Patent Publication Number: US-2023163488-A1

Title: Antenna assembly and electronic device including same

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation application, claiming priority under §365(c), of an International application No. PCT/KR2022/015550, filed on Oct. 14, 2022, which is based on and claims the benefit of a Korean patent application number 10-2021-0139564, filed on Oct. 19, 2021, in the Korean Intellectual Property Office, and of a Korean patent application number 10-2022-0011067, filed on Jan. 25, 2022, in the Korean Intellectual Property Office, the disclosure of each of which is incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     The disclosure relates to a wireless communication system. More particularly, the disclosure relates to an antenna assembly and an electronic device including the same in a wireless communication system. 
     BACKGROUND ART 
     To meet the increased demand for wireless data traffic since deployment of 4th generation (4G) communication systems, efforts have been made to develop an improved 5th generation (5G) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post long-term evolution (LTE) System’. 
     The 5G communication system is considered to be implemented in higher frequency (millimeter (mm) Wave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems. 
     In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud radio access networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, coordinated multi-Points (CoMP), reception-end interference cancellation and the like. 
     In the 5G system, hybrid frequency shift keying (FSK) and quadrature amplitude modulation (QAM) (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed. 
     There has been development of products equipped with multiple antennas to improve communication performance, and it is expected that equipment having far more antennas will be used. As more antenna elements are used for communication devices, there is an increasing demand for an antenna structure for reducing performance degradation during fabrication and assembling processes. 
     The above information is presented as background information only to assist with an understanding of the disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the disclosure. 
     DISCLOSURE 
     Technical Problem 
     Aspects of the disclosure are to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the disclosure is to provide an antenna module and an electronic device including the same, wherein in connection with a dual antenna structure in which antennas are disposed on two different layers while being spaced apart, an adhesive material is disposed between a metal substrate and an antenna substrate, thereby improving antenna assembly assembling performance. 
     Another aspect of the disclosure is to provide an antenna module and an electronic device including the same, wherein antennas are positioned within a layer of a metal substrate in connection with a dual antenna structure in a wireless communication system, thereby providing a high level of antenna performance. 
     Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments. 
     Technical Solution 
     In accordance with an aspect of the disclosure, an antenna assembly is provided. The antenna assembly includes a first flexible printed circuit board (FPCB) for multiple first antennas, a second flexible printed circuit board (FPCB) for multiple second antennas, a metal plate including multiple holes, a first adhesive material layer for bonding between the metal plate and the first FPCB, and a second adhesive material layer for bonding between the metal plate and the second FPCB, wherein the metal plate is disposed such that the multiple first antennas are located in the multiple holes, respectively and the multiple second antennas are located in the multiple holes, respectively. 
     In accordance with another aspect of the disclosure, a radio unit (RU) module is provided. The RU module includes a printed circuit board (PCB), and multiple antenna assemblies, wherein an antenna assembly of the multiple antenna assemblies includes a first flexible printed circuit board (FPCB) for multiple first antennas, a second flexible printed circuit board (FPCB) for multiple second antennas, a metal plate including multiple holes, a first adhesive material layer for bonding between the metal plate and the first FPCB, and a second adhesive material layer for bonding between the metal plate and the second FPCB, and wherein the metal plate is disposed such that the multiple first antennas are located in the multiple holes, respectively and the multiple second antennas are located in the multiple holes, respectively. 
     Advantageous Effects 
     A device and a method according to embodiments of the disclosure improve assembling performance through an adhesive material disposed on an antenna substrate and a metal substrate layer, thereby enabling stable large antenna design. 
     In addition, a device and a method according to embodiments of the disclosure enable integration of multiple antennas such that a high level of antenna performance can be provided. 
     In addition, a device and a method according to embodiments of the disclosure make it possible to efficiently fabricate an antenna assembly through an easily attachable/detachable adhesive material. 
     Other aspects, advantages, and salient features of the disclosure will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses various embodiments of the disclosure. 
    
    
     
       DESCRIPTION OF DRAWINGS 
       The above and other aspects, features, and advantages of certain embodiments of the disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG.  1    illustrates a wireless communication system according to an embodiment of the disclosure; 
         FIGS.  2 A and  2 B  illustrate an example of components of an electronic device according to various embodiments of the disclosure; 
         FIGS.  3 A and  3 B  illustrate an example of functional configuration of an electronic device according to various embodiments of the disclosure; 
         FIG.  4    illustrates an example of a radio unit (radio frequency (RF)) board of an electronic device according to an embodiment of the disclosure; 
         FIG.  5 A  illustrates an example of an RU module according to an embodiment of the disclosure; 
         FIG.  5 B  illustrates an example of a stacking structure of an RU module according to an embodiment of the disclosure; 
         FIG.  6    illustrates an example of a stacking structure of an adhesive-based antenna assembly according to an embodiment of the disclosure; 
         FIG.  7    illustrates an example of assembling of an adhesive-based antenna assembly according to an embodiment of the disclosure; 
         FIG.  8    illustrates an example of a process of an adhesive-based antenna assembly according to an embodiment of the disclosure; 
         FIG.  9    is a diagram illustrating a technical principle of an adhesive-based antenna assembly according to an embodiment of the disclosure; 
         FIG.  10    is a diagram illustrating a principle of an adhesive-based antenna assembly according to an embodiment of the disclosure; 
         FIG.  11    illustrates an example of alignment of an adhesive-based antenna assembly according to an embodiment of the disclosure; 
         FIG.  12    illustrates an example of an air vent hole of an adhesive-based antenna assembly according to an embodiment of the disclosure; 
         FIG.  13    illustrates an example of separation of an adhesive-based antenna assembly according to an embodiment of the disclosure; and 
         FIG.  14    illustrates a functional configuration of an electronic device including an adhesive-based antenna assembly according to an embodiment of the disclosure. 
     
    
    
     Throughout the drawings, like reference numerals will be understood to refer to like parts, components, and structures. 
     MODE FOR INVENTION 
     The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments the disclosure as defined by the claims and their equivalents. It includes various specific details to assist in that understanding, but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the disclosure. In addition, descriptions of well-known functions and constructions may be omitted for clarity and conciseness. 
     The terms and words used in the following description and claims are not limited to the bibliographical meanings, but are merely used by the inventor to enable a clear and consistent understanding of the disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the disclosure is provided for illustration purposes only and not for the purpose of limiting the disclosure as defined by the appended claims and their equivalents. 
     It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a component surface” includes reference to one or more of such surfaces. 
     Hereinafter, various embodiments of the disclosure will be described based on an approach of hardware. However, various embodiments of the disclosure include a technology that uses both hardware and software, and thus the various embodiments of the disclosure may not exclude the perspective of software. 
