Patent Publication Number: US-2023163446-A1

Title: Antenna stack structure

Description:
CROSS-REFERENCE TO RELATED APPLICATION AND CLAIM OF PRIORITY 
     The present application is a continuation application to International Application No. PCT/KR2021/009257 with an International Filing Date of Jul. 19, 2021, which claims the benefit of Korean Patent Application No. 10-2020-0092579 filed on Jul. 24, 2020 at the Korean Intellectual Property Office, the disclosures of which are incorporated by reference herein in their entirety. 
    
    
     BACKGROUND 
     1. Field 
     The present invention relates to an antenna stack structure. More particularly, the present invention relates to an antenna stack structure including an antenna layer and a ground layer. 
     2. Description of the Related Art 
     As mobile communication technologies have been developed, an antenna for implementing a communication of high frequency or ultra-high frequency band is applied to a display device such as a smartphone, various objects or structures such as a vehicle, an architecture, etc. 
     An optical structure such as a polarizing plate and various sensor structures may be included in the display device. Accordingly, when the antenna is included in the display device, proper arrangement and construction of the antenna to avoid an interference between the optical structure and the sensor structure is needed. 
     Additionally, a space to which the antenna can be applied may be limited by the optical structure and the sensor structure. If an additional film or structure is formed for inserting the antenna, an overall thickness and volume of the display device may be increased. 
     Thus, an antenna construction to obtain sufficient radiation and gain properties of the antenna in a limited space is required. 
     For example, Korean Published Patent Application No. 10-2013-0113222 discloses an antenna structure embedded in a portable terminal, but does not sufficiently disclose an antenna design in consideration of both optical and radiation properties in the display device as described above. 
     SUMMARY 
     According to an aspect of the present invention, there is provided an antenna stack structure having improved radiation property. 
     (1) An antenna stack structure, including: an antenna substrate layer; an antenna unit disposed on one surface of the antenna substrate layer, the antenna unit including a radiator and an antenna pad; and a pad ground and an insulating layer disposed at the same level on an opposite surface of the antenna substrate layer facing the one surface, wherein the antenna pad is superimposed over the pad ground in a thickness direction. 
     (2) The antenna stack structure according to the above (1), wherein the antenna pad includes a signal pad electrically connected to the radiator, and a ground pad formed around the signal pad. 
     (3) The antenna stack structure according to the above (1), wherein the antenna stack structure has a radiation area and a pad area in which the antenna pad is located, and the pad ground is formed in the pad area. 
     (4) The antenna stack structure according to the above (1), further including a cover window disposed on the antenna unit. 
     (5) The antenna stack structure according to the above (1), further including a radiation ground disposed on a bottom surface of the insulating layer, wherein the radiator is superimposed over the radiation ground in a thickness direction. 
     (6) The antenna stack structure according to the above (5), wherein the pad ground and the radiation ground are electrically connected to each other. 
     (7) The antenna stack structure according to the above (6), wherein a thickness of the pad ground is greater than a thickness of the insulating layer, and the pad ground is in a lateral contact with the radiation ground. 
     (8) The antenna stack structure according to the above (5), further including a display panel disposed on the bottom surface of the insulating layer, and the display panel serves as the radiation ground. 
     (9) The antenna stack structure according to the above (8), wherein the display panel includes a display device including an electrode layer, and the electrode layer of the display device serves as the radiation ground, wherein the antenna substrate layer or the insulating layer serves as an encapsulation layer covering the display device. 
     (10) The antenna stack structure according to the above (1), wherein the pad ground is in contact with the antenna substrate layer. 
     (11) The antenna stack structure according to the above (1), wherein the radiator has a mesh structure. 
