to a comparative example.

[0010] Hereinafter, the present embodiment will be described in detail with reference to the drawings, in which the same or corresponding parts are designated by the same reference numerals and description thereof will not be repeated.

[0011] (Basic Configuration of Communication Device) Fig. 1 is a block diagram of a communication device 10 to which an antenna module 100 according to the first embodiment is applied. The communication device 10 is, for example, a mobile terminal such as a mobile phone, smartphone, or tablet, or a personal computer with a communication function. An example of the frequency band of radio waves applied to the antenna module 100 according to the present embodiment is millimeter-wave radio waves with center frequencies of 28 GHz, 39 GHz, and 60 GHz. Radio waves of frequency bands other than those mentioned above can also be applied to the antenna module 100 according to the present embodiment.

[0012] 1 , a communication device 10 includes an antenna module 100 and a base band integrated circuit (BBIC) 200 that configures a base band signal processing circuit. The antenna module 100 includes a system in package (SiP) 160 and an antenna device 120.

[0013] The SiP 160 has an RFIC (Radio Frequency Integrated Circuit) 110 sealed therein. The SiP 160 may further have a PMIC (Power Management Integrated Circuit) for managing the power supply system of the RFIC 110 sealed therein. The SiP 160 is an example of a power supply circuit. Note that the power supply circuit only needs to have at least a ground electrode, and does not need to be packaged like the SiP.

[0014] 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, and downconverts the high-frequency signal received by the antenna device 120 and processes the signal in the BBIC 200.

[0015] The antenna device 120 includes a dielectric substrate 130. A plurality of radiation electrodes 131 are arranged on the dielectric substrate 130. FIG. 1 shows four radiation electrodes 131 as an example of a plurality of radiation electrodes. The radiation electrode 131 is, for example, a patch antenna having a substantially square flat plate shape. The number of radiation electrodes 131 arranged on the dielectric substrate 130 may be one, or two or more. The patch antenna is merely one example of a radiation electrode. For example, the radiation electrode may be formed of a dipole antenna or a slot antenna.

[0016] The RFIC 110 includes switches 111A to 111D, 113A to 113D, and 117A, power amplifiers 112AT to 112DT, low-noise amplifiers 112AR to 112DR, attenuators 114A to 114D, phase shifters 115A to 115D, a signal combiner / divider 116A, a mixer 118A, and an amplifier circuit 119A.

[0017] When transmitting a high frequency signal, the switches 111A to 111D and 113A to 113D are switched to the power amplifiers 112AT to 112DT, and the switches 117A and 117B are connected to the transmitting amplifier of the amplifier circuit 119A. When receiving a high frequency signal, the switches 111A to 111D and 113A to 113D are switched to the low noise amplifiers 112AR to 112DR, and the switch 117A is connected to the receiving amplifier of the amplifier circuit 119A.

[0018] The signal transmitted from BBIC 200 is amplified by amplifier circuit 119A and up-converted by mixer 118A. The up-converted high-frequency transmission signal is divided into four by signal combiner / divider 116A, passes through the corresponding signal paths, and is fed to each different radiation electrode 131. By individually adjusting the phase shift of phase shifters 115A to 115D arranged on each signal path, the directivity of the radio waves output from radiation electrode 131 can be adjusted.

[0019] The received signals, which are high-frequency signals received by the radiation electrode 131, are transmitted to the RFIC 110 and then multiplexed in the signal combiner / divider 116A via different signal paths. The multiplexed received signals are down-converted by the mixer 118A, and further amplified by the amplifier circuit 119A before being transmitted to the BBIC 200.

[0020] (Arrangement of RF Pads and Ground Pads) FIG. 2 is a plan view of the dielectric substrate 130. The dielectric substrate 130 has a first main surface and a second main surface that are opposed to each other. FIG. 2 shows the first main surface 11. Hereinafter, as shown in the figure, the normal direction to the first main surface 11 of the dielectric substrate 130 will be referred to as the "Z-axis direction," the longitudinal direction of the dielectric substrate 130 that is perpendicular to the Z-axis direction will be referred to as the "Y-axis direction," and the direction perpendicular to the Y-axis and Z-axis directions will be referred to as the "X-axis direction." In addition, in the following description, the positive direction of the Z-axis in each figure may be referred to as the upper surface side, and the negative direction as the lower surface side.

[0021] When viewed from above in the normal direction (Z-axis direction), the dielectric substrate 130 has a substantially rectangular shape. The dielectric substrate 130 is, for example, a low-temperature co-fired ceramics (LTCC) multilayer substrate. The dielectric substrate 130 may be a multilayer resin substrate formed by stacking multiple resin layers made of resin such as epoxy or polyimide.

[0022] The dielectric substrate 130 may be formed of a multilayer resin substrate formed by laminating multiple resin layers made of a liquid crystal polymer (LCP) having a lower dielectric constant. The dielectric substrate 130 may also be formed of a multilayer resin substrate formed by laminating multiple resin layers made of a fluorine-based resin, a multilayer resin substrate formed by laminating multiple resin layers made of a PET (Polyethylene terephthalate) material, or a ceramic multilayer substrate other than LTCC.