     As used in the description below, the terms indicating components of an electronic device (e.g., “filter”, “amplifier”, “printed circuit board (PCB)”, “flexible PCB (FPCB)”, “antenna element”, “compensation circuit”, “processor”, “chip”, “element”, and “device”), the terms indicating the shape of a component (e.g., “structure”, “assembly”, “connection part”, “contact part”, “guide part”, “protrusion”, and “stator”), the terms indicating a connection part between structures (e.g., “connection part”, “contact part”, “contact element”, “contact structure”, “contact terminal”, “connection element”, “boss”, “conductive member”, and “assembly”), the terms indicating a circuit (e.g., “printed circuit board (PCB)”, “flexible PCB (FPCB)”, “signal line”, “data line”, “feeding line”, “feeding part”, “RF signal line”, “antenna cable”, “RF path”, “RF module”, “RF circuit”, “RFA”, and “RFB”), etc. are provided as examples for the convenience of description. Therefore, the disclosure is not limited to the terms used below, and other terms having the same technical meaning may be used. Further, the terms “unit”, “device”, “member”, “body”, etc. used hereinafter may indicate at least one shape structure or may indicate a unit for processing a function. 
       FIG.  1    illustrates a wireless communication system according to an embodiment of the disclosure. 
     Referring to  FIG.  1   , a wireless communication environment  100  of includes a base station  110  and a terminal  120  as examples of nodes using a wireless channel. 
     The base station  110  is a network infrastructure that provides a wireless connection to the terminal  120 . The base station  110  has a coverage defined as a certain geographic area based on a distance through which a signal can be transmitted. In addition to the base station, the base station  110  may be referred to as a massive multiple input multiple output (MMU) unit, an “access point (AP)”, an “eNodeB (eNB)”, a “5th generation node (5G node)”, a 5G NodeB (NB), a “wireless point”, a “transmission/reception point (TRP)”, an “access unit”, a “distributed unit (DU)”, a “radio unit (RU)”, a “remote radio head (RRH)”, or other terms with equivalent technical meanings. The base station  110  may transmit a downlink signal or may receive an uplink signal. 
     The terminal  120  is a device used by a user, and performs communication with the base station  110  through a wireless channel. In some cases, the terminal  120  may be operated without the user’s involvement. The terminal  120  may be a device that performs machine type communication (MTC) and need not be carried by a user. The terminal  120  may be referred to as “user equipment (UE)”, a “mobile station”, a “subscriber station”, “customer premises equipment (CPE)”, a “remote terminal”, a “wireless terminal”, an “electronic device”, a “terminal for vehicle”, a “user device”, or other terms with equivalent technical meanings. 
     The terminal  120  and the terminal  130  shown in  FIG.  1    may support vehicle communication. In a case of vehicle communication, the standardization of vehicle-to-everything (V2X) technology has been completed in third generation partnership project (3GPP) release 14 and release 15 based on a device-to-device (D2D) communication structure in an LTE system, and efforts are currently underway to develop a V2X technology based on 5G new radio (NR). The NR V2X supports broadcast communication, groupcast (or multicast) communication, and unicast communication between terminals. 
     A beamforming technology is used as one of technologies for reducing propagation path loss and increasing a radio propagation distance. Generally, beamforming uses multiple antennas to concentrate the arrival area of radio waves, or increase the directivity of reception sensitivity in a specific direction. Therefore, communication equipment may include multiple antennas to form a beamforming coverage instead of forming a signal in an isotropic pattern by using a single antenna. Hereinafter, an antenna array including multiple antennas will be described. 
     The base station  110  or the terminal  120  may include an antenna array  112 ,  113 ,  121 , and  131 . Each antenna included in an antenna array may be referred to as an array element or an antenna element. Hereinafter, an antenna array is described as a two-dimensional planar array in the disclosure, but this is merely an embodiment and does not limit other embodiments of the disclosure. An antenna array may be configured in various forms such as a linear array or a multi-layer array. An antenna array may be referred to as a massive antenna array. 
     A main technology to improve the data capacity of 5G communication is a beamforming technology using an antenna array connected to multiple RF paths. The number of components for performing wireless communication has been increased to improve communication performance. Particularly, the number of antennas, RF parts (e.g., an amplifier and a filter) for processing an RF signal received or transmitted through an antenna, and the number of components has been increased and thus a spatial gain and cost efficiency are essentially required in configuring a communication device in addition to satisfying communication performance. 
       FIGS.  2 A and  2 B  show an example of components of an electronic device according to various embodiments of the disclosure.  FIG.  2 A  shows internal components constituting an electronic device and  FIG.  2 B  shows an upper surface, a lower surface, and a lateral surface of an electronic device. 
     Referring to  FIG.  2 A , the electronic device may include a radome cover  201 , an RU housing  203 , a DU cover  205  and an RU  210 . The RU  210  may include an antenna module and RF components for the antenna module. The RU  210  may include an antenna module  213  having an air-based feeding structure according to embodiments of the disclosure to be described below. The antenna module may include a ball grid array (BGA) module antenna. The RU  210  may include an RU board  215  to which RF components are mounted. 
     The electronic device may include a DU  220 . The DU  220  may include an interface board  221 , a modem board  223 , and a CPU board  225 . The electronic device may include a power module  230 , a GPS  240 , and a DU housing  250 . 
       FIG.  2 B  shows a drawing  260  of the electronic device viewed from the top. A drawing  261 , drawing  263 , drawing  265 , and drawing  267  show figures of the electronic device viewed from the left, front, right, and rear side, respectively. Drawing  270  shows the electronic device viewed from below. 
       FIGS.  3 A and  3 B  show an example of functional configuration of an electronic device according to various embodiments of the disclosure. 
     Referring to  FIGS.  3 A and  3 B , the electronic device may include an access unit. The access unit may include an RU  310 , a DU  320 , and a direct current (DC)/DC module. The RU  310  according to embodiments of the disclosure may mean an assembly to which antennas and RF components are mounted. The DU  320  according to embodiments of the disclosure may be configured to process a digital wireless signal, and encrypt a digital wireless signal to be transmitted to the RU  310  or decrypt a digital wireless signal received from the RU  310 . The DU  320  may be configured to perform communication with an upper node (e.g., a centralized unit (CU)) or a core net (e.g., 5G core (5GC) and evolved packed core (EPC)) by processing packet data. 
     Referring to  FIG.  3 A , the RU  310  may include multiple antenna elements. The RU  310  may include at least one array antenna. The array antenna may be formed of a planar antenna array. The array antenna may correspond to one stream. The array antenna may include multiple antenna elements corresponding to one transmission path (or reception path). By way of example, the array antenna may include 256 antenna elements having a 16 × 16 form. 
     The RU  310  may include RF chains for processing a signal of each array antenna. The RF chains may be referred to as “RFA”. The RFA may include a mixer and RF components (e.g., a phase transformer and a power amplifier) for beamforming. The mixer of the RFA may be configured to down-convert an RF signal of an RF frequency into an intermediate frequency, or up-convert an intermediate frequency into a signal of an RF frequency. According to an embodiment of the disclosure, one set of RF chains may correspond to one array antenna. By way of example, the RU  310  may include four RF chain sets for four array antennas. Multiple RF chains may be connected to a transmission path or a reception path through a divider (e.g., 1:16). Although not shown in  FIG.  3 A , according to an embodiment of the disclosure, the RF chains may be implemented as a RF integrated circuit (RFIC). The RFIC may process and generate RF signals provided to multiple antenna elements. 