     (12) The antenna stack structure according to the above (11), wherein the antenna unit further includes a dummy mesh pattern arranged around the radiator. 
     An antenna stack structure according to embodiments of the present invention may include a pad ground overlapping an antenna pad in a thickness direction. A resonance frequency matching and an impedance optimizing may be implemented using the antenna pad, so that a gain and a radiation property at a specific frequency may be improved. Further, the antenna pad and the pad ground may be adjacent to each other to further improve an antenna gain. 
     In some embodiments, an electrode layer of a display panel may serve as a radiation ground, and the antenna stack structure integrated with the display panel may be provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic cross-sectional view illustrating an antenna stack structure in accordance with exemplary embodiments. 
         FIG.  2    is a schematic top planar view illustrating a stacked construction of an antenna unit and a ground layer in accordance with exemplary embodiments. 
         FIG.  3    is a schematic cross-sectional view illustrating an antenna stack structure in accordance with a comparative example. 
         FIG.  4    is a schematic cross-sectional view illustrating a display panel in accordance with exemplary embodiments. 
         FIG.  5    is a schematic cross-sectional view illustrating an antenna stack structure in accordance with exemplary embodiments. 
         FIGS.  6  and  7    are radiation diagrams showing radiation profiles of antenna stack structure of Example 1 and Comparative Example. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     According to exemplary embodiments of the present invention, there is provided an antenna stack structure in which a pad of an antenna unit and a pad ground may overlap each other in a thickness direction. 
     The antenna stack structure may include, e.g., a microstrip patch antenna fabricated in the form of a transparent film. The antenna stack structure may be applied to communication devices for a mobile communication of a high or ultrahigh frequency band corresponding to a mobile communication of, e.g., 3G, 4G, 5G or more, Wi-fi, Bluetooth, NFC, GPS, etc. 
     Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. However, those skilled in the art will appreciate that such embodiments described with reference to the accompanying drawings are provided to further understand the spirit of the present invention and do not limit subject matters to be protected as disclosed in the detailed description and appended claims. 
       FIG.  1    is a schematic cross-sectional view illustrating an antenna stack structure in accordance with exemplary embodiments.  FIG.  2    is a schematic top planar view illustrating a stacked construction of an antenna unit and a ground layer in accordance with exemplary embodiments. For example,  FIG.  1    is a cross-sectional view taken along a line A-A′ of  FIG.  2   . For convenience of descriptions, illustration of an antenna substrate layer  110  and a lower insulating layer  160  interposed between an antenna unit  120  and a pad ground  130 , and between the antenna unit  120  and a radiation ground  190  is omitted in  FIG.  2   .  FIG.  2    illustrates only one antenna unit, but a plurality of the antenna units may be arranged on the antenna substrate layer  110  in an array form. 
     Referring to  FIG.  1   , an antenna stack structure  10  may include the antenna substrate layer  110 , the antenna unit  120 , the pad ground  130  and the lower insulating layer  160 . The antenna stack structure  10  may further include an upper insulating layer  140 , a cover window  150  and/or the radiation ground  190 . 
     The antenna substrate layer  110  may be disposed between the antenna unit  120  and at least one of the pad ground  130  and the radiation ground  190  to serve as a dielectric layer of an antenna. 