[0023] The dielectric substrate 130 does not necessarily have to have a multi-layer structure, and may be a single-layer substrate. A structure corresponding to the dielectric substrate 130 may be formed using a 3D printer.

[0024] A resist layer 140 is formed on the first main surface 11 for the purposes of protecting the substrate and preventing excess solder from adhering. The first main surface 11 has a portion covered with the resist layer 140 and a portion not covered with the resist layer 140 where the first main surface 11 is exposed. The portion of the first main surface 11 that is covered with the resist layer 140 is referred to as the "covered region," and the portion not covered with the resist layer 140 where the first main surface 11 is exposed is referred to as the "exposed region." In the exposed region, the dielectric surface of the dielectric substrate 130 is exposed.

[0025] An RF pad 20 and a ground pad 40 are provided in the exposed region. The RF pad 20 and the ground pad 40 are examples of electrode pads. A via hole 501 is formed in each of the RF pad 20 and the ground pad 40. In the via hole 501, a via is provided that extends from the first main surface 11 to the conductor electrode 132 or the radiation electrode 131 in the dielectric substrate 130.

[0026] A plurality of ground pads 40 are arranged around the RF pad 20. The plurality of ground pads 40 are arranged so as to surround the RF pad 20. Fig. 2 shows an example in which four ground pads 40 are arranged so as to surround one RF pad 20 (see the dashed frame). Note that the ground pads 40 may be arranged in the direction of each vertex of a rectangle formed with the RF pad 20 as the center of gravity.

[0027] In this embodiment, the entire RF pad 20 is exposed from the resist layer 140, and an exposed area exists between the RF pad 20 and the resist layer 140. Similarly, in this embodiment, the entire ground pad 40 is exposed from the resist layer 140, and an exposed area exists between the ground pad 40 and the resist layer 140. The RF pad 20 and the ground pad 60 are not covered by the resist layer 140. That is, in this embodiment, a "clearance resist" is employed as the resist structure. A resist structure that is comparable to the "clearance resist" is known as an "over resist."

[0028] (Clearance Resist and Over Resist) Here, the difference between the clearance resist and the over resist will be explained with reference to Figures 3A, 3B, and 4. Figure 3A is a diagram showing a schematic configuration of the clearance resist. Figure 3B is a diagram showing a schematic configuration of the over resist. Figure 4 is a diagram for explaining that the substrate area required for arranging electrode pads differs between when the clearance resist is used and when the over resist is used.

[0029] The clearance resist (CR) is also called "NSMD (Non-Solder Mask Defined)." The over resist (OR) is also called "SMD (Solder Mask Defined)."

[0030] Here, the difference between clearance resist (CR) and over resist (OR) will be explained using an example in which an electrode pad 30A or an electrode pad 30B is provided on a dielectric substrate 150 including a ground electrode GND. Figures 3A and 3B are side perspective views of the dielectric substrate 150. Figure 4 is a plan view of the dielectric substrate 150.

[0031] 3A, in the case of the clearance resist, a gap exists between the electrode pad 30A and the resist layer 140. In other words, in the case of the clearance resist, the resist layer 140 does not overlap the electrode pad 30A.

[0032] As shown in FIG. 3B, in the case of the over resist, the resist layer 140 overlaps a part of the electrode pad 30B, and the resist layer 140 covers a part of the electrode pad 30B.

[0033] Solder bumps 51 are provided on the electrode pads 30A, 30B to connect the electrode pads 30A, 30B to electrical components such as circuits and electrodes. In the case of clearance resist, the solder bumps 51 are provided on the top surface of the electrode pad 30A as well as on the side surface of the electrode pad 30A. In the case of clearance resist, the bonding area between the solder bumps 51 and the electrode pad 30A is increased by the amount of copper foil provided on the side surface, so the adhesive strength between the dielectric substrate 150 and the electrical components is high.

[0034] In particular, in the case of clearance resist, the solder bumps 51 are poured not only onto the top surface of the electrode pad 30A but also onto the side surfaces, so the side surfaces of the electrode pad 30A are reinforced by the solder bumps 51. On the other hand, in the case of over resist, the electrode pad 30B and the solder bumps 51 are bonded only to the top surface of the electrode pad 30B. For this reason, the over resist has a lower adhesion strength between the dielectric substrate 150 and the electrical component than the clearance resist.

[0035] Furthermore, in the case of over resist, cracks may occur between the electrode pad 30B and the dielectric substrate 150 (at the side surface of the electrode pad 30B) in the process of arranging the solder bump 51 on the electrode pad 30B. Such cracks may occur because thermal stress concentrates between the electrode pad 30A and the via due to thermal contraction between the solder bump 51 and the dielectric substrate 150. In contrast, in the case of clearance resist, the side surface of the electrode pad 30A is reinforced by the solder bump 51, which solves the manufacturing problem that may occur in the process of arranging the solder bump 51 on the electrode pad 30B.