     The RU  310  may include a digital analog front end (DAFE) and “RFB.” The DAFE may be configured to perform interconversion between a digital signal and an analog signal. By way of example, the RU  310  may include two DAFEs (DAFE #0 and DAFE #1). The DAFE may be configured to up-convert a digital signal (i.e., DUC) and convert the up-converted signal into an analog signal (i.e., DAC) in a transmission path. The DAFE may be configured to convert an analog signal into a digital signal (i.e., ADC) and down-convert a digital signal (i.e., DDC) in a reception path. The RFB may include a mixer and a switch corresponding to a transmission path and a reception path. The mixer of the RFB may be configured to up-convert a baseband frequency into an intermediate frequency, or down-convert a signal of an intermediate frequency into a signal of a baseband frequency. The switch may be configured to select one of a transmission path and a reception path. By way of example, the RU  310  may include two RFBs (RFB #0 and RFB #1). 
     The RU  310  as a controller may include a field programmable gate array (FPGA). The FPGA means a semiconductor including a designable logic element and a programmable internal circuit. Communication with the DU  320  may be performed through Serial Peripheral Interface (SPI) communication. 
     The RU  310  may include a local oscillator (RF LO). The RF LO may be configured to provide a reference frequency for up-conversion or down-conversion. According to an embodiment, the RF LO may be configured to provide a frequency for up-conversion or down-conversion of the RFB described above. For example, the RF LO may provide a reference frequency to RFB #0 and RFB #1 through a two-way divider. 
     The RF LO may be configured to provide a frequency for up-conversion or down-conversion of the RFA described above. For example, the RF LO may provide a reference frequency to each RFA (eight per RF chain for each polarization group) through a 32-way divider. 
     Referring to  FIG.  3 B , the RU  310  may include a DAFE block  311 , an IF up/down converter  313 , a beamformer  315 , an array antenna  317 , and a control block  319 . The DAFE block  311  may convert a digital signal into an analog signal or an analog signal into a digital signal. The IF up/down converter  313  may correspond to the RFB. The IF up/down converter  313  may convert a signal of a baseband frequency into a signal of an IF frequency, or a signal of an IF frequency into a signal of a baseband frequency based on the reference frequency provided from the RF LO. The beamformer  315  may correspond to the RFA. The beamformer  315  may convert a signal of an RF frequency into a signal of an IF frequency, or a signal of an IF frequency into a signal of an RF frequency based on the reference frequency provided from the RF LO. The array antenna  317  may include multiple antenna elements. Each antenna element of the array antenna  317  may be configured to radiate a signal processed through the RFA. The array antenna  317  may be configured to perform beamforming according to a phase applied by the RFA. The control block  319  may control each block of the RU  310  to perform a command from the DU  320  and the signal processing described above. 
     Although the base station was described as an example of the electronic device in  FIGS.  2 A,  2 B,  3 A, and  3 B , the embodiments of the disclosure are not limited to the base station. Embodiments of the disclosure may be applied to any electronic device for radiating a wireless signal in addition to a base station including a DU and an RU. 
       FIG.  4    shows an example of a radio unit (RU) board of an electronic device according to an embodiment of the disclosure. 
     Referring to  FIG.  4   , the electronic device amounts to a structure including a separate arrangement of a PCB (hereinafter, a first PCB) to which an antenna is mounted and a PCB (hereinafter, a second PCB) to which array antennas and components (e.g., a connector, a direct current (DC)/DC converter, and a DFE) for signal processing are mounted. The first PCB may be referred to as an antenna board, an antenna substrate, a radiation substrate, a radiation board, or an RF board. The second PCB may be referred to as an RU board, a main board, a power board, a mother board, a package board, or a filter board. 
     Referring to  FIG.  4   , the RU board may include components for transferring a signal to a radiator (e.g., an antenna). One or more antenna PCBs (i.e., the first PCBs) may be mounted on the RU board. One or more array antennas may be mounted on the RU board. By way of example, two array antennas may be mounted on the RU board. According to an embodiment of the disclosure, the array antennas may be arranged on symmetrical positions on the RU board ( 405 ). According to another embodiment, array antennas may be arranged on one side (e.g., a left side) of the RU board and RF components to be described below may be arranged on the other side (e.g., a right side) ( 415 ). Although two array antennas are shown in  FIG.  4   , embodiments of the disclosure are not limited thereto. Two array antennas may be arranged for each band so as to support a dual band, and the array antennas mounted on the RU board may be configured to support 2-transmit 2-receive (2T2R). 
     The RU board may include components for supplying an RF signal to an antenna. The RU board may include one or more DC/DC converters. The DC/DC converter may be used for converting a direct current into a direct current. The RU board may include one or more local oscillators (LO). The LO may be used for supplying a reference frequency for up-conversion or down-conversion in an RF system. The RU board may include one or more connectors. The connector may be used for transferring an electrical signal. The RU board may include one or more dividers. The divider may be used for distributing an input signal and transferring an input signal to multiple paths. The RU board may include one or more low-dropout regulators (LDOs). The LDO may be used for suppressing external noise and supplying power. The RU board may include one or more voltage regulator modules (VRMs). The VRM may mean a module for securing a proper voltage to be maintained. The RU board may include one or more digital front ends (DFEs). The RU board may include one or more radio frequency programmable gain amplifiers (FPGAs). The RU board may include one or more intermediate frequency (IF) processors. Some of the components shown in  FIG.  4    may be omitted or more components may be additionally mounted as the configuration shown in  FIG.  4   . Although not described with reference to  FIG.  4   , the RU board may include an RF filter for filtering a signal. 
       FIG.  5 A  illustrates an example of an RU module according to an embodiment of the disclosure. 
     Referring to  FIG.  5 A , the RU module  501  may include one or more antenna arrays. For example, the RU module  501  may include 4 antenna arrays. One antenna array  503  may include multiple antenna elements. For example, one antenna array  503  may include 256 (=16×16) antenna elements. 
     As technology advances, while transmission output is improved, equivalent reception performance needs to be secured and supporting a dual band is also required. Such requirements cause an increase in volume compared to a size of an existing equipment. In addition, the number of antenna elements for each path increases for equivalent performance or higher performance. For example, instead of a base station which supports 4T4R in an existing single band (e.g., 28 GHz band or 39 GHz band), when supporting 2T2R in a dual band, the number of antenna elements for each path may be increased from 256 to 384. Furthermore, in an equipment for a dual band, an interval between antenna is increased and the entire area for each path is increased. 
     As shown in  FIG.  5 A , the number of antenna elements in a single antenna array may be increased for the purpose of improving performance. For example, the antenna array  510  may include 384 (=24×16) antenna elements. As another example, the antenna array  515  may include 768 (=32×24) antenna elements. The increase in the size of the antenna array causes an increase in the difficulty of assembling an RU module. Particularly, the alignment is a sensitive matter in an ultra-high band (e.g., an mmWave band), and thus implementation of an integrated antenna is required for reducing assembly error and maximizing high degree of alignment. 
     Although, a single large antenna array is illustrated, embodiments of the disclosure are not limited thereto. According to an embodiment of the disclosure, multiple sub arrays may be operated in one antenna array. For example, the antenna array  511  may be used instead of the antenna array  510 . The antenna array  511  may include a sub array on an upper side and a sub array on a lower side. As another example, the antenna array  516  or the antenna array  517  may be used instead of the antenna array  515 . The antenna array  516  may include a sub array on a left side and a sub array on a right side. The antenna array  517  may include a sub array on an upper side and a sub array on a lower side. 