     The antenna substrate layer  110  may include, e.g., a transparent resin material. For example, the antenna substrate layer  110  may include a polyester-based resin such as polyethylene terephthalate, polyethylene isophthalate, polyethylene naphthalate and polybutylene terephthalate; a cellulose-based resin such as diacetyl cellulose and triacetyl cellulose; a polycarbonate-based resin; an acrylic resin such as polymethyl (meth)acrylate and polyethyl (meth)acrylate; a styrene-based resin such as polystyrene and an acrylonitrile-styrene copolymer; a polyolefin-based resin such as polyethylene, polypropylene, a cycloolefin or polyolefin having a norbornene structure and an ethylene-propylene copolymer; a vinyl chloride-based resin; an amide-based resin such as nylon and an aromatic polyamide; an imide-based resin; a polyethersulfone-based resin; a sulfone-based resin; a polyether ether ketone-based resin; a polyphenylene sulfide resin; a vinyl alcohol-based resin; a vinylidene chloride-based resin; a vinyl butyral-based resin; an allylate-based resin; a polyoxymethylene-based resin; an epoxy-based resin; a urethane or acrylic urethane-based resin; a silicone-based resin, etc. These may be used alone or in a combination of two or more thereof. 
     In some embodiments, an adhesive film such as an optically clear adhesive (OCA) or an optically clear resin (OCR) may be included in the antenna substrate layer  110 . 
     In some embodiments, the antenna substrate layer  110  may include an inorganic insulating material such as silicon oxide, silicon nitride, silicon oxynitride, glass, or the like. 
     In some embodiments, the antenna substrate layer  110  may be provided as a substantially single layer. In some embodiments, the antenna substrate layer  110  may include a multilayer structure including at least two or more layers. 
     A capacitance or an inductance may be formed between the antenna unit  120 , and the pad ground  130  and/or the radiation ground  190  by the antenna substrate layer  110 , so that a frequency band at which the antenna stack structure  10  may be operated may be adjusted. 
     In some embodiments, a dielectric constant of the antenna substrate layer  110  may be adjusted in a range from about 1.5 to about 12. When the dielectric constant exceeds about 12, a driving frequency may be excessively decreased, so that driving in a desired high or ultra-high frequency band may not be implemented. For example, if the antenna substrate layer  110  includes glass, the antenna substrate layer  110  may have a dielectric constant from 3.5 to 8. 
     In exemplary embodiments, a thickness of the antenna substrate layer  110  may be from 5 μm to 200 μm. Within this range, gain and efficiency of the antenna may be increased. 
     The antenna unit  120  may be disposed on one surface (e.g., a top surface) of the antenna substrate layer  110 . For example, the antenna unit  120  may be directly formed on the top surface of the antenna substrate layer  110 . 
     The antenna unit  120  may include a radiator  122 , a transmission line  124 , and/or an antenna pad. 
     For example, the antenna unit  120  may include silver (Ag), gold (Au), copper (Cu), aluminum (Al), platinum (Pt), palladium (Pd), chromium (Cr), titanium (Ti), tungsten (W), niobium (Nb), tantalum (Ta), vanadium (V), iron (Fe), manganese (Mn), cobalt (Co), nickel (Ni), zinc (Zn), tin (Sn), molybdenum (Mo), calcium (Ca) or an alloy containing at least one of the metals. These may be used alone or in combination thereof. 
     For example, the antenna unit  120  may include silver (Ag) or a silver alloy (e.g., silver-palladium-copper (APC)), or copper (Cu) or a copper alloy (e.g., a copper-calcium (CuCa)) to implement a low resistance and a fine line width pattern. 
     In some embodiments, the antenna unit  120  may include a transparent conductive oxide such as indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnOx), zinc oxide (ZnOx), indium zinc tin oxide (IZTO), etc. 
     In some embodiments, the antenna unit  120  may include a stacked structure of a transparent conductive oxide layer and a metal layer. For example, the antenna unit  120  may include a double-layered structure of a transparent conductive oxide layer-metal layer, or a triple-layered structure of a transparent conductive oxide layer-metal layer-transparent conductive oxide layer. In this case, flexible property may be improved by the metal layer, and a signal transmission speed may also be improved by a low resistance of the metal layer. Corrosive resistance and transparency may be improved by the transparent conductive oxide layer. 
     In some embodiments, a thickness of the antenna unit  120  may be about 5,000 Å or less, preferably from about 1,000 Å to 5,000 Å. Within this range, a color shift phenomenon from a viewing surface of the antenna stack structure may be suppressed while preventing an increase in resistance of the antenna unit  120 . 
     The radiator  122  may have, e.g., a polygonal plate shape, and the transmission line  124  may extend from one side of the radiator  122  to be electrically connected to the signal pad  126 . The transmission line  124  may be formed as a single member substantially integral with the radiator  122 . 