[0036] In the case of over resist, in order to ensure a bonding surface of the same size as that of electrode pad 30A, the pad diameter of electrode pad 30B needs to be larger than that of electrode pad 30A. This is because the pad surface covered by the resist layer needs to be provided on electrode pad 30B separately from the bonding surface. In other words, when comparing both with the same electrode pad size, clearance resist can ensure a wider bonding surface than over resist.

[0037] As a result, compared to the over resist, the clearance resist can increase the distance between the electrode pads without increasing the size of the dielectric substrate 150. This becomes even more apparent with reference to FIG.

[0038] 4 shows an example in which two electrode pads 30A, 30A are arranged on a dielectric substrate 150 that employs a clearance resist, and an example in which two electrode pads 30B, 30B are arranged on a dielectric substrate 150 that employs an over resist. The pad diameter of the electrode pad 30A is Da, and the pad diameter of the electrode pad 30B is Db. In order to ensure that the same bonding area as that of the electrode pad 30A is ensured for the electrode pad 30B, the pad diameter of the electrode pad 30B must be made larger than that of the electrode pad 30A.

[0039] The distance between adjacent electrode pads 30A, 30A is L1, and the distance between adjacent electrode pads 30B, 30B is also L1. The arrangement width required to arrange the electrode pads 30A, 30A is L2. The arrangement width required to arrange the electrode pads 30B, 30B is L3. As is clear from FIG. 4, "L2<L3" holds.

[0040] In other words, in the case of over resist, in order to ensure the same distance between the electrode pads as with clearance resist, the arrangement width of the electrode pad 30B must be increased. As a result, the substrate surface of the dielectric substrate 150 must be increased. In other words, in the case of clearance resist, the distance between the electrode pads can be ensured without increasing the substrate size of the dielectric substrate 150, as compared to over resist. When a large number of electrode pads (RF pads 20, ground pads 40) are arranged on the dielectric substrate 130 as shown in FIG. 2, the distance between the electrode pads can be ensured more effectively.

[0041] (Use of Clearance Resist) The differences between clearance resist and over resist have been explained above using FIGS. 3A, 3B, and 4. The antenna module 100 according to this embodiment uses clearance resist, as shown in FIG. 2. This increases the adhesive strength between the dielectric substrate 130 and the electrical components, and also solves manufacturing problems that may arise in the process of placing solder bumps 51 on the RF pads 20 and ground pads 40. Furthermore, because the pad diameters of the RF pads 20 and ground pads 40 can be reduced, the distance between the RF pads 20 and ground pads 40 can be ensured without increasing the substrate surface of the dielectric substrate 150.

[0042] When the solder bumps 51 are disposed on the RF pads 20 and the ground pads 40, flux residue adheres to the RF pads 20 and the ground pads 40. Such flux residue may not be removed and may be left on the dielectric substrate 130 as a member for increasing the adhesive strength between the dielectric substrate 130 and the electrical components.

[0043] When the distance between the RF pad 20 and the ground pad 40 is short, the degree of capacitive coupling that occurs between the RF pad 20 and the ground pad 40 increases. This reduces the frequency gain of the antenna module 100 and narrows the frequency band. However, in the present embodiment, the distance between the RF pad 20 and the ground pad 40 can be secured, thereby improving the frequency gain of the antenna module 100 and widening the frequency band.

[0044] (RF Pad 20 Surrounded by Ground Pads 40) Referring again to FIG. 2 , the RF pad 20 and the ground pad 40 will be described. In this embodiment, no resist layer is formed between the RF pad 20 and the four ground pads 40 surrounding the RF pad 20. In other words, when the dielectric substrate 130 is viewed in a plan view from the normal direction, the resist layer 140 is not formed on a line connecting a point on the RF pad 20 and a point on the ground pad 40. Therefore, in this embodiment, the resist layer is removed from a wider area of ​​the first main surface 11 than in the clearance resist illustrated in FIG. 3A . Note that "no resist layer 140 is formed on a line connecting a point on the RF pad 20 and a point on the ground pad 40" means that no resist layer 140 exists on any line connecting any point on the RF pad 20 and any point on the ground pad 40.

[0045] As shown in FIG. 2, the interval between adjacent ground pads 40 is ¼ of the wavelength λ of the radio wave radiated from the radiation electrode 131 (see FIG. 5) provided on the antenna module 100 .

[0046] However, the spacing between adjacent ground pads 40, 40 may be equal to or less than ¼ of the wavelength λ of the radio waves radiated by the radiation electrode provided on the antenna module 100. In particular, the spacing between adjacent ground pads 40, 40 may be equal to or less than ¼ of the wavelength λ corresponding to a frequency in a high frequency band (e.g., 29.5 GHz) of the frequency band of the radio waves radiated by the radiation electrode provided on the antenna module 100.