       FIG.  5 B  illustrates an example of a stacking structure of an RU module according to an embodiment of the disclosure. The stacking structure shown in  FIG.  5 B  is merely an example for explaining a stacking structure of the adhesive-based antenna assembly according to embodiments of the disclosure and embodiments of the disclosure are not limited thereto. 
     Referring to  FIG.  5   b   , the antenna assembly means a combination of radiators, substrates, and adhesive layers corresponding to an antenna array in an RU module. In the disclosure, the antenna assembly may be referred to as other terms having an equivalent technical meaning, such as an antenna unit, a radiation unit, and a radiator unit. 
     Referring to  FIG.  5 B , the electronic device may include an RU module  550 . The RU module  550  may include an antenna assembly  570  having a dual antenna structure. The antenna assembly  570  may include a first antenna part and a second antenna part  561 . The first antenna part may include a main radiator. The main radiator may mean a radiator disposed adjacent to a main board. The second antenna part  561  may include an additional radiator (hereinafter, a second radiator) formed on a cover. The second antenna part  561  may include a metal pillar for supporting the cover. The metal pillar shown in the stacking structure may correspond to most portion of a metal plate excluding a hole. The antenna shown in  FIG.  5 B  is merely an embodiment and is not construed to delimit other embodiments of the disclosure. The radiator corresponds to an antenna element of the antenna array. 
     The main radiator may be disposed on an antenna board  563  (e.g., the first PCB in  FIG.  4   ). The antenna board is a PCB (or a FPCB) to which the antenna elements are mounted and which is distinguished from a FPCB of the second antenna part disposed on the metal plate. Unlike the cross-sectional view shown in  FIG.  5 B , not only one antenna element (e.g., the main radiator) but also multiple antenna elements may be mounted on the first layer of the antenna board  563  according to embodiments of the disclosure. The group of the multiple antenna elements may be an antenna array. 
     The first antenna part may be attached to the PCB. An adhesive material may be disposed on a lower surface of the first antenna part. The first antenna part may be attached to the PCB through the adhesive material. The PCB may mean a main board of the PCB. The PCB may include multiple substrates. Multiple substrates may be stacked in the PCB. The PCB may include a feeding layer. The feeding layer may include an RF line. For example, the RF line may include embedded grounded coplanar waveguide (GCPW). The PCB may include one or more ground layers. A via hole may be formed through layers of the PCB. For example, the PCB may include a via hole formed by a laser process and a via hole formed by a PTH process. According to an embodiment, the PCB may include a low-cost layer formed of FR4 for a coaxial PTH. 
     As described above, the antenna assembly has a dual antenna structure. The dual antenna structure may mean a structure in which a radiator (e.g., an antenna) is disposed on a substrate and an additional radiator is formed on another different substrate. An air layer may be disposed on the radiator and the additional radiator may be disposed on the air layer. The radiator and the additional radiator may be disposed on different layers with reference to the air layer. An air cavity is formed through the air layer. According to an embodiment of the disclosure, the air layer may be formed through a hole of the metal plate. 
     For the dual antenna structure, bonding between the main radiator (hereinafter, a first antenna) and the additional radiator (hereinafter, a second antenna) is required. For example, the main radiator may be implemented on a laminated FPCB. The laminated FPCB may be bonded to the main board through an adhesive such as a bonding sheet. The second radiator may be implemented on a FPCB. An assembly of the FPCB and the metal pillar may be bonded to the laminated FPCB bonded to the main board. However, such an assembling method may cause a high fabrication error as a size of antenna arrays increases due to two-step assembly. The increase in size of a shape of antennas that have been respectively assembled may cause increase in cost and a disadvantageous problem in mass production. 
     To solve the problems described above, embodiments of the disclosure propose a method in which a first radiator and a second radiator are bonded to each other first and the bonded radiator module is attached to a main board other than a method in which a first radiator and a second radiator are sequentially assembled to a main board, an antenna assembly generated by the method, and an RU module including same. The use of an adhesive material instead of a lamination method may simplify assembly and improve performance. 
       FIG.  6    illustrates an example of a stacking structure of an adhesive-based antenna assembly according to an embodiment of the disclosure. 
     Referring to  FIG.  6   , the antenna assembly includes a dual antenna structure. The dual antenna structure is a structure in which a main radiator and an additional radiator are bonded to each other and means multi-layer arrangement of antennas for enhancing radiation performance by positioning an additional radiator in a radiation direction of a main radiator. 
     Referring to  FIG.  6   , the antenna assembly may be bonded to a PCB  601 . The PCB  601  may mean a board to which the antenna assembly bonded. The adhesive-based assembly means, as described above, an integrated assembly in which a first antenna part and the second antenna part having a dual antenna structure are bonded to each other through an adhesive (or adhesive material). The antenna assembly may be referred to as an antenna unit. The antenna assembly may correspond to one antenna array of all antennas (e.g., the antenna array  503  in  FIG.  5 A ). Although not shown in  FIG.  6   , the PCB  601  may include multiple antenna assemblies. The PCB  601  may be referred to as an RU board, a main board, a power board, a mother board, a package board, or a filter board. 
     The antenna assembly has a dual antenna structure. The dual antenna structure may consist of a first antenna part including a main radiator and a second antenna part including an additional radiator. The main radiator of the first antenna part may be bonded to a PCB of a main board to perform a function of radiating a signal. The second antenna part may be stacked substantially parallel with a radiation surface of the main radiator. The additional radiator of the second antenna part may relay or amplify a signal of the main radiator. The first antenna part may include a first pressure sensitive adhesive (PSA)  603 , a first FPCB  605 , and a second PSA  607 . The second antenna part may include a metal plate  609 , a third PSA  611 , and a second FPCB  613 . 
     The first antenna part may include a structure in which the first PSA  603 , the first FPCB  605 , and the second PSA  607  are sequentially stacked. The first PSA  603  is an adhesive material for bonding a board of the main radiator, that is, the antenna board to the PCB  601 . The second PSA  607  is an adhesive material for bonding the metal plate  609  and the first FPCB  605 . The PSA as a pressure-sensitive adhesive is an adhesive in which an adhesive material is activated when pressure is applied to bond the adhesive to the adhesive surface. The adhesion strength is affected by an amount of pressure for allowing an adhesive to be applied to a surface. Although the pressure-sensitive adhesive (PSA) for low temperature pressure or roll pressure is exemplified as an adhesive material in the disclosure, a drawing or specific description does not delimit embodiments of the disclosure. The PSA may be manufactured to maintain appropriate adhesion and persistency at room temperature in general. According to various embodiments, there are adhesives manufactured to normally operate at low temperature or high temperature (e.g., a thermosetting bonding sheet). 
     The first FPCB  605  may be a substrate (or antenna board) on which the main radiator is mounted. Although the FPCB is exemplified as a board to which a radiator is mounted, it is to be understood that a PCB or another substrate other than the FPCB may be used. 