     In some embodiments, the antenna pad may include a signal pad  126  and may further include a ground pad  128 . For example, a pair of the ground pads  128  may be disposed with the signal pad  126  interposed therebetween. The ground pads  128  may be electrically separated from the signal pad  126  and the transmission line  124 . 
     In an embodiment, the ground pad  128  may be omitted. The signal pad  126  may be formed as an integral member at an end portion of the transmission line  124 . 
     In some embodiments, an end portion of the antenna unit  120  may be electrically connected to a circuit connection structure. The circuit connection structure may include, e.g., a flexible printed circuit board (FPCB). 
     The antenna pad may be electrically connected to an antenna driving integrated circuit (IC) chip through the circuit connection structure such as the flexible printed circuit board. Accordingly, a feeding and a driving control to the antenna unit may be performed by the antenna driving IC chip. 
     The driving IC chip may be directly disposed on the flexible circuit board. For example, the flexible circuit board (FPCB) may further include a circuit or a contact electrically connecting the driving IC chip and the antenna unit. The flexible circuit board (FPCB) and the driving IC chip may be disposed to be adjacent to each other, a signal transmission/reception path may be shortened and a signal loss may be suppressed. 
     In an embodiment, the antenna unit  120  may be formed as a mesh structure. For example, the antenna unit  120  may be directly formed on the top surface of the antenna substrate layer  110  by a sputtering process. 
     In exemplary embodiments, the radiator  122  may have a mesh structure. In some embodiments, the transmission line  124  connected to the radiator  122  may also have a mesh structure. 
     The radiator  122  may include the mesh structure, so that transmittance may be improved even when the radiator  122  is disposed in a display area of a display device, thereby preventing electrodes from being visually recognized and preventing an image quality from being deteriorated. 
     A dummy mesh pattern may be disposed around the radiator  122  and the transmission line  124 . The dummy mesh pattern may be electrically and physically spaced apart from the radiator  122  and the transmission line  124  by a separation region. 
     For example, a conductive layer including the above-described metal or alloy may be formed on the antenna substrate layer  110 . The conductive layer may be partially etched along a profile of the radiator  122  and the transmission line  124  to form a separation region while forming the mesh structure. Accordingly, the antenna unit  120  and the dummy mesh pattern isolated by the separation region may be formed on the antenna substrate layer  110 . 
     In some embodiments, the signal pad  126  may be formed as a solid structure to reduce a feeding resistance. For example, the signal pad  126  may be disposed in a non-display area or a light-shielding area of the display device to be bonded or connected to a flexible circuit board and/or an antenna driving IC chip. 
     Accordingly, the signal pad  126  may be disposed at an outside of a user&#39;s viewing area. In an embodiment, the signal pad  126  may substantially consist of a metal or alloy. 
     The pad ground  130  may be disposed on an opposite surface (e.g., a bottom surface) of the antenna substrate layer  110 . The pad ground  130  may be formed on an opposite side of the antenna unit  120  with respect to the antenna substrate layer  110 . The antenna pad may be superimposed over the pad ground  130  in a thickness direction of the antenna stack structure  10 . In this case, a resonance frequency and an impedance may be adjusted using the antenna pad. Accordingly, an antenna gain and a radiation property may be improved. 
     In exemplary embodiments, the pad ground  130  may contact the surface of the antenna substrate layer  110 . For example, the pad ground  130  may be formed directly on the surface (e.g., the bottom surface) of the antenna substrate layer  110 . In this case, a distance between the pad ground  130  and the antenna pad of the antenna unit  120  may be reduced. Accordingly, the antenna gain may be further improved and the impedance may be effectively matched. 