[0047] (Structure of Antenna Module 100) FIG. 5A is a side perspective view of the antenna module 100 according to this embodiment. FIG. 5B is a diagram schematically illustrating the structure of a stripline SLa. FIG. 5C is a diagram schematically illustrating the structure of a stripline SLb. As shown in FIG. 5A , a radiating electrode 131 that radiates radio waves is provided on the dielectric substrate 130. The radiating electrode 131 is disposed on the dielectric substrate 130 at a position away from the first main surface 11. Therefore, the radiating electrode 131 is provided, for example, at a position on the dielectric substrate 130 closer to the second main surface 12 than to the first main surface 11. The radiating electrode 131 may be provided on the second main surface 12. The radiating electrode 131 may be provided on the dielectric substrate 130 so that a portion of the radiating electrode 131 is exposed from the second main surface 12. Note that FIG. 5A illustrates one radiating electrode 131 as a representative example of the multiple radiating electrodes 131 shown in FIG. 1 .

[0048] A ground electrode GND11 and a ground electrode GND21 are provided on the dielectric substrate 130. The ground electrode GND11 is disposed on the dielectric substrate 130 closer to the first main surface 11 than the radiation electrode 131 so as to face the radiation electrode 131.

[0049] The dielectric layer of the dielectric substrate 130 on which the ground electrode GND21 is provided is the same as the dielectric layer of the dielectric substrate 130 on which the RF pad 20 and the ground pad 40 are provided. The ground electrode GND21 is disposed on the first main surface 11 of the dielectric substrate 130 so as to face the ground electrode GND11. The ground electrode GND11 is an example of a first ground electrode. The ground electrode GND21 is an example of a second ground electrode.

[0050] The ground electrode GND11 is electrically connected to the ground electrode GND21 through the via 152, and is also electrically connected to the ground pad 40 through the via 151. Therefore, the ground electrode GND11, the ground electrode GND21, and the ground pad 40 are at the same potential through the vias 151 and 152.

[0051] An SiP 160 including an RFIC 110 is disposed on the dielectric substrate 130. The SiP 160 includes ground electrodes GND 31 and 32 and an RF pad 21. The ground electrodes GND 31 and 32 and the RF pad 21 are provided on the bottom surface of the SiP 160. The SiP 160 is an example of a power supply circuit. The ground electrodes GND 31 and 32 are an example of a third ground electrode.

[0052] The SiP160 is connected to the RF pad 20 and the ground pad 40. Furthermore, the SiP160 is connected to the ground electrode GND 21. More specifically, the RF pad 21 of the SiP160 and the RF pad 20 of the dielectric substrate 130 are connected by solder bumps 51, the ground electrode GND 31 of the SiP160 and the ground pad 40 of the dielectric substrate 130 are connected by solder bumps 51, and the ground electrode GND 32 of the SiP160 and the ground electrode GND 21 of the dielectric substrate 130 are connected by solder bumps 51.

[0053] The dielectric substrate 130 is provided with power supply wirings 201 and 202 and a conductor electrode 132 that connect the RF pad 20 and the radiation electrode 131. The power supply wirings 201 and 202 and the conductor electrode 132 connect the SiP 160 and the radiation electrode 131 via the RF pads 20 and 21. The power supply wirings 201 and 202 and the conductor electrode 132 are an example of a power supply line that connects the RF pad 20 and the radiation electrode 131. The conductor electrode 132 is arranged to face the ground electrode GND11.

[0054] Strip lines SLa and SLb including a conductor electrode 132 and a ground electrode GND11 are formed on the dielectric substrate 130. The strip line SLa is formed in a portion where the ground electrode GND11 and the ground electrode GND21 face each other across the conductor electrode 132. The facing distance Ha between the conductor electrode 132 and the ground electrode GND11 is the same as the facing distance Ha between the conductor electrode 132 and the ground electrode GND21. That is, the facing distance between the conductor (conductor electrode 132) and the shield (ground electrodes GND11 and GND21) in the strip line SLa is Ha. Note that the facing distance Ha between the conductor electrode 132 and the ground electrode GND11 and the facing distance Ha between the conductor electrode 132 and the ground electrode GND21 do not have to be the same. In this case, it is sufficient that the facing distance Hb is at least longer than the facing distance Ha between the conductor electrode 132 and the ground electrode GND21.

[0055] The strip line SLb is formed in a portion where the ground electrode GND11 and the ground electrode GND32 face each other across the conductor electrode 132. The opposing distance Hb between the conductor electrode 132 and the ground electrode GND32 is longer than the opposing distance Ha between the conductor electrode 132 and the ground electrode GND11. That is, in the strip line SLb, the opposing distance between the conductor (conductor electrode 132) and one shield (ground electrode GND11) is Ha, and the opposing distance between the conductor (conductor electrode 132) and the other shield (ground electrode GND32) is Hb.

[0056] As described above, the feeder line of the antenna module 100 includes the stripline SLb having a different gap size relative to the conductor. The distance from the conductor electrode 132 to the ground surface on the first main surface 11 side is longer for the stripline SLb than for the stripline SLa. Therefore, it is necessary to achieve capacitance matching between the stripline SLa and the stripline SLb. In this embodiment, from the viewpoint of such capacitance matching, the feeder line (conductor electrode 132) is designed so that the line width in the X-axis direction of the portion corresponding to the stripline SLb is larger than that of the portion corresponding to the stripline SLa.