     The second antenna part may include a structure in which the metal plate  609 , the third PSA  611 , and a second FPCB  613  are sequentially stacked. The metal plate  609  may provide a metal pillar for forming an air layer between the main radiator of the first FPCB  605  and the additional radiator of the second PCB  613 . The number of holes of the metal plate  609  may correspond to the number of radiation elements of the first FPCB  605 . The number of holes of the metal plate  609  may correspond to the number of radiation elements of the second FPCB  613 . That is, the number of holes of the metal plate  609  may correspond to the number of antenna elements of the antenna array. 
     The third PSA  611  is an adhesive material for bonding the metal plate  609  and the second FPCB  613 . The description of the first PSA  603  and the second PSA  607  may be applied to the third PSA  611  in an identically or similarly manner. 
     The second FPCB  613  may be a substrate (or antenna board) on which the additional radiator is mounted. Although the FPCB is exemplified as a board to which a radiator is mounted, it is to be understood that a PCB or another substrate other than the FPCB may be used. 
     The adhesive-based antenna assembly according to embodiments of the disclosure may include a hole structure for each of multiple antenna elements of the antenna array. The metal plate  609  may include a hole for each of the multiple antenna elements of the antenna array, that is, each radiator. The second PSA  607  may include a hole for each of the multiple antenna elements of the antenna array (i.e., a radiator of the first antenna part). The third PSA  611  may include a hole for each of the multiple antenna elements of the antenna array, that is, a radiator of the second antenna part. A shape of the hole formed through a plate may be a circle, a polygon, or any other shape. An area of a hole region may be larger than an area of the radiator surface. 
       FIG.  7    illustrates an example of assembly of an adhesive-based antenna assembly according to an embodiment of the disclosure. 
     Referring to  FIG.  7   , the adhesive-based assembly means, as described above, an assembly in which a first antenna part and the second antenna part having a dual antenna structure are bonded to each other through an adhesive (or adhesive material). 
     Referring to  FIG.  7   , a first structure  710  means the first antenna part of the dual antenna structure of an existing antenna structure. The first structure  710  may include a structure in which an adhesive, a FPCB, and a radiator (e.g., copper) are sequentially stacked. To prevent corrosion, a cover layer may be formed through coating around the radiator. A second structure  720  means the second antenna part of the dual antenna structure of an existing antenna structure. The second structure  720  may include a structure in which a metal plate, an adhesive, and a radiator (e.g., copper) are sequentially stacked. Similar to the first structure  720 , to prevent corrosion, a cover layer may be formed through coating around the radiator. A metal pillar of the second structure  720  may be bonded to the FPCB of the first structure  710 . 
     A method of sequentially bonding the first structure  710  and the second structure  720  may easily cause a fabrication error in actual assembling due to bonding through two bonging methods when multiple elements are included. As the number of antenna elements increases, the area of a substrate layer increases. This is because the area of the large substrate layer may cause high tolerances during assembly. 
     A method will be assumed that after the first structure  710  and the second structure  720  are bonded, the bonded structure is bonded to a PCB (i.e., a main board). When the first structure  710  and the second structure  720  are bonded (hereinafter, a first bonding), the metal pillar is directly bonded to the FPCB, thus still causing a tolerance (e.g., a height difference and interval difference for each radiator). An antenna operation in an mmWave band may be more sensitive to this tolerance. Thereafter, due to the bonding (hereinafter, a second bonding) between the bonded structure and the PCB, additional distortion may be caused or a degree of the tolerance having occurred in the first bonding increases. To solve the above-mentioned problems, the disclosure proposes an antenna structure including an adhesive material disposed between the FPCB of the first antenna part and the metal layer of the second antenna part. 
     The first structure  760  may include a structure in which an adhesive, a FPCB, and a radiator (e.g., copper) are sequentially stacked. In a radiation layer, an adhesive layer may be disposed on a portion other than an area in which the radiator is disposed. In other words, the adhesive layer may include a hole, and the radiator may be disposed on a corresponding hole. A metal pillar  771  means a metal plate. The metal plate may include a hole corresponding to the radiator, and a portion excluding the hole may function as a pillar in a stacking structure. Due to the disposition of the adhesive and the metal pillar  771 , the radiator may not need a separate cover layer. That is, unlike the first structure  710 , the first structure  760  may not include a cover layer. 
     The second structure  773  may include a structure in which an adhesive, and a FPCB are sequentially stacked. Unlike the second structure  720 , the radiator (e.g., copper) may be disposed inside the metal pillar, that is, disposed facing downward. The adhesive layer may include a hole, and the radiator may be disposed on a corresponding hole. Due to the disposition of the adhesive and the metal pillar  771 , the radiator may not need a separate cover layer. That is, unlike the first structure  710 , the first structure  760  may not include a cover layer. 
     The first structure  760 , the metal pillar  771 , and the second structure  773  may be aligned. According to an embodiment, the first structure  760  and the second structure  773  may be aligned such that a first radiation surface and a second radiation surface are substantially parallel with each other. The first structure  760 , the metal pillar  771 , and the second structure  773  may be aligned such that the first radiation surface and the second radiation surface are located inside a hole of the metal plate. It is because the metal pillar  771  formed by the hole of the metal plate needs to ensure isolation while not obstructing a signal path of the radiator. The metal pillar  771  may be bonded to the first structure  760 . The second structure  773  may be stacked on a structure  781  in which the first structure  760  and the metal pillar  771  are bonded to each other. An antenna assembly  790  may be formed through the above-described alignment and stacking (or bonding). 
     The bonding order shown in  FIG.  7    is merely one example and is not construed to delimit embodiments of the disclosure. It is to be understood that the second structure  773  may be bonded on the metal pillar  771 , and the bonded structure may be stacked on the first structure  760 . 
     Copper is exemplified as a metal for a material of the radiator in  FIG.  7   . However, embodiments of the disclosure are not limited thereto. According to another embodiment of the disclosure, nickel (Ni) or tin (Sn) may be additionally used for plating. 
       FIG.  8    illustrates an example of a process of an adhesive-based antenna assembly according to an embodiment of the disclosure. 
     Referring to  FIG.  8   , a first process  810  shows a stacking process of a dual structure antenna of an RU module. A first antenna part corresponds to the first structure  710  in  FIG.  7   . A second antenna part corresponds to the second structure  720  in  FIG.  7   . The first antenna part (i.e., a FPCB to which an antenna is disposed or laminated FPCB) is stacked on a PCB (i.e., a main board), and the stacked assembly is pressurized. According to an embodiment of the disclosure, low-temperature compression may be performed. An adhesive material of an antenna assembly may be a PSA. According to an embodiment of the disclosure, high-temperature, high-pressure compression may be performed. An adhesive material of an antenna assembly may be a thermosetting adhesive material. Thereafter, the second antenna part is bonded to the assembly. Bolt-assembly may be used for fixation of the second antenna part. One or more bolts may be disposed to penetrate the second antenna part, the first antenna part, and at least one layer of the PCB. 
     A second process  860  shows a stacking process of an adhesive-based antenna assembly according to embodiments of the disclosure. 
     The adhesive-based antenna assembly may be disposed on the PCB, and the adhesive-based antenna assembly may be pressurized. The pressure may be applied in a direction perpendicular to a surface of the PCB for solid bond between the first antenna part and the second antenna part and solid bond between the antenna assembly and the PCB. According to an embodiment, low-temperature compression may be performed. An adhesive material of an antenna assembly may be a PSA. According to an additional embodiment, one or more bolts may be disposed to penetrate the antenna assembly and at least one layer of the PCB. 