     In exemplary embodiments, the antenna stack structure  10  may include a pad area PA where the antenna pad is located and a radiation area RA except for the pad area PA. The radiator  122  may be formed in the radiation area RA. In some embodiments, the pad ground  130  may be formed only in the pad area PA and may not extend to the radiation area RA. 
     For example, the pad ground  130  may include a conductive layer. The conductive layer may include a metal or a conductive metal compound. Preferably, the pad ground  130  may be formed of a low-resistance metal so that the frequency and the impedance may be effectively adjusted and matched. 
     For example, silver (Ag), gold (Au), copper (Cu), aluminum (Al), platinum (Pt), palladium (Pd), chromium (Cr), Titanium (Ti), tungsten (W), niobium (Nb), tantalum (Ta), vanadium (V), iron (Fe), manganese (Mn), cobalt (Co), nickel (Ni), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), or an alloy thereof may be used without a consideration of transparency. Preferably, the low-resistance metal may include copper, aluminum, a silver-palladium-copper alloy, and/or a copper-calcium alloy. 
     In exemplary embodiments, a thickness of the pad ground  130  may be from 100 nm to 25 μm. For example, if the pad ground  130  is formed in the pad area PA of the antenna substrate layer  110  by a metal deposition process (e.g., a sputtering process), the thickness of the pad ground  130  may be from 100 nm to 1 μm. For example, if the pad ground  130  is formed by a mechanical method such as a metal printing or coating, the thickness of the pad ground  130  may be from 5 μm to 25 μm. 
     In exemplary embodiments, the pad ground  130  may be electrically connected to the ground pad  128  of the antenna unit  120 . For example, the pad ground  130  and the ground pad  128  of the antenna unit  120  may be connected through a via or a contact penetrating the antenna substrate layer  110 . 
     In some embodiments, the pad ground  130  may be electrically connected to the ground pad  128  of the antenna unit  120  through a ground wire bypassing a side surface of the antenna substrate layer  110 . In this case, the antenna gain may be improved. 
     The lower insulating layer  160  may be formed at the same layer or at the same level as that of the pad ground  130 . For example, the lower insulating layer  160  may be in contact with the bottom surface of the antenna substrate layer  110 . In some embodiments, the lower insulating layer  160  may cover the bottom surface of the pad ground  130  or surfaces of the pad ground which are not in contact with the antenna substrate layer  110 . 
     In exemplary embodiments, the lower insulating layer  160  may include at least one of an organic insulating layer and an inorganic insulating layer. 
     The organic insulating layer may include polyacrylate, polymethacrylate (e.g., PMMA), polyimide, polyamide, polyvinyl alcohol, polyamic acid, polyolefin (e.g., PE, PP), polystyrene, polynorbornene, phenylmaleimide copolymer, polyazobenzene, polyphenylenephthalamide, polyester (e.g., PET, PBT), polyarylate, a cinnamate-based polymer, a coumarin-based polymer, a phthalimidine-based polymer, a chalcone-based polymer, an aromatic acetylene-based polymer, etc. These may be used alone or in a combination thereof. 
     For example, the organic insulating layer may be formed by coating and drying a composition including the above-mentioned polymer material. A thickness of the organic insulating layer may be from about 1 μm to 5 μm, preferably from about 1.5 μm to 2.5 μm. 
     The inorganic insulating layer may include a single layer or a multi-layered structure, and may be formed of a metal oxide or a metal nitride. For example, the inorganic insulating layer may include at least one of SiNx, SiON, Al 2 O 3 , SiO 2  and TiO 2 . 
     For example, the inorganic insulating layer may be formed as a SiON layer or a SiO 2  layer, or a bilayer of SiON and SiO 2  layers. 
     For example, the inorganic insulating layer may be formed by a deposition process such as chemical vapor deposition (CVD) process. The inorganic insulating layer may have a thickness from about 100 nm to 1,000 nm, preferably about 200 nm to 400 nm. 
     In exemplary embodiments, the lower insulating layer  160  may further include an adhesive layer such as an optically clear adhesive (OCA) layer, an optically clear resin (OCR) layer, or the like. For example, the radiation ground  190  may be attached to the organic/inorganic insulating layer or the antenna substrate layer  110  using the adhesive layer. 
     In exemplary embodiments, a thickness of the adhesive layer may be from about 25 μm to 300 μm. 