[0057] More specifically, since the distance from the conductor electrode 132 to the ground plane is closer to the strip line SLa than to the strip line SLb (Ha<Hb), the capacitance of the strip line SLa is greater than the capacitance of the strip line SLb. For this reason, from the viewpoint of adjusting the characteristic impedance, the strip line SLa is designed to be thinner than the strip line SLb so that its reactance is greater.

[0058] On the other hand, since the distance from the conductor electrode 132 to the ground plane of the stripline SLb is greater than that of the stripline SLa (Ha<Hb), the capacitance of the stripline SLb is smaller than that of the stripline SLa. For this reason, from the viewpoint of adjusting the characteristic impedance, the stripline SLb is designed to be thicker than the stripline SLa so that its reactance is smaller.

[0059] In this way, in the portion where the line width is large, the conduction resistance is small, and the conductor loss is reduced. Therefore, when the line width is adjusted so that the strip lines SLa and SLb have the same characteristic impedance, the conductor loss of the strip line SLb is smaller than that of the strip line SLa. Therefore, the transmission loss (heat loss) of the strip line SLb can be reduced more than that of the strip line SLa. This contributes to raising the antenna gain of the antenna module 100 across the entire frequency band.

[0060] The gap size is different between the stripline SLa and the stripline SLb. Therefore, the feed line of the antenna module 100 includes a portion where the striplines SLa and SLb with different gap sizes are connected in series.

[0061] As shown in Fig. 5B, the strip line SLa includes a dielectric layer between the conductor electrode 132 and the ground electrode GND 11, and a dielectric layer between the conductor electrode 132 and the ground electrode GND 21. In contrast, the strip line SLb includes a dielectric layer between the conductor electrode 132 and the ground electrode GND 11, a dielectric layer between the conductor electrode 132 and the first main surface 11, and an air layer between the first main surface 11 and the ground electrode GND 32 (see Fig. 5C). The air layer is formed between adjacent solder bumps 51 on the first main surface 11. The dielectric layer and the air layer form an insulator.

[0062] In this way, the feeder line of the antenna module 100 includes a portion in which two striplines SLa and SLb having different gap sizes and containing different insulator compositions are connected in series. Hereinafter, this portion in which two striplines SLa and SLb having different gap sizes and containing different insulator compositions are connected in series will be referred to as a "stripline SLab."

[0063] 6 is a side perspective view of an antenna module 1000 according to a comparative example. The antenna module 1000 according to the comparative example differs from the antenna module 100 according to the present embodiment in that only a single stripline SLa is formed on the feed line.

[0064] 6 , in the antenna module 1000, the ground electrode GND2100 provided on the first main surface 11 of the dielectric substrate 1300 extends closer to the RF pad 20. Therefore, in the antenna module 1000, a "portion where the ground electrode GND2100 does not exist" is not generated in the portion where the ground electrode GND11 and the ground electrode GND32 face each other across the conductor electrode 132. As a result, in the antenna module 1000, a stripline SLa is formed, but a stripline SLb like that in the antenna module 100 according to the present embodiment is not formed.

[0065] (Comparison of Equivalent Circuits Between the Present Embodiment and the Comparative Example) Fig. 7A is a diagram showing an equivalent circuit of the antenna module 100 according to the present embodiment. Fig. 7B is a diagram showing an equivalent circuit of the antenna module 1000 according to the comparative example. The antenna module 1000 differs from the antenna module 100 in the configuration of the strip line. To further facilitate understanding of the present embodiment, it is assumed that the antenna module 1000 employs an over resist. Therefore, the antenna module 1000 differs from the antenna module 100, which employs a clearance resist, in that it employs an over resist.

[0066] Because the antenna module 1000 employs an over resist, the antenna module 1000 is unable to ensure a sufficient distance between the electrode pads, as is the case with the antenna module 100. As a result, the antenna module 1000 is unable to ensure a sufficient distance between the RF pad 20 and the ground pad 40, and a non-negligible amount of capacitive coupling occurs between the RF pad 20 and the ground pad 40.

[0067] 7A, the equivalent circuit of the antenna module 100 includes a stripline SLab in which a stripline SLa and a stripline SLb are connected in series. In contrast, the equivalent circuit of the antenna module 1000 does not include the stripline SLb (see FIG. 7B).

[0068] Furthermore, the equivalent circuit of the antenna module 1000 includes a capacitance Ca due to capacitive coupling between the RF pad 20 and the ground pad 40. In contrast, in the antenna module 100, a sufficient distance is ensured between the RF pad 20 and the ground pad 40, and therefore such capacitance Ca is not included in the equivalent circuit.

[0069] Next, differences in antenna characteristics between the present embodiment and the comparative example will be described with reference to Figures 8A, 8B, 9A, 9B, and 11. As can be seen from the equivalent circuit, the present embodiment and the comparative example differ in two respects: (i) the presence or absence of capacitance Ca, and (ii) the configuration of the strip line. Capacitance Ca occurs when an over resist is used as the resist structure, but does not occur when a clearance resist is used as the resist structure. Therefore, the "presence or absence of capacitance Ca" is affected by the resist structure.