     The antenna assembly may be an assembly in which different materials such as a metal and an adhesive material are bonded. The antenna assembly may include structures bonded to each other with an adhesive and may be bonded to the PCB (i.e., a main board) in one assembly through a single compression process. 
       FIG.  9    is a diagram illustrating a technical principle of an adhesive-based antenna assembly according to an embodiment of the disclosure. 
     Referring to  FIG.  9   , the adhesive-based antenna assembly includes a dual antenna structure. The dual antenna structure may emit a signal with low dielectric loss by forming an air cavity between a main radiator of a first antenna part  960  and an additional radiator of a second antenna part  973 . For example, the electronic device may be required to be constantly operated. By way of example, a base station may be constantly in ON state. Here, air is isolated due to an enclosed space of a metal layer, and compression and expansion of the isolated air may cause radiation performance degradation of an antenna. To reduce quality fluctuation, the antenna assembly according to embodiments of the disclosure may include a hole  910  through a substrate of the second antenna part  973 . The FPCB on which the additional radiator is disposed, that is, the FPCB of the second antenna part  973  may include the hole  910  formed therethrough. The FPCB may correspond to the FPCB  613  in  FIG.  6   . The hole  910  may be an air vent hole for discharging air. Air trap (a phenomenon in which air collects within a designated area) may be prevented through the hole  910 . 
     A metal plate may be required to have holes formed therethrough for each antenna element, that is, as many as the number of antenna elements for allowing a signal of a radiator to penetrate. A method for manufacturing the metal plate may employ punching or etching, stacking PCBs, or plating. The actually formed holes may not match each other in height and area. For example, if areas of holes corresponding to antenna elements are different or heights of the metal pillars are different, isolation performance difference occurs, causing interference. In addition, for example, radiation performance difference may occur between the first antenna part  960  and the second antenna part due to the height difference of the metal pillars. To minimize the performance difference, the antenna assembly according to embodiments of the disclosure may include an adhesive material  920 . 
     The adhesive material  920  is disposed around a radiator to perform a function of facilitating bonding between the metal pillar and each FPCB. In the adhesive-based antenna assembly according to embodiments of the disclosure, the adhesive material  920  (e.g., the second PSA  706  and the third PSA  611  in  FIG.  6   ) is disposed between bonding of the FPCB and the metal pillars. The adhesive material  920  functions to facilitate responding to flatness changes. In addition, the adhesive material  920  functions to compensate an assembly tolerance during bonding so as to maintain uniform spacing between antenna arrays. In addition, the adhesive material  930  may be disposed to facilitate bonding between the PCB and the antenna assembly. According to additional embodiment, as shown in  FIG.  13    to be described below, the adhesive material may be disposed for rework, that is, detachment and re-attachment after the bonding between the PCB and the antenna assembly. The adhesive material may include a material configured to foam at a predetermined temperature for rework. 
     A radiator  971  is a component for radiating a signal. Although copper is exemplified as the radiator  971  in  FIG.  9   , it is to be understood that other materials other than copper may be used as an element for feeding in embodiments of the disclosure. According to an embodiment, the radiator  971  may not include a cover layer. Due to the removal of the cover layer, the radiator may be located in a hole surrounded by the metal pillars  972 , which is a hole area of the metal plate  972 . The antenna assembly includes an antenna radiator  971  disposed on a lower surface of the FPCB of the second antenna part  973 , instead of an antenna radiator that is conventionally positioned upward. As the cover layer for preventing corrosion is not included, size reduction of an antenna assembly may be achieved. Instead of the cover layer, the metal pillars for bonding the first antenna part  960  and the second antenna part  973  perform isolation and shielding functions. In addition to size reduction, radiation performance may be also improved by positioning radiators in each hole of the metal plate. 
     According to an embodiment of the disclosure, the adhesive material  920  may be disposed such that a height of the adhesive material  920  is lower than a height of the radiator  971  with reference to the FPCB of the first antenna part  960 . The adhesive material  920  may be disposed such that a height of the adhesive material  920  is lower than a height of the radiator  971  with reference to the FPCB of the second antenna part  973 . To maximize the shielding effect by the metal pillars, the adhesive material  920  may be configured to have a thickness thinner than a thickness of the radiator  971 . By way of example, the thickness of the adhesive material  920  may be about 45 µm-50 µm, and may be reduced due to pressure during antenna assembly assembling. The thickness of the radiator may be 50 µm. 
     Copper is exemplified as a metal for a material of the radiator in  FIG.  9   . However, embodiments of the disclosure are not limited thereto. According to another embodiment, nickel (Ni) or tin (Sn) may be additionally used for plating. 
       FIG.  10    is a diagram illustrating an isolation principle of an adhesive-based antenna assembly according to an embodiment of the disclosure. The isolation means a degree to which two signals are independently separated. The lower the isolation performance, the greater the interference. 
     Referring to  FIG.  10   , in bonding  1010 , a first antenna part is stacked on a main PCB. In bonding  1020 , a second antenna part is stacked on the first antenna part. This conventional bonding method may not eliminate an error formed during manufacturing a hole of a metal plate because the metal plate is directly bonded to a FPCB. A gap  1030  caused by height difference of the metal plate around one radiator may cause isolation performance degradation and thus cause a degradation in antenna performance. 
     To solve the above-described problem, the antenna assembly according to embodiments of the disclosure may include an adhesive layer. The adhesive layer may correspond to the second PSA  607  in  FIG.  6   . The adhesive layer may reduce an effect caused by a difference during bonding between the first antenna part and the second antenna part. 
     In bonding  1060 , an adhesive-based antenna assembly is stacked on the main PCB. Thereafter, pressure  1070  is applied to the antenna assembly and the main PCB. A low-temperature compression (e.g., cold press) or roll press process may be used together with a vision align automatically recognizing a fiducial mark for assembly. As the first antenna part and the second antenna part are already bonded and the adhesive layer is located between the metal plate and the FPCB, even before or after the main PCB is assembled, performance degradation due to the gap  1080  is lower than performance degradation due to the gap  1030 . According to an embodiment of the disclosure, the adhesive layer may be conductive. According to another embodiment, the adhesive layer may be non-conductive. A characteristic of the adhesive layer may vary according to a feeding structure of an antenna implemented in the FPCB. 
       FIG.  11    illustrates an example of alignment of an adhesive-based antenna assembly according to an embodiment of the disclosure. 
     Referring to  FIG.  11   , in bonding  1060 , an adhesive-based antenna assembly is stacked on a main PCB. Alignment  1120  is an important factor in this stacking. According to an embodiment, a FPCB and a PCB (i.e., a main board) of the adhesive-based antenna assembly may be coupled through an adhesive material. Here, after coupling, precise alignment  1120  may be required to prevent deterioration of feeding performance. The alignment may mean that the antenna assembly is located within a designated area of a surface of the PCB when viewing the surface of the PCB from above. An example of evaluation of the alignment  1120  may include pass or fail. In case that a distance between a first fiducial mark of the antenna assembly and a second fiducial mark of the PCB is less than a predetermined threshold value ( 1151 ), an RU module having the antenna assembly bonded thereto may pass the alignment evaluation (good-quality product). However, in case that a distance between the first fiducial mark of the antenna assembly and the second fiducial mark of the PCB is equal to or larger than a predetermined threshold value ( 1152 ) or the first fiducial mark are not aligned to each other ( 1153 ,  1154 ), the RU module having the antenna assembly bonded thereto may not pass the alignment evaluation. 