       FIG.  3    is a schematic cross-sectional view illustrating an antenna stack structure in accordance with a comparative example. Detailed descriptions on elements and structures substantially the same as or similar to those described with reference to  FIG.  1    are omitted. 
     Referring to  FIG.  3   , an antenna stack structure  20  of a comparative example may not include the pad ground  130  disposed on the bottom surface of the antenna substrate layer  110 , but may include the radiation ground  190  disposed on the bottom surface of the lower insulating layer  160 . 
     In this case, a distance between the antenna unit  120  and the radiation ground  190  may be increased by a thickness of the lower insulating layer  160 . In this case, the antenna gain may be decreased, and the impedance may not be effectively adjusted. 
     For example, if the display panel  200  serves as the radiation ground  190 , the display panel  200  may be attached to the antenna stack structure via the lower insulating layer  160  including the adhesive layer, and a distance between the antenna unit  120  and the display panel  200  may be increased. 
     However, according to exemplary embodiments, even though the display panel  200  is attached to the antenna stack structure by the lower insulating layer  160  serving as the adhesive layer, the pad ground  130  may be formed on the bottom surface of the antenna substrate layer  110 . Thus, a distance from the pad ground  130  to the antenna unit  120  and the antenna pad may be decreased. Accordingly, the antenna gain and impedance matching may be enhanced. 
     In exemplary embodiments, the radiation ground  190  may be disposed on a surface (e.g., a bottom surface) of the lower insulating layer  160  opposite to the antenna substrate layer  110 . For example, the radiation ground  190  may be disposed under the pad ground  130 . In this case, the pad ground  130  and the radiation ground  190  may be electrically and physically separated. 
     The radiator  122  of the antenna unit  120  may be superimposed over the radiation ground  190  in the thickness direction of the antenna stack structure  10 . In this case, the radiator  122  and the entire antenna pad may be utilized to adjust the resonance frequency and impedance of the antenna. 
     In an embodiment, the radiation ground  190  may be formed only in the radiation area RA and may not overlap the antenna pad. In an embodiment, the radiation ground  190  may entirely cover the antenna unit  120  in a planar view. 
     In exemplary embodiments, the upper insulating layer  140  may be disposed on the antenna unit  120 . The upper insulating layer  140  may cover the top surface of the antenna unit  120 . The upper insulating layer  140  may include at least one of an organic insulating layer and an inorganic insulating layer substantially the same as those used for the lower insulating layer  160 . 
     In some embodiments, the upper insulating layer  140  may further include an upper adhesive layer including a pressure-sensitive adhesive (PSA) or an optically transparent adhesive (OCA) that may include an acrylic resin, a silicone-based resin, an epoxy-based resin, etc. can 
     The upper adhesive layer may attach the cover window  150  to the antenna unit  120  or the organic/inorganic insulating layer. In some embodiments, the upper adhesive layer may be omitted, and the organic/inorganic insulating layer may be directly attached to the cover window  150 . 
     The cover window  150  may be disposed on the antenna unit  120 . The cover window  150  may be disposed on an opposite side from the antenna substrate layer  110 . The cover window  150  may be disposed on a viewing surface or an outermost surface of the antenna stack structure  10 . 
     The cover window  150  may include, e.g., glass or a flexible resin material such as polyimide, polyethylene terephthalate (PET), an acrylic resin, a siloxane-based resin, etc. 
     In some embodiments, a thickness of the cover window  150  may be from about 10 μm to 100 μm. Preferably, the thickness of the cover window  150  may be from about 30 μm to 60 μm. 
       FIG.  4    is a schematic cross-sectional view illustrating a display panel in accordance with exemplary embodiments. 
     Referring to  FIG.  4   , the display panel  200  may include a panel substrate  205 , a display device and an encapsulation layer  250  covering the display device. The display device may include an electrode layer, a pixel defining layer  220  and a display layer  230 . The electrode layer may include a pixel electrode  210  and an opposing electrode  240 . 