[0070] Therefore, in the following, we will first explain the antenna characteristics (antenna gain and return loss) by focusing on the "resist structure" that affects the presence or absence of capacitance Ca, then explain the antenna characteristics (heat loss) by focusing on the "strip line configuration," and finally explain the difference in overall antenna characteristics (antenna gain) between this embodiment and the comparative example. Note that graphs referred to in the following explanation show simulation results related to the antenna characteristics.

[0071] (Antenna characteristics - from the viewpoint of resist structure) Fig. 8A is a diagram showing an equivalent circuit of an antenna module 1000A employing a clearance resist. Fig. 8B is a diagram showing an equivalent circuit of an antenna module 1000B employing an over resist. Fig. 9A is a graph showing the antenna gain of the antenna module represented by each of the equivalent circuits shown in Figs. 8A and 8B. Fig. 9B is a graph showing the return loss of the antenna module represented by each of the equivalent circuits shown in Figs. 8A and 8B.

[0072] As shown in Fig. 8B, the equivalent circuit of the antenna module 1000B employing the over resist includes a capacitance Ca. In contrast, the equivalent circuit of the antenna module 1000A employing the clearance resist does not include the capacitance Ca (see Fig. 8A).

[0073] Here, in order to match the simulation conditions other than the capacitance Ca, it is assumed that both the antenna module 1000A and the antenna module 1000B have a strip line SL with a line length of L1.

[0074] 9A and 9B show simulation results for the antenna gain and return loss of the antenna module 1000A and the antenna module 1000B. As is clear from the graphs for antenna gain, the antenna module 1000A has improved antenna gain and a wider frequency bandwidth than the antenna module 1000B in the high-frequency band. Furthermore, as is clear from the graphs for return loss, the antenna module 1000A has improved return loss and a wider frequency bandwidth than the antenna module 1000B in the high-frequency band.

[0075] In order to prevent the generation of capacitance Ca, the antenna module 1000A employs a clearance resist. In the antenna module 1000A, energy is released into radio wave space without being absorbed by capacitance Ca. As a result, it is believed that the antenna gain of the antenna module 1000A has improved.

[0076] (Antenna Characteristics - From the Viewpoint of Stripline) FIG. 10 is a graph showing the heat loss of the stripline of the antenna module 100 according to the present embodiment and the heat loss of the stripline of the antenna module 1000 according to the comparative example.

[0077] The antenna module 100 has a stripline SLab, and the antenna module has a stripline SLa. Figure 10 shows simulation results showing heat loss in the stripline SLab and the stripline SLa.

[0078] The inventors calculated the heat loss of each of the striplines SLab and SLa while changing the line length of each of the striplines SLab and SLa to 0.5 mm, 1 mm, and 3 mm.

[0079] From the graph shown in FIG. 10, it can be seen that the strip line SLab has less heat loss than the strip line SLa across the entire frequency band, regardless of whether the line length is 0.5 mm, 1 mm, or 3 mm.

[0080] (Antenna Characteristics - Present Embodiment and Comparative Example) FIG. 11 is a graph showing the antenna gain of the antenna module 100 according to the present embodiment and the antenna gain of the antenna module 1000 according to the comparative example.

[0081] When performing the simulation, the line length of the stripline SLab was set to 4 mm. To standardize the simulation conditions, the line length of the stripline SLa of the antenna module 1000 was also set to 4 mm. Of the striplines SLab, the line length of the stripline SLa was set to 1 mm, and the line length of the stripline SLb was set to 3 mm. In other words, the line length of the stripline SLb was set longer than the line length of the stripline SLa.

[0082] 11, it can be seen that the antenna module 100 has a higher antenna gain across the entire frequency band than the antenna module 1000. In particular, it can be seen that the frequency bandwidth of the antenna module 100 is wider than that of the antenna module 1000 in the high frequency band.

[0083] By employing the clearance resist, the antenna module 100 can reduce the capacitance that occurs between the RF pad 20 and the ground pad 40. This is thought to contribute to improving the antenna gain, particularly in high frequency bands (for example, a frequency band around 29.5 GHz).

[0084] The antenna module 100 further includes a stripline SLab, and this configuration is believed to contribute to increasing the antenna gain across all frequency bands. In particular, the greater the proportion of the stripline SLb in the stripline SLab, the greater the effect on increasing the antenna gain (see FIG. 10 ). Therefore, it is desirable to configure the stripline SLab so that the stripline SLb is longer than the stripline SLa.

[0085] The configuration example related to this simulation shows an example of a configuration in which the line length of the stripline SLb is longer than the line length of the stripline SLa. The longer the line length of the stripline SLb, the more preferable. However, it is sufficient that at least the stripline SLb is configured in the antenna module 100. For example, the antenna module 100 may have the stripline SLb but not the stripline SLa. Alternatively, the line length of the stripline SLb may be shorter than the line length of the stripline SLa. The line length of the stripline SLb may be longer than the opposing distance Ha shown in FIG. 5.