       FIG.  12    illustrates an example of an air vent hole of an adhesive-based antenna assembly according to an embodiment of the disclosure. 
     Referring to  FIG.  12   , as described above, the contraction or expansion of air due to heat may cause defect of an antenna assembly in an unpredictable period. The antenna assembly of the disclosure may include an air vent hole to solve the problem. 
     Referring to  FIG.  12   , in bonding  1210 , an adhesive-based antenna assembly is stacked on a PCB (i.e., a main PCB). An upper substrate (e.g., the FPCB of the second antenna part and the FPCB  613  in  FIG.  6   ) of the adhesive-based antenna assembly may include a hole  1220 . The hole  1220  may be formed to discharge air so as to prevent performance deterioration due to an air trap. The hole  1220  may be formed in a space between an area for a radiator and a shielding area (i.e., an area in which a metal pillar is disposed) formed by pillar bonding on one surface of the FPCB. 
     Unlike the hole  1220 , a hole may be disposed in other areas of the FPCB for the same purpose, that is, air ventilation. The air vent hole  1231  may be disposed in a radiator mounting area. The air vent hole  1232  may be disposed at both sides of a radiator in a size smaller than the radiator. Referring to the second example  1243 , four air vent holes  1232  may be arranged for each circular radiator (the radiator of the second antenna part) at an interval of 90 degrees. The air vent hole  1233  may be disposed in a space between radiators. Referring to the first example  1241 , the air vent holes  1233  may be arranged for each space between a circular radiator (the radiator of the second antenna part) and a circular radiator. 
       FIG.  13    illustrates an example of separation of an adhesive-based antenna assembly according to an embodiment of the disclosure. 
     Referring to  FIG.  13   , rearrangement may be required due to a defect after an adhesive-based antenna assembly is attached to a PCB (i.e., a main board). For example, arrangement between the adhesive-based antenna assembly and a PCB of an RU board may be misaligned. The adhesive-based antenna assembly may be required to be configured to facilitate attachment/detachment for improving production efficiency. 
     The adhesive-based antenna assembly according to embodiments of the disclosure may include an adhesive material on a lower surface (e.g., the FPCB of the first antenna part) thereof. The adhesive material may include the first PSA  603  in  FIG.  6   . The adhesive material may be configured to cause releasing when exposed to a specific temperature environment. For example, the adhesive material may be a material having adhesion at room temperature but losing adhesion at high temperature. By way of example, the adhesive material may be a thermal release tape (or a foaming tape), or the adhesive material may be a foam release-type adhesive tape. 
     Referring to  FIG.  13   , a first state  1310  indicates an adhesive-based antenna assembly at room temperature. The adhesive material on the lower surface has adhesion such that the adhesive-based antenna assembly may be bonded to the PCB through the adhesive material. The adhesive-based antenna assembly may be fixed to one surface of the PCB due to the adhesion of the adhesive material of the lower surface. A second state  1330  indicates an adhesive-based antenna assembly at high temperature. The adhesive material of the lower surface may foam at high temperature. The foaming of the adhesive material may cause loss of adhesion of adhesive material. The adhesive-based antenna assembly may be separated from the PCB due to releasing. 
     Although not shown in  FIG.  13   , after releasing, the adhesive-based antenna assembly may be bonded to the PCB again through re-arrangement. As such, an RU module may be produced without reproduction of the adhesive-based assembly and the PCB from scratch. 
     According to embodiments of the disclosure, an antenna assembly may include: a first flexible printed circuit board (FPCB) for multiple first antennas; a second flexible printed circuit board (FPCB) for multiple second antennas; a metal plate including multiple holes; a first adhesive material layer for bonding the metal plate and the first FPCB; and a second adhesive material layer for bonding between the metal plate and the second FPCB, wherein the metal plate is disposed such that the multiple first antennas are located in the multiple holes, respectively and the multiple second antennas to be located in the multiple holes, respectively. 
     The first adhesive material layer may include multiple first holes equal to the number of the multiple holes of the metal plate, and the second adhesive material layer may include multiple second holes equal to the number of the multiple holes of the metal plate. 
     The first adhesive material layer may be disposed such that the multiple first antennas are respectively located in the first multiple holes with reference to the first adhesive material layer, and the second adhesive material layer may be disposed such that the multiple second antennas are respectively located in the second multiple holes with reference to the second adhesive material layer. 
     The first FPCB and the second FPCB may include one or more air-vent holes for discharging air. 
     The one or more air-vent holes may be formed in an area of one surface of the second FPCB excluding an area in which the multiple second antennas are arranged, and an area bonded to the second adhesive material layer. 
     A first surface of the second FPCB, on which the multiple second antennas are arranged may be disposed to face a first surface of the first FPCB on which the multiple first antennas are arranged. 
     A thickness of the first adhesive material layer may be thinner than a thickness of each of the multiple first antennas. 
     The antenna assembly may not include a cover layer for each of the multiple first antennas and the multiple second antennas. 
     The antenna assembly may further include a third adhesive material layer to be bonded to a printed circuit board (PCB) of a radio unit (RU), and the third adhesive material layer may be bonded to a second surface of the first FPCB opposite to the first surface of the first FPCB on which the first multiple antennas are arranged. 
     The third adhesive material layer may be configured to maintain adhesion in a first temperature range and to lose adhesion in a second temperature range not overlapping the first temperature range. 
     According to embodiments of the disclosure, a radio unit (RU) module may include: a printed circuit board (PCB) and multiple antenna assemblies, and an antenna assembly of the multiple antenna assemblies may include: a first flexible printed circuit board (FPCB) for multiple first antennas; a second flexible printed circuit board (FPCB) for multiple second antennas; a metal plate including multiple holes; a first adhesive material layer for bonding between the metal plate and the first FPCB; and a second adhesive material layer for bonding the metal plate and the second FPCB, wherein the metal plate is disposed such that the multiple first antennas are located in the multiple holes, respectively and the multiple second antennas to be located in the multiple holes, respectively. 
     The first adhesive material layer may include multiple first holes equal to the number of the multiple holes of the metal plate, and the second adhesive material layer may include multiple second holes equal to the number of the multiple holes of the metal plate. 
     The first adhesive material layer may be disposed such that the multiple first antennas are respectively located in the first multiple holes with reference to the first adhesive material layer, and the second adhesive material layer may be disposed such that the multiple second antennas are respectively located in the second multiple holes with reference to the second adhesive material layer. 
     The first FPCB and the second FPCB may include one or more air-vent holes for discharging air. 
     The one or more air-vent holes may be formed in an area of one surface of the second FPCB excluding an area in which the multiple second antennas are arranged, and an area bonded to the second adhesive material layer. 
     A first surface of the second FPCB, on which the multiple second antennas are arranged, may be disposed to face a first surface of the first FPCB on which the multiple first antennas are arranged. 