     The display device and the encapsulation layer  250  may be sequentially formed on the panel substrate  205 . 
     A pixel circuit including a thin film transistor (TFT) may be formed on the panel substrate  205 , and an insulating layer covering the pixel circuit may be formed. The pixel electrode  210  may be electrically connected to, e.g., a drain electrode of the TFT on the insulating layer. 
     The pixel defining layer  220  may be formed on the insulating layer to expose the pixel electrode  210  to define a pixel area. The display layer  230  may be formed on the pixel electrode  210 , and the display layer  230  may include, e.g., a liquid crystal layer or an organic light emitting layer. Preferably, the display layer  230  may include the organic light emitting layer, and the display panel  200  may be an OLED panel. 
     The opposing electrode  240  may be disposed on the pixel defining layer  220  and the display layer  230 . The opposite electrode  240  may serve as, e.g., a common electrode or a cathode of the display panel  200 . The encapsulation layer  250  for protecting the display panel  200  may be stacked on the opposing electrode  240 . 
     In exemplary embodiments, the display panel  200  may serve as the radiation ground  190 . For example, the electrode layer (the pixel electrode  210  or the opposing electrode  240 ) of the display panel  200  may serve as the radiation ground  190 . Preferably, the opposing electrode  240  having a relatively large area may be provided as the radiation ground  190 . 
     In exemplary embodiments, the encapsulation layer  250  may serve as the antenna substrate layer  110  or the lower insulating layer  160 . In this case, the display panel  200  and the antenna stack structure  10  may be integrated to provide a thin film structure. 
     In exemplary embodiments, a polarizing layer may be disposed between the antenna unit  120  and the window cover  150 . For example, the polarizing layer may be formed on a top surface of the antenna substrate layer  110 . 
     The polarizing layer may include a coated polarizer or a polarizing plate. The coating-type polarizer may include a liquid crystal coating layer including a polymerizable liquid crystal compound and a dichroic dye. In this case, the polarizing layer may further include an alignment layer for providing an alignment to the liquid crystal coating layer. 
     For example, the polarizing plate may include a polyvinyl alcohol-based polarizer and a protective film attached to at least one surface of the polyvinyl alcohol-based polarizer. 
     The upper insulating layer  140  may be disposed between the polarizing layer and the antenna unit  120 . For example, the upper insulating layer  140  may be formed on the surface of the antenna unit  120  or the polarization layer, and then the antenna unit  120  and the polarizing layer may be attached to each other. 
     In example embodiments, the antenna stack structure may further include a touch sensing structure. 
     The touch sensing structure may include, e.g., capacitive sensing electrodes. For example, column direction sensing electrodes and row direction sensing electrodes may be arranged to cross each other. The touch sensing structure may further include traces connecting the sensing electrodes and a driving IC chip with each other. The touch sensing structure may further include a substrate on which the sensing electrodes and the traces are formed. 
       FIG.  5    is a schematic cross-sectional view illustrating an antenna stack structure in accordance with exemplary embodiments. Detailed descriptions on elements and structures substantially the same as those described with reference to  FIG.  1    may be omitted. 
     Referring to  FIG.  5   , a pad ground  131  of an antenna stack structure  11  may be thicker than a lower insulating layer  160 . In this case, the pad ground  131  may protrude from one surface of the lower insulating layer  160 . 
     In some embodiments, a radiation ground  191  and the pad ground  131  may be electrically connected to each other. For example, the radiation ground  191  may contact the pad ground  131 . In this case, the pad ground  131  and the radiation ground  191  may have improved electromagnetic capacity while forming a ground combined structure. Accordingly, an antenna gain may be improved and an impedance matching may be effectively implemented. 
     In some embodiments, when the display panel  200  serves as the radiation ground  191 , the opposing electrode  240  of the display panel  200  may be connected to the pad ground  131 . 