[0086] As described above, in this embodiment, a clearance resist is used as the resist structure, and in particular, when the dielectric substrate 130 is viewed in a plan view from the normal direction, the resist layer 140 is not formed on a line connecting a point on the RF pad 20 and a point on the ground pad 40. According to this embodiment, the distance between the RF pad 20 and the ground pad 40 can be ensured without increasing the size of the first main surface 11 of the dielectric substrate 130, thereby reducing the occurrence of capacitive coupling between the RF pad 20 and the ground pad 40, which adversely affects the antenna gain. As a result, according to this embodiment, the antenna gain of the antenna module 100 can be improved.

[0087] In this embodiment, the antenna feed wiring includes a stripline SLab. The stripline SLab includes a portion in which two striplines SLa and SLb, which have different gap sizes and contain different insulator compositions, are connected in series. According to this embodiment, the antenna gain of the antenna module 100 can be increased across the entire frequency band.

[0088] (Modification) Fig. 12 is a diagram showing a modification of the dielectric substrate 130 shown in Fig. 2. As an example of the "clearance resist," Fig. 2 shows an example in which an exposed region extends over the entire area surrounding the RF pad 20 and the ground pad 40. However, as shown in Fig. 12, a resist layer 140 may be provided on the dielectric substrate 130 as the "clearance resist" so that an exposed region is formed in the portion where the RF pad 20 and the ground pad 40 face each other, and a covered region is not formed in the portion where the RF pad 20 and the ground pad 40 do not face each other.

[0089] In the modified example, the area of ​​the first main surface 11 of the dielectric substrate 130 covered by the resist layer 140 is larger than in the example of "clearance resist" shown in Fig. 2. Similar to the example shown in Fig. 2, the modified example is an example of a configuration in which "the resist layer 140 is not formed on a line connecting one point on the RF pad 20 and one point on the ground pad 40."

[0090] [Aspects] It will be understood by those skilled in the art that the above-described embodiments are specific examples of the following aspects.

[0091] (Item 1) An antenna module according to one embodiment comprises a dielectric substrate having opposing first and second main surfaces, an RF pad arranged on the first main surface, a first ground pad arranged on the first main surface, and a radiating electrode arranged on the dielectric substrate at a position different from the first main surface, wherein the dielectric substrate has a resist layer formed on the first main surface, and when the dielectric substrate is viewed in a plan view from the normal direction, the resist layer is not formed on a straight line connecting a point on the RF pad and a point on the first ground pad.

[0092] (Item 2) The antenna module of item 1, wherein a plurality of ground pads including a first ground pad are arranged on the first main surface, and the plurality of ground pads are arranged so as to surround the RF pad.

[0093] (Item 3) The antenna module of item 2, wherein the number of the ground pads is four.

[0094] (4) In the antenna module of any one of paragraphs 1 to 3, the RF pad and the first ground pad are not covered with a resist layer.

[0095] (Item 5) An antenna module according to item 2 or 3, further comprising a power supply line connecting the RF pad and the radiation electrode, wherein the spacing between adjacent ground pads among the plurality of ground pads is equal to or less than 1 / 4 of the wavelength of the radio waves emitted by the radiation electrode.

[0096] (Item 6) The antenna module of any one of Items 1 to 4 further includes: a first ground electrode arranged on the dielectric substrate closer to the first principal surface than the radiation electrode so as to face the radiation electrode; a second ground electrode arranged on the dielectric substrate on the first principal surface so as to face the first ground electrode; a feed line connecting the RF pad and the radiation electrode; and a feed circuit, wherein the feed circuit includes a third ground electrode, and the feed circuit is connected to the RF pad and the first ground pad, and the feed line includes a conductor electrode arranged so as to face the first ground electrode; and a strip line including the conductor electrode and the first ground electrode is formed on the dielectric substrate, and the strip line includes a first strip line in which the first ground electrode and the second ground electrode face each other across the conductor electrode, and a second strip line in which the first ground electrode and the third ground electrode face each other across the conductor electrode.

[0097] (Item 7) In the antenna module of item 6, the line length of the second stripline is longer than the line length of the first stripline.

[0098] (Clause 8) In the antenna module of clause 6 or clause 7, when the dielectric substrate is viewed in a plane from a direction perpendicular to the normal direction, the first strip line includes a dielectric layer between the conductor electrode and the first ground electrode and a dielectric layer between the conductor electrode and the second ground electrode, and the second strip line includes a dielectric layer between the conductor electrode and the first ground electrode, a dielectric layer between the conductor electrode and the first main surface, and an air layer between the first main surface and the third ground electrode.