     A thickness of the first adhesive material layer may be thinner than a thickness of each of the multiple first antennas. 
     The antenna assembly may omit a cover layer for each of the multiple first antennas and the multiple second antennas. 
     The antenna assembly may further include a third adhesive material layer to be bonded to the PCB, and the third adhesive material layer may be bonded to a second surface of the first FPCB opposite to the first surface of the first FPCB on which the first multiple antennas are arranged. 
     The third adhesive material layer may be configured to maintain adhesion in a first temperature range and to lose adhesion in a second temperature range not overlapping the first temperature range. 
       FIG.  14    illustrates a functional configuration of an electronic device including an adhesive-based antenna assembly according to an embodiment of the disclosure. 
     Referring to  FIG.  14   , the electronic device  1410  may correspond to one of the base station  110  or the terminal  120  in  FIG.  1   . According to an embodiment, the electronic device  1410  may correspond to a base station device configured to support mmWave communication (e.g., frequency range 2 in 3GPP). The embodiments of the disclosure include the antenna structure mentioned with reference to  FIGS.  1 ,  2 A,  2 B,  3 A,  3 B,  4 ,  5 A,  5 B, and  6  to  13    as well as the electronic device including the antenna structure. The electronic device  1410  may include an RF equipment having an air-based feeding structure. 
       FIG.  14    shows a functional configuration of the electronic device  1410 . The electronic device  1410  may include an antenna part  1411 , a power interface part  1412 , a radio frequency (RF) processor  1413 , and a controller  1414 . 
     The antenna part  1411  may include multiple antennas. The antenna performs a function for transmitting or receiving a signal through a wireless channel. The antenna may include a radiator formed of a conductor or a conductive pattern formed on a substrate (e.g., a PCB). The antenna may radiate an up-converted signal on a wireless channel or obtain a signal radiated by other devices. Each antenna may be referred to as an antenna element or an antenna component. In some embodiments, the antenna part  1414  may include an antenna array in which multiple antenna elements form an array. The antenna part  1411  may be electrically connected to the power interface part  1412  through RF signal lines. The antenna part  1414  may be mounted on a PCB including multiple antenna elements. The antenna part  1411  may be mounted on a FPCB. The antenna part  1411  may provide a received signal to the power interface part  1412  or radiate a signal provided by the power interface part  1412  into the air. 
     The power interface part  1412  may include a module and parts. The power interface part  1412  may include one or more IFs. The power interface part  1412  may include one or more LOs. The power interface part  1412  may include one or more LDOs. The power interface part  1412  may include one or more DC/DC converters. The power interface part  1412  may include one or more DFEs. The power interface part  1412  may include one or more FPGAs. The power interface part  1412  may include one or more connectors. The power interface part  1412  may include a power supplier. 
     The power interface part  1412  may include areas for one or more antenna modules mounted thereon. For example, the power interface part  1412  may include multiple antenna modules for supporting MIMO communication. An antenna module according to the antenna part  1414  may be mounted to the corresponding areas. The power interface part  1412  may include a filter. The filter may perform filtering for transferring a signal of a desired frequency. The power interface part  1412  may include a filter. The filter may perform a function to selectively identify a frequency by generating a resonance. The power interface part  1412  may include at least one of a band pass filter, a low pass filter, a high pass filter, or a band reject filter. That is, the power interface part  1412  may include RF circuits for obtaining signals in a frequency band for transmission or a frequency band for reception. The power interface part  1412  according to various embodiments may electrically connect the antenna part  1414  and the RF processor  1413 . 
     The RF processor  1413  may include multiple RF processing chains. The RF chain may include multiple RF elements. The RF elements may include an amplifier, a mixer, an oscillator, a DAC, an ADC, and the like. The RF processing chain may correspond to an RFIC. For example, the RF processor  1413  may include an up converter for up-converting a digital transmission signal in a baseband into a transmission frequency and a digital-to-analog converter for converting an up-converted digital transmission signal into an analog RF transmission signal. The up converter and the DAC form a portion of a transmission path. The transmission path may further include a power amplifier (PA) or a coupler (or combiner). In addition, for example, the RF processor  1413  may include an analog-to-digital converter (ADC) for converting an analog RF reception signal into a digital reception signal and a down converter for down-converting a digital reception signal into a digital reception signal in a ground band. The ADC and the down converter form a portion of a reception path. The reception path may further include a low-noise amplifier (LNA) or a coupler (or divider). RF components of the RF processor may be implemented on a PCB. The base station  1410  may include a structure in which the antenna part  1414 , the power interface part  1412 , and the RF processor  1413  are sequentially stacked. Antennas, RF components of the power interface part, and the RFICs may be implemented on separate PCBs and filters between PCBs may be repeatedly coupled to each other to form multiple layers. 
     The processor  1414  may control general operations of the electronic device  1410 . The processor  1414  may include various modules for performing communication. The processor  1414  may include at least one processor such as a modem. The processor  1414  may include modules for digital signal processing. For example, the processor  1414  may include a modem. When transmitting data, the processor  1414  may generate complex symbols by coding and modulating a transmission bit stream. In addition, for example, when data is received, the processor  1414  may restore a bit stream by demodulating and decoding a baseband signal. The processor  1414  may perform functions of a protocol stack required by a communication standard. 
     Referring to  FIG.  14   , a functional configuration of the electronic device  1410  is described as equipment for which the antenna structure of the disclosure may be utilized. However, the example shown in  FIG.  14    is merely a configuration for the utilization of the RF filter structure according to various embodiments of the disclosure described through  FIGS.  1 ,  2 A,  2 B,  3 A,  3 B,  4 ,  5 A,  5 B, and  6  to  14   , and the embodiments of the disclosure are not limited to the components of the equipment shown in  FIG.  14   . Accordingly, an antenna module including an antenna structure, other type of communication equipment, and an antenna structure itself may also be understood as embodiments of the disclosure. 
     The methods according to embodiments described in the claims or the specification of the disclosure may be implemented by hardware, software, or a combination of hardware and software. 
     When the methods are implemented by software, a computer-readable storage medium for storing one or more programs (software modules) may be provided. The one or more programs stored in the computer-readable storage medium may be configured for execution by one or more processors within the electronic device. The at least one program may include instructions that cause the electronic device to perform the methods according to various embodiments of the disclosure as defined by the appended claims and/or disclosed herein. 
     The programs (software modules or software) may be stored in non-volatile memories including a random access memory and a flash memory, a read only memory (ROM), an electrically erasable programmable read only memory (EEPROM), a magnetic disc storage device, a compact disc-ROM (CD-ROM), digital versatile discs (DVDs), or other type optical storage devices, or a magnetic cassette. Alternatively, any combination of some or all of them may form a memory in which the program is stored. Further, a plurality of such memories may be included in the electronic device. 
     In addition, the programs may be stored in an attachable storage device which may access the electronic device through communication networks such as the Internet, Intranet, Local Area Network (LAN), Wide LAN (WLAN), and Storage Area Network (SAN) or a combination thereof. Such a storage device may access the electronic device via an external port. Further, a separate storage device on the communication network may access a portable electronic device. 
     While the disclosure has been shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims and their equivalents.