     Hereinafter, preferred embodiments are proposed to more concretely describe the present invention. However, the following examples are only given for illustrating the present invention and those skilled in the related art will obviously understand that various alterations and modifications are possible within the scope and spirit of the present invention. Such alterations and modifications are duly included in the appended claims. 
     Example 1 
     The radiator  122 , the transmission line  124 , the signal pad  126  and the ground pad  128  as illustrated in in  FIG.  2    were formed using a Cu—Ca alloy on a COP dielectric layer having a thickness of 40 μm. The radiator  122  and the transmission line  124  were formed of a mesh pattern, and the signal pad  126  and the ground pad  128  were formed as a solid pattern. 
     An APC alloy was deposited by a sputtering process in the pad area PA on a bottom surface of the dielectric layer to form a pad ground having a thickness of about 300 nm. Specifically, the pad ground was formed to cover an entire area of each of the signal pad  126  and the ground pad  128  in a planar view. 
     A transparent adhesive layer having a thickness of 100 μm was formed to cover the bottom surface of the dielectric layer and the pad ground, and then was attached to an OLED display panel including a metal opposing electrode to prepare an antenna stack structure. 
     Example 2 
     The pad ground was formed by printing a silver paste to have a thickness of 10 μm instead of depositing the APC alloy from Example 1. 
     A transparent adhesive layer having a thickness of about 100 μm on a portion of the bottom surface of the dielectric layer where the pad ground was not formed. The OLED panel was attached to a bottom surface of the transparent adhesive layer. 
     COMPARATIVE EXAMPLE 
     An antenna stack structure was fabricated by omitting the pad ground from Example 1 
     Experimental Example 1: Analysis of Radiation Property 
     Radiation profiles of the antenna stack structures of Example 1 and Comparative Example were analyzed to obtain diagrams of  FIGS.  6  and  7   , respectively. 
     Referring to  FIGS.  6  and  7   , the antenna stack structure of Example 1 provided the radiation profile more circular than that of Comparative Example to show a relatively uniform radiation property with respect to a directivity angle. 
     Experimental Example 2: Evaluation of Antenna Gain 
     Gains (dBi) of the antenna stack structures of Examples and Comparative Examples were analyzed within a 26 to 30 GHz range. The results are shown in Table 1 below. 
     
       
         
           
               
               
             
               
                   
                 TABLE 1 
               
             
            
               
                   
                   
               
               
                   
                 Frequency (GHz) 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                   
                 26.0 
                 26.5 
                 27.0 
                 27.5 
                 28.0 
                 28.5 
                 29.0 
                 29.5 
                 30.0 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 Example 1 
                 3.16 
                 4.57 
                 5.08 
                 5.39 
                 4.22 
                 3.51 
                 2.88 
                 2.47 
                 2.07 
               
               
                 Example 2 
                 3.64 
                 4.91 
                 5.49 
                 5.80 
                 4.81 
                 3.97 
                 3.24 
                 2.89 
                 2.47 
               
               
                 Comparative 
                 −3.45 
                 −5.28 
                 −5.68 
                 −3.4 
                 0.91 
                 3.07 
                 4.24 
                 3.65 
                 3.06 
               
               
                 Example 
               
               
                   
               
            
           
         
       
     
     Referring to Table 1, the antenna stack structure of the Examples provided remarkably improved antenna gains around the frequency of 28.0 GHz compared to that of Comparative Example. Further, the antenna stack structure of the Examples showed a broadband antenna radiation having improved antenna gain in the frequency range from 26 GHz to 30 GHz.