[0099] (Item 9) An antenna module according to another aspect includes a dielectric substrate having opposing first and second main surfaces, a radiation electrode arranged on the dielectric substrate in a direction perpendicular to the dielectric substrate, a first ground electrode arranged on the dielectric substrate closer to the first main surface than the radiation electrode so as to face the radiation electrode, a second ground electrode arranged on the dielectric substrate on the first main surface so as to face the first ground electrode, a feed circuit, and a feed line connecting the feed circuit and the radiation electrode, wherein the feed circuit includes a third ground electrode and the feed line includes a conductor electrode arranged so as to face the first ground electrode, and a strip line including the conductor electrode and the first ground electrode is formed on the dielectric substrate, and the strip line includes a first strip line in which the first ground electrode and the second ground electrode face each other across the conductor electrode, and a second strip line in which the first ground electrode and the third ground electrode face each other across the conductor electrode.

[0100] (10) A communication device according to one aspect is equipped with the antenna module according to any one of the first to ninth aspects.

[0101] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims.

[0102] 10 Communication device, 11 First main surface, 12 Second main surface, 20, 21 RF pad, 30A, 30B Electrode pad, 40 Ground pad, 51 Solder bump, 100, 1000, 1000A, 1000B Antenna module, 110 RFIC, 111A to 111D, 113A to 113D, 117A Switch, 112AR to 112DR Low noise amplifier, 112AT to 112DT Power amplifier, 114A to 114D Attenuator, 115A to 115D Phase shifter, 116A Signal combiner / divider, 118A Mixer, 119A Amplifier circuit, 120 Antenna device, 130, 150, 1300 Dielectric substrate, 131 Radiation electrode, 132 Conductor electrode, 140 Resist layer, 151, 152 via, 160 SiP, 200 BBIC, 201, 202 power supply wiring, 501 via hole, Ca capacitance, GND, GND11, GND21, GND31, GND32, GND2100 ground electrode, SL, SLa, SLb, SLab strip line.

Claims

1. An antenna module comprising: a dielectric substrate having opposing first and second principal surfaces; an RF pad arranged on the first principal surface; a first ground pad arranged on the first principal surface; and a radiation electrode arranged on the dielectric substrate at a position different from the first principal surface, wherein the dielectric substrate has a resist layer formed on the first principal surface, and when the dielectric substrate is viewed in a plan view from the normal direction, the resist layer is not formed on a straight line connecting a point on the RF pad and a point on the first ground pad.

2. The antenna module according to claim 1, wherein a plurality of ground pads including the first ground pad are arranged on the first main surface, and the plurality of ground pads are arranged so as to surround the RF pad.

3. The antenna module according to claim 2, wherein the number of said plurality of ground pads is four.

4. The antenna module according to any one of claims 1 to 3, wherein the RF pad and the first ground pad are not covered by the resist layer.

5. An antenna module as described in claim 2 or claim 3, further comprising a power supply line connecting the RF pad and the radiation electrode, wherein the spacing between adjacent ground pads among the plurality of ground pads is equal to or less than 1 / 4 of the wavelength of the radio waves emitted by the radiation electrode.

6. The antenna module according to any one of claims 1 to 4, further comprising: a first ground electrode arranged on the dielectric substrate closer to the first principal surface than the radiation electrode so as to face the radiation electrode; a second ground electrode arranged on the dielectric substrate on the first principal surface so as to face the first ground electrode; a feed line connecting the RF pad and the radiation electrode; and a feed circuit, wherein the feed circuit includes a third ground electrode, the feed circuit is connected to the RF pad and the first ground pad, and the feed line includes a conductor electrode arranged so as to face the first ground electrode, a strip line including the conductor electrode and the first ground electrode is formed on the dielectric substrate, and the strip line includes: a first strip line in which the first ground electrode and the second ground electrode face each other with the conductor electrode between them, and a second strip line in which the first ground electrode and the third ground electrode face each other with the conductor electrode between them.

7. The antenna module according to claim 6, wherein the line length of the second stripline is longer than the line length of the first stripline.

8. The antenna module according to claim 6 or 7, wherein, when the dielectric substrate is viewed in a plane from a direction perpendicular to the normal direction, the first strip line includes a dielectric layer between the conductor electrode and the first ground electrode, and a dielectric layer between the conductor electrode and the second ground electrode, and the second strip line includes a dielectric layer between the conductor electrode and the first ground electrode, a dielectric layer between the conductor electrode and the first main surface, and an air layer between the first main surface and the third ground electrode.

9. An antenna module comprising: a dielectric substrate having opposing first and second main surfaces; a radiation electrode arranged on the dielectric substrate in a direction perpendicular to the dielectric substrate; a first ground electrode arranged on the dielectric substrate closer to the first main surface than the radiation electrode so as to face the radiation electrode; a second ground electrode arranged on the dielectric substrate on the first main surface so as to face the first ground electrode; a feed circuit; and a feed line connecting the feed circuit and the radiation electrode, wherein the feed circuit includes a third ground electrode, and the feed line includes a conductor electrode arranged so as to face the first ground electrode, a strip line including the conductor electrode and the first ground electrode is formed on the dielectric substrate, and the strip line includes: a first strip line in which the first ground electrode and the second ground electrode face each other across the conductor electrode, and a second strip line in which the first ground electrode and the third ground electrode face each other across the conductor electrode.

10. A communication device equipped with the antenna module according to any one of claims 1 to 9.

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